Use of activated charcoal to reduce injury to selected cucurbits by ethalfluralin or pendimethalin

The vining nature of cucurbit crops makes mechanical cultivation for weed control difficult. Most cucurbits are injured by many of the commonly used herbicides; therefore, very few are presently labeled for weed control. Activated charcoal has been shown to protect various crops from herbicide injury. Comparisons of ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)- 2,6-dinitro-4-(trifluoromethyl)benzenamine] and pendimethalin [N-(l-ethylpropyl)- 3,4-dimethyl-2,6-dinitrobenzenamine] using two activated charcoal treatments were made on cucumbers (Cucumis sativus L.), summer squash (Cucurbita pepo L.), cantaloupes (Cucumis melo L.) and watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] in 1980 and 1981 at three locations in Tennessee. Ethalfluralin and pendimethalin were applied preplant incorporated at rates of 0.8 and 1.7 kg/ha. Activated charcoal was applied in a 2.5 cm band at a rate of 280 kg/ha, or as a seed coat-ing. Data were collected on seedling stand, vigor reduction, weed con-trol and fruit yield. In these studies activated charcoal reduced herbicide phytotoxicity to seedlings in most cases, resulting in greater plant survival and subsequent higher yields. Cucumber, squash and watermelon cultivar trials were conducted in 1981. The chemical treatments were ethalfluralin applied at 1.4 kg/ha preemergence, and pendimethalin applied at 0.84 kg/ha preplant incorporated with no activated charcoal or an activated charcoal band applied at 280 kg/ha. Plants in ethalfluralin treated plots produced fruit yields as high as those from the weed-free checks. Activated charcoal banding was effective in reducing crop injury by pendimethalin. Six cucumber cultivars were grown on agar with several rates of pendimethalin or ethalfluralin. 'Sweet Slice' and '420 Green Pak' were the most sensitive, and 'Poinsett-76' and 'Ashley' were the most tol-erant to the herbicides.