Crop sensitivity to isoxaflutole and enhancing the margin of selectivity

Isoxaflutole, a preemergence herbicide for use in corn, causes bleaching of plant tissue and plant death at low rates. A concern regarding widespread use of isoxaflutole is the unintentional exposure of high-value, minor acreage crops that may be sensitive. Isoxaflutole is absorbed by roots and foliage, and exhibits systemic activity. Isoxaflutole is converted to diketonitrile, the herbicidally active compound, following plant uptake. Michigan is not among the states in which isoxaflutole has obtained registration, due to potential exposure to sensitive, high-value, crops.; Nine minor acreage crops were evaluated for their sensitivity to preemergence applications of isoxaflutole and to foliar exposure from irrigation water. Dry bean were consistently among the most sensitive of the plants evaluated while onion was the least sensitive, regardless of the nature of exposure. Concentrations of isoxaflutole as low as 5 mug/l in 2.54 cm of irrigation water injured navy bean 20%, while onion was injured 20% by 194 mug/l in 2.54 cm of irrigation water. Isoxaflutole at 9 g/ha injured navy bean 20% at 14 DAT while isoxaflutole at 54 g/ha caused the same level of injury to onion. Black bean, navy bean, and sugarbeet were the most sensitive crops evaluated, (average I20 = 10 g/ha), alfalfa, cucumber and tomato exhibited a more moderate level of sensitivity (average I20 = 13 g/ha), and adzuki bean, carrot and onion were the least sensitive of the evaluated plants to isoxaflutole (average I20 = 36 g/ha). Isoxaflutole application rates are 75--140 g/ha in corn.; Studies were conducted to enhance the margin of selectivity including a series of studies to decrease the leaching of isoxaflutole and compare it with the leaching of the herbicide safeners furilazole and R-29148. Isoxaflutole leached to a depth of 26 cm following 6.25 cm of simulated precipitation. R-29148 was localized from 0 to 18 cm in the soil column and furilazole was primarily located between the depths of 0 and 8 cm. Since isoxaflutole was leaching more than the two safeners, polymer carriers were used to reduce leaching. Reformulation of the WDG formulation with either of two polymers reduced leaching compared to the commercially available formulations of isoxaflutole. Polymeric formulation B reduced leaching the most.; Herbicide safeners and water repellent adjuvants were evaluated for reducing postemergence injury from isoxaflutole. Water repellent adjuvants were evaluated for potential use with flumioxazin and pendimethalin. The water repellent DC 1-6184 reduced retention of all three herbicides on corn, cabbage, wheat, and tomato. The water repellents DC 2-1322 and DC 772 did not consistently reduce retention. DC 1-6184 reduced injury when herbicide applications were made to plant foliage only, no soil contact. The herbicide safeners furilazole and R-29148 decreased corn injury from preemergence isoxaflutole applications. However, the inclusion of those herbicide safeners increased injury when applications were made to corn at the two- and four-leaf growth stages. DC 1-6184 did not reduce isoxaflutole injury to corn when applied postemergence, unless a herbicide safener was also included.