STUDIES ON POTATO LEAFHOPPER (Empoascafabae)

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DAMAGE IN ALFALFA M. A. FARIS, H. BAENZIGER, and R. P. TERHUNE Ottawa Research Station, Agriculture Canada, Ottawa, Ontario KIA 0C6. Contribution no. 616, received 5 June 1980, accepted 2 Dec. 1980.

M. A., BeeNzrcnn, H.,rNo TEnnuNE, R. P. 1981. Studies on potato leaftropper (Empoasca fabae) damage in alfalfa. Can. J. Plant Sci. 6l: 62j-$2.

Fanrs,

Alfalfa dry matter production, plant height, protein content, and in vitro digestibility (IVD) were measured in first- and second-year plantings of six alfalfa cultivars grown under natural potato leaftropper infestation with and without methoxychlor treatment for control of the pests. All treated plots yielded more dry matter than the untreated check, except Angus in 1978. Plant height and protein conrent were higher and IVD was less in the treated plots. All cultivars were susceptible to leafhopper infestation; however, Angus was the least affected. Leafhopper injury was season-specific and damage carry-over from one season to another occurred but was less than from one cut to the next. On a mesur6 la production de matibre sdche, la hauteur des plants, la teneur prot6ique et la digestibilit6 in vitro de plantations de premibre et deuxidme ann6es de six cultivars de luzerne infest6s naturellement par la cicadelle de la pomme de terre avec et sans traitement antiparasitaire au m6thoxychlore. Toutes les parcelles trait6es sont plus productives (matidre sbche) que le t6moin non trait6, sauf Angus en 1978. La hauteur des plants et la teneur prot6ique sont plus 6lev6es, mais la digestibilit6 est plus faible, dans les parcelles trait6es. Tous les cultivars sont sensibles aux d6gits de la cicadelle, mais Angus est le moins touch6. Les d6gits sont saisonniers et les effets de I'infestation peuvent se faire sentir d'une ann6e d I'autre, mais moins que d'une coupe a la sulvante.

The potato leafhopper Empoasca fabae

(Harris) causes serious damage to alfalfa (Medicago sativaL.) in the north-central and northeastern U.S. (Kindler et al. 1973). In Ontario, this pest causes a substantial loss in

alfalfa yield and quality some

years,

particularly during dry seasons when plants are under stress (.A,nonymous 1980). Damage appears particularly serious in the year of seeding in fields seeded without a companion crop. This practice, often referred to as direct seeding, has become popular in recent years as it provides one or two cuts of high quality alfalfa in the year of seeding. The first cut of established fields escapes injury but, as leafhoppers become more prevalent in late June to mid-August, damage may become severe. Symptoms of leafhopper

attack include yellowing and purpling of Can. J. Plant Sci.

6l:

foliage, reduction in size of leaves (Fig. 1), shortening of internodes, proliferation, resetting ofnew shoots, killing ofleaves and leafdrop and reduction of vitamin A (Medler and Fisher 1933). Infected plants suffered substantial reduction in total growth, forage yield and important components of quality such as carotene and protein when the infestation was moderate to heavy (Kindler et al. 1913), Damage caused in the year of

seeding may also reduce yield in the following year by weakening of the stands (Ellis et al. 1980).

The studies reported here were conducted at the Ottawa Research Station to determine the loss in yield and quality due to leafhopper

injury, identify differences in susceptibility to leafhopper attack among six alfalfa cultivars, and examine the effectiveness of chemical control.

625 632 (Julv 1981)

625

626

CANADIAN JOURNAI OF PLANT SCIENCE

MATERIALS AND METHODS Experiments were conducted from 1977 to 1979

at the

Ottawa Research Station. The first

l) was established in as a splirplot in strips with four

experiment (experiment

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1911

repiications. Whole plots were sprayed with methoxychlor (control) vs. unsprayed (check), and arranged in strips across each replication for ease of insecticide application. The subplots ( I .2 X 6 m) were the following six alfalfa (.Medicogo sotiva L.) cultivars: Angus, Saranac, Thor,

Algonquin, Iroquois and Vernal. This design sacrifices precision on the main effects in order to provide higher precision on the interactions. This

was seeded on 27 May. Methoxychlor (507c WP) was sprayed on 12,22 July and 8 Aug. at the recommended rate (6.6 kg EC/ha). Plant height, protein content and in vitro digestibility (IVD) were sampled on 25 July and 23 Aug. Protein content was measured with an infrared analyzer and procedures developed by Tilley and Teny (1963) were used to determine lVD. Plots were harvested on 23 Aug. and dry matter yield (kg/ha) was measured. Regrowth experiment

height was recorded

on l3 Oct. In

f978, methoxychlor was sprayed on 5 and 14 July, as was done in 1977, even though signs of insect damage were not evident. Three cuts were taken on 16 June, 24 July and 13 Sept. Plant height, protein content and IVD were determined at each cut.

The second experiment (experiment 2) was

seeded on 24 May 1978. It was modified by increasing the number of main plots to four: (l) no spray (check); (2) early spray, 5 July; (3) late spray. l4 July: and (4) l\\o sprays. i.e.. one ()n each date. The first cut was taken on l4 Aug. and the second on l5 Sept. Plant height, protein content and IVD were determined at each cut. In 1979, methoxychlor was applied 10 and 20 July as early and late sprays, respectively. Three cuts were obtained on 20 June, 8 Aug. and l3 Sept. and dry matter yield (kg/ha) was measured. Data from the two experiments were subjected to analysis of variance, and correlation analyses were performed between the different measurements.

Fig.

1.

RESULTS AND DISCUSSION Experiment 1 In 1911 , yellowing from potato leafhopper damage was evident in the unsprayed test on I 8 July. Plant height was reduced by the pest as observed in the check as compared to the

sprayed plots (Table I, Fig. l). Fiegrowth height was decreased by 28.1%, in the unsprayed plots as compared to the, sprayed

treatments (Table l ), indicating that leafhopper injury affected gro'*'th after removal of the attacked foliage. Flowever, regrowth did not show toxicity s\/mptoms from leafhopper feeding. Regrowth height on

I3

Oct . in the sprayed plots avera ged 40. 2

cm compared Io 28.9 cm in the unsprayed plots. Angus was the least affected (Table

l). Sprayed plants averaged 67o more protein than unsprayed plants (Table 2). [n plants sampled 4 wk later, the decrease in protein

content due to leafhoppers reaclted

l8Vo

(Table 2).

On 25 July, IVD was higher in sprayed than in unsprayed plots. However, on 23 Aug., IVD was lower in the sprayed plots (Table 2). lnitially, leafhoppers piercing alfalfa leaves and leafstems suck out the juices, which may result in the lower IVD of unsprayed plots . Subsequently, foliage turns

yellow, and plants become weakened and dwarfed. It appears that the leaf-stern ratio is reduced by leafhopper infestation, since the stems contain most of the fibrous portion of

the plant. This may explain ',vhy the higherr in IVD

damaged plots tended to be than the sprayed plots on 23 Aug. ('table 2). Our findings support that infested plants have higher dry matter content than plants protected against leafhoppers, as previously reporred by Kindler et al. (1973). ln 1911 , dry matter yields averalged 3624 and I 883 kg/ha from sprayed and unsprayed

Differences in alfalfa foliage color, height and density due to leafhopper damage between b - early spray, c : late spray and, d : early and late spray, 1978

treatments: a : no spray, (experiment 2).

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Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by MICHIGAN STATE UNIV on 01/28/17 For personal use only.

FARIS ET

AL.

l-*'r - sy.;rer €€r; -irod :: NNNOdNd d =H

POTATO LEAFHOPPER DAMAGE

OO,*nN--

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i'-

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nnhnnnh

hnnono66

xioiri*oiride NOONdNN*

^9P

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attack affects quality by increasing IVD. However, IVD and yield were negatively

(r

I

p !

E

and

regrowth height on 18 Oct. (r : 0.82). Plant height was negatively correlated with IVD (r : -0.61), which showed that leafhopper

93€r€dr -rNdOf@ d n.d r r s s

-ii

Total mean yields of unsprayed plots in both 1911 and 1978 were TJVo less. Angus

in

'

c--^

difTeronce.

was the least affected (Table 3). Yield losses

I

!-

reflect the carry-over effect of I91'/

(Table 3). This indicates that there was no carry-over effect in Angus. In Thor, where the yield reduction in 1911 was 39o/o, l9l8 yields were l27o less than the sprayed plots,

odC-*€r dddN--

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FARIS I,T

Table

4.

AL.

POTAII) LEAFHOPPER DT\]\IACE

Experiment 2 The primary objectives of this experiment

Simple conelation coefficients among alfalfa

characters of the 1977 potato leaftopper experiment

Date and

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Characters

correlated

7

Julv

23

r

Aus.

13 Oct.

control. Leafhoppers attacked the newly seeded 1978 alfalfa; however, no leafhopper infestation occurred in the second year of the

DM yield Regrowth height Height (cm) 23 Aug. with Protein 7o 0.41x* 0.63+**

I\aD DM yield Regrowth ht

Protein

Vo 7

0.39*x

-

8++

-0.61

0.89+x* -

0.49***

Regrouth ht

production (Table 5). The unsprayed plots

-

averaged 20.5 cm in height compared to the

_0.02 0.

cn of the two-sprays treatment. The late spray was more effective than the early spray. The two sprays gave better control than one spray alone (Table 5). In relative order of yield, the two-sprays treatment yielded the highest, followed by the one late 42.3

l8 0.10

Protein 7o 23 Aug. with

IVD

1977 seeded trial (experiment I ). This confirms that leafhopper attack is more severe in the seeding year. The most pronounced effects of leafhopper injury were reduced plant height and dry matter

0.82+**

July with

IVD DM yield

were to confirm the results obtained rn 1911 and determine if one or more methoxychlor sprays were required for effective leafhopper

values

Height (cm) 7 July with Heighr (cm) Protein Vo 0.15 IVD 0.31*

629

0.35x

DM yield Regrowth ht

IVD 7 July with DM yield

spray and the one early spray, with

the

no-spray check yielding the lowest. Protein content at cut I was lowest in the unsprayed alfalfa and greatest for the two-sprays

Regrowth ht IVD 23 Aug. with DM yield Regrowth ht

DM yield with Regrowth ht

*Significant at the 0.05 level; **significant at the 0.01 level; *xxsignificant at the 0.001 level.

treatment; however, differences were not significant. At the first cut, IVD followed the same trend as observed in experiment 1; i.e., decreased IVD associated with the two sprays treatment.

In the second cut, differences between treatments were not as pronounced as in the f,trst cut, because leafhoppers were not

summarizes the manifestation of leafhopper effects in height reduction, lower dry matter

present (Table

yields and reduced regrowth vigor.

between treatment yields could be attributed

Table

5.

differences

Character means of six alfalfa cultivars of the 1978 (experiment 2) potato leafhopper experiment

Dry

Treatment

No spray One early spray One late spray Two sprays SE of differences 9)

(df:

5). However,

Height matter Protein IVD (cm) at (kg/ha) Vo at at cutl cutl cutl cutl

20.5 4r5 15.9 26.2 862 16.7 33.7 1638 16.8 42.3 2086 16.9 1.5 2.11 0..19

61 63 62 58

1.2

Dry

Height matter Protein (cm) at (kg/ha) Vo at cut2 cut2 cut2

29.1 29.4 32.9 33.5 1.1

tr20 t212 t448 t495 39.7

24.5 22.1 22.1 22.2 0.4

IVD at

cut2 '72

70 70 12

0.5

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630

CANADIAN JOTJRNAL OF PLANT SCIENCE

to the carry-over effects of the infestation before the first cut. In the unsprayed plots, reduced plant height and dry matter yield

d6*ndc\o €@n*o66 o+nsnns

pected.

--rrsl€€ +O.@O-hS

indicate the weakening of the plants. However, there was no effect on protein percent (cut l) and IVD (cut 2) from the attack, an observation which is not unexThere was no difference in yield among the six alfalfa cultivars except with the early spray at cuts 1 and 2 (Table 6). The early spray increased yield by 39Vc over the unsprayed check, the late spray averaged 457o more yield than the early spray, the two sprays yielded 167o more than the one late spray, and the two s.prays yielded l33%a more than no spray (Table 7). This proved that the one-spray treatments were not completely efficient. In the early

treatment, this may be attributed to migration of leafhopper adults after the

toxicity of the insecticide disappeared. In the late treatment, damage was caused before the leafhoppers were controlled. The yields of Angus and Iroquois were reduced less by the attack than the other cultivars. However, there were no significant differences among

-+dSnSs d N

ra d

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Plant height at cut I correlated significantly with dry matter yield at cut I (r : 0.88) and cut2(r: 0.61). Plantheight and dry matter yield correlated significantly at cut 2 0 : 0.71). This is the same trend as

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the cultivars with the late spray or the two-sprays system. The only significant differences were with the early spray treatment where Thor, Saranac and Angus yielded highest and Algonquin lowest.

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in the 1977 data. Similarly, dry matter correlated negatively with IVD at cut I (r : seen

-0.49). Total yield correlated positively

with plant height (r

CONCLUSIONS Results of this study indicate that leafhopper

in

a

:

0.89) and dry matter at cut 1 (r : 0.98), and dry matter at cut2 (r : 0.70), and negatively with IVD at cut I (r : -0.45) (Table 8).

direct-seeded alfalfa fields cause plant stunting, reduced dry matter

infestations

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FARIS ET

Table'7. Total dry

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Angus Saranac

Thor Algonquin Iroquois Vemal Mean

POTr\TO LEAFIIOPPER DANtr\(lE

631

matter yields (experiment 2) and yield increases between treatments

(l) Cultivars

AL.

No spray l6O4a l5l.'7 a l4o5a 1383 a l7l1 a 1591 a 1535

Vo

(.2)

yield

increase (3) Early of2 Late spra) over spray 2076bc 29 3O46 a 2264a 49 3148 a 2458a 75 3ll0a

of

c

bc bc 2t35 2039 2010

Vo

1978

yield

increase

(4)

of4 3

Two

3

over 2

I

l90l

yield

Vo

increase

in

yield

of4 over I

over

sprays

o/o

increase

a a

9 9

a a

l8

t62

51

3331 3439 3616 3515

24

158

39

27

108

t21

37 19

28'76 a

3280a

6l

3716a

l3

1t'7

30 39

3058 a 3086

48 45

3751 a 358 1

l6

i33

136

a-c Means in each column followed by the same letter are not significantly different at the 0.05 level of significance

yield, lower protein content and slightly higher IVD values. Yield reductions were

Table

8.

Simple conelation coefficients among alfalfa characters of the 1978 potato leafhopper (experiment 2)

substantial in some cultivars and all sDraved

plots yieldcd more dry matrer rhin the unsprayed check. Beneficial effects of leafhopper control might be further improved by development of more precise pest

control practices than those used in these experiments. It is clear that optimum protection in the establishment year cannot be achieved with one methoxychlor spray, since this insecticide does not have lons

Rate and/ values

Lut Character

yield o/c prote\n IVD yield protein IVD

lowed. Properly managed stands may be at a growth stage that is unattractive to leafhoppers when they first appear (early to mid-July), or the second cut may have been

harvested before

the damage

appeared.

Delayed harvesting of the second cut due to adverse weather or delayed timing of the first cut have resulted in damaged second crops. All cultivars tested were susceDtible to

leafhopper lttack. There was some indication that Angus was less affected. Plants with varying degrees of resistance could be selected from Angus or other lines to improve tolerance to leafhoppers in new strains, sin.ce this practice has been

0.40*** 0.61***

0.88*** -0.08

_0.48+E*

_0.508**

Total yield Plant height (cut 2) with

0.12

0.89+r+

DM

0.2'7**

o/c

O.l2

_0.71xx* -0.01

-0. l7

Total yreld

0.39E+

I

-0.04

DM yield (cut l) with 0.55* * *

DM yield

stands in the year of seeding. In established stands, damage was not obvious when the

recommended cutting schedule was fol-

l) with

DM

In

1978, field observations at Ottawa clearly indicated that leafhopper damage was most severe in direct-seeded alfalfa

correlated (14 Aug.)

Plant height (cut Plant ht

lasting effects.

Cut 2 (15 Sept.)

l

protein IVD %

_0.49++*

Total yield DM yield (cut 2) with 70 protein IVD

Vo

Total yield protein (cut I ) with 70 protein

IVD IVD

0.11 0.98+x8

0. l8 -0.15

-o.02

_0.03 0.70*+

+

-0.07 -0.03

0.37xx4

Total yield 7o protein (cut

_0.51***

0.26**

-0.18 2) with

Total yield

0.21x _0.49+

+

*

IVD (cut 1) with IVD Total yield IVD (cut 2) with Total yield

_0.45+**

o.2'7**

-0.12

0.10 *Significant at the 0.05 level; *+significant at the 0.01 level: **xsisnificant at the 0.001 level.

632

CANADIAN JouRNAr OF PLANT SCIENCE

successful in similar cases (Sorensen et al. 1912).

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The results from experiment I showed that the average yields of

also 1977

leafhopper-damaged plots were about 5Vo lower in 1978 when compared to the sprayed

plots. Visual observation of the test

area

suggests that this reduction might be due to

reduced vigor of the alfalfa plants and/or heavy weed infestation. Similarly in cut 2 of experiment 2, a substantial carry-over effect of earlier leafhopper damage was evident despite the absence of visible symptoms in

It is concluded that alfalfa plants are weakened by leafhopper attack,

the regrowth.

and that this could cause persistence

problems in alfalfa stands. For these reasons it appears desirable to

incorporate tolerance

or

reslstance to

leafhoppers in new cultivars. Alternatively, additional studies should be carried out to identify the most effective economical and

environmentally safe methods for control of the potato leafhopper in alfalfa.

ACKNOWLEDGMENTS The authors wish to thank Dr. W. L. Seaman and F. E. Sabo for reviewing the manuscript.

ANONYMOUS. 1q80. Field crop recommendations. Ont. Min. of Agric. and Food Publ. 296. p. 51.

BAENZIGER.

H. 1978. Potato

leafhopper

damage in alfalfa. Forage notes, Agriculture Canada 29: 83-84. ELLIS. C. R., MORRIS, G. W. and BEREZA' K. 1980. Potato leafhopper in alfalfa. Ont. Min. order of Agric. and Food. AGDEX l2l1622 no.80-046. KINDLER, S. D., KEHR, W. R., OGDEN, R. L. and SCHALK, J. M. 1973. Effect of potato leafhopper injury on yield and quality of resistant and susceptible alfalfa clones. J. Econ Entomol. 66: 1298-1302. MEDLER. J. E. and FISHER, E. H. 1953.

Leafhopper control with methoxychlor and parathion to increase alfalfa hay production. J. Econ. Entomol. ,16: 5l l-5 13. NEWTON, R. C. and BARNES, D. K. 1965. Factors affecting resistance of selected alfalfa clones to the potato leafhopper. J. Econ. Entomol. 58:435-439. SORENSEN, E. L., WLSON, M. C. ANd

MANGHTZ, G. R. 1972. Breeding for insect resistance. In M. C. H. Hanson, ed. Alfalfa science and technology. Agronomy l5.pp. 37 l-390. Amer. Soc. of Agron., Madison, Wis. TILLEY. J. M. A. and TERRY, R. A. 1963. A two-stage technique for the in vitro digestion of forase crops. J. Br. Grassl Soc. 18: 104-111.

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