The aphid midge is a cecidomyiid fly. Although most
species in this family form plant galls, this species is free-living
feeds on aphids, often providing important biological control.
research has shown that predator-prey ratios of at least 1 larva to 15
aphids are suitable for control. Pupae overwinter in the orchard.
somewhat resemble mosquitoes and are seldom noticed. They are
Larvae are slender orange maggots, about 1/10 inch long (2 mm), found
aphid colonies (Plate 151). They may be very common, especially in
IPM blocks. Mean fecundity exceeds 200 eggs per female. Eggs are
and may be laid singly or in groups, in numbers proportional to aphid
Larvae may detect prey within only a very limited area. After a larva
an aphid, a toxin is injected which immobilizes the prey. The larva may
feed on a single aphid for several hours to a day. The rate of kill
on the size of prey. One study reported larvae killing 5.2 large or
small green peach aphids per larva. Killing rates of 40-80 aphids per
have been reported. Some disagreement may arise from the fact that at
prey densities, aphid midge larvae will kill more than they consume,
consuming or leaving uneaten some prey. Nevertheless, this level of
voracity is low relative to some other groups of aphid predators.
larvae are able to complete development at fairly low prey densities, a
desirable trait for biological control. The larval developmental period
is 12-17 days; 15-32 days are spent as pupae.
Aphid midge, Aphidoletes aphidimyza
One Canadian study reported that complete aphid
was achieved in a few days at ratios of 5 apple aphids per midge egg.
control was provided at 8-12 aphids per egg, and no control was
by 12-14 aphids per egg. Massachusetts research has shown that
ratios of at least 1 midge larva to 15 aphids are suitable for control.
This species appears well suited to our orchards
with normally high humidity. This species overwinters in the orchard
may not become active early enough (mid-June in Massachusetts) to
early-season control. Late instar larvae are stimulated to enter
by decreasing light levels in the fall. In the fall, mature larvae
to the soil where a cocoon is formed. Pupation occurs in the spring.
See image in Alaska site.
from a chapter in the Mid-Atlantic Orchard
Guide, entitled Aphid Predators,
by D. G. Pfeiffer
and H. W. Hogmire
E-mail to: Douglas G. Pfeiffer