The efficacy of preemergence (PRE) applications of ethalfluralin or pendimethalin incorporated with irrigation was compared with mechanical preplant incorporated (PPI) applications at equivalent rates in peanut. PRE applications of herbicides followed by irrigation were as effective as PPI applications in controlling Texas panicum, southern crabgrass, and crowfootgrass. Split PPI/PRE applications of ethalfluralin were more effective than PPI applications in controlling Texas panicum in 2 of 3 yr. Sequential postemergence applications of clethodim or sethoxydim increased the control of Texas panicum when ethalfluralin or pendimethalin controlled Texas panicum less than 82%. No differences in peanut yield were observed between PPI or PRE applications of either ethalfluralin or pendimethalin.

Field studies were conducted near Marianna, FL during 1999 and 2000 to evaluate weed control and peanut response to PPI treatments of diclosulam alone, PRE treatments of flumioxazin alone, and in systems with POST commercial standard herbicides. Diclosulam and flumioxazin alone did not control sicklepod. Paraquat plus bentazon plus 2,4-DB applied early POST fb chlorimuron plus 2,4-DB or imazapic controlled sicklepod and pitted morningglory at least 83%. These treatments were equal to or greater than diclosulam or flumioxazin with or without paraquat plus bentazon plus 2,4-DB, or the same system fb 2,4-DB mid POST. Peanut yield was similar when treated with diclosulam or flumioxazin fb the standard early POST (EPOST) system, flumioxazin alone, or imazapic alone. Peanut treated with diclosulam alone or paraquat plus bentazon plus 2,4-DB fb 2,4-DB yielded lower than other treatments because of late-emerging Florida beggarweed. Peanut treated with chlorimuron, regardless of which soil-applied herbicide was used, yielded less due to a longer period of interference from Florida beggarweed, sicklepod, and pitted morningglory because of the timing of chlorimuron application (60 d after planting).

Field studies were conducted from 2000 to 2002 to evaluate yellow nutsedge control and peanut yield when diclosulam and imazapic were applied at the rate recommended by the manufacturer (1×) and reduced (1/2×) rates in single and twin-row planting patterns. In 2001, both diclosulam and imazapic applied to the twin-row pattern at the full and reduced rate provided better yellow nutsedge control than herbicide applications to the single-row spacing. Because of excessive rainfall in 2002, yellow nutsedge control was considerably reduced with all treatments. Imazapic at the full rate (71 g/ha) controlled yellow nutsedge 80 to 96% in the twin-row pattern, and 79 to 86% in single-row spacings. Yellow nutsedge control was less than 65% when diclosulam and imazapic were applied at the reduced rate. The twin-row configuration yielded higher than the single-row pattern when averaged across herbicides in 1 yr. All herbicide treatments enhanced yield relative to the nontreated control, except the reduced rate of imazapic in 2002. This study revealed that to fully maximize yellow nutsedge control, the full rate of either imazapic or diclosulam should be applied to peanuts planted in a single or twin-row spacing. However, these treatments may not necessarily increase peanut yields.