Cereal rust mite eggs have hatched and are feeding on timothy leaves across southeastern Pennsylvania, according to Penn State University agronomists. Also known as timothy mites, cereal rust mites are active only in early spring and are generally not a problem after first cutting. The agronomists say now is the time for timothy growers to check fields. Be sure to check whole fields, edges and the middle of fields. Look for purple or wrapped leaves, especially in fields with a history of timothy mite problems. Under magnification (20x), the mites look like white maggots laying in troughs between the leaf veins. The eggs are round and clear to white or reddish in color.

The mites feed on the surface cells of the leaves between the veins. This causes the leaves to curl, as if drought-stressed. This damage is said to be obvious in April when there is plenty of soil moisture and little transpiration is occurring. The mites can reduce yield by 30-100%. In addition, herbage has a brownish color that lowers timothy’s market value.

Penn State agronomists say Sevin XLR Plus is the only known and registered method of controlling cereal rust mites. It should be applied at 3 pints/acre with at least 20 gallons of water or UAN (25 gallons are better). The timing of the application is typically mid- to late April or three to four weeks after greenup on fields with a history of mites and/or when 25% of the plant tillers are beginning to curl.

Read more about cereal rust mites and cereal rust mite treatment in the Penn State Field Crop News at fcn.agronomy.psu.edu/2008/fcn0805.cfm, or read about cereal rust mites at www.ento.psu.edu/extension/factsheets/cerealrust.htm.