Which insects are devouring your cotton?

You can't rid your cotton fields of yield-robbing pests if you don't know which insects are helping themselves to your buffet line of green leaves, squares, blooms and bolls. That's the advice of Extension entomologists.

Knowing pest insect population levels at any given time in the growing season is the key to achieving the dual goals of avoiding excessive yield loss to insects and avoiding excessive control costs, according to Mississippi cotton insect management guidelines.

That means growers must scout their cotton fields every three to four days during the growing season in order to monitor the quickly evolving pest populations making a home in their cotton crop. Entomologists say obtaining accurate estimates of pest populations require time consuming sampling procedures because of the high egg-laying capacity and rapid development rate of most insects.

It is generally recommended that producers sample randomly chosen plants, keeping a running count of the number of plants examined and the number of insects found so that scouting results can be reported as percent infested plants.

“Because of the relatively high unit value of cotton, and the fact that many cotton insects feed directly on the fruit, the treatment thresholds for many pests are relatively low. Consequently, insecticide applications are often necessary to control pest populations in cotton,” states Mississippi's insect control guidelines.

According to state statistics, more than a dozen different species of insect pests attack the Delta's cotton crop each year, with each capable of causing economic yield loss to varying degrees.

In terms of estimated yield loss, Mississippi generally ranks the budworm/bollworm, tarnished plant bug, stinkbug, thrips, cotton aphid and fall armyworm among the most damaging cotton insects affecting the state's crop. Historically, the boll weevil has ranked among the top most damaging pests, but it has fallen off the charts in recent years due to the boll weevil eradication program.

In 2002, the budworm/bollworm complex ranked as the state's most damaging insect, followed by the plant bug and then thrips.

The tarnished plant bug is considered to be a key pest of Mississippi cotton because the early season treatments that are often necessary to control plant bugs destroy beneficial insects and thus increase the potential for outbreaks of pests such as aphids and tobacco budworms, the cotton insect guidelines state.

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