ABSTRACT

Field experiments were conducted in 1992 at the Mississippi Agricultural and Forestry Experiment Station, Delta Branch Experiment Station (DBES) and the Southern Weed Science laboratory (SWSL), USDA-ARS both located at Stoneville, MS, to evaluate broadleaf weed control systems which included post-over-the-top (POT) applications of DPX-PE350 (Staple^R). Grass control was maintained using conventional herbicides. Experimental design was a randomized complete block with a factorial arrangement of treatments. Factors included a preemergence application of fluometuron (Cotoran^R, Meturon^R) plus norflurazon (Zorial^R) at 0.8 + 1.0 lb ai/A or no preemergence application and POT applications of Staple at either 0, 0.75, or 1.0 oz ai/A. POT timings at the Delta Branch Experiment Station were made at weed stages of cotyledon to 1-leaf and 3- to 4-leaf. These treatments were compared to a standard weed control system consisting of a preemergence application of fluometuron plus norflurazon at 0.8 + 1.0 lb ai/A followed by an early post directed spray (E-PDS) of methazole (Probe^R) plus MSMA at 0.5 + 2.0 lb ai/A A nonionic surfactant was used at a rate of 0.25% v/v with all applications of Staple. At DBES, visual weed control ratings were taken 14 days after last treatment (DALT). Weed species evaluated were spotted spurge, (Egphorbia maculata L.), pitted morningglory (Ipomoea lacunosa L.), prickly sida (Sida spinosa L.), and common cocklebur (Xanthium strurnatium L.),

At DBES, spotted spurge control increased from 74% to 94% and prickly sida control increased from 81% to 89% with Staple at 1.0 oz ai/A when compared to the 0.75 oz ai/A. Control of pitted morningglory and common cocklebur were the same with both rates of Staple. A PRE application of fluometuron plus norflurazon followed by Staple at 1.0 oz ai/A applied at 3- to 4-leaf offered 92% common cocklebur control. This did not differ from the control standard of 87%. Fluometuron plus norflurazon followed by Staple at 1.0 oz ai/A applied at the 3- to 4-leaf stage resulted in 85% pitted morningglory control and was similar to the standard. Staple applied without the benefit of a PRE application resulted in 76% pitted morningglory control. There were no differences observed between treatments for control of prickly sida or spotted spurge with all systems providing greater than 94% control.

At the Southern Weed Science Laboratory, weed species evaluated were velvetleaf (Abutilon theophrasti Medik.), pigweed species (Amaranthus sp.), spurred anoda (Anoda cristata L.), entireleaf morningglory (Ipomoea hederacea var. integriscula Gray), and prickly sida, POT timings were made at weed stages of cracking (E-POT), 1- to 3-leaf (M-POT), and 4- to 7-leaf. Visual control ratings were taken 6 weeks after the last Staple application. A 1.0 oz ai/A rate of Staple was chosen to make comparisons between weed control system. Greatest control of velvetleaf (99%) was observed when Staple was applied M-POT following a preemergence application of fluometuron plus norflurazon. This differed form the control standard which offered 72% control. Greater than 98% control of pigweed species was obtained by all control systems evaluated. For control of spurred anoda, all systems containing Staple resulted in >98% control which was better than the standard (82%). Entireleaf morningglory control was 99% for both the E-POT and the M-POT applications when preceded by a standard PRE application. This differed from the control standard which resulted in 90% control. Pitted morningglory control was 98% for Staple applied M-POT with a PRE herbicide and 75% for the control standard. There was no difference in control of prickly sida when compared to the control standard. Staple applied E-POT with PRE application and Staple applied M-POT with a PRE application resulted in yields of 1749 and 1662 lb/A, respectively, and was higher than the control standard of 845 lb/A.