A 16-yr Survey on Levels of Johnsongrass (Sorghum halepense) in Arkansas, Louisiana, and Mississippi

Abstract

A survey was conducted in Mississippi from 1976 and in Arkansas and Louisiana from 1977 through 1991 to determine annual variation of johnsongrass infestation in cotton and soybean fields. The survey route was 1534 km long. Levels of johnsongrass infestation were estimated in 752 ± 296 cotton fields and 884 ± 407 soybean fields in each year of the survey. The area of fields surveyed annually was 47 000 ± 21 000 ha of cotton and 52 000 ± 19 000 ha of soybeans. Johnsongrass was present in 55 to 90% of the cotton fields. The percent of cotton fields with johnsongrass was about the same in 1991 as in 1976–77. About 90% of the soybean fields in Mississippi and Louisiana had johnsongrass, but only 70 to 80% of soybeans fields in Arkansas had johnsongrass. Soybean fields with 1 to 5% levels of infestation increased slightly in Mississippi but remained about the same in Arkansas and Louisiana. Soybean fields with infestations of 6% or more slightly decreased in Arkansas and Louisiana but not in Mississippi. It was estimated that johnsongrass reduces the average annual value of harvested cotton $5.8 ± 1.9 million and soybeans $23.7 ± 0.6 million in the three states.