Timothy hay growers in New Jersey should begin scouting for cereal rust mites, says Bill Bamka, ag agent with Rutgers University Extension in Burlington County.

Bamka began receiving reports of the mites in hayfields in the southern part of the state early last week. He notes that cereal rust mites can reduce yields by 30-70% and can also discolor the hay, making it less marketable.

A Rutgers fact sheet advises growers to use a 20X hand lens to scout for eggs and juvenile mites. “Carefully inspect each leaf blade, paying particular attention to the areas in between the leaf veins,” the fact sheet reads. “Since mites migrate primarily by wind movement, repeated trips to each field are recommended before first cutting.”

It notes that there are no established economic threshholds for the pest. But treatment is recommended in fields with a previous history of cereal rust mites and/or when 25% of the plant tillers exhibit curled tips on the new leaf blades within several weeks after green-up. Treatment options in New Jersey include chemical control with Sevin XLR Plus and mechanical control via close mowing in late fall or early winter.

“While there is some evidence that close mowing in early spring may lower mite numbers by reducing the leaf area available for egg deposition, the practice could also reduce early season vigor,” the fact sheet warns.