Peanut Genotype Response to Interference from Common Cocklebur

Weeds can cause serious yield reductions in peanut ( Arachis hypogaea L.). Genetic differences have been found in several crop species for tolerance to weed competition, but no such findings have been reported for peanut. Field experiments were conducted in 1987 and 1989 near Gainesville, FL, to determine the effects of interference by common cocklebur ( Xanthium strumarium L.) on pod yields of four peanut genotypes (‘NC 7’, BL‐8, BL‐10, and F8143B). Effects on leaf and stem dry weight, leaf area, and node number also were measured. The genotypes were grown with and without common cocklebur interference. The entire section of peanut row on either side of the cocklebur plants was harvested at 45, 90, and 135 days after planting (DAP). Two increments were harvested separately, one 0 to 25 cm and the other 25 to 50 cm from the cocklebur plant. At 45 DAP, few differences were noted in response to cocklebur competition. At 90 DAP, weed competition reduced shoot dry weight, stem dry weight, leaf area, and node number for all genotypes except F8143B. By 135 DAP, measured vegetative traits were reduced for all genotypes in both years. Competition reduced vegetation of NC 7 more than the other genotypes, while F8143B was less affected. At distances of 0 to 25 cm from cocklebur, pod yields were reduced by 50% for NC 7, 30% for BL‐10, 26% for BL‐8, and 13% for F8143B. Cocklebur plants 25 to 50 cm from peanut had less effect on pod yields; F8143B was least affected and NC 7 most affected at this distance. This indicates there is potential for developing peanut cultivars with improved competitive ability against weeds. Such cultivars would be beneficial in situations where pesticide usage needs to be reduced.