An evaluation of CGA-43089 to protect grain sorghum from alachlor and metolachlor injury

Field studies were conducted to determine: (1) if seed protectant CGA-43089 [α-(cyanomethoximino)-benzacetonitrile] will protect grain sorghum (Sorghum bicolor L. Moench.) from the phytotoxicity caused by alachlor [2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-l-methylethyl)acetamide] applied at different rates, and (2) the susceptibility of two grain sorghum cultivars to alachlor and metolachlor applied with and without the protectant.

The effects of CGA-43089 at two rates (0, and 1.25 g/kg of seed) and alachlor or metolachlor at four rates (0, 2.2, 3.4, and 4.5 kg/ha) on two grain sorghum cultivars (Funk G-251 and Funk G-623GBR) were studied in experiments conducted at the Main Experiment Station, Knoxville, the Ames Plantation Experiment Station, Grand Junction, and the Martin Experiment Station, Martin, during 1978. Parameters measured at each location were percent vigor reduction, plant population, panicle production, mature plant height, average grain sorghum panicle weight, and grain yield.

Early herbicide injury, as noted by vigor and stand reduction, was later expressed as reduced yields where nontreated seed were used. In general, the vigor reduction was less at 60 days after planting than at 30 days after planting. With CGA-43089 seed treatment, plant population, panicle production, and grain yield tended to be greater. The effect of seed treatment or herbicide application on plant height and average grain sorghum panicle weight was somewhat inconsistent.

Plants of cultivar Funk G-251 tended to be shorter than those of cultivar Funk G-623GBR across practically all treatments.

In general, cultivar Funk G-251, although nonbird resistant, appears to be better suited for production in Tennessee than cultivar Funk G-623GBR due to earlier maturity.