ABSTRACT

Applications of Command and insecticide safeners continues to be of interest among cotton producers in velvetleaf-infested areas. Many producers prefer Temik insecticide, which does not safen cotton from Command injury, over the organophosphate insecticides such as Disyston and Thimet which provides adequate safening. The objective of this study was to determine if reduced Disyston rates could be combined with Temik to provide the desired level of safening.

In 1992 a split-plot experiment was conducted on a Tiptonville fine sandy loam with 1.7% organic matter and pH of 6. 0.In-furrow insecticide treatments (main plots) were:Temik at 0.50 lb ai/A plus 0, 0.25, 0.5 and 0.75 lb ai/A of Disyston; Disyston, alone, at 0.75 lb ai/A; and a no-insecticide check. Preemergence (PRE) herbicide treatments (sub plots) were: Cotoran at 1.2 lb ai/A plus 0, 0.25, 0.5, 0.75 and 1.0 lb ai/A of Command; Command at 0.75 lb ai/A alone; Zorial at 0.75 lb ai/A preplant incorporated (PPI) followed by Cotoran plus Zorial, PRE at 1.2 and 0.75 lb ai/A, respectively; and a no-herbicide check. All treatments included Treflan at 0.75 lb ai/A, PPI; Terraclor and Ridomil at 1.0 and 0.094 lb ai/A in-furrow, respectively. Cotton 'Deltapine 54151 was planted and treatments were applied on June 2. A 1.35 inch rainfall occurred the next day. Weed control and crop injury were rated 4, 7 and 11 weeks after planting. Stand counts were taken 32 days after emergence and seed cotton yield was determined at maturity.

Cotton injury from command at 1.0 lb ai/A plus Cotoran was not greater than 20% across all insecticide treatments that received Disyston at all rating times. Cotton injury from Command was significantly higher with unsafened insecticide treatments. All rates of Command plus Cotoran caused no significant reductions in plant stands or yield when applied to plots receiving Disyston alone or any combination of Temik plus Disyston. In unsafened insecticide treatments, Command at rates of 0.5 lb ai/A and higher caused significant reductions in plant stands and seed-cotton yields. There were no significant differences in plant stands or yield among insecticide treatments with the split application of Zorial plus Cotoran. Seed cotton yields increased as the Disyston rate increased in the Temik plus Disyston combinations within any herbicide treatment. Weed control was lower with Command alone at 0.75 lb ai/A as compared to the Command plus Cotoran combinations. There were significant weed control differences among insecticide treatments, but they were not consistent across herbicide treatments.

All reduced rates of Disyston in combination with Temik provided adequate safening of cotton to Command. Seed cotton yields were highest with Temik plus Disyston at 0.5plus 0.75 lb ai/A, respectively.