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Hessian Fly

CROPS IMPACTED: wheat, barley, rye, native grasses

Hessian Fly


Family: Cecidomyiidae

hessian-fly-2 hessian-fly-3

About Hessian Fly

Reproduction and Life Cycle

The Hessian fly usually has 2 generations annually; however, if there is high moisture throughout the growing season, there can be a total of 3 generations. The first generation will appear in the spring and the second at the start of fall. The third would appear in July or August.The generation in the fall will lay their eggs on volunteer plant leaves, often wheat, barley or rye, and will die a few days later. The eggs will soon hatch small larvae that will begin eating plants right above the root. When they feed off of the plants juices they inject their saliva into the plant, seriously stunting its growth. This can occur even if there is only a single larva per plant. The larvae will overwinter as puparium. They will surface as fully grown flies in the springtime and will then begin laying eggs. When this generation hatches, the larvae will feed on the leaf sheath of the host plants and will often cause the stalk to break before harvest. This development stage will last 2 to 3 weeks. The maggots will then enter their hardened larval skin and will stay in this stage until the fall.

Male and female adults will both emerge in the morning, males first, later followed by the females. The females will sit on the leaf of a plant and attract males with a sex pheromone that they release with their abdomen. Once they mate, the female will deposit her fertilized eggs in rows on the surface of wheat plants. She can lay as many as 200 eggs, which take up to 10 days to hatch.

Hessian Fly Identification and Habitat


An adult fly is about 3mm long and has a similar appearance to that of a mosquito. They are typically gray with pointy abdomens and are known to be a very delicate insect. Since the Hessian fly eggs are red-orange in colour, the female’s abdomen is a similar shade. The males are usually black or brown in colour and are smaller than the females. While this insect can fly, it is incapable of travelling far distances and they are known to only live 72 hours. When the Hessian fly first hatches, they are orange, but within a few days they will take on a white appearance, still remaining in the first instar stage. Their size will increase as they mature, growing to be about 6mm in the third instar stage and developing a green coloration that will appear as a stripe down their back. After the larvae feed for 2 to 3 weeks, they will develop their puparium, which is dark brown, shiny, hard, and looks like flaxseed.


The Hessian fly is an extremely destructive pest that is located throughout the United States. It is generally known to damage wheat plants, but can also infest barley and rye. If a wheats crop is not tilled, Hessian fly population is generally much greater since they feed on the remaining stubble, thus continuing its life cycle. When the larvae emerge from their puparium, they can lay their eggs on the volunteer wheat that pops up, or on the cover-crop that was planted. This will give the larvae a place to overwinter and feed on once spring comes.

Hessian Fly Management and Control Methods

Cultural Control

There are several wheat varieties grown that are resistant to the Hessian fly. Additionally, if you plant your wheat after the “fly-free” date (usually later in the fall after the first freeze), you can greatly reduce the Hessian fly population. Another important management method for the Hessian fly is to practice crop rotation. Due to the fact that Hessian flies depend on overwintering with wheat stubble and feeding off of it when spring comes, planting a different crop where wheat had been planted the year before will help reduce their population. Also, if you keep your new wheat locations at a safe distance (usually over 400 yards) from where the old wheat fields were, this can kill off the adults as they are unable to fly long lengths. Disking your wheat stubble can also kill the remaining Hessian flies in the ground. Instead of this, you can burn the wheat remains to reduce the fly’s population; however, this will not completely rid this pest from your field since many remain under the soils surface. In order to have effective control of this pest, it is recommended to use as many of these methods as possible and to include the use of both cultural and chemical methods.

Chemical Control

A chemical control method that has been found to have an effect on Hessian flies is to treat your seeds with either Cruiser; or Gaucho;. These products are only recommended if this pest poses a high threat to your crops, as these treatment plans are expensive. You can also use long residual spray insecticides, such as Warrior®. Apply this soon after wheat appears out of the ground. This insecticide is capable of not only killing the adults, but also any eggs on the wheat leaves and new larvae. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy. After applying insecticides it is important to irrigate sprayed area to increase the insect control. That being said, a large rainfall or irrigation soon after the application can reduce the concentration insecticides. It is important to note that management practices should be done as soon as possible because once an infestation is noted, the damage to your plants will have already been done and treatment after this point will not have much of an effect.

Latin / Alternative Hessian Fly Names

  • • Mayetiola destructor
  • • Barley midge