The raspberry crown borer, Bembecia
marginata, bores into and damages the lower cane or crown
area of raspberries, blackberries, loganberries, and boysenberries,
as well as wild thimbleberries and salmonberries. Attacked canes
become spindly, cane vigor is reduced, and canes often break
off at ground level.
 
(Above) Borer inside
raspberry cane.
(Below) Adult
raspberry crown borer.
(Left) Raspberry crown borer injury
shows in cane at right in photo, healthy cane on left in photo.
The adult moth looks like a black and yellow wasp. It flies in
the daytime and can be seen in berry fields from late July to
late September. In some years it will still be seen into October.
Each female moth lives about a week and lays some 100 eggs singly
on the undersides of the berry leaves. After about 30­60
days the egg hatches into a small caterpillar which crawls down
to the base of the cane and forms an overwintering cell. The
majority of the eggs hatch in October. In spring the caterpillar
bores further into the cane where its feeding causes swelling
or galls at or below the soil surface. These swellings, often
accompanied by crumbles of insect droppings, are especially noticeable
in October. Again the caterpillars overwinter, this second season
in a tunnel in the cane. In the spring, feeding continues in
the fleshy part of the crown. The caterpillars when fully grown
in late June to July are white, about 1­1 1/2 inch long,
with a brown head. Pupation occurs just under the bark surface
in the lower part of a mature cane and the moths emerge from
July to September. The life cycle requires two years, and both
very large and very small caterpillars can be found in infested
canes in April and May.
Dig out and burn infested,
"galled" canes and crowns in late fall or early spring.
Biological controls have done little to suppress this pest.
Thoroughly spray the crown and lower two feet of cane area with
a registered insecticide. Spray sometime between October 1 and
March 1. This drenching spray treatment affects only the young
caterpillars; to control an infestation, the spray will have
to be repeated again a year later to interrupt the two-year life
cycle of the borer. Do not apply more than twice per season.
Specific chemicals are not mentioned here because they can change
rather rapidly. Consult with a County agent, professional entomologist,
or Master Gardener who has access to the PNW Insect Control
Handbook­­which is revised annually.
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By Arthur L. Antonelli, Ph.D.,
Washington State University Cooperative Extension entomologist,
WSU Puyallup.
Use pesticides with care. Apply
them only to plants, animals, or sites listed on the label. When
mixing and applying pesticides, follow all label precautions
to protect yourself and others around you. It is a violation
of the law to disregard label directions. If pesticides are spilled
on skin or clothing, remove clothing and wash skin thoroughly.
Store pesticides in their original containers and keep them out
of the reach of children, pets, and livestock.
College of Agriculture and Home
Economics
Issued by Washington State University
Cooperative Extension and the U.S. Department of Agriculture
in furtherance of the Acts of May 8 and June 30, 1914. Cooperative
Extension programs and policies are consistent with federal and
state laws and regulations on nondiscrimination regarding race,
color, gender, national origin, religion, age, disability, and
sexual orientation. Evidence of noncompliance may be reported
through your local Cooperative Extension office. Trade names
have been used to simplify information; no endorsement is intended.
Revised May 1997. Subject codes 352, 232 A EB0920 |
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