This past week I have come across several unusual insects and plant injury in cotton fields of the Mid-Coast. This terminal death was first noticed on several cotton plants in one of our field trials. The terminal of 8 plants with in 3-4 feet of row were dead. Some of the branches on these plants were also wilted. No apparent disease symptoms were found on the leaves. The stems broke easily at the lowest part of the plant showing injury but the stem below looked healthy so I don’t think this is a vascular disease.
We also found a few plants in an adjacent field showing similar symptoms.
I consulted several other entomologists who suggested this was caused by a bug similar to the three-cornered alfalfa hopper. Possibly a leafhopper or sharpshooter.
Upon sampling the field with a sweep net, one leafhopper was found in 10 sweeps but it escaped before I could get it in a vial. I found a picture of a similar insect in my collection of my pictures from several years ago.
Fortunately, I could only find about 20 plants with dead terminals or branches in the two fields. So, although an insect causing terminal death is a scary think to have in our cotton fields, this is only occurring on a very small number of plants in a field and is not an economic problem.
In another field, I noticed a small butterfly visiting cotton blooms. This was the Gray Hairstreak. The larvae of this hairstreak is the cotton square borer. The cotton square borer is a small green caterpillar having a velvety appearance. This caterpillar will feed on cotton squares but is rarely found to cause economic damage.