Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES
Peachtree Borer
Borers
that feed under the bark of peach trees are one of the most serious pest
problems in commercial peach orchards and in home peach plantings. Borers also
attack cultivated plums, cherries, nectarines, and apricots, and wild cherries
and plums. There are two species of borers: the peachtree
borer (Synanthedon exitiosa),
which is sometimes referred to as the greater peachtree
borer, and the lesser peachtree borer (Synanthedon pictipes). The peachtree borer is common in young nonbearing trees or in
unmanaged plantings, while the lesser peachtree borer
is common in large managed orchards.
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Damage The peachtree borer attacks healthy bark near the soil line,
usually just below the ground line or in the lower 30 cm (12 inches) of the
trunk. Borers can kill young trees when trunks are girdled by feeding. Borers
feed on the growing inner bark of trees, and tunnel between the inner bark
and the sapwood. The bark eventually peels off of damaged areas. Damage
weakens the tree and predisposes it to attack by other pests and diseases. A
gummy mass mixed with sawdust is usually found on the outer bark at the place
where a borer started an attack. Entries are often found where there are
cankers or wounds caused by other factors such as winter injury. Appearance The
adult peach tree borers are moths that look more like wasps than moths. The
adult female peachtree borer has a distinctive
appearance; she has a dark blue-black body with an orange band on the
abdomen, dark blue front wings, and clear hind wings. The adult male is
blue-black, marked with narrow yellow bands on the abdomen, thorax, head, and
leg; front wings and hind wings are clear but the edges and veins are
outlined with blue-black scales. The male is 18 to 33 mm long, the
transparent portions of his wings are strongly tinged with yellow, and at
least 3 to 4 narrow bands of yellow are usually visible on the abdomen. Eggs
are small, oval, reddish brown, and hard. The larva is dull white with a
brown head and three pairs of short jointed legs. Larvae are 1.5 mm (1/16
inch) when first hatched, and 30 mm (5/4 inch) when fully grown. |
Figure 1-Peachtree
borer larva (1), cocoon (2), empty pupal case
(3), and cocoon with pupa emerging (4). From
Gossard & King, 1918, Ohio Agric. Experiment
Station Bulletin 329. |
Life
Cycle
Peachtree
borer has only one generation per year. It over winters as an inactive larva
under the bark, and resumes feeding and completes its larval stages in spring
and early summer. When fully grown, the larva pupates under bark or in the soil
near the tree base, then emerges as a new adult. The
adult is the only stage that leaves the tree.
In
central Ohio, peachtree borer adults start to emerge
in mid-June; emergence peaks in midsummer and extends into September. Emergence
is greater on days after a rain. Soon after adults emerge, the female moths lay
eggs under bark scales or on rough bark. Each female lays about 400 eggs. Eggs
hatch in eight to ten days into larvae that bore into the tree.
Monitoring
While
pruning in early spring, growers should look for symptoms of peachtree borer activity at the base of the tree. If
symptoms are found, then a more intensive control strategy is needed than if
symptoms are not found.
Non-Chemical
Control
Natural
Control Ants,
spiders, and lacewings prey on larvae in exposed locations, and birds feed on
larvae and adults. These natural enemies are not capable of adequately
controlling borers.
Mechanical
Control In small
plantings, borers can be effectively controlled by killing larvae mechanically.
In the spring at the time buds are bursting, insert a knife or wire into holes
that indicate where borers are located, with the intention of smashing the
larvae. This can also be done in late fall.
Chemical
Control
Chemical
control is preventive when insecticide is applied to trees before borer eggs
hatch, so that small borer larvae contact a toxic residue as they crawl into
trees. Control may also be achieved by fumigant action of the insecticide,
which can kill larvae already in trees at the time of application. An
insecticide with long residual action gives the best control of peachtree borer. Protection from peachtree
borer is most critical during the first three to five years after planting.
When new trees are planted, the roots and crowns should be dipped in
insecticide before planting; this will protect them from borers during their
first year. In established plantings, insecticide should be applied as a bark
drench at a rate of one-half to one gallon of spray mix per tree. Thorough
coverage is necessary. The insecticide should run down the trunk and soak the
ground at the base of the tree. Any prunings, debris,
or weeds at the base of trees should be removed so that they do not block the
treatment.
Timing
The
best time to treat and the number of insecticide applications needed for peachtree borer control depend on whether trees are known
to be infested with this pest. One insecticide treatment is adequate in
orchards where trees' show little or no sign of peachtree
borer infestation; the best time to treat is at the time of peak adult flight,
which is usually in early August. In orchards where borer injury is found on
most trees, two treatments should be made: the first about 10 days after adults
begin to emerge (late June) and the second at peak emergence about six weeks
later (early August).
Insecticides
in Home Fruit Plantings
Lindane or multipurpose orchard pesticide may be used, and some
brands of chlorpyrifos (Dursban),
endosulfan, and carbaryl (Sevin) are labeled for this use in home plantings.
Insecticide should be applied to the bark by a paint brush or a hand sprayer.
Information obtained through the Ohio State Extension Factsheet
HYG-2032-94
Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES