The Hessian fly (Mayetiola destructor) is a world conqueror. Having originated in the Middle East, long ago it spread to most wheat producing regions of the world. It is, in fact, one of the earliest documented invasive species in North America, first reported in New York in 1779. Today, it continues to be a major pest of wheat, and its ability to form galls for protection during larval development make it a formidable opponent for growers and pest managers.
Thus, a multifaceted approach is recommended for Hessian fly control, and a new guide in the open-access Journal of Integrated Pest Management outlines the fly’s biology and life cycle and an array of tactics that can be combined to manage the pest.
“We wanted to inform readers of opportunities to integrate Hessian fly management methods into an integrated pest management (IPM) program to enhance control of the Hessian fly and other insect pests of wheat,” says Ryan Schmid, a Ph.D. student in entomology at Kansas State University and lead author of the guide.
The Hessian fly does its damage during its first- and second-instar larval stages, which last for two to three weeks. During that time, larvae feed on the wheat stem, which can injure the plant and result in stunted growth, lodging due to weakened stems, and reduced seed production (or even failure to produce seeds at all). After pupating, adult Hessian flies live just one to four days, in which time they mate and females lay eggs on wheat leaves.
• planting of resistant wheat cultivars • delayed planting until after Hessian fly activity has ceased in the fall • destruction of volunteer wheat that emerges prior to planted wheat • foliar and seed-treatment insecticides • biological control via parasitoid wasps
“Although these control methods can impact Hessian fly populations when applied individually, they are more effective when used in combination as part of an IPM program,” Schmid says.
For instance, parasitoid wasps are adept at hunting down Hessian fly pupae, even at low densities, meaning they are particularly useful in combination with resistant wheat cultivars; the Hessian fly larvae that survive to their pupal stage on the resistant wheat are preyed on by the wasps, thereby also slowing the development of Hessian fly populations that are resistant to the resistant wheat.
A complicating factor in Hessian fly management is its variability in growth period based on temperature. In northern regions (Kansas and northward in the U.S.), it completes two generations in a year, but in southern states it completes three to six generations. It also belongs to a large family, Cecidomyiidae, in which many species form galls on the plants it feeds on. “Gall formation has helped the Hessian fly to become a major pest of wheat by limiting the effectiveness of insecticidal foliar sprays against the economically damaging larvae,” Schmid says. “Farmers are left with management decisions that must be applied prophylactically prior to or at the time of planting.”
Schmid’s Ph.D. work at Kansas State is focused on the Hessian fly, such as its behavioral response to potential attractants that could be used to improve monitoring traps.
“Future research focusing on the development of monitoring techniques, time to sample, and treatment thresholds would help to advance the effectiveness of Hessian fly IPM,” Schmid says.