The Online Gardener's Handbook
2010
Chapter 5: Fruit
Apple, Crabapple, Pear
Table of Contents
- Introduction
- Apple, Crabapple
- Pear
- 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
