Annual field surveys and estimates have been made to determine losses in cotton production due to major weed species. for each weed, yields of weedy and weed-free cotton were calculated at four locations in each of two counties of the Texas High Plains.

Greater losses from weeds were documented by field surveys as compared to estimates in 1979 and 1980. Field survey losses were more closely related to estimated losses in 1981-1985. In 1983, 1984 and 1985, greater field survey losses were documented from johnsongrass and woollyleaf bursage as compared to estimated losses. Losses due to pigweed were less in the field survey. In 1985, cotton greatest losses of cotton in 1985 were caused by pigweed, silverleaf nightshade, johnsongrass and woollyleaf bursage. For all other species, estimates and field survey losses were closely related. The following table lists the estimated and surveyed yield percentage reductions for eleven important weed species.