COMMON PROBLEMS WITH TROPICAL FRUIT TREES IN THE HOME LANDSCAPE Jonathan H. Crane, Tropical Fruit Crop Specialist, University of Florida, IFAS, Tropical Research and Education Center, Homestead

2009

COMMON PROBLEMS FOR TROPICAL FRUIT CROPS IN THE HOME LANDSCAPE Pollination Issues  Plant nutrition Issues  Watering Issues  Environmental Issues – freezing, flooding, wind, light, and salinity  Soil amendment Issues 

POLLINATION

POLLINATION ISSUES 

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Some fruit species are dioecious, i.e., have separate male and female trees and you need both to produce fruit, e.g., mamoncillo (genip) and some papaya cultivars. Some cultivars of some fruit crops require cross pollination, i.e., you need two different cultivars to set fruit. For example, „B-17‟ carambola, „Possum Purple‟ passion fruit. Many fruit species/cultivars do better with cross pollination, e.g., many avocado cultivars and some mango cultivars. Some fruit crops like Annonaceae (e.g., sugar apple) are pollinated by beetles not honey bees. If the beetle population is not sufficient then pollination may not occur. Hand pollination is an option to increase the percent fruit set, improve fruit quality, and yields.

SPECIES WITH POTENTIAL POLLINATION PROBLEMS   

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Avocado Carambola Annona (sugar apple) Atemoya Papaya Passion fruit Lychee Sapodilla

SPECIES GENERALLY WITHOUT POLLINATION PROBLEMS   

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Mango Banana Longan Mamey sapote Guava

POLLINATION ISSUES Avocado  Cultivars that do not require cross pollination: „Waldin‟, „Lula‟, and „Taylor‟.  Cultivars that require cross pollination „Pollock‟ and „Booth 8‟.  Bottom-line: avocado fruit set and fruit production increases when cross pollination occurs.  Solution: Plant complimentary avocado cultivars (A+B types) or scout neighborhood for other avocado trees that may be able to pollinate your tree.

Carambola  Cultivars that require or do much better with cross pollination: „B-10‟ and „B-17‟.  Cultivars that do not require cross pollination: „Arkin‟, „Kary‟, „Sri Kembangan‟, and many others.  Solution: Plant a cultivar that does not require cross pollination or plant more than one cultivar.

POLLINATION ISSUES Annona (sugar apple) + Atemoya  Requires pollination by Nitidulid (sap) beetles or may be hand pollinated.  Normally flowers open functionally as female first and then become functionally male.  May be hand pollinated for improved fruit shape, size, and production.

Papaya  There are 3 basic papaya plant types – male, female, bisexual plants.  There are no fruit set issues with bisexual trees.  However, female trees require pollination from either male trees or bisexual trees.  Male trees generally do not set fruit and when they do it is of inferior quality.

POLLINATION ISSUES Passion fruit  Purple types and some purple x yellow hybrids require cross pollination.  Yellow types generally do not require cross pollination to fruit well.  Hand pollination is easy – put on cotton gloves and place pollen on your fingers from one flower then touch the stigma of other flowers.

Some fruit species do that do not require cross pollination have been shown to improve their fruit set and production when cross pollinated  Lychee  Sapodilla  Guava

Female stage

Avocado flower

Male stage

Female

Male

Sugar apple flower

Carambola inflorescence Axillary flowering common Complete (bisexual) flowers

Papaya flower types Male plant, inflorescence, and flower

Bisexual and female

Passion fruit flower honey bee steeling nectar

Anther (male part) Stigma (female part)

PLANT NUTRITION

PLANT NUTRITION ISSUES 

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A major fruit tree are secondary and micronutrient element deficiencies. - magnesium (secondary), iron, manganese, and zinc. Lack of essential elements affect plant health and thus decrease plant growth, flowering and fruit production. Lack of consistent fertilization results in poor tree health and/or biannual fruit production (i.e., a lot of fruit 1 year and little to none the next). Lack of or too much nitrogen reduces flowering and fruit production. Typically homeowners do not consistently fertilize their trees or when they do fertilizer they over apply fertilizer which either causes damage to the leaves (salt-burn) or vigorous leaf and shoot growth and little to no flowering.

Iron deficiency, carambola

Boron deficiency, avocado

Zinc deficiency, mango

Magnesium deficiency, avocado

PLANT NUTRITION ISSUES 

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The major theme to emphasize is to follow the recommendations in the factsheets (http://edis.ifas.ufl.edu or http://trec.ifas.ufl.edu/fruitscapes/). Simply, it is better to use small amounts of fertilizer frequently during the warmer months of the year (March-April to September). Fertilizer applications during the late fall-winter period are either less effective or undesirable depending upon the fruit crop.

Solutions to secondary and micronutrient deficiencies  Use a foliar micronutrient mix and apply to the leaves 3-4 times per year (anytime from March-Sept.).  Ideally purchase and apply a soil drench of chelated iron 2-4 times per year. Alternatively, you can try a mix of iron (iron sulfate or iron oxide) and compost and apply to the soil under the tree canopy.

WATERING

WATERING ISSUES 

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Over watering is especially a problem in landscapes with automatic sprinkler systems. Over watering  causes oxygen starvation in the root zone.  leaches plant nutrients beyond the root zone. Under watering is an issue for young trees just planted, during the first 3 years or so, or mature trees with a lot of fruit (except mango).  Young trees need consistent watering during dry periods to survive or grow.  Many fruit crops with fruit need consistent watering during dry periods to either hold the fruit to maturity or to produce high quality fruit. Examples include carambola, longan, lychee, and papaya. In contrast, some fruit crops such as established mango trees should rarely be watered. Watering (especially overwatering) may reduce fruit quality.

SOIL AMENDMENTS

SOIL AMENDMENTS 

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Soil amendments are commonly  top soil,  muck,  sludge,  sand, and  compost or some mixture thereof. However, because improper use of a soil amendment may harm the health of trees and the diversity of amendments and confusion about their use, i.e., how to tell a good one from a poor one, and how to use it, many people do not recommend using soil amendments. However, if soil amendments can be very useful and beneficial if used properly.

SOIL AMENDMENTS 

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Soil amendments such as top soil, sand, and well composted sludge and compost should only be used in a limited amount in the planting hole. Furthermore, these materials should only be mixed with the native soil in no more than a 60% native soil/40% amendment mixture. The reason for this is that if too much soil amendment is used, movement of water between the soil in the planting hole and the native soil may be impeded leading to root rot and decline of the tree.

ENVIRONMENTAL ISSUES

ENVIRONMENTAL ISSUES 

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Freezing temperatures are the most common problem faced by homeowners with fruit trees in the home landscape. Flooding can be a problem in low lying areas or during/after tropical storms and hurricanes. Wind damage can be a problem especially if trees are allowed to become overgrown. Salinity water and/or soil is a problem in some areas, especially along the coast and in the Keys. Constant low light levels leads to loss of tree canopy, poor fruit production, and lower fruit quality.

FREEZING TEMPERATURES

SITE SELECTION 

Geographic location • near coast is warmer • S or SE side near large bodies of water • the leeward side (S, SE) of wind breaks may be colder than the windward (N, NW) side • low lying areas are colder than higher elevations

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Urban residents - planting  near buildings is generally warmer  in the SE side of the yard  trees planted under the canopy of other trees  near large bodies of water

RECOMMENDATION SITE SELECTION - TEMPERATURE Canal

Warm

Warm area adjacent to canal North NE coldest area East

West Warm South Moderately warm area

N

Banana grown adjacent to a southwest wall protects the plants during cold weather.

In contrast, the shade from the banana plants cool the southwest wall in summer.

Mango tree in southeast area of the landscape about 30 ft from the street.

Young mamey sapote tree – sugar apple tree in northeast area of landscape adjacent to a canal and wall of the home (warm site).

Star fruit tree with bambo and wind break.

„Sweetheart‟ lychee along east side of home.

CLEAN CULTURE 

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Definition: The absence of vegetation i.e. grass and weeds on the grove floor. Benefit: Allows solar heat to penetrate soil surface and be “stored” for re-radiation at night. Note: mulch and grass prevents penetration of solar radiation into soil. The mulch may be pulled back from November to March to facilitate exposure of the bare ground to sunlight.

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Not highly effective in south Miami-Dade County because the high porosity of the rockland makes the soil a poor conductor of heat. In areas with sandy soils, removing sod or pulling mulch back to the outside the drip-line weeks ahead of cold weather may allow the soil to act as a source of heat during cold weather (called a heat bank).

Clean culture – day time

Drip-line

Drip-line

Mulch pulled back

No grass or mulch from about the drip-line to the trunk

Clean culture – night time

Drip-line

Drip-line

Mulch pulled back

No grass or mulch from about the drip-line to the trunk

PREFREEZE WATERING 

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Water has a high capacity to store heat. Irrigating the ground under and around the fruit trees several days prior to a cold/freeze event will increase the soil‟s capacity to store and re-radiate heat during freezing temperatures.

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The greater the surface area wetted the greater the soil heat storing capacity. Irrigating during the daytime prior to the night of a predicted freeze is not recommended, especially if it is already cold and/or windy.

SOIL BANKS AND TREE WRAPS 

Soil banks  effective for young trees  effective for young trees planted in sandy soils  Use: clean soil, mound up 2-3 ft, check bank/tree trunk for insects and diseases  remove bank after danger of freeze/ frost is over

Not possible with rockdale soil.

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Tree wraps may be made out of fiberglass insulation and chicken wire • only delay heat loss • should be constructed of material with a high insulation value • need to be removed after winter Only effective for young trees. Not tested on tropical fruit crops.

Soil bank

Tree wrap

PLASTIC TREE COVERS     

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Types: individual and row/Quonset-hut type. May provide some protection. Has been used on young orange trees. Has not been tested on tropical fruit crops. Caution: any tree surface touching the cover may be damaged. Expensive and time consuming to implement. Some people place lights under the cover for heat.

FLOODING

FLOODING ISSUES  

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Soils with a hardpan in the soil profile which impedes water drainage. Areas where the water table may rise into the root zone, is near the soil surface and/or fluctuates into the root zone. The effect of excessively wet soils on plants depends upon their inherent flood tolerance, the growth stage of the plant (i.e., actively growing vs dormant), the duration of wet soil conditions, time of year (e.g., summer vs winter), and how often the area experiences excessively wet soil conditions. Low lying areas are prone to flooding or excessive water in the root zone.

POTENTIAL SOLUTIONS TO AVOID EXCESSIVE SOIL MOISTURE AND FLOODING 

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Shallow sandy soils with a hardpan may require augering through the hard pan to improve soil drainage and/or construction of mounds or beds for safely planting tropical and subtropical fruit trees in the home landscape. Construction of mounds made from native soil may increase the amount of roots above flood waters.

MOUND CONSTRUCTION 

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Select sites in the landscape that do not flood. In places that have high water table or periodically flood, plant trees on mounds constructed of native soil. Mounds should be 1-3 ft high and 3-10 ft in diameter.

Aerial view of 3-10 ft dia. mound

1-3 ft Side view of mound

RECOMMENDATIONS TO AVOID OR MINIMIZE FLOODING DAMAGE On sites that may periodically flood select only flood tolerant fruit species (see fact sheet HS202).  On sites with a hardpan, if possible dig into or auger planting holes past the hardpan to improve water drainage.  On low lying sites plant fruit trees on beds. 

WIND

WIND AND STORM DAMAGE 

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The most reliable method for minimizing and avoiding severe wind damage to tropical fruit trees in the home landscape (and possibly to your home) is to maintain trees at a reasonable height with annual or biannual pruning. Fruit trees should be maintained at a height where cultural practices and harvesting can all be done from the standing on the ground. Training young trees and maintaining mature trees at a reasonable height will reduce storm damage to the tree and surrounding structures and landscape. Very large trees should be pruned by a licensed and insured arborist.

Table 1. Recommended plant height for tropical fruit trees grown in the home landscape in Florida. Common Name

Scientific Name

Recommended Maintenance Tree Height (ft)

Abiu

Pouteria caimito

8-12

Atemoya

Annona cherimola x A. squamosa

8-12

Avocado

Persea Americana

10-15

Banana

Musa hybrids

Black sapote

Diospyros digyna

12-15

Caimito (star apple)

Chyrsophyllum cainito

8-12

Canistel (egg fruit)

Pouteria campechiana

10-12

Carambola

Averrhoa carambola

6-12

Cashew

Anacardium occidentale

10-12

Citrus

Citrus species

10-14

Cocoa

Theobroma cacao

6-8

Coconut

Cocos nucifera

---

Coffee

Coffea arabica, C. canephora

5-15

Guava

Psidium guajava

3-12

Jaboticaba

Myrciaria cauliflora

8-12

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Common Name

Scientific Name

Recommended Maintenance Tree Height (ft)

Jackfruit

Artocarpus heterophyllus

8-14

Longan

Dimocarpus longana

10-15

Loquat

Eriobotrya japonica

6-12

Lychee

Litchi chinensis

10-15

Macadamia

Macadamia integrifolia and M. tetraphylla

12-14

Mamey sapote

Pouteria sapota

12-15

Mamoncillo

Melicocus bijugatus

12-15

Mango

Mangifera indica

6-15

Pineapple

Annanas comosus

---

Pitaya

Hylocereus undatus and hybrids

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Sapodilla

Manilkara zapota

12-15

Soursop

Annona muricata

8-12

Spondias

Spondias species

8-12

Sugar apple

Annona squamosa

8-12

Teaz

Camellia sinensis

5-6

White sapote

Casimiroa edulis and C. tetrameria

10-15

LIGHT

LIGHT EXPOSURE AND TREE SPACING 

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In general, fruit crops grow and produce best when exposed to full sunlight. Shaded trees tend to be weak growing and less productive. The lower limbs of mature trees may be lost if shaded for too many hours of the day, resulting in fruit trees that only have fruit far from the ground.

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The ultimate size of fruit trees varies with species and growing conditions. Some have the potential to grow very large (e.g., mango, avocado, sapodilla), others are inherently smaller (e.g., guava, sugar apple, jaboticaba).

LARGE TREES 

Avocado, mango, lychee, mamey sapote, longan, sapodilla, and loquat should be planted 24-30 ft or more from buildings, electrical wires, and other trees.

TREE SPACING

SMALL TREES 

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Carambola, sugar apple, atemoya, and guava should be planted 20 ft or more from buildings and other trees and should be selectively pruned and maintained at a manageable height each year. Jaboticaba are small bush-like trees and may be planted 10 ft away from buildings and other trees.

TREE SPACING AND PRUNING 

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These trees should be selectively pruned and maintained to a manageable height each year. Managing tree height and spread is key to maintaining sufficient light levels and the lower fruit producing canopy of fruit trees.

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Young trees may be trained to a low stature by selecting the initial branches and increasing the number of branches. Periodic selective pruning of mature trees to open the canopy and to limit the spread of the canopy will maintain light levels throughout the canopy.

SALINITY

SALINITY AND ACCESS TO WATER  

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Salinity is the amount of salts in the soil solution or irrigation water. Salts may accumulate in the soil adjacent to the coast or canals by irrigation with saline water and/or salt water intrusion. Salinity is measured by how well an electric current can flow through the soil solution or irrigation water; the higher the salinity the higher electrical conductivity (EC) or total dissolved salts (TDS).

SALINITY AND ACCESS TO WATER You can have your water tested for salinity*

Water quality

dS/m

TDS (total dissolved salts) ppm

Excellent

0.25

175

Good

0.25-0.75

175-525

Permissible

0.75-2.0

525-1400

Doubtful

2.0-3.0

1400-2100

>3.0

>2100

Unsuitable

* Contact your local UF County Cooperative Extension Service.

SALINITY AND ACCESS TO WATER 

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Most tropical fruit crops are not tolerant of saline soil conditions, saline irrigation water, and salt spray. Exceptions to this are coconut palm and to a limited extent guava. Symptoms of salinity stress include: marginal leaf chlorosis, leaf drop, poor plant vigor/growth – tree decline, stem dieback, tree death.

SALINITY – RAINFALL AND IRRIGATION If you have saline water (doubtful, unsuitable):  Plant trees away from areas that experience or have experienced salt water intrusion.  Find a source of good quality water (municipal water source). Water can be treated but it is expensive.  Grow salt tolerant fruit crops (e.g., coconut, guava).  Fertilize trees frequently with small amounts rather than periodic large amounts.  Periodically (every 3-6 months) over-irrigated the soil around your trees to “flush” excess salts from the root zone.  Keep water off the leaves when irrigating as the salts in the irrigation water will damage them.

FOR MORE INFORMATION Contact your local Master Gardener Trainer, Horticulture, or Agricultural Extension Agent.  Visit websites: 

 SolutionsforYourLife

http://solutionsforyourlife.ufl.edu/  EDIS http://edis.ifas.ufl.edu  FruitScapes http://trec.ifas.ufl.edu/fruitscapes/