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‘Tis the season for winter grain mites

Winter grain mites feed on small grains, ryegrass, and other hosts in the winter.  In Georgia, damage from these pests usually occurs between Thanksgiving and early January.  The mites thrive in cool temperatures.  The optimum temperature for development is between 44 and 55 degrees Fahrenheit (Herbert and Malone 2009).

Damage occurs most often in fall-planted small grains and ryegrass that have been over seeded into pastures and other perennial grass sod.  Damage looks like frost damage (silvery gray, leaf tips may turn brown).  It can apparently start in a patch then radiate out.  Plants may die or become severely stunted.  Risk factors include a prolonged drought period, non-rotated fields, sandy or lighter soils, and use of organic matter as a fertilizer.  Fall populations develop from eggs laid the previous spring.

The adults are black with red legs, about 1 mm in diameter. The mites are very active, and can be found feeding on the leaves, particularly the underside of the leaves.  When disturbed, the mites jump down to the ground. They are light and temperature sensitive.  Therefore, they are harder to find on the plants on a sunny day.  Scout for these insects on a cool cloudy day, or at dawn or dusk or at night using a flashlight.  When populations are large, the mites are easy to find in the thatch.  A sweep net can be used to scout for the mites when the temperature is between around 45 to 60 degrees Fahrenheit.

If significant feeding damage is discovered, an application of a pyrethroid insecticide may be needed.  Be sure to follow all directions on the pesticide label, and choose an insecticide that is labeled for the site. In the case of small grains over seeded in a grass pasture, the insecticide must be labeled for perennial grass forage as well as for small grains. If you have any questions, please contact the extension office at 706-468-6479.