Highlights of 30 Years of Research on TPB in the Mississippi Delta

The tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois), is a mirid species indigenous to North America. It is extremely well adapted to its habitat in the mid-South, and can feed and reproduce on most plant species in the mid-South when they bloom or have developing fruit. TPB nymphs produce adults in diapause on weed hosts in response to decreasing day lengths during the fall (beginning in September). Diapausing adults can overwinter on weed hosts or in plant debris, and adults overwintering in plant debris break diapause during January using an internal clock. Diapausing adults on weed hosts can break diapause at any time (despite the diapause-maintaining day lengths) in response to a good food source (weed hosts) and warm temperatures. This allows them to become reproductive and increase the size of the overwintering generation or produce an earlier F1 generation. The pest status of the TPB has changed from that of a minor pest of cotton in the mid-South thirty years ago to being the main pest of cotton at the present time. This increase in pest status was partly due to several agricultural and technological changes. These changes included boll weevil, Anthonomous grandis (Boheman), eradication and the use of transgenic cotton to control lepidopterous pests. Both of these changes decreased insecticide use in cotton which allowed TPB to increase in number. A large increase in early soybean and maize acreage (which are both TPB reproductive hosts) with a corresponding decrease in cotton acreage over the past ten years also favored increased numbers of TPB in cotton. Most importantly, many TPB populations in the mid-South have insecticide resistance to carbamate, organophosphate, and pyrethroid insecticides used for their control. This has increased control costs to growers and decreased yields. Several non-insecticidal control measures have been researched in an effort to provide additional control of TPB. These include cultural control, parasitoids, nectariless cotton, and mycoinsecticides. Most of these control measures need additional research and development before they could be combined with insecticides in an integrated control program for TPB in cotton.