| Plum curculio, a snout beetle, is an important pest
on stone fruits like plums, cherries, and peaches.
Plum curculio is one of the most serious pests of
peach trees; they lay eggs within the fruit and both
adults and larvae feed on the fruit, causing brown
rot of the fruit. On apples, plum curculio is
considered the second most damaging pest after
codling moth.
Symptoms and Diagnosis
Plum curculio beetles, Conotrachelus nenuphar, can
be found on plum, cherry, peach, and apple trees,
less commonly on nectarine and pear trees. Fruit
may fall prematurely, in late May and June. The skin
of infected fruit has small crescent-shaped blemishes
that eventually become swollen and knotted. Upon
closer examination, larvae may be seen feeding near
the blemishes. Infested fruit is often hard and
misshapen. The larvae create holes in the fruit skin
when they leave the fruit to pupate. These holes are
clean-cut and free of frass or webbing.
Life Cycle
Plum curculio beetles are dark brown, about 1/4
inch long, and have a prominent snout, measuring
about 1/3 the length of their bodies. They have four
characteristic humps on their wing covers. Adults
may overwinter in the soil or in hedgerows near host
trees. These adults emerge from their overwintering
sites to feed on trees in early spring. Females lay
eggs within the fruit. The larvae that emerge from the
developing fruit have grayish-white, worm-like
bodies with brown heads and can be seen on
infested trees in late summer. Larvae may feed on
the fruit for 2–3 weeks before they burrow into the
ground to pupate. Adults emerge in mid- to latesummer
to cause more feeding damage on mature
fruit before they overwinter.
Integrated Pest Management Strategies
1. Shake infested trees. In backyards with only a
handful of infested trees, plum curculios may be
shaken out of infested trees. This technique works
best early in the day when the beetles are
sluggish. Lay paper or cloth underneath the trees
to collect the beetles. Destroy the collected
beetles.
2. Clean up fallen fruit in which eggs or larvae may
be developing.
3. Cultivate the soil surrounding infested trees in
late spring or early summer to destroy pupating
larvae that may have fallen to the ground with the
fruit or pupae that may be developing in burrows
in the ground.
4. Apply insecticides when populations of adult
beetles are severe. Apply a rotenone or carbaryl
(Sevin) spray to curb feeding damage and prevent
beetles from laying eggs. It is important to delay
application of the pesticide until after flower
petals drop to avoid harming pollinating insects.
Reapply pesticides two more times, at 10–14 day
intervals. Other pesticides registered for use
include azadirachtin (Bio-Neem, Margosan-O),
Beauvaria bassiana, malathion, methoxychlor,
and pyrethrins. |
