Development and utilization of dicamba-, glufosinate-, and 2,4-D-resistant crop cultivars will potentially have a significant influence on weed management in the southern United States. However, off-site movement to adjacent nontolerant crops and other plants is a concern in many areas of eastern North Carolina and other portions of the southeastern United States, especially where sensitive crops are grown. Cotton, peanut, and soybean are not resistant to these herbicides, will most likely be grown in proximity, and applicators will need to consider potential adverse effects on nonresistant crops when these herbicides are used. Research was conducted with rates of glufosinate, dicamba, and 2,4-D designed to simulate drift on cotton, peanut, and soybean to determine effects on yield and quality and to test correlations of visual estimates of percent injury with crop yield and a range of growth and quality parameters. Experiments were conducted in North Carolina near Lewiston-Woodville and Rocky Mount during 2009 and 2010. Cotton and peanut (Lewiston-Woodville and Rocky Mount) and soybean (two separate fields [Rocky Mount] during each year were treated with dicamba and the amine formulation of 2,4-D at 1/2, 1/8, 1/32, 1/128, and 1/512 the manufacturer's suggested use rate of 280 g ai ha−1and 540 g ai ha−1, respectively. Glufosinate was applied at rates equivalent to 1/2, 1/4, 1/8, 1/16, and 1/32 the manufacturer's suggested use rate of 604 g ai ha−1. A wide range of visible injury was noted at both 1 and 2 wk after treatment (WAT) for all crops. Crop yield was reduced for most crops when herbicides were applied at the highest rate. Although correlations of injury 1 and 2 WAT with yield were significant (P ≤ 0.05), coefficients ranged from −0.25 to −0.50, −0.36 to −0.62, and −0.40 to −0.67 for injury 1 WAT vs. yield for cotton, peanut, and soybean, respectively. These respective crops had ranges of correlations of −0.17 to −0.43, −0.34 to −0.64, and −0.41 to −0.60 for injury 2 WAT. Results from these experiments will be used to emphasize the need for diligence in application of these herbicides in proximity to crops that are susceptible as well as the need to clean sprayers completely before spraying sensitive crops.

Utilization of glufosinate resistant corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] is becoming increasingly important in weed management strategies, especially where glyphosate resistance is a major problem. However, glufosinate drift to adjacent non‐tolerant crops and direct application to sensitive crops are concerns. Research was conducted to determine peanut (Arachis hypogaea L.) yield response to glufosinate applied at rates ranging from 0.015 to 0.48 lb ai/acre when peanut was 4 to 6 inches in diameter. Visible injury increased and pod yield decreased relative to non‐treated peanut when glufosinate was applied at approximately 0.08 lb/acre (approximately one sixth the manufacturer's suggested use rate for most crops). Cubic functions were significant when plotting visible injury and percent reduction in pod yield versus glufosinate rate, and visible injury and pod yield were negatively correlated (P < 0.0001, r2 = −0.845). These results suggest that early season visible injury three weeks after application is a relatively good predictor of yield loss when glufosinate injury occurs in peanut.

Glufosinate is a broad‐spectrum, contact herbicide that is currently applied to genetically engineered row crops that tolerate exposure to the compound. Flue‐cured tobacco (Nicotiana tabacum L.) is susceptible to glufosinate, yet it is commonly grown in close proximity to tolerant crops in North Carolina. The impact of glufosinate drift on flue‐cured tobacco is not known. Research was conducted in North Carolina to test the effects of sublethal rates of glufosinate (0.270, 0.135, 0.067, 0.034, 0.017 lb a.i. acre–1) on flue‐cured tobacco injury, yield, visual quality, financial value, and leaf chemistry. Simulated drift was imposed approximately 5 wk after transplanting. Visual injury increased with exposure rate and ranged from 15 to 83% and from 10 to 83% 1 and 2 wk after treatment, respectively. Cured leaf yield was reduced by 45% at the highest sublethal exposure rate and exhibited a linear decline of 47 lb acre–1 for every 0.01 lb glufosinate acre–1. Visual quality and per acre financial value were not affected by glufosinate, most likely due to the loss of necrotic tissue and late‐season plant growth compensation. Residues of glufosinate in green and cured leaves were likewise not detected. Producers and commercial applicators should exercise caution when applying glufosinate around flue‐cured tobacco because of the injury and yield loss that can result from physical spray drift, as well as the inability to sell tobacco that has been exposed to a pesticide that is not labeled for application.