The Online Gardener's Handbook 2010
Chapter 5: Fruit
Apple, Crabapple, Pear

Table of Contents

  1. Introduction
  2. Apple, Crabapple
  3. Pear
  4. Learn More

Introduction

In this chapter, a description of various pests of pome fruit will be provided along with suggested management options. These management options will not include the use of pesticides. Some biopesticides and certain reduced risk pesticides are still available to the homeowner for controlling weeds and pests in lawns and gardens. For more information, refer to Chapter 2 of this handbook and the Ministry of the Environment's website. For suggestions on managing specific weeds and pests, consult local horticulturalists, Master Gardeners or your local garden supply centre.

NOTE FOR TREE OWNERS: There is an exception under the ban that allows you to hire a licensed exterminator authorized to use commercial pesticides to maintain the health of your tree. This exception applies only to pests that threaten the tree's health. For example, the exception cannot be applied to a pest that impacts the quality of the fruit but will not kill the tree itself. To obtain this exception, licensed exterminators are required to obtain a written opinion from a professional tree care specialist that a pesticide is necessary to maintain tree health. For more information, contact the Ministry of the Environment.

Note that many fruit trees can tolerate some damage, particularly to the foliage, without suffering lasting impacts. Pest descriptions below include suggestions for cultural controls however in many situations these may not be necessary.

Apple, Crabapple

Ornamental fruiting crabapples are attacked by the same insects and diseases as apples. See also Chapter 6 - Ornamental Plants.

Codling Moths

The adult codling moth is greyish brown with lacy lines on forewings and fringed hindwings. The larva is 2.5 cm long, pink, with a brown head. Eggs are laid on the fruit and the larvae enter and grow inside. Dark sawdust-like material is evident at the entry hole and infested fruit often drops before maturity. When fruit are cut open, evidence of larva feeding on the seeds is obvious. This damage distinguishes this pest from Oriental fruit moth, another common pest of apple, which also tunnels inside the fruit, but burrows in the flesh of the fruit (not the seeds).

Management Options

Natural enemies will attack larvae as they leave fruit and crawl towards tree trunks, however population control is less than for other insect pests. Regularly gather and destroy infested or dropped fruit by throwing it in the garbage can or burying it at least 60 cm deep. This will reduce the insect population next summer. Wrap a cardboard or burlap band around tree trunks starting in mid June - some larvae will collect under the bands. Dispose of larvae in a plastic bag or bucket of soapy water. Twist tie pheromone lures designed to help reduce codling moth populations by disrupting mating are commercially available, however these are designed for use in commercial orchards with at least 10 continuous acres of trees, and so are unlikely to be effective in most home gardens.

Black Rot and Frog-eye Leaf Spot

Black rot on fruit and frog-eye leaf spot on leaves are fungal diseases. They often occur on unsprayed trees in late summer just before fruit maturity. Small, tan-centred spots with darker borders - frog eyes - appear on the leaves. On fruit, small, purple or red spots turn dark brown as they expand; older, larger spots may also have rings of black specks.

Affected fruit will rot completely in storage. The fungus survives in fruit on and under the trees, as well as in cankers and dead twigs.

Management Options

Avoid planting near woodlots which are potential sources of disease. No cultivars are completely resistant to black rot, but some are less susceptible to the disease. Plant these tolerant varieties where available. Pruning out disease limbs and dead wood is an important practice to reduce inoculum sources. Destroy diseased material. Destroy mummified fruit and, at the end of the season, remove all fallen fruit.

Fire Blight

Fire blight is a serious bacterial disease of apples and pears. The fire blight bacteria is found in most areas of the province where apples are grown, but has caused most damage in southwestern Ontario. Blossoms are usually first to be infected and wilt, turn brown or black and shrivel. The disease spreads to spurs and leaves, and young twigs turn black and shrivel later in the summer. Eventually the leaves turn brown or black and begin to ooze, and droop at the tip creating a shepherds crook. Sunken reddish-brown bark lesions that ooze an orange-brown liquid may appear on larger branches. Warm weather and high humidity or rain favour the spread of this disease. If blossoms are infected, bees and other pollinators spread the bacteria to blooms on healthy shoots or trees. Fruit become infected during the growing season through wounds caused by insects and damage by high winds, rain or hail. Infected fruit first appear grey, green or water soaked and later become shrivelled, dark brown and mummified.

Management Options

Remove and destroy twigs 25 cm below the affected part. If pruning shears are used, dip blades in a solution of 1 part chlorine bleach to 4 parts water after each cut. Succulent growth is susceptible to fire blight infection, so avoid heavy application of nitrogen fertilizer avoid excessive winter pruning which stimulates vegetative growth the following season. Suckers (water sprouts) are good entry points for fire blight into large branches, limbs and trunks. Break them out periodically during the early growing season. Control plant sucking insects such as leafhoppers, aphids and plants bugs to minimize wounds to leaf and shoot tissue. Plant tolerant varieties, if available. Abandoned pear trees and rosaceous ornamental plants will harbour this disease.

Scab

Scab is the most common and serious disease of apples throughout Ontario. Occasionally, it will also affect pears, especially "Flemish Beauty". Olive-green spots appear on leaves; with time, they turn dark brown and black. On fruit, dark, irregular spots appear; if spotting is severe, the skin cracks and the fruit is deformed. Leaves may drop and the crop in the following year may be reduced. The fungus which causes the scab overwinters on dead leaves on the ground. Spores are discharged into the air by spring rain and infect young apple leaves and fruit.

Management Options

Gather and burn or mulch fallen leaves in autumn. Unfortunately, if there are neglected apple trees in the immediate area, this will not provide adequate management. Once the scab fungus becomes established on a tree, each rain causes new infections. When planting new trees, opt for resistant varieties.

Tentiform Leafminers

Tentiform leafminer larvae leave speckled blotches of tented, hollowed out leaf tissue. Adults are tiny (3-4 mm long) moths with brown and white markings. There are three generations per year. The first begins in spring when eggs are laid on the underside of new leaves at the tight cluster stage to pink stage of blossom development (see Flowering Stages on Fruit). Larvae feed between leaf surfaces for 4 to 5 weeks where they create mines or tunnels. They pupate in the mines and then emerge to complete one generation. Low to moderate levels of leafminers (1-7 mines per leaf) do not require control. High levels of infestation, however, will cause the fruit to be undersized and will lead to premature fruit drop.

Management Options

Control of this insect is often unnecessary as populations are reduced by natural enemies. Damage by the leafminer is more severe when trees have been stressed. The best prevention, therefore, is to maintain the health of your trees. Gathering and burning or mulching fallen leaves in autumn can help to reduce populations.

Apple Maggots or Railroad Worms

Apple maggots, or railroad worms, are a problem in most areas of Ontario. The 6 mm long adult fly is black with yellow legs and yellow markings on its abdomen. It lays its eggs on the fruit from late June until mid-August. The small white maggots that emerge create extensive tunnels, causing the surface to be bumpy and the fruit to drop. When full-grown, the maggots move from the overripe fruit into the soil where they overwinter. If unsprayed apple trees are in the neighbourhood, this insect is very difficult to control.

Management Options

Hang sticky red balls or yellow traps, available at garden centres, in the tree to trap the adults and prevent egg laying. These can be made more attractive by using apple maggot lures. Gather the fruit as it drops and throw it in the garbage can or bury it at least 60 cm deep to reduce maggot flies and damaged fruit the following summer. Encourage your neighbours to do the same. Destroy wild and unsprayed apple, prune and hawthorn trees in the vicinity if possible.

Powdery Mildew

Powdery mildew is a white, felt like fungus that covers the leaves and stems of apple terminals. Infected leaves become narrow, folded, discoloured and brittle. During the summer these leaves often turn brown and die. Severely infected shoots are dwarfed.

Powdery mildew is sometimes a problem on the young shoots of apple trees. The most susceptible varieties are Cortland, Ida Red and Jonathan.

Management Options

Prune out infected terminal shoots, twigs and branches. Improve air circulation and light penetration around the tree. Plant less susceptible varieties where available.

Aphids

Aphids are a common problem on apple and sweet cherry and less so on sour cherry. They attack the growing end of twigs throughout the summer, sucking sap and causing leaves to curl, pucker and turn yellow. Fruit is affected when infestation is severe. A sooty deposit is found on the apple fruit. Control is very difficult once this insect becomes established and leaves are curled. The rosy apple aphid, one of the important aphid species affecting apple, feeds on leaf and flower bud clusters and leads to slightly different damage than other aphid pests of fruit trees. Rosy apple aphid feeding can result in rolled leaves and clusters of misshapen apples.

For more information, refer to the aphids section of Chapter 1.

Management Options

Manage nitrogen levels in plants (avoid over fertilizing) to prevent excessive lush terminal growth and help reduce aphid populations. Hand suckering in early June removes unnecessary vegetative growth that attracts aphids. Unpruned trees provide favourable conditions for aphids. A cool wet spring also favours aphid development by providing conditions unfavourable for aphid parasites and predators. There are many natural predators, parasites and pathogens of aphids which can help keep populations below damaging levels. Commercially available aphid natural enemies can also be purchased (see Chapter 2) and may help provide control in some cases.

Oriental Fruit Moth

See Insects and Diseases Affecting Many Fruit Crops.

Obliquebanded Leafroller

While several leafrollers will attack apples in Ontario, the obliquebanded leafroller is the most common. This insect has an extremely wide host range and feeds on all species of fruit trees, hardwoods (e.g. maple, hawthorn and crab apple), grey dogwood and brambles (e.g. raspberry and blackberry). The insect overwinters as larvae, becoming active early in the spring, and there are two generations per year. The caterpillar is up to 20-30 mm in length and light to dark to yellowish green, with a dark brown to black head, and the adult moths are light tan to dark brown with darker bands on the wings. Damage includes spring feeding on buds, leaves and flowers and various types of feeding on the fruit - including single "pin pricks", multiple tiny circular excavations or extensive, shallow feeding channels.

Management Options

Diligent hand thinning of fruitlets to singles makes less favourable feeding sites. Prune to maintain an open canopy, and avoid excess nitrogen. Although obliquebanded leafroller larvae attack all apple cultivars, some sustain greater amounts of damage, perhaps because they are more difficult to thin and have larger leaves. Plant more tolerant varieties, if available.

Pear

Codling Moths

Codling moths lay eggs in the pear fruit, and the larvae enter and grow inside. See apple section for more information.

Black Rot and Frog-eye Leaf Spot

These diseases are caused by a fungus, and often occur on unsprayed trees in late summer just before the fruit matures. See apple section for more information.

Fire Blight

See Apple section for more information.

Scab

Scab is the most common and serious disease of apples throughout Ontario, but it can also affect pears, especially the variety Flemish Beauty. See apple section for more information.

Pear Leaf Blister Mites

Pear leaf blister mites cause blisters and dark, dead spots on the leaves of pear. If severe, the tree may be weakened. For more information, see Mites section in Insects and Diseases Affecting Many Fruit Crops.

Management Options

If symptoms are restricted to a few leaves, pick them off before the blisters redden and dispose of them.

Pear Psylla

Psylla are sucking insects that are related to aphids and leafhoppers and resemble very small cicadas as adults. The most obvious symptom of pear psylla is the honeydew that surrounds the insect on the leaf. Later, the honeydew turns black and sooty. Hot weather before and during the blossom period favours heavy infestations. If severe, leaves turn pale with dead areas, fruit is dwarfed and trees are weakened. The honeydew may also be found in late summer, as there are several generations.

The adults are reddish-brown, emerging in early spring to lay eggs on twigs. Both the adults and larvae feed by sucking the sap.

Management Options

Syrphids, ladybugs and lacewings are known to feed on psylla and may help reduce populations.

Pear Slugs

Pear slugs are the larvae of sawflies and are not true slugs. The slime-covered larva is 1 cm long, dark green at first and later orange. It feeds on leaves of pear, cherry and plum, creating large ragged holes or leaving only a framework of veins. Telltale slime trails are also present.

Management Options

Dust larvae with talc or dry, fine soil to dry them out. It may also be possible to dislodge them using a strong spray of water.

Oriental Fruit Moth

See Insects and Diseases Affecting Many Fruit Crops.

Obliquebanded Leafroller

See Apple section.

Learn More

 


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 25 July 2005
Last Reviewed: 28 June 2010