Document Type

Insect, Pest and Disease Control - Cotton

Abstract

Prior to bloom, the primary hemipteran pest of cotton in the Mid-South is the tarnished plant bug (TPB). Cotton fleahopper and clouded plant bug are other hemipteran pests that are occasionally observed. These pests reduce yields by feeding on squares (flower buds), which often shed. Mid-sized or larger squares may not shed, but feeding injury is generally evident in the form of yellow staining on the surface of the square and damaged anthers in flowers (i.e., dirty blooms). Square loss can delay maturity and sometimes reduce yield. Delays in crop maturity, even when not causing yield loss, can increase mid-and late-season control costs for cotton arthropod pests. To compound the problem in the Mid-South, TPB has developed resistance to some insecticides. This has contributed to higher control costs and crop losses since 1995.

In contrast to mid-season populations of plant bugs, prebloom populations of tarnished plant bug are relatively sporadic in most areas. Considerable work has been done to determine the most efficient and accurate methods for sampling TPB and their damage during the prebloom stages of cotton plant development. Thus, agricultural pest managers are comfortable with TPB sampling procedures in prebloom cotton. Sweep-net samples and square retention counts are typically recommended at this time to determine the appropriate timing of insecticide applications. However, some pest managers have not been as comfortable with existing treatment thresholds for tarnished plant bugs in prebloom cotton. Consequently, TPB control recommendations sometimes include applications of insecticide to sub-threshold infestations, or preventative applications are made based on crop developmental stages or other criteria without regard to infestation levels.

In the Mid-Southern states, universities’ Extension recommendations for controlling TPB in prebloom cotton are similar. Most states recommend an insecticide application during the first two weeks of squaring if populations reach or exceed eight tarnished plant bugs per 100 sweeps using a 15-inch diameter sweep net. During the third week of squaring and until bloom, a threshold of 15 or 16 plant bugs per 100 sweeps is suggested. Monitoring square loss also is recommended with the intent of maintaining retention during the prebloom period at 80 percent or higher. Treating sub-threshold infestations of TPB is generally recommended if square retention is below 80 percent.

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