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Hessian Fly: Generational challenge for Delta wheat growers, breeders

Small pest causes big issues year after year for Louisiana wheat growers.

Raney Rapp, Senior Writer

June 5, 2024

4 Min Read
Hessian Fly Pupae
Hessian fly pupae in wheat. Raney Rapp

Hessian flies weigh in at only half the size of an average mosquito, but their in-field impacts, and year-over-year infestations cause big issues for Louisiana wheat growers.

A short reproduction cycle – occurring over about two and a half weeks – alongside a long residual life for pupae in–field mean Hessian flies cause significant impacts in the Delta region.

“We had a really nasty Hessian fly nursery last year in Baton Rouge,” said Louisiana State University wheat geneticist Noah DeWitt. “Many of the fields Steve Harrison and I scouted in 2023 ended up with a total crop loss.”

In 2024, later planting due to drought, accompanied by colder winter temperatures appears to have staved off the worst effects of Hessian fly infestation. However, DeWitt warned one warm winter could once again turn the tide to heavy populations and in turn heavy damage.

“Hessian fly really loves the part of the world where the winters don't get too cold, with long sustained temperatures in the 50s, 60s, 70s, and even in the low 80s,” DeWitt said. “When we plant early, which is why a lot of times we have Hessian fly-free dates, and when you have moderate falls, winters and then nice, warm springs, you can really increase infestations.”

Hessian fly pupae can live in soil and stubble for over two years. After one field infestation, susceptible fields often produce another damaging fly population soon after.

“Hessian fly infestation is what we call a winter infestation,” DeWitt said. “When you have a lot of fly activity prior to jointing, it kind of looks like a low vernalization symptom. You get patchiness, you get a reduced number of tillers and the tillers that are there look stunted. Sometimes the head doesn't quite come out appropriately and you get these kinds of sick looking big dark green flag leaves. In a heavy field, it can lead to very significant loss of yield.”

Prepare with quality seed

“The best way to manage Hessian fly is first, to plant resistant varieties,” said LSU entomologist James Villegas. “The second way, is using seed treatment products.”

In response to heavy Hessian fly infestation in 2023, LSU’s wheat breeding program included a large resistance testing nursery for the current growing season.

“One of the things we're working on in the breeding program is trying to not only evaluate existing varieties, but to develop lines that have strong resistance,” DeWitt said. “We often think of what we call greenhouse resistance or strong or Antibiosis resistance, as well as what we call tolerance because both of those can be beneficial in breeding.”

Major gene resistance is a product of the plant having a resistance gene that recognizes Hessian flies and generates an immune response to prevent the fly from infesting the plant. H-13 is one of the last few resistance genes still viable in Wheat in Louisiana, as insects can quickly pinpoint a resistant gene and formulate a resistant response of their own.

“We're also working on developing what we call quantitative or field resistance, or you may call it a tolerance to Hessian fly,” DeWitt said. “That may not be the single gene for gene reaction that we see in those Antibiosis interactions. Tolerance can be a little bit more robust, because there's less selective pressure and the mechanism is a little bit more complex. So, the hope of that is to develop varieties that aren't just relying on a single resistance gene, but also have good background resistance.”

Identify larvae, pupae

The best way to identify a Hessian fly infestation is scouting fields for larvae and pupae. Hessian fly adults look similar to mosquitos, with a body size of roughly half and most are dark brown or black with females having a reddish abdomen.

“Adults are short-lived, so most of them die within a day or two,” Villegas said. “It's really hard to find the adults in the field unless you're specifically looking for them.”

Hessian fly larvae are easier to find, but harder to identify against other species. The larvae are white and nondescript, but later develop wing coloration on their backs.

“What we see most when we look at hessian fly and injury in the field are the pupae,” Villegas said. “The pupae looks light brown and is the size of a flax seed. Typically, you see it at the base of the plant.”

Identifying Hessian flies and injury are critical not only for the current growing season, but for subsequent years as well.

“This year when I got a call for a field with Hessian fly infestation, it was the same field as last year,” Villegas said. “The pupae of Hessian fly, the ones you see that are brown, can stay in the field in soil and stubble up to two years.”

Wheat fields planted in fly-tolerant varieties at the appropriate planting date have the best chance of avoiding significant damage in a Hessian fly-friendly growing season. As breeders make significant progress in identifying and cultivating multiple types of resistance, hopefully Hessian fly becomes a problem of the past.

Read more about:

Pest Management

About the Author(s)

Raney Rapp

Senior Writer, Delta Farm Press

Delta Farm Press Senior Writer

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