Black Grass Bugs invade area

by Jim Keyes, USU Extension

Black Grass Bugs have already started making their appearance in San Juan County this spring. These small bugs are native to western rangelands, but can move into wheat fields planted nearby causing some damage.

Every spring the female of the species lays her eggs in native range grasses or in introduced wheatgrass varieties. The eggs overwinter in these host grasses.

In the spring the eggs hatch, and the bugs begin feeding on the leaves sucking the chlorophyll from the plants. Damaged vegetation appears straw-colored similar to frost bite.

Wheat plants are usually able to sustain quite a bit of black grass bug feeding without a loss in yield. The same goes for native and planted range grasses.

There are a couple of ways to control these invaders. The first is by grazing or burning the host grasses in the fall, and thereby removing the eggs that have been laid.

Insecticides can be used, but it takes a very sharp pencil to determine whether or not a control program will be economical. Wheat that is stressed by moisture, fertility or other pests will be affected more severely.

If a control program is warranted, one well timed application of insecticide may reduce bug numbers to a non-economic level for many years. If control is successful, the insecticide cost is spread over several years. Malathion or Seven are insecticides labeled for black grass bug control on rangeland and grass seed production.

For more information, contact the San Juan County Extension Office.