DPX-T9595 is a new sulfonylurea herbicide candidate from Du Pont for selective over-the-top broadleaf weed control in cotton (Gossypium spp.). T9595 controls troublesome weeds such as cocklebur (Xanthium pennsylvanicum), pitted morningglory (Ipomoea lacunosa), ivyleaf morningglory (Iponoea hederacea), entireleaf morningglory (Ipomoea hederacea var. Integriuscula), smallflower morningglory (Jacquemontia tamnifolia), sharppod morningglory (Ipomoea richocarpa), hemp sesbania (Sesbania exaltata), redroot pigweed (Amaranthus retroflexus), spotted spurge ( Euphorbia emaculata), and ragweed (Ambrosia artemisiifolia) and suppresses or controls sicklepod (Cassia obtusifolia), Russian thistle (Salsola kali var. tenuifolia), velvetleaf (Abutilon theophrasti), and silverleaf nightshade (Solanum elaeagnifolium) at 1/16 to 1/8 ounces active ingredient per acre. The compound is formulated as a 25 per cent dry flowable for ease in handling and rapid dissolution in the spray tank.

Herbicidal performance is best when T9595 is applied with nonionic surfactant to actively growing weeds in the cotyledon to five leaf stage. The herbicide typically shows a safety factor of two to four times the rate required for broadleaf weed control when applied to actively growing cotton at or beyond the three to five true leaf growth stage.

T9595 is selective because cotton metabolizes the herbicide to an inactive compound; whereas, susceptible weeds do not. Immature cotton leaves do not metabolize T9595 as well as mature cotton leaves and may show transient chlorosis or growth retardation shortly after herbicide application. Mature cotton leaves and new cotton leaves formed after application of T9595 show little or no injury response. The more rapid metabolism of T9595 in mature leaves explains in part why field studies show that older cotton shows a wider safety margin than younger cotton.

Consistent with other sulfonylurea herbicides, T9595 inhibits the formation of the essential amino acids, isoleucine, leucine, and valine, by inhibiting acetolactate synthase, a key enzyme for biosynthesis. Once T9595 reaches the target site in a susceptible plant, cell division and plant growth immediately cease. The stunted plant slowly exhibits chlorosis followed by necrosis and subsequent death. One to two weeks may elapse before full herbicidal effects are apparent.

Toxicological results with T9595 are very favorable will acute lethal doses of 11,000 mg/kg for rats and 7,600 mg/kg for mice. Sub-acute feeding studies are also favorable with no gross effects observed at doses up to 2,200 mg/kg/day in the diet for rats and 1,520 mg/kg/day for mice.

T9595 will be widely tested in 1988 to better define weed control spectrum, margin of crop safety, and rotational crop considerations. These critical issues must be resolved before T9595 can be developed into a product.