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Timothy Mites Active at this Time of Year

Posted: April 21, 2014

If your timothy looks drought stressed in April, get a magnifying glass out.

A little over 10 years ago, hay growers in south central PA began noticing drought like symptoms in their timothy fields; upon further examination, a very small pest, the Cereal Rust Mite Abacarus hystrix (Nalepa) was identified. Since that time, this cool-season pest has caused headaches for many growers, particularly in southeastern Pennsylvania where it seems to have spread to the majority of fields, reducing growth and crop quality. To determine whether this pest is active in your timothy fields, scout fields for signs of damage. Look for leaf blades that are rolled up tightly, rather than leaf blades that are flat and normally expanded. The feeding of the mites causes leaves to roll up, presumably to provide the mites with better protection and microclimate. The mites are microscopic and challenging to see even with good magnification.

Treatment is recommended if 25% of tillers show the leaf curling within several weeks of green-up. Chemical options are limited, but Sevin XLR has a supplemental label allowing its use against mites on timothy in PA. Applicators need to use high pressure to force the material into the leaf rolls. See Penn State’s fact sheet for more details.

Contact Information

John Tooker
  • Extension Specialist
Phone: 814-865-7082