The Enid News and Eagle, Enid, OK

March 30, 2013

Insect issues showing up in wheat crop

By Roger Don Gribble
Enid News and Eagle

ENID, Okla. — While my NCAA basketball bracket has gone up in smoke with the likes of Florida Gulf Coast University and Wichita State University moving into the Sweet 16, it does allow for more time to focus on wheat fields in northwest Oklahoma.

Recently, I got to see the first brown wheat mites of the year. While some producers might be gazing at their brackets, these guys are feeding on wheat at a rapid pace in a year that we do not need any more surprises.

These mites are small, about the size of a period that you see at the end of my sentence. They are a metallic black to brown in color and have four pairs of yellowish legs. You might note the legs at the front of this insect are just slightly longer than the back three pairs of legs, giving the insect a slightly raised appearance.

The biggest problem I am seeing right now is that brown wheat mites can complete a life cycle in as little as 10 to 14 days in this area. Cooler weather means they will have just a little longer life cycle here. Bad news is in northwest Oklahoma, we might see as many as three generations of these insect pests.

Brown wheat mites are dry weather pests of wheat. They will cause problems in wheat that already is stressed by lack of moisture in this growing season. They feed on wheat by piercing plant cells in the leaf, creating a fine stripping in the leaf that will give the plant a grayish cast. As feeding continues, the wheat plant may turn a yellowish bronze color, wilt and then die.

I usually use a threshold of about 100 per feet of row as a treatment level. This count could be slightly higher where producers think they might have adequate moisture. This threshold might be lower if your wheat crop continues under drought stress.

Either way you choose, be sure and check your fields on a regular basis for these and other insects in wheat. I might also mention that brown wheat mites do not like rainfall. A really good rain might be the best control practice a producer could experience.

Greenbugs and bird cherry oat aphids also are being seen in wheat at this time, but at levels far below treatment thresholds. You can drop by your Oklahoma Cooperative Extension Service Office to pick up a copy of Current Report 7194, Management of Insect and Mite Pests in Small Grains. This report will describe the insect pests and some control options if treatment thresholds are met.

As your wheat crop pushes forward to harvest, I also might mention the latest news on the disease front. Bob Hunger is monitoring both leaf rust and stripe rust in Oklahoma. He has not found either of these in Oklahoma currently, but he is monitoring Texas and Arkansas, who are reporting a high level of both leaf and stripe rust.

Your OCES county ag educator will help you keep track of insect and disease pressures on the wheat crop in your area.

Gribble is Oklahoma Cooperative Extension Service northwest area agronomist.