Insect and Disease Control on Fruit

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Insect and Disease Control on Fruit

Author:	OMAFRA Staff
Creation Date:	25 July 2005
Last Reviewed:	20 December 2005

The Gardener's Handbook > Chapter 6: Fruit > Insect and Disease Control on Fruit

Preventive Measures
Poor Flowering, Pollination and Fruit Set
Pesticides
Spray Programs
Descriptions and Treatments
All Fruit (except strawberry)
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Preventive Measures

To guard against problems with your fruit trees, follow good cultural practices Chapter 2 - Integrated Pest Management such as pruning and destroying affected fruit. Buy only varieties of fruit that are known to be compatible for cross-pollination.

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Poor Flowering, Pollination and Fruit Set

Pests are not the only cause of poor flowering. Abiotic damage is often the culprit. This includes:

temperature extremes or fluctuations during winter that kill flower buds
early spring frosts, after flower buds have begun to swell, that kill flower tissue
over-fertilization or excessive pruning during the previous season that results in excessive vegetative growth

Poor fruit set can occur for a variety of reasons as well:

damage to pistil and stamens before the flower blooms prevents pollination and fertilization
cool, wet weather during bloom discourages pollination by bees
excessive fruit load during previous growing season, particularly in apples and pears, will reduce fruit load in the current growing season. To minimize this problem, thin fruit in late June or early July.

Some fruit are self-fruitful - they will pollinate themselves without requiring a second cross-pollinating tree. Others such as sweet cherries are cross-pollinated and require other trees with compatible pollen in the area; some, such as apples, also require varieties with a similar flowering date. Be sure to purchase named varieties which are compatible for cross-pollination.

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Pesticides

Some of the pest problems described in this manual are common in commercial operations, but may not occur in your home garden if you are not located in a commercial fruit production area. Spraying for them is unnecessary and unwise. Keep in mind, however, that neglected apple, pear and plum trees, which grow throughout Ontario, are sources of many harmful insects and diseases.
For a successful Treatment program, careful timing of sprays and thorough application of the correct pesticides are necessary.

Recommended Products

For up to date recommendations on pest management options consult local horticulturalists, Master Gardeners or your local garden supply centres.

Insecticides

To control certain insects, apply preventive sprays before eggs are laid. The insects which require preventive spraying are listed on the following pages.

Fungicides

Preventive fungicide applications are necessary to protect foliage and fruit against fungal infection. If applied after infection takes place, most fungicides can not stop development of the disease, but they may prevent further spread. Repeat applications are required to protect new foliage and to renew protection. Fungicides are not harmful to bees.

Apply fungicides before rainfall to allow residue time to dry and reduce loss during rainfall.

No-Spray Interval

A product's no-spray interval is the time that must be allowed between the last application and the harvesting of the fruit to avoid harmful residues. It varies for each product and each kind of fruit. Consult the product label for the no-spray interval and follow the instructions carefully.

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Spray Programs

Prevention of many insects and diseases is necessary and easier to achieve by following a spray program, particularly for fruit trees.

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Descriptions and Treatments

Insects and diseases are listed under each fruit. If, however, you cannot find the pest to suit your symptoms, look in the "All Fruit" section below.

Where a disease or insect applies to more than one fruit, the full discussion is provided only once, and page references provided for all other fruits.

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All Fruit (except strawberry)

Crown Galls

Crown galls are caused by bacteria present in most garden soils that gain entrance through wounds in the plant. It is common on all types of fruit trees, raspberries, grape, bush fruits, and many others. Galls or woody swellings develop on the roots or base of a plant.

Treatment

Cultural control: Remove galls with a sharp clean knife or secateurs. Clean tools and hands in a solution of 1 part bleach to 4 parts water to prevent further spread. Whenever possible, avoid unnecessary wounds, and do not buy plants with galls on roots. Replace soil where a severely affected plant has grown.

Chemical control: None are known at this time.

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Caterpillars

Several kinds of caterpillars damage fruit trees. The tent caterpillar is the most common, building large silken nests in the branch forks. Tent caterpillars are black and hairy with white stripes on their back and narrow brown and yellow lines with blue dots on their sides. Leafrollers spin a light web around leaves, rolling them together. They feed inside the protected area from shortly after buds open until about three weeks after petal fall.

Treatment

Cultural control: When tents are noticed in spring, remove and destroy caterpillars or prune the affected twigs and branches. Do this in the evening when most worms are in the tent. In early spring, prune out or rub off egg masses. They appear as dark brown, styrofoam-like collars 1 cm wide around twigs and branches.

Chemical control: Spray only if many tents are found or if other types of caterpillars are a problem. Apply insecticides before leaves are rolled and tied together, because caterpillars will not consume or be touched by the residue if protected in a silken shelter. For up to date recommendations on pest management options consult local horticulturalists, Master Gardeners or your local garden supply centres.

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Curculios

Curculios are 6 mm dark brown weevils with prominent snouts that lay eggs in apple, pear, plum and occasionally peach and cherry soon after flower petals have fallen. A crescent-shaped scar develops on the fruit. Wounds on apple often exude sap that dries to a white crust. The greyish white larvae tunnel in the fruit and cause it to drop early.

Treatment

Cultural control: Spread a sheet of plastic under the tree and shake the branches. Adults will fall onto the sheets and can be destroyed. Remove and destroy all fallen fruit.

Chemical control: Spray after bloom as soon as most petals have fallen and repeat as indicated on the product label. For up to date recommendations on pest management options consult local horticulturalists, Master Gardeners or your local garden supply centres.

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Mites

Mites are tiny spider-like red or brown pests that feed on the underside of leaves. They are difficult to see without the aid of a hand lens. Mites suck the chlorophyll from the leaves causing small white dots and bronzing when severe. Control measures are not necessary unless the leaves start to turn bronze, usually during hot, dry weather.

Treatment

Cultural control: On young or dwarf trees, blast the undersurface of the leaves with water to wash mites away. Repeat as indicated on the product label. This approach is not successful on large trees.

Chemical control: Other pest may keep mite populations at acceptable levels, making special sprays unnecessary. For up to date recommendations on pest management options consult local horticulturalists, Master Gardeners or your local garden supply centres

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Scale Insects

Scale insects live under hard-shelled caps or scales on the bark of trees and cause damage by sucking sap and reducing the vigour of the tree. Depending on the species, scales look like small grey oyster shells or round brown knobs.

Treatment

Cultural control: A light infestation may be kept in check by birds and beneficial insects.

Chemical control: The only effective control is an early spring application while buds are still dormant. If severe, spray the following spring before leaf buds break, thoroughly wetting bark. For up to date recommendations on pest management options consult local horticulturalists, Master Gardeners or your local garden supply centres.

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Silverleaf

Silverleaf is caused by a fungus that invades trees through pruning wounds. Apples, apricots, gooseberries, peaches, plums, raspberries and sour cherries, as well as several woody ornamentals are susceptible. Symptoms include the development of a metallic, silver sheen on the leaves and browning and streaking inside the branches. Branches or entire trees may be killed once the sapwood is invaded. The fungus produces shelf-like fruiting bodies up to 2.5 cm in diameter under branches and in the bark. These bodies are abundant and bright purple after autumn rains.

Treatment

Cultural control: Avoid pruning trees when they are most susceptible to infection, from sap flow in early spring until after bloom. If possible, avoid large pruning cuts. Remove dead trees and tree branches nearby which might be sources of the fungus. Removing affected branches may not save an infected tree, as the fungus is often well established throughout the tree by the time symptoms develop.

Chemical control: None are known at this time.

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Plant Bugs

Plant bugs feed with their piercing, sucking mouthparts on young developing apples, peaches, pears, and nectarines causing sunken pits - catfacing - to form. Peaches, apricots and nectarines may also secrete an amber gum. On peach trees particularly, the insects also feed on young shoots, causing wilting and dying back.

Adult tarnished plant bugs (TPB) are brown, while the four-lined plant bugs (FLPB) are greenish-yellow with four black stripes. Both are triangular in front, 6-7 mm long and about half as wide. They are very active, readily flying when disturbed. Young TPB are light green, while young FLPB are bright red, each with dark spots and markings. TPB can be a problem throughout the season, while FLPB is prevalent in late spring and summer.

Treatment

Cultural control: Thoroughly clean the garden in the fall as plant bugs overwinter as nymphs or adults in garden trash and weeds.

Chemical control: Insecticide may be applied when plant bugs are first noticed in spring, especially after flowering when young fruits are expanding, and later when migrating adults appear. For up to date recommendations on pest management options consult local horticulturalists, Master Gardeners or your local garden supply centres.

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