Several field experiments were conducted at the Northeast Research Station near St. Joseph in 1988-89 and 1989-1990 to evaluate various options for control of annual weeds that emerge in late fall and winter in fallow bed cotton production. One experiment evaluated the safety of preplant treatments of 2,4-D low volatile ester (LVE) at various treatment-to-planting intervals. Other experiments evaluated fall residual herbicide treatments and treatments applied in the spring to established weeds. These experiments were repeated on the same plots in the second year of study. Other experiments concentrated on control of specific weeds.

Treflan 1.5 lb/A preplant incorporated (PPI) provided excellent control of henbit, shepherdspurse and annual bluegrass, but little control of sibara. Zorial 1.2 lb/A PPI provided satisfactory control of sibara, shepherdspurse and annual bluegrass, but little control of henbit. Treflan + Zorial (1.5 + 1.2 lb/A) PPI and Goal 0.3 lb/A preplant surface applied provided excellent control of each of these species. Carolina geranium and cutleaf evening primrose populations increased in Treflan and Zorial treatments during the second year of study, but not in treatments containing Goal.

Excellent control measures for establishment henbit, sibara, shepherdspurse, and annual bluegrass were found in evaluations of spring treatments. These included early February application of Goal + Roundup (0.2 + 0.5 lb/A) and Gaol + Gramoxone (0.2 + 0.4 lb/A), sequential treatments of 2,4-D LVE 1.0 1.0 lb/A in early February followed by (fb) Roundup in late march and re-bedding in early February fb re-bedding in late march, and late March applications of Goal + Roundup (0.2 + 0.5 lb/A), Goal + Gramoxone (0.2 + 0.4 lb/A), and Gramoxone 0.5 lb/A. Roundup 1.0 lb/A provided inconsistent control of henbit, but excellent control of other species.

Smartweed in the 3 to 4-leaf stage was controlled by Roundup 1.0 lb/A and Gramoxone 0.5 lb/A or Gramoxone 0.63 lb/A + cototan, Bladex, or Caparol 0.5 lb/A all achieved approximately 90% control of cutleaf evening primrose. 2,4-D LVE 1.0 lb/A applied 60 days preplant did not injure cotton and was highly effective on primrose.