Spring emergence of adult flies occurs shortly thereafter. These flies deposit eggs on leaves of wheat plants in the jointing stage. The newly hatched larvae move from the site of egg-laying downward behind the leaf sheaths to the nodes, where feeding is initiated. Damage Figure 5. Wheat damaged by Hessian fly.
Damage is related to degree of infestation by the Hessian fly larvae.
Even a single larva can cause significant damage to a wheat plant because salivary toxins released while feeding interfere with normal wheat growth. Plants attacked at the one-leaf stage may be killed outright. Wheat attacked later will be severely stunted, with perhaps the first tillers killed and plant growth delayed. Young plants or tillers infested in the fall often die during the winter. Plants attacked in the spring have shortened and weakened stems that may eventually break just above the first or second node, causing plants to lodge near harvest.