In fighting one of the most virulent of wheat pests, Hessian flies, producers are equipped with the rough equivalent of a well-stocked toolbox of pliers, wrenches and utility knives but nothing like a sledgehammer to deliver a knockout blow.

Hessian flies cannot be eradicated; they can only be understood. But by understanding them and employing a management system based on a knowledge of their life cycle, growers can substantially reduce the risk of Hessian fly damage.

As threats to wheat go, Hessian flies rank behind barley yellow dwarf year in and year out, but the effects of the mosquito-like flies are potentially devastating.

“Hessian flies get every grower’s attention because when you get a really bad infestation you end up with a field where there is no harvestable wheat and that either must be plowed under, harvested as hay or used as a cover crop,” says Kathy Flanders, a professor in the Department of Entomology and Plant Pathology at Auburn University and an Alabama Cooperative Extension System entomologist.

The species spends its summers in brown puparia that are called flaxseeds because they bear a close resemblance in color and shape to these seeds. They begin to emerge into adulthood in late August or early September.

 “They come out looking for volunteer wheat or a couple of alternative hosts such as little barley,” Flanders says. “It’s the next generation that ends up infesting production wheat fields.” 

Adults lay eggs on the leaves, and the maggots feed in protected areas on the plants.

”Depending on where you’re located in Alabama, you can have multiple generations — some occurring in late fall, others in late winter and early spring.”

With interest in wheat planting on the sharp rise in recent years, Flanders says producers should make themselves fully aware of the risks.

“As wheat acreage increases, the number of over-summering puparia also increase,” she says, “and as these adults come out and fly, the chances of their finding wheat is higher.”

For this reason, understanding the life cycle of the Hessian fly constitutes the frontline of control measures, Flanders says, who stresses that effective managements starts from the very beginning — during planting.