WINTER MOTH, Operophtera
brumata (L.) (Introduced)
BRUCE SPANWORM, O.
bruceata (Hulst) (Native)
Pest Status: Both species are polyphagous
(feed on many host plants). Periodic outbreaks of winter moth have occurred
on shade trees, apples and blueberries in Victoria, Vancouver, Richmond
and Delta. Bruce spanworm tends to be present in these areas and occasionally
reaches damaging levels. Both species are found throughout the Fraser Valley
and may be seen in cranberries.
Life cycle and feeding habits: Winter
moth and spanworm eggs hatch in March or early April. Larvae begin feeding
on leaves, flowers and buds of deciduous ornamental and fruit trees. Larvae
may be seen in early April through mid-May as they hang down on silken
threads from the trees. The wind will blow them to neighbouring trees and
larvae will also fall on cranberry beds located close to trees.
Larvae are pale green with a light whitish
stripe along the side. They vary in length from less than 2 mm (1/16 inch)
upon hatching to over 13 mm (1/2 inch) at maturity. Larvae have a pale
green head, three pairs of front legs, and two pairs of hind legs. The
number of hind legs distinguishes these larvae from leafrollers. Fully
grown larvae are 2 cm (7/8 inch) long and have three white stripes on each
side. When larvae have finished feeding they drop to the ground and pupate
in the soil. Male moths fly during winter in November, December and sometimes
January. Although the female moths are flightless, larvae may be carried
by the wind and eggs and larvae can be inadvertently transported in or
on vehicles or containers. Spanworm adults generally emerge one to two
weeks later in the fall than winter moths. Spanworm males can be separated
from winter moth males by the presence of a small dot on the hind wing
of the spanworm that is not seen on the winter moth. There is one generation
per year of both species.
Monitoring: Since the same pheromone
attracts males of both species, it is possible to trap them from November
to January. However, the pheromone is difficult to synthesize and rarely
available. Winter moth or spanworm larvae will be detected during monitoring
for blackheaded fireworm. Winter moth/spanworm larvae make tents similar
to those made by fireworm larvae. Winter moth/spanworm larvae are most
often found near infested deciduous trees or blueberries.
Control: Chemical control is usually
not necessary but, if high populations are found, insecticides recommended
for fireworm will also provide control of winter moth/spanworm larvae.
Larvae and pupae of both species are subject to attack by parasitic and
predatory insects. Pupae may or may not be killed by flooding at harvest.
 |
 |
| Winter moth
larva |
Bruce spanworm
larva |
 |
Bruce spanworm
showing diagnostic dot on
hindwing; Winter moth showing absence
of
hindwing dot |
©2000 Minister of Public Works and Government Services Canada
|
industry
health
