Cereal Rust Mite in Timothy

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Cereal rust mites have piercing-sucking mouth parts and damage timothy by feeding on bulliform cells which play an important role in reducing water loss during drought stress. Cereal rust mite feeding injury on timothy results in stunted plants, often exhibiting signs of drought stress, even if there is adequate soil moisture. If your timothy is slow to “green-up” and appears stunted or leaf blades are curled, check for cereal rust mites by selecting a few random plants throughout the field and examining the leaf blade for mites and eggs. A 20X hand lens is recommended. There are no economic thresholds that have been established for cereal rust mites. However, treatment is recommended if a field has a previous history of rust mites and/or when 25% of the plant tillers exhibit curled tips on the new leaf blades within several weeks following green-up. The only approved and effective chemical control for cereal rust mite in grasses grown for hay is Sevin XLR Plus. Spray volume of at least 20-25 gallons per acres should be used.

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