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Timothy mite is a cool-season pest that has caused headaches for many timothy growers, particularly in southeastern Pennsylvania, where it seems to have spread to the majority of fields, reducing growth and crop quality.

Extension entomologist John Tooker expects that with early-season warmth this year, populations will be active earlier than normal.

To determine whether this pest species is active in your timothy fields, scout fields for signs of damage and the mites’ presence.

Mite feeding causes leaf blades to roll up, presumably to provide the mites with better protection and microclimate. Look for leaf blades that are rolled up tightly, rather than leaf blades that are flat and normally expanded.

The mites are very small, so to see them you will need a good hand lens or other magnifying device. Pick rolled leaves from around the field and inspect them carefully; mites tend to occur in grooves between the leaf veins.

Treatment is recommended if 25% of tillers show the leaf curling within several weeks of green-up.

Chemical options are very limited, but Sevin XLR has a supplemental label in Pennsylvania allowing its use against mites on timothy.

Treatments need to use high pressure to force the material into the leaf rolls. See Penn State’s fact sheet for more details: bit.ly/PSUmite

Leon Ressler is a Penn State Extension educator in Lancaster County.

Leon Ressler is a Penn State Extension educator based in Lancaster County, Pennsylvania.

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