Fruit Pest Management

Many gardeners derive a great deal of satisfaction from growing their own fruit.  This endeavor, however, is not as simple as one might hope. There are many insect and disease organisms, and pruning and cultural management functions that must be considered in both planning and maintaining a home orchard. Many problems can be avoided before planting fruits: it is important to consider site selection, soil fertility, size and type of plants, and, most importantly, varieties of fruits, since they all relate to pest control. Many aspects of pest control can be facilitated by the use of dwarf or semi-dwarf trees, insect and disease resistant cultivars, and by purchasing plants certified to be disease-free.

This is a general guide for pest control for apples, pears, peaches, plums, cherries, apricots, blueberries, strawberries, brambles and grapes. Fruit may have additional  problems that need attention. To aid in identification of insect and disease problems, contact the University of Rhode Island's College of the Environment and Life Sciences Outreach Center Plant Protection Clinic. For a small fee, an insect or disease problem will be identified, and a control recommendation given. The address is: Plant Protection Clinic,  College of the Environment and Life Sciences Outreach Center, 3 East Alumni Avenue, Kingston, RI 02881.

Apples

The first step in apple pest management is to plant trees that are resistant to apple scab. This will eliminate the need to apply up to eight fungicide treatments during the growing season. There are many disease-resistant cultivars available, such as Liberty,Freedom, Macfree, etc. By using disease-resistant trees, a dormant oil spray, and sticky  red spheres to catch apple maggot flies, pesticide sprays can be limited to two or three applications per season. To control summer diseases (sooty blotch and fly speck) Captan or Captan/benomyl should be applied starting in early June and then every two to three weeks until mid-August.

Red sticky spheres can control apple maggot flies without the use of pesticides. Spheres should be placed within the canopy between 4 and 6 feet high. Use one to eight traps per tree, depending on tree size (one per dwarf tree, two to four per semi-dwarf or four to eight per full size standard tree). Ideally, set out one trap for every 150 apples.

If the use of red sticky spheres for control is impractical because of size or number of trees, the red sticky spheres can still be used to monitor apple maggot fly activity for proper timing of an insecticide application. One or two spheres per home orchard can be used to determine presence of apple maggot flies. When one to two flies per trap are captured, a half-rate spray of phosmet has been shown to control apple maggot flies.

Disease Resistant Apple Trees: Liberty, Redfree, Nova-Easyro, Macfree, and Jonafree are all resistant to both apple scab and cedar apple rust. Make certain the cultivar is resistant to both diseases before buying it, since both diseases occur in Rhode Island. Some disease-resistant apple tree suppliers are:

1. Hilltop Fruit Trees (Formerly Hilltop Nurseries) 1-800-253-2911 or http://www.hilltopfruittrees.com/availability.html

2. Raintree Nursery 1-360-496-6400 or http://www.raintreenursery.com/

3. Miller Nurseries 1-800-836-9630 or http://www.millernurseries.com/

4. Cummins Nursery 607-227-6147 or http://www.cumminsnursery.com/

5. Rocky Meadow Orchard & Nursery 1-513-354-1494 or http://henryfields.com/article.asp?ai=151

Disease-Susceptible Apples: Disease susceptible apple trees require the same insect control as disease resistant trees. They also require use of a fungicide to protect against apple scab. Captan or Captan/Benlate should be applied  as soon as green tissue is showing in April, and should be applied every 7–10 days until the beginning of June. Continue with Captan or Captan/Benlate every two to three weeks until mid-August or early September (depending upon cultivar harvest date) to protect  against summer diseases. CAUTION: DO NOT MIX OIL AND CAPTAN, SERIOUS FOLIAGE INJURY CAN RESULT. DO NOT USE CAPTAN WITHIN SEVEN DAYS OF AN  OIL SPRAY. As with disease-resistant trees, an insecticide may be needed at petal fall and again 10–14 days later.

Begin apple maggot fly control at the end of June with red sticky spheres, or with half-rate phosmet applications.Two or more sprays may be required for apple maggot flies depending upon your cultivars and insect pressure.

Pears

Pears are relatively pest free compared to apples. Pears may require a dormant oil application for pear psylla, an insecticide application (phosmet) for plum curculio, and usually no fungicides for the entire season. Pear psylla is the biggest insect problem because it is resistant to most insecticides. Apply a dormant oil in early April just as the flower buds begin to swell. Spray oil again 7-10 days later. Apply an insecticide at petal fall if plum curculio is a problem. Pears will occasionally have disease problems, but protectant fungicide applications are not warranted unless it is known that the varieties are susceptible or they are in an area where diseases are common.

Stone Fruits

The stone fruits may be difficult for home orchardists to grow because of a disease called brown rot that affects the fruits. Brown rot attacks all stone fruits. There are no disease resistant varieties available. To aid in the control of brown rot, remove and destroy all diseased and mummified fruits after harvest and mulch in early spring with 3–4 inches of sawdust or other good mulching material. Blighted twigs and cankers should also be pruned out. This will eliminate much of the disease inoculum.

The first fungicide spray for brown rot control should be applied just before bloom when many of the pistil tips extend  above the buds. The number of sprays required during bloom varies from year to year. Spray a fungicide every 4–5 days if damp, cool weather persists through bloom. Plan on a total of three fungicide treatments: just before bloom or early bloom, mid-bloom, and late bloom.

Black knot is another fungus of plums and cherries. It affects twigs, branches, and fruit spurs. Prune out and destroy all diseased wood during late winter. Make cuts 6–8 inches below any visible black knot swellings. Apply Captan in the spring just before buds open or plant resistant cultivars. Of the European varieties, Damson, Lombard, Shropshire, and Stanley are very susceptible. Bluefre is also susceptible. Bradshaw, Early Italian, Fellenburg, Methley, and Milton are moderately susceptible. President is a resistant variety. Japanese varieties are generally less susceptible than most American varieties.

The first fungicide spray for brown rot control should be applied just before bloom when many of the pistil tips extend above the buds. The number of sprays required during bloom varies from year to year. Spray a fungicide every 4–5 days if damp, cool weather persists through bloom. Plan on a total of three fungicide treatments: just before bloom or early bloom, mid-bloom, and late bloom.

Black knot is another fungus of plums and cherries. It affects twigs, branches, and fruit spurs. Prune out and destroy all diseased wood during late winter. Make cuts 6–8 inches below any visible black knot swellings. Apply Captan in the spring just  before buds open or plant resistant cultivars. Of the European varieties, Damson, Lombard, Shropshire, and Stanley are very susceptible. Bluefre is also susceptible. Bradshaw, Early Italian, Fellenburg, Methley, and Milton are moderately susceptible. President is a resistant variety. Japanese varieties are generally less susceptible than most American varieties.

Blueberries

Blueberries are perhaps the easiest fruit for homeowners to grow because they generally require no insecticides or fungicides. The blueberry maggot fly may need to be controlled with sphere traps: place one red or green sticky sphere baited with ammonium acetate or ammonium carbonate within the canopy of each bush to capture flies. Ammonium-baited yellow sticky cards placed in a “V” formation over the canopy will also capture many flies. One big problem with blueberries is that birds love them too. To keep birds away, place a net over the plants prior to the berries turning blue. During years of high gypsy moth populations an insecticide containing Bacillus thuringiensis may be needed at petal fall.

Strawberries

When growing strawberries many problems can be avoided before planting. First, choose a site that was not recently planted in turf because turf harbors many root grubs and root weevils that may be troublesome to strawberries. Also make sure the soil is well drained. Choose strawberry varieties that are resistant to root diseases and buy plants that are certified virus free. Renovate strawberry beds every year: in the fall, mow plants to 2-3 inches and rototill between rows. Remove mowings and dispose of all old debris to remove disease spores (do not compost). Avoid applying too much nitrogen to strawberry plants. Apply fertilizers after harvest.

Gray mold is a common disease that becomes visible on maturing fruit. Many gardeners plant a few extra strawberries, figuring that if some get grey mold, they will still have plenty of fruit. Using this strategy, no fungicide applications are required. If spraying fungicides is acceptable to the gardener, grey mold can be controlled by applying benomyl during bloom. If cool, rainy weather persists to prolong bloom, plan on three fungicide treatments (early-, mid-, and late-bloom). Some strawberry growers may need to apply one insecticide pre-bloom against tarnished plant bugs, which feed on strawberry buds and blossoms causing damage that results in small, deformed, seedy berries. If significant tarnished plant bug injury has been a problem in the past, apply one spray of Malathion just before the flower buds open.

Brambles (Raspberries, Blackberries, etc.)

Brambles are an excellent choice for the home grower because pesticide treatments are generally not needed. The best prevention against diseases and insect pests is a clean berry patch. Start with healthy certified stock from dependable nurseries. Keep the canes thinned out to maximize light penetration and air circulation. Canes should be thinned to about 6-8 inches apart. All old canes should be removed as soon as they finish bearing and the prunings should be destroyed (do not compost).

Brambles are shallow-rooted and thus are poor competitors for water and nutrients, making a mulch desirable. Straw or sawdust maintained at a depth of 4 – 6 inches will retain moisture and suppress weed growth. Weed control also improves aeration and reduces disease occurrence. Avoid applying too much nitrogen. 

Brambles are susceptible to gray mold. One (at bloom) or two fungicide (benomyl) applications may be needed to control this disease. If it is a particularly wet bloom, three fungicide treatments (early, mid and late bloom) may be needed. As with strawberries, no fungicide treatments are needed if a few extra plants are planted so some fruit with grey mold can be tolerated.

Grapes

Growing grapes may be difficult due to several grape diseases, which can be particularly troublesome if the growing site is located in a wet area with poor air circulation. If, on the other hand, the vines receive good air circulation fungicide sprays may be reduced to two (or fewer) per season, depending upon the cultivar. To encourage good air circulation, plant rows parallel to prevailing winds, remove all weeds from around the vines, and keep vines well pruned. There is also evidence that removing one leaf above and below the fruit cluster can greatly reduce disease pressure. Planting varieties that are less susceptible to grape diseases will also help manage grape pests: Cascade, Dechaunac, Delaware, and Ives are grape varieties that are only slightly susceptible to black rot and botrytis bunch rot.

Sanitation is an important part of grape disease and insect management. Remove and destroy all diseased clusters from vines at the end of the season. Prune out old or diseased wood on the vines, rake and destroy (do not compost) all prunings and leaves from beneath the trellis. Continue to prune out diseased or injured fruit and foliage during the growing season. Mulching or cultivating beneath the trellis will cover or destroy any mummified berries lying on the ground. These berries provide the black rot disease inoculum for spring infections. Powdery mildew may develop during some seasons but it is not necessary to apply preventative fungicides. If leaves become covered with the white powdery fungus, a sulfur spray may be applied. Do not apply sulfur to Concord or other sulfur-sensitive varieties.

Several insects attack grapes, but many of these can be removed by hand during the growing season. Grape tomato galls can be removed and destroyed when they are first noticed (mid-June). Berries infested with grape berry moths can be pruned out and destroyed when the grapes are forming. Another pest, grape phylloxera is an aphid-like insect that forms galls on leaves and causes new leaves to curl. Remove and destroy leaves infested with this pest. Japanese beetles and rose chafers can also be removed by hand if especially numerous. Grapes can tolerate a great deal of Japanese beetle leaf feeding with no damage to grape cluster quality.

Pesticides

Fruits can be attacked by many insect and disease organisms that often require either insecticides or fungicides for control. These chemicals can be purchased separately or mixed together as a multipurpose fruit spray. A multipurpose fruit spray usually contains three pesticides: Methoxychlor for chewing insect control, Malathion for sucking insect control, and Captan for disease control. The fungicides available to home owners include Captan, Benlate, sulfur, fixed coppers, and Bordeaux mixture. The main problem with a multipurpose fruit spray mix is that a fungicide or an insecticide may be needed at various times during the growing season, but not both. This is especially true during bloom when an insecticide is not applied but a fungicide may be necessary. Insecticides cannot be applied during bloom because bees are pollinating the flowers.

To insure pesticides will be effective over the years, it is important to prevent pests (insects and diseases) from becoming resistant to chemicals. Pests develop resistance to chemicals most rapidly when they are constantly exposed to the chemical. For this reason, use pesticides only when necessary and at labeled rates. Benlate is especially prone to resistance development, so use Captan, sulfur, fixed coppers, or Bordeaux mixture whenever possible.

Pesticides are poisonous, therefore, gardeners should be aware of any hazards associated with pesticides they are applying.

Take appropriate steps to minimize exposure to humans, animals, and the environment. Although chemicals listed in this guide are relatively low in toxicity to humans and warm blooded animals, safety measures should be followed carefully. Keep pesticides in a locked cabinet, away from children and pets. THE LABEL MUST BE READ IN ITS ENTIRETY BEFORE SPRAYING! Particular attention should be paid to the antidote/treatment in case of an accidental poisoning. Avoid breathing mist or allowing mist to contact skin. If the label instructs, wear protective clothing. 

Purchase wettable powder formulations where possible, especially if pesticides will be stored in an unheated garage duringthe winter. Do not store pesticides at high temperatures (more than 86o F) or allow liquid formulations to freeze. Optimum storage temperatures are between 65 and 80 o F.

Before spraying, learn the pests that may be present at various times during the development of the fruit. It is also helpful to learn insect and disease life cycles so the applications can be timed for optimum control. Identify damage to fruit at harvest and learn when to control the problem in subsequent years. You can tolerate more damage to leaves by aphids, leafminers, mites, and leafhoppers than direct damage to the fruit.

Insecticides

Horticultural (Superior) spray oils are used as dormant sprays to control scale insects and aphid and spider mite eggs. 

Malathion: Malathion is a pesticide that is used to kill many insects, including aphids, spider mites, scale insects, house flies, and mosquitoes, on agricultural crops, on stored products, on golf courses, in home gardens, and in outdoor sites where trees and shrubs are grown at home. It will also control a large number of other sucking and chewing insects that attack fruits, vegetables, ornamentals, and stored products. Malathion is harmful by swallowing, inhalation, or skin contact; avoid breathing the spray mist and avoid contact with skin. Wash hands thoroughly after handling malathion and change contaminated clothing. Biological activity of malathion remains practically unvaried for two years in undamaged original containers in cool storage (77 – 86o F).

Methoxychlor: Methoxychlor (sold under the trade names Marlate®, Chemform, and Methoxy-DDT) is a contact and stomach insecticide effective against a wide range of pests encountered in agriculture, in households, and on ornamental plantings. It is registered for use on fruits, vegetables, forage crops, and shade trees. It is one of a few organochlorine pesticides that have seen an increase in use since the ban on DDT because of its relatively low toxicity, relatively short persistence in biological systems, and long residual action against many species of insects. It should be stored in a cool, dry place.

Phosmet: Phosmet (trade names for products containing the compound include Appa, Decemthion, Imidan, Kemolate, Fesdan, Prolate, PMC and Safidon; it is also found in combination with other insecticides such as carbophenothion) is a non-systemic, organophosphate insecticide used on both plants and animals. It is mainly used on apple trees for control of coddling moth, though it is used on a wide range of fruit crops for the control of aphids, suckers, mites, and fruit flies. Imidan has the highest rating given by both the Cornell and PSU guides for plum curculio control. Phosmet is rapidly broken down in soil to non-toxic products. The compound persists longer in dry soil than in moist soil. Phosmet is a moderately toxic compound by ingestion but requires the signal word WARNING on the label because it is more highly toxic by other routes of exposure. It has a moderately high toxicity through the skin and a very high toxicity through inhalation.

Fungicides

Captan: Captan is a non-systemic fungicide used to control diseases of many fruit, ornamental, and vegetable crops. Captan controls: scab, black rot, botrytis, sooty blotch, fly speck, and summer rots on apples; brown rot and leaf spots on stone fruits; dead arm, downy mildew, and black rot on grapes; and a wide variety of fungus diseases on small fruits, berries, ornamentals, and vegetables.

Captan is compatible with most insecticides but cannot be used with oil sprays. It has been listed by EPA as a probable human carcinogen. When using Captan, avoid contact with skin or clothing and wash hands and face thoroughly with soap and water after use and before eating or smoking. Store in a cool, dry place. Persons entering a treated area within four days following application must wear protective clothing.

Benomyl: Benomyl (products are sold under the commercial names Agrodit, Benex, Benlate, Benosan, Fundazol, Fungidice 1991, and Tersan) is a systemic fungicide that is selectively toxic to microorganisms and to invertebrates, especially earthworms. It is used against a wide range of fungal diseases of fruits. It has extremely low toxicity and is unlikely to present an acute hazard during normal use, but it is important not to contaminate water, food, or feeds by storage or disposal. As a result of conflicting studies, the EPA classified benomyl as a possible human carcinogen

The following funcicides are phytotoxic under certain conditions.

Bordeaux Mixture (hydrated lime + copper sulfate): Primarily a fungicide, Bordeaux mixture acts as a repellent against many insects. It has a long residual action and has been used for control of many fruit diseases, including black rot, downy mildew, and powdery mildew of grapes. However, it can cause plant injury and due to the lime (high pH) it is not compatible with many other pesticides. Bordeaux mixture is generally unsafe to use on fruit crops after the ¼-inch green stage (New York State Pesticide Recommendations 1988). Bordeaux mixture is prepared according to a three part formula: e. g., 2-6-100 where the first number is pounds of copper sulfate, the second number is pounds of hydrated lime, and the third number is gallons of water. Bordeaux mixture is generally regarded as safe as far as mammalian toxicity is concerned.

Fixed Copper (copper hydroxide, copper oxychloride sulfate, copper tetra calcium oxychloride and tri-basic copper sulfate):

These formulations are referred to as "fixed" because the toxic copper ion is relatively insoluble, making them safer than Bordeaux mixture for use on fruit crops. However, the addition of spray (hydrated) lime is still required to obtain the necessary degree of safety for use on many fruit crops, depending on the time of application. Fixed coppers are effective against many diseases but are limited in use to certain sprays on grapes, pears, and sour cherry because of injury to fruit and foliage. In general, the fixed copper compounds are more compatible than Bordeaux mixture with other pesticides. All fixed coppers are generally regarded as safe as far as mammalian toxicity is concerned.

Sulfur: The most commonly used form of sulfur is the wettable form. Wettable sulfurs are finely divided sulfur particles with a wetting agent added, allowing the sulfur to be mixed with water and remain in suspension. The wettable sulfurs are most readily available as dry wettable powders containing 95% sulfur or as fused bentonite sulfur containing 30% or 81% sulfur, depending on the brand. Flowable sulfur products are also available. They have the advantages over wettable sulfur of being effective at slightly lower rates, and having better retention on foliage.

Dry wettable sulfur can be used with moderate effectiveness in early season sprays for apple scab control. It may be used up to and including bloom without substantially reducing fruit set. Fruit russeting and reduction in yield may result if used under high temperature conditions which often occur during post-bloom sprays.

Sulfur is very effective against powdery mildew of apple, cherry, and grape. Sulfur is used on stone fruits for control of brown rot but has not been as effective as most other brown rot fungicides. It also provides good control of peach scab, but is not effective against Rhizopus rot. All sulfur fungicides are generally regarded as safe as far as mammalian toxicity is concerned.

Adapted from: Heather H. Faubert, Steven R. Alm, David B. Wallace, Richard A. Casagrande, and Lisa Tewksbury (Revised July 21, 2000); and Extoxnet, A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis

Useful Websites  

 http://counties.cce.cornell.edu/suffolk/grownet/TREFRUIT/culturalpestmgm....