Resistance Test Helps Plan Rye-Grass Control

Agronomist Kevin Pearcy noticed that rye-grass was becoming harder to control on two farms in Essex. He asked Bayer to help by testing for resistance to pre-emergence chemistry which helped Mr Pearcy adapt rye-grass control tactics.

“When I asked for the tests from Bayer, I didn’t expect them to come back showing such serious resistance to residual chemistry,” he says. The test results were RRR resistance to flufenacet and pendimethalin, and RR resistance to prosulfocarb’ three of the most widely used pre-em actives.

“I had noticed a difference in weed control between rye-grass and black-grass, but I thought it was due to the life-cycle of rye-grass. In fact, the problem was much worse, but it’s better to know what you are fighting against and understand what you can do with tools available.”

Overall, the results were not a big surprise to Mr Pearcy. He is well aware how reliant grass weed control has been on a limited number of actives in cereals. His clients are using cultural controls and varying the rotation, but winter cereals are still the dominant crop putting pressure on any actives.

To deal with the resistance situation, he now uses more prosulfocarb at pre-em because it is less affected by resistance. Flufenacet products like Liberator (flufenacet + diflufenican) still feature to control black-grass, brome, wild oats and susceptible rye-grass.

“Effective pre-emergence control relies on five things: seedbed quality, application technique, soil moisture, soil temperature, and the date seed breaks dormancy. Only two of those are under our control, for the other three we are relying on the season so pre-em chemistry is only part of the solution.”

Cultural controls are a vital part of Mr Pearcy’s weed control strategy, but these are not straightforward either. “Cultural controls against rye-grass are tougher than against black-grass. Late drilling and spring cropping are helpful, but you don’t see the huge benefit you get in black-grass situations.

Nevertheless, farmers are moving towards spring crops because there are limited options against both black-grass and ryegrass.”

Mr Pearcy doesn’t expect to require a Bayer resistance test again for rye-grass in Essex because he already understands the problem here. But if he sees similar issues in other regions, he would use a test to understand any resistance issues with individual actives to properly plan his control programme.