SENECA FALLS, NY ­– Weeds: they reduce yields, contaminate crops and seem to infest fields year after year. No matter how much you spray, they come right back the next season, ready to take over your acres.

To offer some helpful advice, Vipan Kumar, associate professor and weed management specialist at Cornell University’s School of Integrative Plant Science Soil & Crop Sciences Section, presented “A Fresh Look at Weed Management” at the New York Soil Health Field Day hosted recently by Rodman Lott & Son Farms.

Herbicide-resistant pigweed varieties Palmer amaranth and water hemp are making headway in New York. Although a relative newcomer to Cornell, Kumar is familiar with these weeds from his prior post at Kansas State University.

“Palmer amaranth is the number one weed challenge in Kansas,” Kumar said. “We need to be proactive in controlling these.”

Herbicide-resistant Palmer amaranth populations have been identified in Steuben, Orange, Genesee, Wayne, Seneca and Livingston counties in New York. Kumar believes that targeting the weed seed bank is essential in combatting pigweed. With Palmer, one female plant can produce five million seeds.

Technology like transgenic crop seeds can help, but “are these sustainable and economic?” Kumar posed. “It may manage it for a year or two, but they’ll likely become resistant.”

He promotes using cereal rye as a cover crop to reduce emergence, density, size/biomass and seed production. In his research at Kansas State, he found planting cereal rye reduced seed production of Palmer amaranth by 68%.

Take a ‘fresh look’ at weed control

Palmer amaranth has been making inroads in New York and other Northeastern areas. Photo courtesy of Vipan Kumar, Ph.D./Cornell

“Growing cereal rye alone won’t offer season-long control for late emergent Palmer amaranth,” Kumar warned. Applying a post-herbicide helps control those.

Summer covers could include millets or sorghum/sudangrass.

“Planting green resulted in high accumulation of cover crop biomass at the time of termination,” Kumar said. “High cover crop biomass reduced pigweed densities and size, and ultimately reduced herbicide selection pressure.”

Using mechanical tools to reduce Palmer amaranth seeds can also help control the weeds by destroying their seeds. Kumar’s research found that only 5% of the seeds remained undamaged. This can help farmers dramatically reduce their pigweed issues the following year.

“This can also be used to control volunteer wheat,” Kumar said. “It can save on Roundup.”

Using a chaff liner can concentrate weed seeds at soybean harvest. The equipment puts the seeds in a narrow row to contain them.

Kumar also showed examples such as zapping weeds with electricity, an inter-row weed mower reducing weeds between rows, using artificial intelligence to destroy weeds, a spray drone, automated weeders and a laser weeder.

“There’s a lot of emphasis on soil health, but which is healthier?” he asked, showing a photo of a field with thriving crops and minimal weeds and a crop struggling to compete with a massive pigweed infestation.

by Deborah Jeanne Sergeant