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 mitesâ 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.