by: Tom Royer, OSU Extension Entomologist
Our winter wheat has taken a beating this winter, with cold weather hanging on and some areas not getting that thirst quenching precipitation to help it get a great jump start this spring. In addition, I have received scattered reports of brown wheat mites showing up and causing problems. Producers need to remain alert so that their wheat is not suffering dual problems of dry growing conditions PLUS brown wheat mite.
Brown wheat mite is small (about the size of this period.) with a metallic brown to black body and 4 pair of yellowish legs. The forelegs are distinctly longer that the other three pair. Brown wheat mites can complete a cycle in as little as 10-14 days. They will undergo up to 3 generations each year, but have probably already completed at least one or two by now. Numbers will likely decline if a hard, driving rain occurs. Spring populations begin to decline in mid-late April when females begin to lay “diapause” eggs.
Brown wheat mite causes problems in wheat that is stressed from lack of moisture. They feed by piercing plant cells in the leaf, which results in “stippling”. As injury continues the plants become yellow, then dry out and die. These mites feed during the day, and the best time to scout for them is in mid-afternoon. They do not produce webbing and will quickly drop to the soil when disturbed. They are very susceptible to hard, driving rains, but until then they can cause yield loss when present in large numbers
Research suggests that a treatment threshold of 25-50 brown wheat mites per leaf in wheat that is 6-9 inches tall is economically warranted. An alternative estimation is “several hundred” per foot of row.
Check CR-7194, Management of Insect and Mite Pests in Small Grains for registered insecticides, application rates, and grazing/harvest waiting periods. It can be obtained from any County Extension Office, at www.wheat.okstate.edu, or by clicking here.