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University
of Rhode Island GreenShare Factsheets
Viburnum
Leaf Beetle
Pyrrhaltla
virburni
Coleoptera: Chrysomelidae
The
viburnum leaf beetle, a native of Europe, is expected to move into
southern New England states in the near future. The beetle has been
present in New York State, Maine and Quebec, Canada for a number
of years. Both the immature and adult stages are serious defoliators
of many viburnums.
The
viburnum leaf beetle 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 starts 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.
Adapted
from the University of Massachusetts Extension Service, 2001
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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