Phytotoxicity of Delayed Applications of Flumioxazin on Peanut (Arachis hypogaea)

Abstract

Trials were conducted under weed-free conditions in 2001, 2002, and 2003 on a loamy sand soil in Georgia to investigate the phytotoxicity of flumioxazin on peanut, and in separate trials, the effects on peanut maturity. The first study evaluated time of flumioxazin application (0, 2, 4, 6, 8, and 10 d after planting [DAP]) and flumioxazin rate (nontreated, 71, and 105 g ai/ha). Peanut (variety ‘C99R’) were seeded 3.2 cm deep and irrigated immediately after seeding. Flumioxazin applied to peanut 6, 8, and 10 DAP significantly injured peanut (20 to 59%) early season, with more phytotoxicity from flumioxazin at 105 g/ha than 71 g/ha. However, peanut stand was not reduced by any of the times of application or rates. Peanut recovered by midseason, except in cases of severe (up to 49%) visual phytotoxic injury. Peanut yields were not affected by either flumioxazin application timing or rate. The second study (variety ‘Georgia Green’) evaluated flumioxazin applied at 105 g/ha at varying intervals after planting to determine the phytotoxic effects on peanut maturity using the hull-scrape method. Peanut maturity was delayed by flumioxazin when applied 1 d after planting and later. These results show that the optimum time of application is from immediately after planting to 2 d after planting, but ideally, the application should be made immediately after planting. The highest recommended flumioxazin rate, 105 g/ha, is not significantly phytotoxic when applied within the recommended range of timings and has no effect on yield. However, there is potential for yield loss as peanut maturity is delayed in cases of severe injury.