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Hessian Fly
The hessian flyer can usually be controlled by planting resistant varieties
and/or planting after fly-free date, which varies from early September to
early October. Plowing under infested fields immediately after harvest can
also help. Volunteer wheat can be disked under to prevent later summer
infestations.
The hessian fly is similar in appearance and size to a small mosquito. The
life span of the adult is generally no more than 5 days. The hessian fly
completes two generation per year. The spring generation emerges from the
flaxseed stage when the average daily temperature is 45° to 50° F.
Emergence usually occurs over several weeks, during which time females lay
eggs on wheat leaves (in some cases rye or barley). The newly hatched
maggots work their way under the leaf sheath near the nodes. Maggots change
to puparium about the wheat heads out, and remain in stubble as "flaxseeds"
until fall. Adults of the fall generation begin emerging about early
September and live about three days, during which time the females lay eggs.
Larvae hatch and begin feeding on young wheat seedlings.
Plant injury caused by larval feeding stunts the plant. Stunted plants
usually wither and die. If they survive, their growth and yield are reduced.
Significant grain yield reduction can be expected when 20% or more of the
tiller are infested. Infested tiller are dark green.
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