Bug of the Month – Viburnum Leaf Beetle
This
native of Europe feeds exclusively on many different species of viburnum, which
include:
Viburnum
opulus (and
cultivars),
V.
dentatum, and
V. rafinesquianum.
Adults have also been found feeding and laying eggs on
V.
lentago,
V.
acerifolium, and
V. trilobu.
This pest
over-winters as an egg on the twigs of the host plant. Eggs hatch in May of the
following year and the young larvae begin feeding on the host plant foliage.
Larvae are usually found feeding together in groups. Pupation occurs 8-10 weeks
later and the first adults begin to appear around the middle of July. Adults are
active up until the first frost. Mating occurs, starting in July, and the female
will chew small holes in the twigs where she lays her eggs. She then proceeds to
cover these individual eggs with excrement giving the bark of these twigs a
roughened appearance. Each female produces up to 500 eggs. (Source:
Insects That Feed on Trees and Shrubs.
Johnson and Lyons).
Both
the larvae (immatures) and the adults feed voraciously on the foliage of the
host plants. Heavily attacked plants will have every leaf skeletonized by this
pest. It is the only pest that causes such injury to viburnums. Adults are small
and brown and somewhat difficult to see. The immatures are dark in color and can
be found feeding in groups on the host foliage.
Homeowners need to be aware of the signs of this beetle’s injury along with
knowing what the different life stages look like. One should also monitor for
the eggs on the stems of viburnums. When found, this pest should be treated to
limit its injury and spread. Physical removal of this pest from the host plant
is difficult to obtain especially when many plants are involved. Therefore,
pesticide treatments may be necessary to manage this pest, once found.
Source: Insects & Mites – Defoliators – Viburnum Leaf Beetles, UMass Extension, University of Massachusetts at Amherst, http://www.umassgreeninfo.org/fact_sheets/defoliators/viburnum_leaf_beetle.html