Weed management programs utilizing genetically transformed cotton for tolerance to Roundup and subsequent utility in existing weed management programs provide options to: control weeds in conventional and reduced tillage; allow a wide window for effective application timing; economically control a broad spectrum of weeds; and control weeds in an environmentally sound manner.

Field studies were conducted in transgenic cotton (Gossypium hirsutum L.) in 1995 at Alexandria and St. Joseph, LA to compare Roundup (glyphosate) postemergence at 1 qt product/A (applied once or twice) to commercial treatments. Plots were four rows wide with the center two rows treated. Commercial standards were applied at labeled rates for soil types or weed sizes. Induce was added to Roundup mixtures at 0.5% v/v.

At Alexandria treatments were applied in 10 GPA. Soil conditions varied from wet to dry during the growing season. At this location Roundup was applied only once to Cotton that was 5 in at the 4 leaf stage alone or following Cotoran (fluometuron) preemergence, Treflan (trifluralin) preplant incorporated, or Cotoran plus Treflan. These treatments were compared with preemergence herbicides followed by the postemergence herbicide Staple (pyrithiobac) or postemergence directed herbicides at one and three applications. Roundup was applied to entireleaf morningglory (Ipomoea hederacea var. integriuscula Gray) that was 4 to 6 in with 4 to 6 leaves, hophornbeam copperleaf (Acalypha ostryifolia Riddell) 2 to 4 in with 2 to 4 leaves, and barnyardgrass [Echinochloa crus-galli (L.) Beauv.] 4 in with 4 leaves. Roundup was applied 3 wk following planting.