ABSTRACT

Interaction of Clomazone, Fluometuron, and Norflurazon with In-furrow Insecticides

Positive and negative interactions among in-furrow insecticides and herbicides used in cotton have been documented. These interactions include the safening effect of disulfoton (Di-Syston) and phorate (Thimet) with clomazone (Command) use, and the injury enhancement of these insecticides with diuron (Karmex, Direx) and possibly fluometuron use. With the increased interest in Command use by Arkansas cotton growers more information concerning these interactions is needed.

A test was established near Rohwer, Arkansas to evaluate cotton injury, thrips control, and yield with selected in-furrow insecticides and herbicide combinations. Three insecticides were used; 0.5 lb ai/A aldicarb (Temik) , 0.75 lb ai/A disulfoton, and 0.75 lb ai/A phorate applied in-furrow with four herbicide treatments; preemergence (PRE) applications of 0.8 lb ai/A fluometuron, 1.0 lb ai/A clomazone, 0.8 + 1.0 lb ai/A fluometuron + clomazone, and 0.75 ai/A norflurazon (Zorial) preplant incorporated (PPI) followed by 0.8 lb ai/A fluometuron. The test design was a split-plot with four replications.

There was no interaction effect on cotton injury among in-furrow insecticides and herbicides tested. The cotton treated with aldicarb and clomazone did not display expected severe injury. This may have been due to the low intensity but not the amount of activating rainfall after planting and herbicide application. Four days after planting and treatment 0.72 inches was received, and by 14 days 1.78 inches was received. There was a significant injury response among herbicide treatments. Averaged across insecticides, at 20 days after treatment, fluometuron + clomazone resulted in the greatest injury followed by clomazone, norflurazon PPI + fluometuron PRE, and fluometuron. By 46 days after treatment only fluometuron + clomazone resulted in greater injury compared to fluometuron alone. The effect of insecticide used on cotton injury was significant at only the 20 day after treatment rating date. Averaged across herbicides, aldicarb caused greater injury compared to disulfoton and phorate. Lack of thrips control with disulfoton and phorate may have confounded herbicide injury. At 24 days after planting phorate rated 7 and disulfoton rated 6 on a 1 - 10 scale of thrips damage. Aldicarb rated 2. None of the aforementioned effects resulted in significant yield differences. This may have been due to the effects of thrips damage and possibly the low yields, 2700 lbs (seed cotton) average per acre.

Interaction of Propanil and In-furrow Insecticides

Cotton and rice are often grown in neighboring fields in Arkansas. Propanil drift to cotton is therefore a concern. Propanil is considered a contact herbicide with little soil activity. Proper propanil application precautions are sometimes overlooked when applied near cotton prior to emergence.

A test was established near Rohwer, Arkansas to evaluate cotton injury with 0.5 lb ai/A aldicarb (Temik) and disulfoton (Di-Syston) used in-furrow, and propanil applied preemergence and postemergence at full (4.0 lb ai/A) and drift rates (0.4 and 0.04 lb ai/A). The test design was a split-split-plot design with four replications. Within two days of planting 0.30 inches of rain was received. Propanil was applied preemergence three days after planting. Postemergence propanil treatments were applied to cotton with the first true leaf expanding.

There was a significant three way interaction among insecticides, method of propanil application, and propanil rate. At 14 days after treatment, propanil applied preemergence caused injury at only 4.0 lb ai/A. Injury was not observed until just prior to the 14 day rating date soon after 0.72 inches of rain. Aldicarb treated cotton displayed more injury than disulfoton 73 versus 48%. This difference was also noted in plant height, maturity, and yield. At 14 days after treatment propanil applied postemergence caused injury at all rates evaluated with no effect from insecticide treatment. This response was also noted in plant height and yield.