Disease and Insect Management in the Home Orchard
Fruit Disease Information Note No. 2
Homeowners who grow fruit in backyards or small orchards find that diseases and insect pests often ruin the entire crop and in some instances damage the tree itself. It is difficult to produce noninsect-damaged and disease-free fruit. In some years it may be possible to grow acceptable fruit without the use of pesticides, but in most years a few well-timed insecticide and fungicide sprays are needed. The effects of many pest problems can be reduced if several things are considered prior to buying and planting fruit trees. One of the most important factors is selection of an area suitable for growing fruit trees. Fruit trees prefer full sunlight and moist but well-drained soil having a pH of 6.0-6.5. Second only to having a good location is selection of fruits and fruit cultivars that are adapted to your area of North Carolina. If environmental conditions are not suitable for growing fruits, pest and disease problems are more difficult to manage and in some instances cannot be controlled. Additionally, fruit quality will likely be poor. Your county extension agent can usually tell you what fruits and which cultivars of these fruits are best suited for your area. It is important to buy only quality trees that are disease and insect free. Also check the roots to be sure they have not been allowed to become dry. Large is not always better; a tree 3-4 feet in height is much easier to establish than a taller tree. Furthermore, most fruit trees should be cut-back to a 2-3 foot height when planted, and the new growth trained. Planting a tree this size also reduces stress on the root system allowing the tree to become better established during the first year after planting. A grass and weed-free area around the tree should be maintained.
Once trees are planted, they require regular maintenance. Fruit trees need to be properly trained and annually pruned so that sunlight can penetrate through the tree. Pruning should also be done to remove damaged and diseased wood and to stimulate new growth. Pruning out dead wood and removal of mummied fruit is the most important cultural practice that can be done to reduce disease losses. Fertilization and lime application to maintain proper tree growth and soil pH are usually necessary yearly. The goal of fertilization is to produce adequate tree growth to support a quality fruit crop, not to produce excessive tree growth.
Although the extent of pest injury can vary from year to year depending on environmental conditions, certain fruit are more likely to have problems than are others. Stone fruits generally require more care than pome fruits. Tree fruits requiring the most care to those requiring the least are nectarine, peach, cherry, plum, apple, and pear.
Conditions favoring disease development or insect occurrence vary depending on the particular disease or insect. Generally, warm, rainy or damp conditions are very conducive for the development of tree fruit diseases. For best control of diseases, fungicides and bactericides should be applied before rainfall. There are specific times of the year when certain pests can most easily be controlled. Also during the growing season, at certain stages of tree growth, fruit are more susceptible to particular diseases and insects and damage is likely to be greater than during other times of the growing season.
Scale insects are often a serious pest of fruit trees. Use of a dormant oil such as Volck at the rate of 5 tablespoons per gallon of water (8 fl. oz. per 10 gallons) just before green tissue appears is most effective against scale insects. Oil also helps in the control of mites and aphids. On peaches and nectarines, the application of a copper-containing fungicide before the buds swell in late winter prevents leaf curl disease. Some cultivars of peaches and nectarines are less susceptible to leaf curl than are other cultivars.
All fruit should be picked before becoming over-ripe. Also, no fruit should be allowed to remain on the trees after ripening. All fruit should be picked and if not consumed, removed from the fruit-growing area. This helps reduce many disease and insect problems for later-ripening fruit and for the following year. Use of rigorous cultural and sanitation practices can usually reduce the number of sprays needed.
The pesticides selected for use in this information note were chosen because they are relatively safe to the user and the environment near the home, effective against a wide range of fruit diseases and insects and are usually available at many garden centers. For individuals with only a few trees, the combination fruit sprays available at garden centers may be most convenient. Some fungicides for use on fruit trees contain copper which is an effective fungicide but most fruit trees are quite sensitive to copper which can cause leaf and fruit spots and defoliation. Remember, pesticides are designed to kill pests and as such they should be used, stored, and disposed of only as instructed on the container label. Always read and follow the directions on the container label before using the pesticide.
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Apples
During the early part of the growing season, apple scab, powdery mildew and fire blight are the principle disease problems. Apple scab affects both the fruit and foliage and infections can result in defoliation and malformed fruit. Powdery mildew primarily affects the foliage and is characterized by white fungal growth on the surface of affected leaves. Fire blight, a bacterial disease, can be particularly destructive during the bloom period causing blossom blight and shoot and branch dieback as the bacteria grow from the blossoms into the shoots. In the Piedmont and Coastal Plain, cedar apple rust can be destructive on susceptible cultivars when they are grown in close proximity to the Eastern red cedar (the alternate host of the fungus on which cedar galls develop). Infections are characterized by yellow spots on the leaves and fruit. During the summer period, bitter rot, black rot and white rot, can all be destructive, particularly in poorly pruned trees with dead wood within them. The most common diseases during the summer period are sooty blotch and flyspeck. The pathogens which cause these diseases grow on the cuticle of the fruit, but do not cause any damage to the fruit themselves. For more information on apple diseases see A Growers Guide to Apple Insects and Diseases in the Southeast (available for $4.00 from Extension Assistant Director - Communications, Alabama Cooperative Extension Service, Auburn University, AL 36849-5623).
Apply the combination spray when the first green tissue is visible and repeat at 7-day intervals until blossoms begin to open. Overall disease control will generally be better if captan is used instead of sulfur. However, acceptable apples can be produced with sulfur although sprays may need to be applied more frequently than suggested for the captan combination spray. DO NOT apply the combination spray during bloom because the insecticides can kill bees and other pollinating insects. However, spraying with streptomycin (AGRI-MYCIN) during bloom at the rate of 1 teaspoon per gallon of water (0.8 oz per 10 gallons) will aid in the control of fire blight. When flower petals begin to drop, make another application of the combination spray and repeat at 2 to 3 week intervals until 3 weeks before harvest. Use a 2-week interval if weather conditions are wet or there have been disease or insect problems in past years. Where cedar apple rust is a problem, include myclobutanil (IMMUNOX or KGRO 1.55%) at 1/2 fl oz per gallon of water (5.0 fl oz per 10 gallons) in the sprays beginning at tight cluster and continuing for one month after bloom.
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Pears
Pears are affected with many of the same diseases as apples with the exception of pear scab, which has not been reported in North Carolina, and cedar apple rust, which does not occur on pear. Fire blight tends to be more severe on pear than apple and can kill large limbs and even entire trees of susceptible cultivars. Pear leaf spot (fabraea leaf spot) can be important on some cultivars. Captan is not registered for use on pears. Use benomyl (Benlate) 1 teaspoon per gallon of water (3 tablespoons per 10 gallons).
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Peaches and Nectarines
The most common diseases encountered on peaches and nectarines are leaf curl, peach scab, and brown rot of fruit (the same fungus also causes blossom blight). Leaf curl can be controlled with a single application of Bordeaux mixture, fixed coppers or lime-sulfur (use rates recommended on product label). The spray for leaf curl must be applied during the dormant season before buds swell. Peach and nectarine foliage is very sensitive to copper and can be injured, thus copper should not be sprayed when leaves are present.
Use two dormant oil sprays at 2-week intervals before green tissue is present to control white peach scale. When flower petals begin to drop, apply the combination spray and repeat at 2 to 3-week intervals until 3 weeks before anticipated harvest. The two sprays beginning at petal-fall are critical and provide good control of the insects plum curculio and Oriental fruit moth and the fungal disease peach scab. Most insecticides should not be used within the 2 to 3 week period before harvest (check product label for specific instructions). However, a fungicide is needed for brown rot control because this is the time this fungal disease is most damaging. If weather conditions are wet and brown rot has been a problem previously, 2 to 3 applications of myclobutanil (Immunox or KGRO 1.55%) at 1/2 fl oz per gallon of water (5.0 fl oz per 10 gallons) should be used starting approximately 3 weeks prior to anticipated harvest. Use the formulation labeled for bearing fruit trees that does NOT contain insecticide. If sulfur is used for brown rot control, spray every 5 to 7 days starting 3 weeks before anticipated harvest when weather conditions are wet.
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Cherries and Plums
The fungal disease, black knot, can occur on branches of cherries and especially plums. This is most common when these fruit trees are grown near wooded areas that contain wild cherry. Pruning out these knots as soon as observed and spraying a fungicide such as BENLTATE starting early bloom with 2 to 3 additional sprays 7 to 10 days apart can aid in reducing black knot. The disease most commonly encountered on cherries and plums is brown rot. Apply the first combination spray when the flower petals begin to drop and repeat at 2 to 3-week intervals until 3 weeks before anticipated harvest. If weather conditions are wet, apply 1 to 2 fungicide (myclobutanil) sprays as recommended for peaches during the 3-week preharvest period to reduce brown rot.
The peach tree borer can cause serious damage on the trunks of peach, nectarine, cherry, and plum trees. Damage caused by this insect can lead to tree death. To control peach tree borers, apply endosulfan 50W (Thiodan) at the rate of 2 tablespoons per gallon of water (7 oz per 10 gallons) to the lower limbs, trunk and base of the tree the first week in September.
Additional Tips
- Use person
al protective
equipment such as clothing, gloves, and a respirator as recommended
on the product label.
- Mix fresh
spray for each application. Do not save spray mixture for the next application.
This is not only unsafe, but the pesticide loses its activity and can
also damage the sprayer. Carefully calculate the amount of spray needed
so that excess does not result and create a disposal problem.
- Do not
spray an insecticide during bloom because it is likely to kill pollinating
insects such as honeybees.
- Spray
carefully and thoroughly to cover all parts of flowers, leaves, and
fruit until a noticeable amount of water begins to drip from the foliage.
Shake the sprayer often while spraying so that the chemicals do not
settle out.
- In most
cases for disease control, apply the pesticide prior to rainfall; however,
sprays should not be applied closer than 2-3 hours before rainfall to
allow for sufficient drying.
- Pesticides
should be stored in a safe location that is cool and dry. Liquids should
not be stored where the temperature will drop below 32 degrees F.
- Read and
observe the instructions on the container label for the time interval
between the last pesticide application and reentry into orchard or harvest.
This interval may vary depending on the pesticide.
Combination
Spray for Disease and Insect Control
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Pesticide
|
Rate
(for 1 gallon of water)
|
Rate
(for 10 gallons of water)
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|
Fungicide
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| Captan 50% WP | 1 tablespoon | 5 oz. |
| Sulfur 80-90% WP | 3 tablespoons | 10 oz. |
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Insecticide
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| Imidan 50% WP (phosmet) | 1 tablespoon | 3 oz. |
| Malathion 25% WP | 2 tablespoons | 7 oz. |
| Methoxychlor 50% WP | 2 tablespoons | 7 oz. |
*Although
these pesticides will control most diseases and insect pests, there are
certain tomes that a substitue or additional pesticide is recommended
for control of a specific pest or disease. These have been mentioned for
the specific fruit crop.
**Sevin 50% WP (carbaryl) at a rate of 2 tbsp. per gallon of water (7
oz. per 10 gallons) may be substituted for methoxychlor. However, do not
apply Sevin within the 2-week period after bloom of apples because excessive
fruit thinning may occur.
***Sulfur if applied when temperatures are high (>85 F) may cause phytotoxicity.
More detailed
information about the identification and control of fruit tree diseases
and insects and the growing of treefruits can be obtained in the following
publications available at your county extension office:
Diseases of Tree Fruits in the East. North Central Regional Ext. Publication
No. 45
Peach Diseases
and Insects in North Carolina. AG-146
Integrated
Management of Apple Pests in North Carolina. AG-378
Nematode
Control on Peaches and Management of the Peachtree Short Life Complex.
Fruit
Disease Information Note No. 8
Black
Knot of Plum and Cherry. Fruit Disease Information Note No. 4
Fire
Blight of Apple and Pear. Fruit Disease Information Note No. 3
Peach
Scab. Fruit Disease Information Note No. 6
Integrated
Mite Control on Apple. Entomology Fruit Insect Note #A-1
Tree
Fruit Production for Home Use. AG-28
Growing
Peaches in North Carolina. AG-30
Growing Pears
in North Carolina. AG-80
Apple
Insects and Diseases in the Southeast. Alabama Cooperative Extension
Service Circular ANR 838
Other Resources
Fruit
Disease Information Notes
Plant
Disease Information Notes Homepage
Horticulture
Information Leaflets Homepage
North
Carolina Insect Notes
North
Carolina Agricultural Chemicals Manual
NCCES
Educational Resources
For assistance with a specific problem, contact your local Cooperative
Extension Service Personel.
Recommendations
of specific chemicals are based upon information on the manufacturer's
label and performance in a limited number of trials because enviornmental
conditions and methods of application by growers may vary widely, performance
of the chemical will not always conform to the safety and pest control
standards indicated by experimental data. All recommendations for pesticide
use were legal at the time of publication, but the status of registration
and use patterns are subject to change by actions of state and federal
regulatory agencies.
Published by North Carolina Cooperative Extension Service Distributed
in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment
and program opportunities are offered to all people regardless of race,
color, national origin, sex, age, or disability. North Carolina State
University at Raleigh, North Carolina A&T State University, U.S. Department
of Agriculture, and local governments cooperating.
Webpage reformatted Dec. 2000 by A.V. Lemay