Brown wheat mite populations are high

If you're seeing tiny black specs on your drought-stressed wheat, it may be brown wheat mites.

Those black specs are actually mites
feeding on the plant tissue.

Brown wheat mites thrive during these currently dry conditions that we're seeing this March and can often be found on dryland wheat. The best time to scout for them is on clear, warm afternoons when they are actively feeding. If it is an especially windy day, it may be hard to see the mites as they will move to the base of the plant. They can also be found on the soil surface, sometimes dispersing from the plants when disturbed. Mites will pierce the plant cells when they feed, which causes a stippling appearance on the leaves. Feeding can cause yellowing of the plants, and heavy damage can cause plants to dry out and die.

Stippling of the leaf caused by brown wheat mite feeding.

Brown wheat mites are characterized by their long front legs, which are twice as long as their body. They're extremely small, approximately the size of a period at the end of this sentence. All mites are female, and can complete their life cycle from egg to adult in 10-14 days. In late April females will start to lay white eggs, signaling a natural decline in the population and meaning control is not necessary. 

Notice the reddish-brown mite in the center of the leaf.

There isn't a solid economic threshold for brown wheat mites, although it is estimated to be several hundred mites per row foot in the early spring. Miticides may not economically control this pest if we don't get a good rainfall and the crop is unable to respond to the treatment. If we get a rain of at least 1/3 inch, it will quickly reduce mite numbers. Turning on irrigation can also accomplish this. Management decisions should be based on the number of mites as well as the crop's ability to recover once mite numbers are lowered.

Wheat damaged by mite feeding and drought stress.