What is in this article?:
- Understanding Hessian fly is key to control
- First rule of thumb
• 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.
First rule of thumb
“The first rule of thumb is to avoid early planting, because that puts producers at higher risk not only for Hessian fly, but also for a disease known as barley yellow dwarf spread by aphids,” she says.
Farmers should plant during the recommended planting dates for wheat for their particular region. Planting too late results in loss of yield potential because of various agronomic factors.
The risks associated with this pest should be of special concern to producers who are not running rotation systems.
“If farmers are not rotating, if they’re running continuous wheat or soybean double-cropping systems, they should be concerned that the Hessian flies are going to be out in their fields and ready to start the cycle again each fall.”
Stubble burning is one option to address over-summering of winter pupae, but this only provides partial control.
“Some of them will escape by falling into cracks in the soil, but it is a practice that can mitigate the problem.”
Farmers who have not adopted no-till or minimal-tillage systems should also consider tilling immediately after wheat harvest as an added safeguard.
“A key concern is getting rid of any volunteer wheat that may act as hosts for the first generation that will work to build up future generations of the pests,” Flanders says.
Hunting plots are typically planted early and can serve as hosts of the first generation of flies. Consequently, these plots should be planted in something other than wheat, Flanders says.
Likewise, choosing something other than wheat as a cover crop reduces overall risk to production fields.
“As a general rule, save wheat for wheat production and plant wildlife plots and cover crops to non-hosts such as oats or ryegrass or some other alternative crop,” Flanders stresses.
Resistant varieties are yet another option for controlling Hessian flies, but, like other practices, they are no panacea.
“Right now, there are a few varieties — those that carry the H-13 gene — that carry more resistance than other varieties,” she says.
Older varieties carrying the H-7 and H-8 genes also appear to offer some benefit in some parts of the state, though the most effective ones are the handful equipped with the H-13 gene, Flanders says.
“If you can get your hands on one of those varieties they are a good management tool and don’t cost more,” she says.
Few insecticidal options are available to kill Hessian flies. High rates of approved seed treatments provide some control, but may not be economical.
The immature Hessian flies feed behind the leaf sheaths, so foliar spraying of insecticides has to be targeted toward adults. But predicting when the adults are present is difficult.
Flanders cites research in North Carolina demonstrating that spraying an insecticide immediately following wheat emergence may be another effective way to manage the flies, though at this point this is backed up with no hard evidence from tests in Alabama.