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Figure 1. Wheat plots at Central Research Station in Baton Rouge showing symptoms of Hessian fly injury. (Photo by J. Villegas)
A serious infestation of Hessian fly in wheat was observed this year in south Louisiana. Reports indicate that severe infestations have been detected in LSU AgCenter wheat varietal trials at Central Research Station in Baton Rouge and high levels of infestation were also observed in a producer’s fields near Bunkie (Fig. 1). This level of damage has not been observed in over a decade, making this year's infestation particularly concerning. Hessian flies are active when temperatures are between 40° and 80° F, with warm winters like 2023 being conducive to a greater number of insect cycles. The severity of the infestations highlights the need to take proactive measures to manage this pest.
Hessian Fly is one of the most destructive insect pests of wheat globally. The adult Hessian fly is a small, mosquito-like fly that is about 2–3 mm (0.7–0.12 inch) long. Adult females are reddish brown to black in color while adult males are brown or black and are slightly slender (Fig. 2). The adult female typically lays 250–300 eggs in its one to two-day lifespan. Eggs are deposited on the leaves and when they hatch, the larvae would initially feed on the leaves and eventually burrow into the stem. Feeding by larvae can result in stunted growth, yellowing, and even death of the plant. Feeding injury can also cause lodging. Complete crop failure can occur in severe infestations.
Figure 2. Adult female Hessian fly. (Photo by Scott Bauer - USDA ARS)
The pupae of the Hessian fly are reddish-brown and resemble a flaxseed-like cocoon (Fig. 3). They are typically found at the base of the plant but can also be detected within the stem near the head (particularly when egg-laying occurs in Spring). The pupae can survive in the soil for up to two years, and it is important to note that Hessian fly infestations can occur in both Fall and Spring seasons, especially in Louisiana where the temperature is warmer compared to other wheat-producing states.
One way to manage Hessian
fly infestations is to plant resistant varieties of wheat. Resistant varieties significantly
reduce the damage caused by this pest, and producers should consider using
these varieties whenever possible. Additionally, insecticidal seed treatments
can be used to protect the crop from Hessian flies particularly if infestations
occur in Fall. In cases of severe infestations, foliar applications of
insecticides may be necessary. However, insecticide applications must be used
judiciously and only when necessary and are only effective at controlling adult
flies.
Figure 3. Larvae and pupae of Hessian fly found on wheat plants at the Central Research Station in Baton Rouge. (Photos by J. Villegas)
