Minnesota Commercial Flower Growers Association Bulletin Serving the Floriculture Industry in the Upper Midwest

IN THIS ISSUE 1

Factors Affecting Clematis Rooting

7

Recommended Calcium Levels

8

Calcium

9

Media Test Review

10 L a n d - G r a n t Universities Urged to Broaden Research Beyond Traditional Agricultural Mission 12 Cropping Systems for Greenhouse Tomatoes 14

Scheduling a Greenhouse Tomato Crop

15 Nutrition f o r Greenhouse Tomatoes 20

Man aging Micron u t r i e n t s in the Greenhouse

25

Minnesota Commercial Flower Growers 1992 Short Course

26

Whitefly Q & A f o r Bedding Plant Producers

29

Impact of the Floriculture Industry in Minnesota

37

Research Update

Volume 41, Number 4

July, 1992

FACTORS AFFECTING CLEMATIS ROOTING John Erwin and Debra Schwarze Universityof Minnesota

Research was supported b y Donahue’s Greenhouses (Fairbault, MinneFota), the Minnesota Commercial Flower Growers Association, the Minnesota Agriculture Experiment Station and the Minnesota Extension Service.

[ntroduction Clematis production has increased significantly in Minnesota juring the last 5 years. Although clematis have been propagated for jecades, the method of propagation has essentially not changed. T‘raditionally, clematis are propagated in a washed sand based media without IBA application. Stuck cuttings are then placed in a humidity tent until rooting. Rooting generally takes 6 weeks. We conducted a study to determine the influence of cultivar, media type, IBA and the node position from which a cutting is taken on Zlematis rooting.

Materials and Methods Cuttings were taken from plants of C l e m a t i s c v s ,Jackmani’, ‘Contesse d e Bouchard’, ‘Gypsy Queen’ m d Clematis purpurea plena zlegans on March 5, 1991. Stock plants were composed 3f 5 nodes each. Node numbers were assigned from 1 a t the base of the plant to 5 a t the tip of the stem. Cuttings were treated with or without

Minnesota Flower Growers Bulletin

- July,

Volume 41, Number 4

1992

Table 1. Summary of analysis of variance identifying the significance of medium, cultivar a n d node position on the time for clematis cuttings to root, root d r y weight a n d primary root number after 8 weeks. Time to Root (days)

Term Cultivars varied in their time of root initiation, primary root number and root dry weight.

Root Dry Primary Root Weight (grams) Number

***

Medium Node Position Cul tivar Medium x Node Position Medium x Cultivar Node Postion x Cultivar Medium x Node Position x Cultivar

*** ***

** *** n.s. n.s. n.s. n.s.

*** n.s.

***

***

*Q

n.s. n.s. n.s. n.s.

*** * n.s.

Significant factors indicated by *(0.05), **(0.01), ***(0.001) or n.s. (non-significant) through Tukey's H.S.D. 0.1% IBA (indole-3-butyric acid) and placed in a humidity chamber in 1 of 5 different media: 1) 100% washed sand (ws), 2) 50% washed sand and 50% sphagnum peat (wp), 3) 50% sphagnum peat and 50% perlite (sp), 4) 100% perlite (PT),or 5) 50% sphagnum peat, 25% perlite a n d 25% vermiculite (pv) Time of root initiation, root dry weight gain a n d primary root number were determined. Root d r y weight and primary root number were collected after 8 weeks. T h e time of rooting was defined 3s when primary root length was equal to Dr exceeded 0.5 cm in length.

Both Gypsy Queen and C l e m a t i s purpurea plena elegans rooted after 38 days. In contrast, Jackmani rooted significantly later,i.e. 48 days.

The experiment was organized as a 4 x 5 x 2 x 5 factorial with cultivar, medium, IBA treatment a n d node position assigned as main factors. There were 5 cuttings per treatment.

Hormone Effects: IBA had no significant effect on clematis rooting.

Cultivar Effects: Cultivars varied in their time of root initiation, primary root number a n d root d r y weight (Table 1 and 2; Figure 1). Both Gypsy Queen and Clematis purpurea plena elegans rooted after 38 days. In contrast, Jackmani rooted significantly later, i.e. 48 days (Table 2; Figure la).

Table 2. The effect of medium type on time of rooting, root d r y weight a n d primary root number, after 8 weeks, of Clematis cvs Jackmani, Contesse d e Bouchard, Gypsy Queen a n d Clematis purpurea plena elegans. Numbers presented are treatment means across cultivar, IBA treatment and node position. Medium TY Pe

ws WP SP PT PV

Time to Root (days) 36.2 44.7 46.0 38.4 41.6

Root Dry Weight (grams)

a b bc a ab

.068 .020 .016 .086 .056

2

a bc c a a

Primary Root Number 7.3 4.2 4.3 6.3 5.3

a bcd cd ab b

Minnesota Flower Growers Bulletin

-

July, 1992

a

a

50

bcd cd

d

Gypsy

purpurea

40

n

UJ

s

0

3

30

c

0 0

K

20

0 c

? i

i=

10

0

Jackmani Contesse

Contesse de Bouchard a n d Clematis purpurea plena elegans had a significantly greater root d r y weight after 8 weeks compared to Jackmani a n d Gypsy Queen (Table 2; Figure lc). Contesse d e Bouchard had the greatest root d r y w e i g h t ( 0 . 0 7 4 g) a n d Jackmani had the lowest root d r y weight (0.026 g) (Table 2; Figure lc).

Cultivar

b

-8 ,

C

.-cC CI

5 t n

Volume 41, Number 4 Gypsy Queen had the greatest primary root number, 7.4 per cutting (Table 2; Figure lb). Contesse d e Bouchard a n d Clematis purpurea plena elegans had intermediate levels of primary root number. In contrast, Jackmani had the lowest primary root number with only 1/2 the primary root number (3.7 primary roots per cutting) as Gypsy Queen (Table 2; Figure lb).

6-

L.

P)

0

E a

z CI

0 0

K

r

z

Gypsy Queen had the greatest primary root number, 7.4 per cutting.

Contesse de Bouchard had the greatest root dry weight (0.074 g) and Jackmani had the lowest root dry weight (0.026 9).

L

.-

h Jackmani Contesse

Gypsy

purpurea

Cultivar

C

0.08

-

bc C

n

UJ

s

Q

0.06

-

0.04

-

0.02

-

3

Ea

.-

s

a

P

n c

0 0

K

n.oo -.---

Jackmani Contesse

Gypsy

purpurea

Cultivar

Figure 1. Variation in rooting time (a), primary root number per cutting (b) and root dry weight (c) of Clematis cv Jackmani, Contesse d e Bouchard, Gypsy Queen a n d Clematis purpurea plena elegans.

3

Medium Effects: Medium significantly affected time to root, primary root number and root d r y weight (Table 1). WS, P T a n d PV resulted in significantly earlier rooting than either WP or SP across cultivar, IBA treatment a n d node position (Figure 2). ‘Sticking’ cuttings into WS resulted in the earliest rooting, 36 days (Table 3; Figure 2a). In contrast, sticking cuttings in SP resulted in the slowest rooting, 46 days (Table 3; Figure 2a). Rooting cuttings in WS or PT resulted in the greatest primary root number. In contrast, rooting cuttings in WP, SP or PV reduced primary root number. WS resulted in the greatest

Medium significantly affected time to root, primary root number and root dry weight.

Rootingcuttings in WS or PT resulted in the greatest primary root number.

Minnesota Flower Growers Bulletin 50

40

Root dry weight after 8 weeks was greatest when cuttings were placed in WS, PT or PV.

-

-

Volume 41, Number 4

July, 1992

bc

b

-

7

ab

a

-

7

30 20 -

10

-

0-

ws

WP

PT

SP

PV

Media Type

a-

a ad 7

6-

d bcd

cd

4-

2-

0-

ws

WP

SP

PT

PV

Medium Type

Node position had a significant effect on time to root and root dry weight after 8 weeks; node position did not have asignificant effect on primary root number.

0.10

-

0.08

-

0.06

-

0.04

-

0.02

-

0.00 -r

f= a

ws

WP

SP

PT

PV

Medium Type

Effect of medium on time to root (a), primary root number per cutting (b) and root dry weight (c) of Clematis cv Jackmani, Contesse de Bouchard, Gypsy Queen and Clematis purpurea plena zlegans. 4

Root d r y weight a f t e r 8 weeks was greatest when cuttings were placed in WS, P T or PV. Root d r y weight was significantly reduced when cuttings were placed in WP or SP. Root d r y weight across cultivars and node positions was greatest when cuttings were placed in PT, 0.086 g (Table 3; Figure 2c). In contrast, root dry weight across cultivars a n d node positions was the lowest when cuttings were placed in SP, 0.016 g (Table 3; Figure 2c).

Node Position Effects: a

a

primary root number (7.3 per cutting) across cultivar, IBA treatment a n d node position (Table 3; Figure 2b). In contrast, rooting cuttings in WP resulted in the lowest primary root number (4.2 per cutting) across cultivar, IBA treatment a n d node position (Table 3; Figure 2b).

Node position had a significant effect on time to root a n d root d r y weight a f t e r 8 weeks; node position d i d not have a significant effect on primary root number (Table 1). The time of rooting of a cutting decreased as cutting position increased from 1 to 2 then increased as node position increased from 2 to 5 across cultivars a n d media (Figure 3a). In contrast, root d r y weight a f t e r 8 weeks increased slightly as node position increased from 1 to 2 then decreased as node position became more distal (Figure 3b).

Minnesota Flower Growers Bulletin y

E

45.079

-

-

July, 1992

5.3635~+ 1 . 1 2 8 9 ~ ~ 2RA2 = 0.081

71 0

1

0

2

3

4

I

0

5

6

Node Position (basal to distal)

0.3 U

0

0

0 0.2

0.1

-

y = 5.7605e-2 + 1.282%-2x

-

4.193%-3xA2

R"2 = 0.116

U

-

0.0 1 '

Node Position (basal to distal) Figure 3. Variation in rooting time (a) and root dry weight (b) of Clematis cv Jackmani, Contesse d e Bouchard, Gypsy Queen and Clematis purpurea plena elegans propagated from cuttings originating from different node positions on stock plants.

Discussion Clematis varied greatly in their ability to root among cultivars a n d species (Table 2). Of the cultivars which were difficult to root, such as Jackmani, media type plays a greater role as evidenced by the significant medium x cultivar interaction on root d r y weight (Table 1).

Volume 41. Number 4 The traditional method of rooting cuttings i n WS resulted in earlier and greater rooting than any of the other medium types other than PT. IBA had no effect on rooting a n d appeared to be unnecessary. Interestingly, the degree of clematis rooting did not seem to be related to media structure; rooting was similar between media with very different structures such as WS and, PT. Instead, time of rooting and the earliness of rooting appeared to be related to the p H of the medium; both WS and P T had the highest pH values of the medium types, 8.2 a n d 8.6, respectively, compared to SP and PV, 4.6 a n d 4.4, respectively.

The traditional method of rooting cuttings in WS resulted in earlier and greater rooting than any of the other medium types other than PT.

When time of rooting, primary root number and root dry weight were regressed against media pH a significant relationship was found in all cases. Time of rooting decreased as pH increased (Figure 4a). Primary root number and root d r y weight after 8 weeks increased as pH increased (Figures 4b a n d 4c).

Conclusions

Clematis appears to have a relatively high optimal pH for earliness of rooting a n d root development. Typically, better rooting is achieved i n peat based medium compared to sand based media in other plant species. Therefore, better and/or earlier rooting may be achieved in clematis if a peat-based media is used which is pH adjusted to 7.08.0. Although there were significant effects of node position on time of rooting a n d 5

Clematis varied greatly in their ability to root among cultivars and species.

When time of rooting, primary root number and root dry weight were regressed against media pH a significant relationshipwas found in all cases.

Minnesota Flower Growers Bulletin 46

Clematis appears to have a relatively high optimal pH for earlinessof rooting and root development.

y

zz

-

July, 1992 -

51.429

1.5517X

R"2

I

Volume 41, Number 4 0.538

0

46 44

42

root d r y weight, they were not great. However, the data suggest that the 2 most distal cuttings d o not have as great a potential for rooting as nodes lower down on the stem.

40 38

8/

y = 2.4136

+

0.47350X

R"2 = 0.484

0 7-

6-

5v,0,, n

Therefore, better and/or earlier rooting may be achieved in clematisif a peatbased media is usedwhich is pH adjusted to 7.08.0.

,

.

~

4

4

5

7

6

8

9

Medium pH 0.10

y =

-

1.5246e-2

+

9.9516e-3X

R"2 = 0.407

0 0.08 -

0.06

-

0.04

-

0.02 -

0.00 f

0

0

I

5

.

,

6

.

,

.

7

,

8

.

9

Medium pH Figure 4. The effect of medium PH on time to root

[a), primary root number (b) and root dry weight after 21 days (c) of Clematis. Data presented are means $cross cultivars and stock plant node positions.

6

vfinnesota Flower Growers Bulletin - July, 1992 Volume 41, Number Table 3. T h e effect of cultivar on time of rooting, root d r y weight a n d primary root number of Clematis cvs Jackmani, Contesse de Bouchard, Gypsy Queen a n d Clematis purpurea plena elegans. Numbers presented are treatment means across medium a n d nodes. Time to Root (days)

Cultivar

Root Dry Weight (grams)

Primary Root Number

Jackmani

48.4 a

.026 a

3.7 a

Contesse d e Bouchard

41.3 bcd

.074 bc

5.4 b

Gypsy Queen

38.4 cd

0.34 a

7.4 c

Clematis purpurea plena elegans

38.4 d

0.65 c

5.3 b

RECOMMENDED CALCIUM LEVELS Gary W. Hickman

Reprinted f r o m the American Greenhouse Vegetable Grower, Summer 1992, Volume 19, Number 2

For optimum greenhouse vegetable production, adequate nutrient solution or soil concentration of essential elements is necessary. Many published recommendations exist f o r calcium levels and are summarized below. Calcium Nutrient Solution Concentration - 136-300 ppm Soil Nutrient Level - 200-1000 ppm

Leaf Tissue Cucumber - 1-3% Tomato - 2-3% Lettuce - 1-2% Pepper - 3%

7

Minnesota Flower Growers Bulletin

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July, 1992

Volume 41, Number 4

CALCIUM Kosh and Ferguson, Harrow, Ontario

Reprinted from the American Greenhouse Vegetable Grower, Summer 1992, Volume 19. Number 2

Calcium, a n important element in plant mineral nutrition, is necessary for the structure, stability and formation of membranes. It plays a n important role in cell wall structure. Calcium is also of Calcium, an lmimportance in some enzyme systems and portant element a t the nuclei, where a lack of calcium in plant mineral nutrition, is nec- would result in improper cell division. essary for the Early symptoms of calcium deficiency in structure, stabll- general is evident i n the younger growity and formation ing tips of the plants (i.e., growing points of stems a n d roots and younger leaves). of membranes.

SYMPTOMS Tomatoes

Calcium uptake into the plant is determined by root activity.

Marginal yellowing/chlorosis with slight interveinal chlorosis. Leaflets remain small and curl upwards.

As symptoms progress, leaf tips and margins wither. Growing point dies.

Cucumbers Younger leaf margin yellowing and turn upwards and short internodes. Interveinal chlorosis and necrosis (white spots). Older leaves downward cupping with puckered interveinal areas. Growing point dies.

Peppers The movement of calcium in the plant Is mainlyvla the xylem vessels as well as cell to cell movement.

Calcium uptake into the plant is determined by root activity. Factors such as root temperature, moisture a n d oxygen availability in the rooting media, the electrical conductivity (EC) a n d the supply of calcium strongly influence absorption. T h e movement of calcium in the plant is mainly via the xylem vessels as well as cell to cell movement. Factors that influence water absorption and movement directly influence the movement of calcium within the plant. Blossom end rot (BER) occurs when there is calcium deficiency a t the distal end of the fruit. In numerous cases, BER may be prevalent where there is a n adequate supply of calcium in the media a n d leaf tissue tests indicate good to excellent levels. This is the result of too high a transpiration pull caused by low relative humidity and/or too high venting. Too vegetative a plant also causes a similar situation as the transpiration pull is too high to allow for adequate calcium movement to the fruit. Fruit is most sensitive to BER 1.5 to 3 weeks a f t e r flowering. During this period cell division a n d expansion is high a n d more sensitive to calcium. Xylem vessels must be established adequately to ensure proper calcium distribution. Cultivar sensitivity to BER can now be explained as the ability of the f r u i t to develop xylem vessels a t the distal end of the fruit. T h e more sensitive cultivars do not establish adequate xylem tissues.

Stunted growth and dark green leaves. Fruit smaller and darker green.

As symptoms progress, leaves are smaller, yellow and margins upturned. Growing point dies.

8

Too dramatic a change in fruit growth rate also increases sensitivity to BER. The supply of calcium is unable to keep u p with the demand resulting in internal BER that manifests into common BER as the f r u i t expands.

Minnesota Flower Growers Bulletin - July, 1992 Volume 41, Number 4 This may be caused by dramatic light BER. Recommended strategies f o r change (Extended cloudy period fol- optimum use of calcium include: lowed by very sunny conditions), too large a drop i n root zone EC over a short Proper greenhouse environment time period. In all cases, rapid changes Proper feed program in f r u i t expansion rates influence the Balanced plant (fruit load) Maintenance of steady f r u i t growth incidence, severity a n d frequency of The grower needs to maintain the pH in the 6.2 to 6.8 range to avoid problems caused by a high pH.

MEDIA TEST REVIEW Debra J. Schwarze Universityof Minnesota

Crop

pH

SS

NO,

NH,

Poinsettia

6.6

109

109

10

P

K

Ca

Mg

9 60

156

29

Na

Fe

Mn

Zn

B

93 .09

.24

.06

.06

T h e pH in this test is within the normal range. The grower needs to maintain the pH i n the 6.2 to 6.8 range to avoid problems caused by a high pH. By acidifying water a n d monitoring media pH throughout the growing season, this should not be any problem. The soluble salts a r e getting high. A general rule is to maintain the salts level below 125. In the case of this crop, leach once to lower the salts. The ammonium levels are approaching toxic levels. While the ammonium level is within the acceptable limits now, if a n ammonium based fertilizer is being used as we move into a time of year when the temperatures and light levels are decreasing, problems could arise. Be sure to be aware of the ammonium levels in your media to avoid burn problems later in the season. Do not use ammonium based fertilizers after October 1 in Minnesota! T h e nitrate level in this test is on the low side. Nitrogen levels will decrease f u r t h e r if you leach to remove total soluble salts and/or ammonium. Following leaching a single fertilizer application of double strength nitrogen source (400-600 ppm) should be applied. Following this regular applications of 200-300 ppm nitrogen should keep the nitrate level up in the acceptable range (150-250).

1

It is common to have low magnesium levels on early media tests of a crop. Low magnesium levels are often accompanied by lower micronutrient levels. This is the case in this media test. This generally indicates that the grower has not applied magnesium sulfate (epsom salts) or micronutrients. Application of these items can be done approximately once a month through the growing season, a n d they can be applied together. Apply epsom salts at a rate of 8 ounces per 100 gallons of water. Apply micronutrients as a 1/2 rate application once a month. Do not mix with calcium nitrate in a stock tank, they will react and fall out of solution. You can mix magnesium sulfate with micronutrients, and this is a good way to ensure that micronutrient needs are being met, especially in a soilless mix.

9

A general rule is to maintain the salts level below 125.

Do not use ammonium based fertilizers after October 1 in Minnesota!

You can mix magnesium sulfate with micronutrients, and this is a good way to ensure that micronutrient needs are being met, especially in a soilless mix.

Minnesota Flower Growers Bulletin

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July, 1992

Volume 41. Number 4

LAND-GRANT UNIVERSITIES URGED TO BROADEN RESEARCH BEYOND TRADITIONAL AGRICUTURAL MISSION David L. wheeler Scientists and research administratorsare callingon land-grant universities to move beyond their agricultural past and broadentheir research agenda.

The federal government started land-grant universities in 1862 with gifts of land and the expectation that the universities would educate a predominantly agricultural work force.

When the landgrant universitieswere formed, Mr. Stauber said, about 75 percent of American workers made their living in agriculture.

Reprinted f r o m the Chronicle o f Higher Education - April 22, 1992 Scientists and research administrators are calling on land-grant universities to move beyond their agricultural past and broaden their research agenda. Many of the calls f o r change are coming from the land-grant universities themselves, which are struggling to cope with state budget cuts, federal funding that is not expected to increase in the next decade, a n d the changing demographics of rural America. The federal government started landgrant universities in 1862 with gifts of land a n d the expectation that the universities would educate a predominantly agricultural work force. “Land-grant universities were created largely over a concern about rural America,” said Karl N. Stauber, vicepresident f o r programs a t the Northwest Area Foundation, which promotes rural x o n o m i c development from its headquarters i n St. Paul. “The United States the land-grant universities were created to aid a n d assist no longer exists.” [n a meeting sponsored here this month by the Board on Agriculture of the Vational Research Council, agricultural -esearchers, biologists and social scien:ists discussed how land-grant universi:ies could prepare for the future. The eesearch council is the operating agency if the National Academy of Sciences. 4 t the Board on Agriculture meeting, the leads of 52 scientific societies suggested ways i n which land-grant universities could reshape their mission. Scientists and other speakers suggested that the institutions could:

10

Set up interdisciplinary research teams to tackle problems identified by towns, counties and cities. Such a n approach is already being used a t a f e w land-grant universities, including Iowa State a n d Cornell. Move from a model of “industrial agriculture,” which measures productivity chiefly by profits, to a model of “ecological agriculture,” which would take broader environmental a n d consumer concerns into account. Shift from a focus on serving farmers to a broader mission of serving American consumers. “Our clientele is 250 million people,” said David L. Brown, chairman of the rural sociology department a t Cornell University. “We’re helping to feed these people.” Use their research capacity to help citizens of other countries, particularly in rural areas of developing nations. When the land-grant universities were formed, Mr. Stauber said, about 75 percent of American workers made their living in agriculture. Now, after more than a century of increased mechanization on the country’s farms, a mere 2 percent of the population performs agricultural work. The American population, particularly the voters, has moved into suburban areas, where land-grant universities are facing competition from community colleges that are offering con tinuing-educa tion a n d communityservice programs.

Minnesota Flower Growers Bulletin - July, 1992 Volume 41, Number Land-grant universities are also facing federal level for being too narrowly dramatic shifts in their sources of focused on agriculture. “We’re probably financial support. the most confused creature in the landgrant system right now,’’ said Hal E. Administrators of the land grants have Tatum, president of the National Assotraditionally relied heavily on federal ciation of County Agricultural Agents. “formula funds” a n d state appropriations. But formula funds, which allo- Some of the land-grant universities hope cate money according to a n equation to revitalize their public-service tradithat does not take the quality of re- tion with interdisciplinary research teams search a t each institution into account, that would link faculty members i n are not expected to grow in the future colleges of agriculture with those in because many members of Congress schools of business, engineering, law and view them as a n outmoded way of medicine. But administrators say they distributing agricultural-research sup- face formidable barriers in trying to set port. Scientists a t land-grant universi- up such efforts. ties now have to compete with other federal and university researchers for C. Eugene Allen, vice-president of the peer-reviewed grants supported by the University of Minnesota’s Institute of Department of Agriculture. Agriculture, Forestry and Home Economics, said interdisciplinary research At the state level, land-grant universi- teams were slower to produce results ties have suffered from the same bud- than single-discipline teams, even though get cuts with which all public univer- the results of interdisciplinary research sities have had to cope. Particularly might ultimately be more important to hard hit have been land-grant exten- society. Interdisciplinary teams, he said, sion services, which were set up early in have to spend time learning to work this century to help farmers with ad- together and defining common terms. vice based on the latest research. For younger faculty members seeking publication and tenure, those slow starts can damage careers, Mr. Allen said. A Target for Future Cuts In some states, the extension services have expanded their mission to help consumers, new immigrants and innercity residents, but they are still considered a likely target for future federal cuts, which would compound the damage already done a t the state level. In Georgia, f o r example, about 100 of the state’s 500 county extension agents were eliminated last year. T h e university-managed county extension agents are being criticized locally for losing touch with farmers and 4-H Clubs a n d are being attacked at the

Sometimes administrators must overcome outright hostility among researchers i n different disciplines. The Northwest Area Foundation’s Mr. Stauber said that in his visits to land-grant universities he had heard economists call agronomists “dirt clods” and ecologists refer to agricultural economists as “the bastard children of Adam Smith.” “When you do this,” he said, “you degrade your own institution a n d diminish the value of important intellectual pursuits.”

Y

11

Land-grant universitiesare also facing dramatic shifts in their sourcesof financial support.

At thestate level, land-grant universities have sufferedfromthe same budget cuts with which all public universities have hadto cope. Particularly hard hit have been landgrant extension services, which wereset upearly in this century to helpfarmers with advice based on the latest research.

Some of the land-grant universities hope to revitalize their public-service tradition with interdisciplinary research teams that would link faculty members in collegesof agriculture with those In schools of business, engineering, law and medicine.

Minnesota Flower Growers Bulletin

- July,

1992

Volume 41. Number 4

CROPPING SYSTEMS FOR GREENHOUSE TOMATOES Richurd J. McAvoy ExZenswn Specialist GreenhouseCrops University of Connecticut

-

Reprinted f r o m the Connecticut Greenhouse Newsletter, J u n e / J u l y 1992, #I68

Greenhouse tomatoes can be produced in ground beds or above ground using any of a number of inert or noninert growing media.

Greenhouse tomatoes can be produced in ground beds or above ground using any of a number of inert or noninert growing media. In Connecticut, tomatoes are produced in ground beds as well as in peat-lite bags (noninert medium) and in rockwool slabs (an inert medium). In the following review, several production systems, some of the requirements of these systems and some of the benefits a n d liabilities of each system will be discussed.

Tomatoes in Soil Beds Tomato seedlings are transplanted directly i n the soil floor. Parallel trenches four inches deep and six inches wide are prepared in the soil prior to transplant. The soil bed is When repeated crops are produced in the the simplest same house, the beds are tilled and the method of croppH a n d nutrients (primarily phosphorus ping in that it rem d micronutrients) are adjusted bequires low cost tween crops. Sometimes peat or compost setup. is added to improve organic matter content. Soils should be fumigated between x o p s using a chemical agent. Plastic can be used to cover the entire floor of the greenhouse. A white on black material

can be used to suppress weeds a n d reflect light (white side up). Plants are transplanted through the plastic and nutrients a n d water are supplied by drip irrigation. Tile drainage may be required to ensure uniform drainage throughout the house. The soil bed is the simplest method of cropping in that it requires low cost setup (i.e. no beds to build, etc). In addition, there is less of a disposal problem than with artificial media. Soil beds are well buffered i n terms of nutrients a n d water, therefore, control of irrigation and feeding need not be as precise as in other systems. On the negative side, soil fumigation can be a problem as weeds, insects and disease organisms tend to build u p over time. Cool soil temperatures early in the season will slow growth. Several weeks of heating may be required to sufficiently warm the soil prior to transplanting. In the well-buffered soil beds, nutritional a n d pH imbalances are difficult to correct while cropping, and growers may f i n d they have less control over the crop.

Tomato Cropping in Peat Bags Peat-lite media bags are set out in parallel rows in the greenhouse. Bags are usually placed on top of a plastic mulch. Bags a r e irrigated with drip or spray nozzles. Bags are generally reused and the mix is discarded or shredded, fumigated a n d used to grow bedding plants in flats or baskets. Peat-lite media can also be used in troughs built aboveground, but bag culture offers more flexible use of the greenhouse a n d

In the well-buffered soil beds, nutritional and pH imbalances are difficult to correct while cropping, and growers mayfind they have less control over the crop.

12

vlinnesota Flower Growers Bulletin - July, 1992 Volume 41, Number 4 is more commonly used. Peat-lite media if the slabs are deployed i n troughs, or d r y quickly a n d have less buffering simply drained to waste. capacity than soil beds. The frequent need f o r irrigation gives the grower Rockwool has little or no cation exmore opportunities to adjust nutri- change capacity and, because of the tional regimes and control plant growth. limited slab volume, only limited water holding capacity. Water must be supThe relatively low water holding ca- plied frequently, six or more times per pacity a n d limited cation exchange day, and nutrition must be closely monicapacity necessitate frequent irriga- tored. Electrical conductivity a n d p H tion a n d precise control of water distri- must be monitored daily. bution a n d nutrient levels. Soil testing should be done frequently, i.e. on a Rockwool slabs can be steam sterilized or weekly basis. chemically fumigated between crops a n d reused a second time. Disposal of spent slabs has become a significant problem i n Tomato Cropping in Rockwool Europe. Rockwool is a n inert substance which comes in preformed slabs usually three More detailed information on greento four inches square in cross section house tomato culture can be obtained and about three feet in length. The from the following reference materials material is sterile and is used in the and information sources: greenhouse much like lay-flat peat bags. Rockwool slabs are very compact and Growing Greenhouse Tomatoes i n Soil lightweight, making them easy to work and Soilless Media (Publication 1865/E) with. Slabs are irrigated with drip or and Tomato Diseases (Publication 14791 spray stakes located a t the base of each E); available f r o m Communications tomato plant. Nutrients can be recycled Branch, Agriculture Canada, Ottawa, Ontario Canada K 1AOC7.

13

Peat-llte media can also be used in troughs built aboveground, but bag culture offers more flexible use of the greenhouse and Is more commonly used.

Rockwool slabs can be steam sterilized or chemically fumigated between crops and reused a second time.

Minnesota Flower Growers Bulletin

- July,

Volume 41, Number 4

1992

SCHEDULING A GREENHOUSE TOMATO CROP Richurd J. McAvoy Assistant Professor and Extenswn Specialist Greenhouse Crops University of Connecticut

-

Greenhouse tomatoes are usually scheduledto come into production when field tomatoes are not available.

Light during seedling deveiopment wlll also affect the timing of initial flower-

ing.

Reprinted f r o m the Connecticut Greenhouse Newsletter - J u n e / J u l y 1992 # I 6 8 Greenhouse tomatoes are usually scheduled to come into production when field tomatoes a r e not available. In northern sections of the country, such as New England, the field production season occurs late i n summer a n d is short in duration. As a result, greenhouse tomato growers in Connecticut and other parts of New England find they can market greenhouse tomatoes through most of the summer a n d still get a good price.

ment will also affect the timing of initial flowering. Under ideal conditions of high light and warm temperatures, it will take about eight weeks from flowering until first harvest. Seedlings are generally transplanted into the production greenhouse two to three weeks before flowering. Under less than ideal conditions, the period from seed to harvest will be longer than 16 weeks.

The time interval between sowing a crop a n d harvesting ripe f r u i t will vary with the season, since the rate of seedling and f r u i t development are affected by temperature. Light during seedling develop-

Use the schedules listed below as a general guide. Remember, the actual time required will vary between cultivars and with the light a n d temperature conditions in your greenhouse.

Table 1. Scheduling a greenhouse tomato crop.

Crop Season Early Spring

Late Spring

Fall

Development Stage

Time interval

Seed Transplant Harvest

OCt 25-Nov 25 Jan 1-Jan 15 April 1-July

Seed Transplant Harvest

Dec 15-Jan 15 Feb 1-March 1 May 1-July

Seed Transplant Harvest

June 15-July 15 July 20-Augl5 Oct 1-Dec

14

Weeks from seed 9-10 22-23

___ 6-7 19-20

--5

16

dlinnesota Flower Growers Bulletin

- July,

1992

Volume 41, Number 4

NUTRITION FOR GREENHOUSE TOMATOES Richard J. McAvoy Extension Specklist Greenhouse Crops University of Connecticut

-

Reprinted f r o m the Connecticut Greenhouse Newsletter, June/ July 1992 #I68 Greenhouse tomato crop growth and tomato development can be controlled through mineral nutrition. There are two aspects of crop nutrition which the grower must consider. One aspect of nutrition involves the overall level of nutrients available to the plant. Large plants, plants carrying heavy fruit loads a n d rapidly growing plants (i.e. plants growing under conditions of high light a n d warm temperatures) require more total nutrients than do small plants, plants with light f r u i t loads or slowgrowing plants. Nutrient levels can also be used to control the rate of plant growth in a n indirect way - through the effect of total salts on plant water status. As nutrient levels increase, electrical conductivity (EC) increases and less water is available to the plant. A stress is imposed a n d growth slows. By modulating EC, the rate of tomato plant development can be controlled. T h e second aspect of nutrition involves the balance of nutrients available to the

plant. Nutrient balance controls the tendency for the plant to produce either vegetative or reproductive growth. (i.e. leaves and stems vs. flowers a n d fruits). Maintaining the proper balance between vegetative growth and f r u i t load is the key to long-term productivity of the crop. Regulating this balance requires experience and skill. Growers with little experience in growing tomatoes in the greenhouse should follow the guidelines outlined i n this article and keep careful records as to how the crop responds to nutritional changes over time. This process will help growers gain the experience they need. Tomatoes, like other green plants, require all of the basic essential elements for proper growth and f r u i t production. The essential macronutrients, which are supplied as fertilizer salts, are nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. These elements are usually absorbed as nitrate (NO,), phosphate (H2P04), potassium (K'), calcium (Ca2+), magnesium (Mg2+) a n d sulfate (SO,).

Table 1. Total fresh weight gain and nutirent quantities removed f r o m solution b y greenhouse tomatoes produced in the nf t (nutrient f i l m technique) system. Nutrients and Production Data Spacing Total fresh weight Total f r u i t weight N uptake P uptake K uptake Ca uptake Mg uptake

Amount per Plant

Nutrients Ratios: N Relative to Other Nutrients

4 ft2 19 lbs 15 lbs 16.72 grams 2.32 grams 26.73 grams 12.57 grams 3.5 grams 15

1:0.14 1:1.60 1:0.75 1:0.21

Greenhouse tomato crop growth and tomato development can be controlled through mineral nutrition.

Nutrient levels can also be used to control the rate of plant growth in an indirect way through the effect of totai salts on plant water status.

-

Nutrient balance controls the tendency for the piant to produce either vegetative or reproductive growth. (i.e. leavesand stems vs. flowers and fruits)

.

The essential macronutrients, which are supplied as fertilizer salts, are nitrogen, phosphorus, potassium, calcium, magnesium and sulfur.

Minnesota Flower Growers Bulletin Nitrogen is used in the iargesl quantities in terms of total at. oms absorbed by the plant.

- July,

1992

Volume 41, Number 4

Table 2. Recommended fertilizer rates (parts per million) f o r tomatoes cropped in peat-lite and rockwool systems. Peat-lite Bags (PPm)

Stage of Development

N

P

K

Ca

Mg

Fe

Planting to 1st cluster

150-200

50

225-300

80

30

3

0.5

1st to 4th cluster

200-225

50

300-340

80

30

3-5

0.5

4th to finish

225-300

50

340-500

80

30

3-10

0.5

B

Rockwool Slabs (PPm) Potassium is important in fruit ripening and fruit quality, at harvest 90% of the potassium in the plant can be found inthe fruit.

Stage of Development

N

P

K

Ca

Mg

Fe

B

Saturating ;labs

200

62

250

250

36

0.8

0.1

1 ot 6 weeks

235

62

370

190

36

0.8

0.1

Vormal feed

200

62

370

190

36

0.8

0.1

Heavy f r u i t oad

200

62

390

190

36

0.8

0.1

Vitrogen is used in the largest quantities in terms of total atoms absorbed by the d a n t . It is a constituent of amino acids, wotein building blocks, and has a big nfluence on vegetative development and iormal flower development. Nitrogen iptake increases rapidly during fruiting.

0 the micronutrients, only iron (Fe) is required in amounts larger than 1 ppm, iron is usually supplied at rates ranging from three to 10 PPm-

?otassium is second in terms of amounts ibsorbed. Potassium is important in 'ruit ripening and f r u i t quality, at harlest 90% of the potassium in the plant :an be found in the fruit. The ratio of 3otassium to nitrogen is important for :ontrolling vegetative and reproductive yowth.

Phosphorus, magnesium a n d sulfur a r e absorbed in lesser amounts. Phosphorus is required in larger amounts during seed formation. Early in development, phosphorus is important f o r good root formation and is supplied in large amounts a t transplant in starter solutions with formulation like 9-45-15. Magnesium deficiencies show u p as blotchy yellow patches on the lower leaves. Usually, deficiencies can be corrected before yields a r e affected. Of the micronutrients, only iron (Fe) is required in amounts larger than 1 ppm, iron is usually supplied a t rates ranging from three to 10 ppm.

3alcium is third in terms of atoms iccumulated, and deficiencies result in :he common blossom-end-rot symptoms we often see on tomato fruit.

In order to control nutrition, growers need to have a rapid a n d reliable method of monitoring the nutrient status of the cropping medium. The

16

Volume 41, Number vlinnesota Flower Growers Bulletin - July, 1992 essential equipment includes a conduc- ratio of these nutrients to each other tivity meter a n d a pH meter. For more (Table 1). From these numbers, you can detailed analysis, growers should send see that the plants in this study used samples to a commercial lab. Conduc- seven times more nitrogen (N) than tivity (EC) is usually a good indicator phosphorus (P), 60% more potassium (K) of the overall nutrient level in the than N, one-third more N than calcium growing medium. Medium pH affects (Ca) and five times more N than magneindividual nutrient availability. There- sium. Although the actual nutrient fore, as pH varies, the nutrient balance balance will vary during the crop, on average nutrients should be supplied in available to the crop will change. roughly these ratios. In the greenhouse, tomatoes can be planted directly in the soil or in soilless Of course, these numbers d o not tell you substrates. Today most tomato growers when or how to adjust the nutrient levels use some form of soilless culture. In in your management program. For this general, soilless culture can be sepa- purpose, use the recommendations i n rated into two categories: production Table 2 as a guide. Notice there a r e two using inert substrates such as rockwool sets of recommendations, one f o r inert or perlite, a n d noninert media such as growing media (in this case rockwool), peat-lite mixes used in trough culture and the other for noninert media (in this case peat-lite bags). or upright a n d lay-flat bags. T h e recommended nutrient levels diff e r f o r these two systems, however. There a r e many common features to nutrient management t h a t growers should be aware of. First, the absolute quantity of nutrients a plant needs will increase as plant size a n d fruit load increase. Second, the optimal ratio or nutritional balance required by the crop will change as the crop develops. To get a n idea of the general nutrient balance required by the crop, look a t the total nutrients a plant removes from the nutrient solution over the production life of the plant a n d the relative

You will also notice that the ranges recommended are quite broad. T h e actual amount plants require will depend on the growing conditions a n d the f r u i t load on the plant. Determining what is required and how the crop is doing comes with experience. One New England grower uses the schedule in Table 3 a n d does a pretty good job. I think the overall feed rates in this schedule are a little low and the calcium and magnesium levels may be too high a t the end of the crop, but they work for him. A complete feed can be formulated using several different fertilizer salts. Hy-

Table 3. Nutritional schedule used b y a new England grower in peat-lite mix. Peat-lite Bags

Conductivity (EC) is usually a good indicator of the overall nutrient level In the growing medium.

Medium pH affects individual nutrientavaiiabiiity.

To get an idea of the general nutrient balancerequired by the crop, look at the total nutrients a plant removes from the nutrient solutionover the productioniifeof the piant and the relative ratio of these.

(PPm)

Stage of Development

Ca

Mg

Fe

B

210

80

30

3

0.5

50

210

130

45

3

0.5

50

250

130

60

3

0.5

N

P

K

Planting to 2nd cluster

115

50

2nd to 4th cluster

150

4th to finish

165

17

A complete feed can be formulated using several differentfertilizer salts.

Minnesota Flower Growers Bulletin

- July,

1992

Volume 41, Number 4

Table 4. Fertilizers and the N , P , K , Ca and Mg content at d i f f e r e n t rates. Use combinations o f these fertilizers to get the nutrient ratio you want.

Testing is an essential part of nutrient management.

To best manage the crop, growers must learn how to “read” the plant.

Rate (oz/lOO Gallons)

N

Hydrosol (5- 1 1-26)

13

50

Calcium nitrate (1 5.5-0-0)

5.3

62

Potassium nitrate (13-0-44)

1 2 4 10

9.7 19.4 38.8 97

Ammonium nitrate (34% N)

1 2 4

25.3 50.5 101

Sodium nitrate (16% N)

1 2 4

11.9 23.9 47.8

2

--

Fertilizer

Magnesium sulfate (10% Mg)

P

drosol, a 5-11-26 formulation, is a good fertilizer to start with since it contains micronutrients a n d magnesium in addition to N, P a n d K. Calcium nitrate can be used to supply the necessary calcium and some additional nitrogen. Additional potassium can be supplied with potassium nitrate or potassium chloride. Ammonium nitrate or sodium nitrate can be used to augment nitrogen. Note that calcium nitrate can not be mixed in the same stock solution with fertilizer salts containing phosphorus or sulfur. Listed in Table 4 are the fertilizer salts, rates Increase nitro- and levels of macronutrients they progen to increase vide. vegetative development.

Testing is a n essential part of nutrient management. Use the values in Table 5 as target levels to be maintained in peatlite a n d rockwool culture. To best manage the crop, growers must learn how to “read” the plant. Tomatoes produced with a well-balanced feed 18

K

Ca

m

should have a thick stem with dark green foliage. The leaves should be closely spaced (not stretched) and the flower clusters should set f r u i t easily. Flower development, f r u i t set a n d f r u i t development are key indicators to watch, stem thickness is another key indicator. Together these indicators reveal the tendency for vegetative or reproductive development. T h e stem should be about one-half-inch thick a t a point six inches from the growing point. If the stem is thicker than this a n d the top leaves are thick a n d curl down, the plant is too vegetative. Decrease the nitrogen a n d increase the potassium level relative to the nitrogen level. If the stem is too thin, the plant is carrying too much f r u i t load. Increase nitrogen to increase vegetative development.

-

Minnesota Flower Growers Bulletin July, 1992 Table 5 . Test levels in Peat-lite and rockwoo1.l

Volume 41, Number

I (PPm)

EC (mhos/cm)

pH

N

P

K

Ca

Mg

1-2.5

5.5-6.5

30-80

20-50

Pea t-lite 140-400

140-200

25-35

1.5-3

5.5-6.5

200

50

Rockwool 360

185

45

Test levels in Peat-lite are based on a 1:1.5 (soil to water) extraction method. Values from rockwool system are based on solution withdrawn from slab just prior to irrigation.

19

Minnesota Flower Growers Bulletin

-

July, 1992

Volume 41, Number 4

MANAGING MICRONUTRIENTS IN THE GREENHOUSE Paul V. Nelson Reprinted from the North Carolina Flower Growers Bulletin

MICRONUTRIENT EXCESS Excesses Can Cause Deficiencies. Exces;ive application of micronutrients probExcessive appli. ably accounts f o r more micronutrient cation of micro. disorders in the greenhouse than does nutrients ptob. insufficient application. Excessive apably accounts plication of micronutrients, in addition for more microto toxicities, can lead to micronutrient nutrient disorders In the deficiencies. Deficiencies in this case g r e e n h o u s e are due to antagonisms between microthan does insuf- nutrients during plant uptake. When two ficient appllca- nutrients are antagonistic, a super-optima1 concentration of one in the root tion. medium will suppress plant uptake of the other. High root medium levels of iron commonly cause manganese deficiency and to a lesser extent can suppress zinc It is possible to uptake (Table 1). Conversely, high root encounter defi- medium levels of manganese cause iron ciencies of iron, deficiency a n d also to a lesser extent, manganese, cop- zinc deficiency. High levels of copper per or zinc as a cause zinc deficiency and conversely result of excess high levels of zinc cause copper defiapplication of ciency. Thus, it is possible to encounter other micronutri- deficiencies of iron, manganese, copper or zinc as a result of excess application ents. of other micronutrients. These deficiencies can occur even when a normally sufficient concentration of the deficient micronutrient exists in the root medium.

- Vol. 35, No. 5 - October, 1990

What Causes Excesses? Many combinations of micronutrients are used in greenhouses. Each can be safe and effective when used in the role for which it is formulated. Excesses usually occur when multiple combinations of micronutrients are applied. This occasionally happens because some of the micronutrient sources a r e not obvious to the grower. Following are five sources or factors which provide or make micronutrients available. 1) Most root media, whether commercially or self prepared, contain micronutrients. 2) Most commercially formulated greenhouse fertilizers contain micronutrients. Fertilizers prepared by the greenhouse f i r m as an alternative to commercial products are often formulated with micronutrients. Generally, plants respond well to the combination of micronutrients in root media a n d fertilizers.

3) Specific fertilizers are commercially available f o r use in soilless media that have higher micronutrient concentrations than the standard greenhouse fertilizers. The differences in micronutrient content beTable 1. Common micronutrient antagonisms. tween the standard and the soilless media formuHigh soil level of: Results in low plant level of: lations of one given fertilizer analysis are given i n Table 2. The increase iron manganese, zinc of micronutrients in the Generally,plants soilless media formulamanganese iron, zinc respond well to tion ranges from 200 perthe combination cent for iron to 1,000 copper zinc of micronutrients percent f o r molybdenum. in root mediaand This third source of mizinc copper fertilizers. cronutrients can be justi20

Minnesota Flower Growers Bulletin - Julv. 1992 Volume 41. Number 4 Table 2. The content o f individual micronutrients in a general ity just discussed and a soilless media commercial formulation o f 20-10-20 and l e a d t o e x c e s s the micronutrient concentration increase in the soilless media availability. Exformulation. cess presence of one or more memContent (O/o) bers of the micronutrient group can Nutrient Standard Soilless Increase (%) block uptake of another, bringing iron 0.25 0.50 200 about a deficiency of the latter. It is manganese 220 0.125 0.28 then easy to diagnose the total probzinc 0.013 0.08 1 620 lem as a micronutrient deficiency. copper 0.0 18 0.05 280 Without further information, correcboron 0.034 0.10 290 t i o n is u s u a l l y sought by applymolybdenum 0.005 0.05 1000 ing a complete mixture of micronutrients. This makes fied in a soilless root medium the situation worse because the where the pH level is 6.0 or causal nutrients which are i n higher because the availability excess become even higher in of micronutrients is strongly concentration. Even though the reduced in this situation. deficient nutrient-is increased in the root medium, its uptake is not effectively increased. 4) Research has indicated that, as is the case for organic field soils, the optimum pH level for Toxicity Correction. It is seldom possible organic (soilless) greenhouse root to totally correct micronutrient toxicities. media can be one pH unit lower Vigilance should be exercised f o r prethan that desired f o r soil based venting them. When toxicity does occur root media (Peterson, 1982). The there are three steps which can be taken optimum pH range for soil-based to reduce the problem. media is 6.2 to 6.8 while for soilless media it is 5.5 to 6.0. 1) The first and most obvious step is When the pH level decreases, the to stop application of micronutriavailability of all micronutrients. Some fertilizer companies ents except molybdenum inoffer fertilizers without microcreases. Molybdenum availabilnutrients. Otherwise, one can ity decreases; however, defiformulate their own fertilizer ciency of this nutrient is not without micronutrients. known to be a problem in any 2 The second step is to raise the pH floral crop except poinsettia. Thus, growing a t a lower pH of the root medium. T h e availlevel is equivalent to making a n ability of all micronutrients exaddition of micronutrients to cept molybdenum decreases as the plant. Growers who mainthe pH rises. Iron availability tain a pH level below 6.0 should decreases as the pH rises. Iron consider using the standard feravailability decreases ten-fold tilizer formulations. when the pH level is raised one unit. Extreme shifts should be 5) Often the four causes of inavoided. It is sufficient to move creased micronutrient availabilthe pH level to the upper end of 21

When the pH level decreases, the availability of all micronutrients except molybdenum increases.

When toxicity doesoccurthere are three steps which can be taken to reduce the problem.

iron availability decreases tenFold when the pH level is raised one unit.

Minnesota Flower Growers Bulletin Limestone reacts very slowly, thus two to six weeks may be required for a response.

-

July, 1992

Table 3. General minimum and maximum critical foliar levels for floral crops. Nutrient iron

Minimum (ppm)' 40-50**

Maxi mum (PPm)

---

30

500-600

fairly uniform over crops

zinc

20

100-200

highly variable

copper

5

20- 100

highly variable

boron

20-25

100-300

highly variable

0.1-0.5

---

* **

T h e minimum critical foliar levels apply for most but not all floral crops. A high foliar level of manganese will necessitate a higher minimum critical level of iron. Conversely, a higher foliar level of iron will necessitate a higher minimum critical level of manganese. the acceptable range for the crop.

it is important to diagnosethestatus of all micronutrients before Undertaking corrective measures.

Comments on maximum levels

manganese

molybdenum

The high pH caused by these liming materials at the surfacesof such fertilizers can convert ammoniacai nitrogen to ammonia gas which is highly injurious to roots and foiiage.

Volume 41, Number 4

Three methods can be used for raising root media pH. (a) A shift in the fertilization program from ammoniacal nitrogen (urea, ammonium nitrate, ammonium sulfate) to nitrate nitrogen (potassium nitrate, calcium nitrate) sources will bring about a gradual rise in pH. (b) Limestone may be applied to the root medium surface at a rate of approximately 1 Ib/cu yd per 0.1 unit rise in pH desired. This rate is for soilless media. Lower rates may suffice for soil-based media. Limestone reacts very slowly, thus two to six weeks may be required for a response. (c) For a rapid rise in pH, hydrated lime has been used. Caution should be taken to avoid contact with green tissues and neither limestone nor hydrated lime should be applied directly to ammonium containing fertilizers such as MagAmp or Osmocote. T h e high pH caused by these liming materials a t the surfaces of such fertilizers can convert ammoniacal nitrogen to ammonia gas which is highly injurious to 22

roots a n d foliage. One pound of hydrated lime should be suspended in 5 gallons of water a n d then applied to the root medium a t the rate of one pint per sq. ft. (Koths et al., 1980). This is one quarter the volume normally used f o r watering.

3) The third measure which might be taken f o r alleviating a micronutrient toxicity involves manipulation of antagonistic pairs of nutrients. If the micronutrient present in excess is a member of a n antagonistic pair (Table 1) make a n application of the other member of the pair. For example, a n excess of manganese, i n addition to causing manganese toxicity, can result i n iron deficiency. Application of iron alone will suppress manganese uptake a n d will increase iron uptake, thus alleviating both problems. Diagnosing Micronutrient Status. It is important to diagnose the status of all micronutrients before undertaking corrective measures. As discussed, micronutrient disorders can involve one or

vlinnesota Flower Growers Bulletin - July, 1992 Volume 41, Number 4 more nutrients as well as combinations 1) Dilute concentrations may be of toxicities a n d deficiencies. The applied in combination with mapresence of one micronutrient deficronutrients during each fertilciency does not indicate that all other izer application throughout the micronutrients are low. Application of crop cycle. Sources, rates a n d the a complete package of micronutrients final elemental concentration of in a situation where a deficiency/ each micronutrient a r e given in toxicity situation exists will increase Table 4. This table will be helpthe problem. f u l for those growers who formulate their own fertilizer a n d want There a r e three systems f o r diagnosing to apply one or more but not all nutrient status. T h e best diagnostic tool of the micronutrients. When all f o r micronutrients is foliar analysis. of the micronutrients a r e desired Visual observation of symptoms works most commercially prepared ferbut requires that damage be present. tilizers can be used since they Not all damage is reversible. Commercontain all micronutrients. When cial soil tests do not generally identify fertilizers are self-formulated, levels of all micronutrients. On the commercial products containing other hand, accurate tests and stanall micronutrients can be added dards have been established for foliar into the fertilizer. Some of these analysis of all micronutrients. While products include Peters STEM, the minimum a n d maximum critical Peters Compound 11 1 and Miller’s foliar levels f o r micronutrients can Mitre1 M. vary f o r a f e w crops, these values do tend to be fairly standard for most 2) The second method of applicacrops. The general critical foliar levels tion calls for higher concentrafor floral crops are presented in Table tions to be applied one time as a normal watering. See Table 5 f o r sources, rates and final elemental MICRO NUTRIENT DEFICIENCY concentrations to be applied i n a single application. There are three alternative methods of ipplication f o r micronutrients:

rable 4. Sources, rates and final concentration of the micronutrient for continuous roil application of one or more micronutrients with every liquid fertilization.

Micronutrient Source

Weight of source/100 gal 02 grams

Final conc. (PPm)

iron sulfate--20% iron OR iron chelate (EDTA)--12% iron

0.13 0.22

3.7 6.2

2.00 Fe 2.00 Fe

manganese sulfate--28% manganese

0.0 12

0.34

0.25 Mn

zinc sulfate--36% zinc

0.0018

0.051

0.05 Zn

copper sulfate--25% copper

0.0027

0.077

0.05 Cu

borax-- 1 1Yo boron OR solu bo r -2 0% boron

0.030 0.017

0.85 0.48

0.25 B 0.25 B

sodium molybdate--38% molybdenum OR ammonium molybdate--54% molybdenum

0.00035 0.00025

0.0 10 0.007

0.01 Mo 0.01 Mo

23

The presence of one mlcronutrie nt d ef icle ncy doesnot Indicate that all other mlcronutrlents are low.

The best diagnostic tool for micronutrients is foliar analysis.

When all of the micronutrients we desired most commercially prepared fertillzers can be used since they contain all mlcronutrients.

Minnesota Flower Growers Bulletin

- July,

1992

Volume 41, Number 4

~~

rable 5. Sources, rates and final concentration of the micronutrient f o r a single :orrective application of one or more micronutrients applied to the soil.*

Micronutrient Source

Weight of source/100 gal 02 grams

Final conc. (PPm)

iron -~~ sulfate--20% iron OR iron chelate (EDTA)--12% iron

4.0 4.0

113.4 113.4

62.0 Fe 36.4 Fe

manganese sulf ate--28% manganese

0.5

14.2

10.0 Mn

zinc sulfate--36% zinc

0.5

14.2

13.9 Zn

zopper sulfate--25% copper

0.5

14.2

9.3 c u

borax-- 1 1% boron OR so 1u bo r -- 2 0% boron

0.75 0.43

21.3 12.2

6.25 B 6.25 B

~~

Foliar sprays are very useful where root injury due to such factors as disease or poorly drained root medium would seduce root uptake of nutrients.

For soil-based media (>20°/0 soil in media) 0.77 0.027 sodium molybdate--38% molybenum OR 0.54 0.0 19 a mmon i u m mo 1y bd a t e-- 54% mo 1y bd e n u m

0.77 Mo 0.77 Mo

For soilless media sodium molybdate-38% molybenum OR 2.7 1.9 ammonium moly bd a t e -- 54% mol y bde n u m

0.77 Mo 0.77 Mo

* Plant uptake is enhanced by Increased drying time which occurs during the moisttimes inthe morning.

~

77 54

Do not apply combinations without first testing on a small number of plants. Wash solution off foliage after application. 3) The third method involves a single foliar application of micronutrients. Sources, rates and concentrations for foliar sprays are given in Table 6. Foliar sprays are very useful where root injury due to such factors as disease or poorly drained root medium would reduce root uptake of nutrients. However, the greatest risk of plant injury exists with foliar application. Spraying should be avoided during the mid-day heat. The early morning, after sunrise, is a n effective time. Plant uptake is enhanced by increased drying time which occurs during the moist times in the morning. Uptake is also greater in the light period than at night, thus making morning applications more desirable than evening sprays. 24

Literature Cited

Koths, J.S., R.W. Judd, Jr., J.J. Maisano, Jr., G.F. Griffin, J.W. Partok and R.A. Ashley. 1980. Nutrition of Greenhouse Crops. Coop. Ext. Services of the Northeast States. Bul. NE220. Available from Coop. Ext. Ser., Univ. of Conn., Storrs, CT 06268. Peterson, J.C. 1982. Effects of pH upon nutrient availability i n a commercial soilless root medium utilized for floral crop production. Ohio Agr. Res. a n d Devel. Center. Res. Cir. 268, pp. 16-19.

Volume 41, Number VZinnesota Flower Growers Bulletin - July, 1992 Table 6. Sources, rates and final concentration o f the micronutrient f o r single foliar sprays for correcting micronutrient deficiencies.*

Weight of source/100 gal grams

Final conc.

Micronu t r ien t Source

oz

iron sulfate

4.0

113.4

62.0 Fe

manganese sulfate OR maneb fungicide

2.0 label rate

56.7 label rate

40.0 Mn

zinc sulfate OR zineb fungicide

2.0 label rate

56.7 label rate

56.0 Zn

tri basic copper sulfate

4.0

113.4

159.0 Cu

sodium molybdate OR ammonium molybdate

2.0 2.0

56.7 56.7

57.0 Mo 81.0 Mo

*

(PPm)

Do not apply combinations without first testing on a small number of plants. Use the same spreader-sticker product and rate with the above foliar sprays as used with insecticide and fungicide sprays.

MINNESOTA COMMERClAL FLOWER GROWERS 1992 SHORT COURSE Plans f o r the Minnesota Commercial Flower Growers Association Short Course are being finalized. T h e dates for the short course this year are October 27 through 29 (that’s a Tuesday through Thursday). On Tuesday afternoon, the 27th, we will be touring Rosacker’s, Pletscher’s and Koehler and Dramm (with some others in the works), with dinner and the business meeting being held a t Midland Hills Country Club. On Wednesday and Thursday we will be returning to Midland Hills f o r our meetings. Speakers for the two days include, Dave Koranski and Peter Konjoian. This year pesticide recertification will be held on Thursday. More details, including maps, will be in the September bulletin, as well as in special mailings from the MCFGA. 25

1

Minnesota Flower Growers Bulletin

- July,

1992

Volume 41, Number 4

WHITEFLY Q & A FOR BEDDING PLANT PRODUCERS c.Sadof Exlenswn Specialist in OrnumentalEntomologv and

R. Foster Extension Specialist in Vegetable and Fruit EntomorogV Purdue University Here are a list of answers tosome of the questions that we received during the Poinsettia Panic last fall.

Reprinted from Floriculture Indiana This spring many of you may be getting questions about the Poinsettia whitefly from your customers. Here are a list of answers to some of the questions that we received during the Poinsettia Panic last fall. Pay particular attention to question #2 which explains why there is no need to panic. We suggest that you provide a photocopy of questions 1 and 2 to your customers. The remaining questions deal with planning control strategies.

1.

What is a whitefly?

Whiteflies are tiny insects (1/16 inch long) that feed on leaves with sucking mouth-parts. Both the powdery white a d u l t s a n d t h e scale-like immatures feed on the undersides of leaves. The two common whitefly The immature species in Indiana are the greenhouse nymphs of the whitefly (GWF) and the sweet potato GWF are green to whitefly (SWF). T h e immature white, while nymphs of the GWF are green to thoseof theSWF white, while those of the SWF tend to tend to be orbe orange. Pupae of GWF are spiny ange. Pupae of a n d SWF are smooth. GWF are spiny and SWF are smooth.

2. What is the Poinsettia whitefly? There is no insect with the accepted name of “Poinsettia whitefly”. This name has been used by the media to describe a strain of sweet potato whiteflies (SWF) that severely damaged California’s vegetable crop last year. This strain, called “type B” SWF feed on more different types of plants a n d reproduces a t a much faster rate than the normal, or “type A” SWF. Type B SWF feeds on over 300 species of plants including squash, 26

- Volume 6, No. 2 - Spring, 1992 pumpkins, melons, cucumbers, eggplant, peppers, tomato, cabbage, broccoli, cauliflower, poinsettias, bedding plants, especially petunias, geraniums, fuchsia a n d ornamental cabbage a n d numerous other cultivated a n d non-cultivated plants.

3. What does the type B strain of SWF’ mean for Indiana? There is no need to panic. Type B SWF has been around f o r a t least a year or two. We have already seen the telltale silver leaf symptomon squash in greenhouses with SWF i n this state. Growers should be aware that type B SWF does exist, a n d be on the lookout f o r silver leaf on plants in the squash family. You can avoid massive field problems with type B SWF when you avoid transplanting infested seedlings. Treat infested plants before transplanting.

4. How to identify type B strain? First determine if you already have, or are receiving whiteflies in your shipments. Greenhouse growers should put their entire operation on a regular inspection schedule. Purchasers of flower a n d vegetable transplants should inspect plants carefully f o r immature a n d adult whiteflies when they receive them. When possible these purchased plants should be isolated f o r about a week to allow adults to emerge a n d be detected as follows.

Minnesota Flower Growers Bulletin - July, Keep track of your whitefly problem by using yellow sticky cards as adult traps. These are highly attractive to adults when hung about 6 inches above the plant foliage. Just place a single 3" x 5" sticky card for 5. every 500 square feet of greenhouse space. Be sure to place some of the cards near vents and doorways where If whiteflies can enter. Second determine if you have SWF. After you f i n d whitefly in a trap, start turning over leaves and looking f o r the immature form on plants near the trap. Adult whiteflies usually prefer to feed on the young leaves. The immature form is about 1/16" long a n d scale-like. The immature of SWF are generally orange, unlike the GWF which tend to be whitish or green. Finally determine if you have the type B strain of SWF. Plant zucchini from seed in your greenhouse, or quarantine area. When the type B strain feeds on plants is causes a distinct leaf discoloration called

Volume 41, Number 4 1992 silver leaf. Leaf surfaces get a silver color because the upper leaf surface Keep track of begins to separate from the lower your whitefly problem by usleaf surf ace.

What should I do if I have type B SWF in my greenhouse? you have type B SWF on plants that you are intending to transplant in to the field, it is important that you control them before you get to the field. You have much more control over the environment in the greenhouse and much less area to cover. If you don't have the type B SWF under control by the time you begin transplanting, you may be setting yourself up for some of the problems that growers in the southwestern U.S. have had.

6. Should I plan to use routine sprays in my greenhouse to control type B SWF?

ing yellow sticky cards as adult traps.

If you have type B SWF on plants that you are intending to transplant in to the field, it is importantthat youcontrol them before you get to the field.

No. Any pesticide use should be part of a n IPM program. Use the steps listed

Table 1. Recommended Pesticides b y Class. Insecticide Class

Name

Carbamates

bendiocarb (Dycarb)

Organophosphates

acephate (PT 1300, Orthene 75 S) oxamyl (Oxamyl 10 G, Vydate L) d-phenothrin (Sumithrin) thiodan sulfotepp (Plant Fume 103)

Pyrethroids

biphenthrin (Talstar) fluvalinate (Mavrik) resmethrin (PT 1200, Resmethrin)

Any pesticide use should be part of an IPM program.

-

Avermectin

avermectin (Avid)

Insecticidal Soap

insecticidal soap

Growth Regulator

(Kinoprene) Enstar Neem (Margosan-0) (Safe on bracts)

Oils

(Sunspray) 27

not as effective

Minnesota Flower Growers Bulletin

Eliminate all weeds in the greenhouseand d 0-20 feet around your greenhouse. Weeds can hide and foster a whitefly population.

You can greatly increase the effectiveness of your control program byspraying before populations “get out of hand”.

Reduce resistance by rotating Insect iclde classes with each new generation of whitefly.

Be sure to inspect the plants that you have sprayed to give you a indication of spray effectiveness. Remember, not all insecticides work quickly.

- July,

1992

Volume 41, Number 4

above to determine if you have a problem with type B SWF before you initiate any control program. The overuse of insecticides may increase the development of insecticide resistance in the SWF and you may lose the use of some important tools for managing this pest.

cide classes. Rotate your insecticide class every 3 weeks because i t takes about 3 weeks f o r eggs to develop to adults. Table 1 contains the recommended pesticides by class. Always be sure to follow label directions and precautions.

What are some pointers for starting an IPM program directed for type B SWF?

Unlike other classes, Enstar is a growth regulator. It takes a longer time to act on whitefly than other compounds because it kills when nymphs change their skins between growth stages. It is therefore more successful early in the season when the offspring of invading adults establish themselves i n the greenhouse. Enstar is less effective when a larger proportion of the whiteflies are adults. Margosan-0 is effective against all stages.

1. Start clean. Eliminate all weeds in the greenhouse and 10-20 feet around your greenhouse. Weeds can hide and foster a whitefly population. 2. Plant some indicator zucchini plants and inspect regularly for the silver leaf symptom. Silver leaf symptoms will occur in less than 2 weeks.

3. Monitor for whitefly with yellow sticky cards to detect and record early infestations. Heavy infestations of whitefly are much more difficult to control. You can greatly increase the effectiveness of your control program by spraying before populations “get out of hand”. 4. Select an appropriate control tactic and be timely. See Table 1 for different options. 5.

Apply different classes of insecticides to each generation of whitef l y to reduce insecticide resistance. Each class of insecticides kills insects in a different way. When succeeding generations of insects are repeatedly exposed to the same insecticide class they can become less susceptible to its effects. Reduce resistance by rotating insecticide classes with each new generation of whitefly. Mixing insecticides or exposing the same generation to more than one type can simultaneously bring on resistance to multiple insecti-

28

Rescue treatments of low rates of Orthene with synthetic pyrethroid give best control. Consistent application of this use pattern is likely to reduce effectiveness of this rescue. 6. Evaluate tactic effectiveness and the need for continued control.

Be sure to inspect the plants that you have sprayed to give you a indication of spray effectiveness. Remember, not all insecticides work quickly. It may take 5 days, a n d u p to a week i n the case of Enstar, or Margosan-0 to see death of whitefly. The records from your sticky trap counts will also help you determine the effectiveness of your program.

Minnesota Flower Growers Bulletin

- Julv.

1992

Volume 41. Number 4

IMPACT OF THE FLORICULTURE INDUSTRY IN MINNESOTA Debra J. Schwarze and John E. Erwin University of Minnesota

People involved i n the horticulture industries don’t need to be told of the importance of their industry to the economy of the state of Minnesota. However, outside our immediate industry, the value of horticulture is most often over looked and thought of as just the hobby of gardening. Since hobbies a r e often thought of as unimportant, our industry is generally played down. In reality, nationwide, total cash receipts f o r the greenhouse and nurseries industries account for more than 10% of & I f a r m cash crop receipts. This places the urban horticulture industry (nursery a n d floriculture crops) ahead of wheat, cotton or tobacco nationally, yet the support for our industry, in terms of research scientists, is less than 1% of that of wheat.

50

40 m

m a

-m

30

The need to impress the importance of horticulture, and specifically f loriculture, in the state of Minnesota has prompted a survey of wholesale and retail producers, florists and garden centers. The survey, designed by members of industry and university personnel, reported the size and economic value of each operation. Other information the survey collected included number a n d salaries of full- and part-time employees, number of months employees work a n d number of months businesses operate. Total gross sales and growth of the business was also collected.

People involved in the hortlculture industries don’t need to be told of the importance of their industry to the economy of the state of Minnesota.

Letters, explaining the purpose of the survey, and a copy of the questions to be asked were sent out to members of the MCFGA prior to the start of the survey. Over a period of six weeks, university personnel phoned the MCFGA members to record responses to the survey. Response r a t e was 80%. We estimate that this represents 25% of the groducers i n the state according to the number of greenhouse growers reported in the latest USDA Floriculture Survey.

Nationwide,total cash receiptsfor the greenhouse and nurseriesindustriesaccount for more than 10% of farm cash crop receipts.

In looking a t the type of business being operated, 88% said that they were doing a t least some wholesaling. Twenty-five percent of the total companies responding stated that they were strictly wholesale (Figure 1).

The need to impress the importance of horticulture, and specifically floriculture, in the state of Minnesota has prompted a survey of wholesale and retailproducers, florists and garden centers.

m c 0 L

20

n a

5

z

10

0 Wholesale

Retail

Florist

Garden Center

Type of Operatlon

Figure 1. Type of operations run by Minnesota businesses. 29

Minnesota Flower Growers Bulletin

Fourteen percent of busi. nesses are wholesaling and retailingthrough a floral shop and garden center, providing a truly full-service business.

-

July, 1992

Volume 41, Number 4 eraging 43% larger at P 16,003.89 sq ft. The total production area of surveyed businesses in Minnesota is 6,352,218 sq ft. Therange in size is 3,000 sq f t to 648,480 sq f t (Figure 2).

300,001 sqfl and over

250,001lo 300,000sqfl C

0

mo.001 10 250,000sqfl

3

U

e

-

150,001lo 200,000sqfl

0

m

r