Surveys of County Extension agents in cotton producing counties in Texas show the degree of herbicide use since 1973. Preplant incorporated herbicides have increased in use from 51.8 percent in 1973 to 85.1 percent of the acreage treated in 1987. Preemergence herbicide application has remained approximately the same over the years, at between 14.5 and 17.9 percent of the acreage.

Applications of postemergence herbicides decreased slightly from 1973 to 1987 (18.4% to 10.7%). When the overtop herbicides became available the acreage treated postemergence began to increase slightly.

Herbicide usage has influenced the weed spectrum in cotton. Johnsongrass and annual grasses have been reported less frequently on the survey in recent years due to the success of preplant and overtop herbicides. Devil's claw [Proboscidea lousianica (Mill.)], cocklebur (Xanthium pennsylvanicum Wallr.) and sunflower (Helianthus annus L.) have been reported by a larger number of counties in the past few years. Perennials such as field bindweed (Convolvulus arvensis L.), silverleaf nightshade (Solanum elaeaenifolium Cav.), nutsedges (CyRerus spp.) and Texas blueweed (Helianthus cilia@ D.C.) have remained stable, while woollyleaf bursage (Franseria tomentosa Gray) has increased. These broadleaved species and several others which occur in heavy but localized populations are not totally controlled by preplant plus preemergence herbicides.

Postemergence directed applications are needed in many areas of the state to economically control broadleaved weeds and nutsedges. Emphasis has been given to this method in educational meetings with growers in 1987 and 1988 and it will be continued next season.

A survey of Extension weed specialists in several southern states revealed that postemergence directed applications are being used in 99, 99, 90, 25 and 5 percent of the acreage in Arkansas, Louisiana, Mississippi, North Carolina and Tennessee, respectively. Overtop applications vary from year to year based on climate but in 1988 25, 15, 50, 37 and 14 percent of the acreage was sprayed in Arkansas, Louisiana, Mississippi, North Carolina and Tennessee, respectively.

The consensus opinion is that directed applications will be an important part of cotton weed control programs until such time that an overtop material that is active on broadleaved species is labeled.