Friday, August 23, 2019

Managing cotton aphids

Cotton aphids have been more common than normal this season in the Southern High Plains region. Aphids are present in more or less numbers in almost every cotton field. They are often found on the underside of leaves or feeding on the plant terminals. In several fields, aphid infestation is evident with the accumulation of honeydew causing the appearance of sticky and shiny leaf surfaces. I know of a few spots where aphid treatments were necessary. For the most part, however, aphid numbers remain well below economically damaging levels. Beneficial insects (e.g. lady beetles, green lacewing, etc.) are ubiquitous and are working their magic to keep aphid population growth in check. Fields that are treated with broad-spectrum insecticides earlier in the season may not have enough beneficials and will have to be monitored closely for potential aphid outbreaks.  

I would not suggest aphid treatment unless aphids are very numerous, and honeydew is accumulating. Give the beneficials and natural control (rain, aphid fungus, etc.) a chance before the treatment decision is made. Having said that, given the current hot and dry conditions, I wouldn’t let too many aphids suck the juice out of plants that are already under stress either. The action threshold is 40-70 aphids per leaf prior to first cracked boll. Late in the growing season and once open bolls are in the field, honeydew can accumulate on the lint of the open bolls. Even under low infestation levels, cotton aphids can excrete enough honeydew to contaminate the lint, causing “sticky cotton”. The threshold drops down to 10 aphids per leaf after the first cracked boll.

Suggested insecticides are listed in the “2019 Insect and Mite Pests Control Suggestions for Cotton" https://lubbock.tamu.edu/files/2019/08/2019-Cotton-Insect-Control-Suggestions_ENTO090.pdf

For detailed information, checkout our Cotton Aphid fact sheet: https://agrilifecdn.tamu.edu/lubbock/files/2017/07/Cotton-aphid_ENTO074.pdf
Cotton aphids

Cotton aphid colony on the plant terminal

Lady beetle larva

Leaf curling resulted from aphid feeding