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Shelterbelt Centre Pest Leaflets
Willow Redgall Sawfly
Hosts: Willow
Appearance and Life History:
The willow redgall sawfly has
two generations a year, with the
first generation adults emerging
in late May or early June. The
adult sawfly measures
approximately 4 mm in length
and has a black body with
yellow legs. Each adult can
produce 20 to 35 eggs. The
eggs are deposited singly or in
a row on either side of the
mid-rib of the developing
leaves. At each location an egg
is deposited a gall begins to
form. By the time the larvae
hatch the gall is fully
developed. The larvae feed and
develop within the galls for
approximately five weeks. The
full grown larvae are a
yellowish-green color with a
shiny, black head and measure
approximately 7 mm in length.
When full grown, the larvae
drop to the ground and form
cocoons in the topsoil. The
larvae pupate and emerge as
adults approximately two
weeks later in late July or early
August. By mid-September the
second generation larvae are
full grown and drop to the
ground where they overwinter
in cocoons.
![sawfly](/web/20061210135344im_/http://agr.gc.ca/pfra/shelterbelt/pest/83-0218.jpg)
Damage: The adult sawfly
forms the galls on the leaves by
injecting a fluid into the leaf
along with the egg. The galls
measure approximately 8 mm
long, 6 mm wide by 6 mm deep.
The galls appear red on the
upper surface and are
yellowish-green on the
underside. Although the willow
redgall sawfly causes minimal
permanent damage, the galls are
extremely unsightly especially
on ornamental plantings. During
a severe outbreak the galls
cause a reduction in annual
growth.
Chemical control of the willow
redgall sawfly is rarely
required due to parasites and
predators that attack the sawfly
and as the insect causes
minimal permanent damage to
the host. If a severe outbreak is
anticipated, control may be
achieved by applying carbaryl
during the adult flight period.
The flight period of the sawfly
can be monitored using yellow
sticky traps as the adults are
attracted to the color yellow.
For more information contact:
PFRA Shelterbelt Centre
Indian Head, Sask. S0G 2K0
Phone: (306) 695-2284 or Fax: (306) 695-2568
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