The Online Gardener's Handbook
2010
Chapter 5: Fruit
Apricot, Peach, Nectarine, Plum and Prune
Table of Contents
- Introduction
- Apricot
- Nectarine
- Peach
- Plum and Prune
- Learn More
Introduction
In this chapter, a description of various pests of tender 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.
Apricot
Cytospora Cankers
Cystospora is a fungal infection occurring on the trunk and lower
branches that usually enters through wounds in the tree. Twigs develop
brownish-black areas around winter-killed buds or scarred areas
on the bark. By early summer, a gummy substance appears, and later
the bark separates from the wood. The cankers grow larger every
year, and are most conspicuous on the main trunk or scaffold branches.
Management Options
As cytospora enters through wounds in the tree, your best defence
is to control for peach tree borers (see below) and to avoid bark
injury, long pruning stubs, winter injury, or brown rot injury to
twigs. Prune trees in spring, not fall, and remove any dead wood
before the end of June. Do not prune in cool, wet weather. Do not
apply fertilizer after June. Healthy trees growing on well-drained,
deep, sandy soil are less likely to get cankers.
Peach Tree Borers
Peach tree borers attack peach, nectarine, apricot and sometimes
plum and cherry trees. For more information, see Peach.
Bacterial Spot
Bacterial spot causes small, round, tan spots to appear on leaves
which later turn purplish and angular. Small, sunken, round spots
also appear on the fruit and later the fruit cracks. Extended periods
of wet weather encourage the spread and development of the bacteria.
Management Options
Remove all fruit at harvest and remove infected leaves regularly.
When planting, avoid shaded areas with poor air circulation. Keep
trees well pruned to promote air circulation and promote rapid drying
of foliage and fruit. Plant resistant varieties, if available.
Brown Rot
Brown rot is a fungus that attacks various parts of the tree. Blossoms
that become infected shrivel, twigs are killed, and fruit becomes
covered with grey-brown mould and rots rapidly. Infected fruit may
drop or hang on the tree throughout the winter, and mould can develop
on the fruit even after harvesting.
Management Options
Throw all mouldy fruit in the garbage or bury it to reduce infection
next summer. Cut dried fruit (mummies) out of trees when pruning
and dispose of it in the same manner early in the fall. Remove all
remaining fruit from trees at the end of the season. Keep trees
well pruned to promote air circulation and promote rapid drying
of foliage and fruit.
Nectarine
Cytospora Canker
Cystospora is a fungal infection occurring on the trunk and lower
branches that usually enters through wounds in the tree. For more
information, see Apricot.
Leaf Curl
Leaf curl is a fungal disease that affects peaches and nectarines.
Symptoms are noticeable in spring as reddish areas on leaves, which
thicken and blister, causing leaves to curl. Eventually, leaves
turn yellow and drop. Twigs and shoots may also be affected, with
twigs becoming distorted and reddish areas appearing on the fruit
surface. The tree is weakened if disease occurs several years in
succession.
Management Options
Remove and destroy infected leaves as they appear in the spring.
Plant tolerant varieties, if available.
Oriental Fruit Moths
See Insects
and Diseases Affecting Many Fruit Crops.
Peach Tree Borers
Peach tree borers attack peach, nectarine, apricot and sometimes
plum and cherry trees. For more information, see Peach.
Bacterial Spot
Bacterial spot causes small, round, tan spots to appear on leaves
which later turn purplish and angular. For more information, see
Apricot.
Brown Rot
Brown rot is a fungus that attacks various parts of the tree For
more information, see Apricot.
Peach
Cytospora Cankers
Cystospora is a fungal infection occurring on the trunk and lower
branches that usually enters through wounds in the tree. For more
information, see Apricot.
Leaf Curl
Leaf curl causes leaves to curl and reddish blisters to appear.
For more information, see Nectarine.
Oriental Fruit Moths
See Insects
and Diseases Affecting Many Fruit Crops.
Peach Tree Borers
Peach tree borers attack peach, nectarine, apricot and sometimes
plum and cherry trees. The adult or their larvae are seldom seen,
but brown frass and gum appear on the trunk from the scaffold branches
down to exposed roots, due to larval feeding. Gum may also appear
at wounds and on winter-injured bark, which are entry places for
the borers. Young trees may be killed. Older trees are able to survive
light infestations for a few years but may also weaken and die unless
borers are controlled.
Adults are wasp-like moths that lay eggs around the base of the
trunk in late summer and early fall. Caterpillars, 2.5-3.0 cm long
with brownish heads, hatch and burrow into the wood.
Management Options
Wrap strong paper - not tarpaper - around the trunk of young, transplanted
trees up to the lowest branch, and leave in place for at least two
years after planting. Any pruning or accidental wounds should be
scraped clean. If the tree is infested, remove gum and poke flexible
wire into the holes to kill borers. Sterilize the hole with a solution
of 1 part bleach in 4 parts water and seal with putty. Do this in
the spring and fall.
Bacterial Spot
Bacterial spot causes small, round, tan spots to appear on leaves
which later turn purplish and angular. For more information, see
Apricot.
Brown Rot
Brown rot is a fungus that attacks various parts of the tree. For
more information, see Apricot.
Plum and Prune
Apple Maggots or Railroad Worms
Italian and Stanley plums are susceptible to apple maggots, whereas
other plum varieties are not. For more information, see Apples.
Tentiform Leafminers
Adult tentiform leafminers are tiny (3-4 mm long), brown and white
moths. The larvae damage the leaves, creating speckled blotches
of hollowed out, tented tissue. For more information, see Apples.
Pear Slugs
Pear slugs are the larvae of sawflies and are not true slugs. For
more information, see Pears.
Peach Tree Borers
Peach tree borers sometimes attack plum trees. For more information,
see Peach.
Bacterial Spot
Bacterial spot causes small, round, tan spots to appear on leaves
which later turn purplish and angular. For more information, see
Apricot.
Brown Rot
Brown rot is a fungus that attacks various parts of the tree. For
more information, see Apricot.
Black Knot
Black knot is a fungal disease of plum and sometimes cherry. Early
symptoms appear as greenish swelling that expand over a period of
1-2 years to become hard, woody black swellings up to 10 cm long
on branches and small twigs. These eventually girdle and kill the
branches.
Management Options
Remove and burn all infected branches. This should be done in late
winter, before any new growth begins. Do not leave pruned knots
in the garden, as this will serve as a source of new infections.
Knots on bigger limbs can be cut out - make the cut at least 10
cm below the knot as the fungus colonizes the inner bark beyond
the visible swelling. It is important to prune every year, as early
infections are not easy to see. Destroy nearby wild or neglected
plum and cherry trees. Japanese plums are more resistant to this
disease than European varieties. Mature black knots may be naturally
colonized by a parasitic fungus, making them appear creamy-yellow
to pink in colour. Black knots colonized by this beneficial fungus
do not produce spores.
Learn More
