Buctril and Staple applied alone and as tank-mixture combinations

Field experiments were conducted in 1993 at the Cotton Branch Experiment Station (CBES), Marianna, AR and at the Southeast Branch Experiment Station (SEBES), Rohwer, AR to evaluate the efficacy of Buctril (bromoxynil) and Staple (DPX-PE350) applied alone and in all possible tank-mixture combinations. At both locations bromoxynil tolerant cotton was planted. All rates are expressed as lb ai/A. Buctril rates evaluated were 0.25, 0.5, and 1.5 lb/A. Staple rates were 0.015, 0.031, and 0.062 lb/A.

At CBES trifluralin at 0.75 lb/A was applied preplant incorporated (PPI) to all plots. Treatments were applied postemergence over-the-top of cotton as a broadcast spray. Entire test area was cultivated two times. Weed species and height at time of application were: pitted morningglory (Ipomoea lacunosa) 1 to 3 inches, prickly sida (Sida spinosa) 1 to 3 inches, velvetleaf (Abutilon theophrasti) 1 to 4 inches, smooth pigweed (Amaranthus hybridus) 2 to 4 inches. At 13 days after treatment (DAT) Buctril at 1.5 lb/A provided 95 to 100% control of these weeds. Staple at 0.062 lb/A provided 84 to 100% control of the same weeds. Staple at any rate provided excellent control of smooth pigweed. All tank-mixtures of Buctril + Staple provided greater than 80% control of these weeds except Buctril at 0.25 lb/A + Staple at 0.015 lb/A which gave 69% control of prickly sida. Seed cotton yield for plots only receiving trifluralin was 750 lb/A. Seed cotton yield for Buctril at 0.25 lb/A + Staple at 0.015 lb/A was 1977 lb/A. This treatment was not significantly different from the highest yielding treatment of Buctril 1.5 lb/A + Staple 0.062 lb/A which produced 2277 lb/A of seed cotton (LSD 0.05 = 348 lb/A). All other tank-mixtures produced yields within this range (1977 to 2277 lb/A) except for Buctril 0.5 lb/A + Staple 0.015 lb/A which produced a yield of 1871 lb/A.

At SEBES trifluralin at 0.5 lb/A was applied PPI to all plots. Treatments were applied postemergence over-the-top of cotton on a 16 inch band. These plots received one cultivation. At time of application weed species and heights were: entireleaf morningglory (Ipomoea hederacea var. integriuscula) and pitted morningglory 3 to 4 inches, prickly sida and prostrate spurge (Euphorbia humistrata) 2 to 3 inches. A 0.42 inch rainfall occurred approximately 2 hours after herbicide application. At 13 DAT Buctril at 1.5 lb/A provided 96% control of entireleaf and pitted morningglory, lower rates did not provide adequate morningglory control. All rates of Buctril provided ò 90% control of prostrate spurge. Staple at 0.062 lb/A provided 91% control of prostrate spurge. The tank-mixture of Buctril 0.5 lb/A + Staple 0.015 lb/A provided ò 83% control of weed species evaluated. By 41 DAT only Buctril at the full rate (1.5 lb/A) + Staple at any rate (0.015, 0.031, or 0.062 lb/A) gave 80 to 88% control of entireleaf and pitted morningglory, 76 to 81% control of prickly sida, and 90 to 94% control of prostrate spurge. All rates of Staple gave excellent smooth pigweed control.

Staple Preemergence followed by Buctril Postemergence

A field experiment was conducted at SEBES to evaluate Staple applied preemergence (PRE) followed by (fb) postemergence applications of Buctril. All herbicide rates are expressed as lb ai/A. Staple was applied as a broadcast spray at 0.015 and 0.031 lb/A. A standard herbicide treatment, Treflan 0.75 lb/A + Zorial 0.5 lb/A (PPI) fb Cotoran 0.8 lb/A PRE fb Cotoran 0.8 lb/A + MSMA 1.5 lb/A post-directed (PDS) 2 to 6 inch cotton fb Bladex 0.8 lb/A + MSMA 1.5 lb/A PDS 6 to 10 inch cotton, was included.

Buctril at 1.0 lb/A was applied at two timings following Staple PRE applications. The first Buctril application was to cotton 2 to 6 inches and weeds 1 to 4 inches in height. The second Buctril application was applied 18 days later when weeds were 1 to 3 inches in height. Because of the size of the cotton this application had to be applied as a post-directed spray to get adequate coverage of weeds. End of season control for Treflan at 0.75 lb/A PPI fb Buctril provided 90 to 91% control of entireleaf and pitted morningglory and prostrate spurge, 84% control of prickly sida but inadequate control of smooth pigweed. Staple PRE at either 0.015 or 0.031 lb/A fb Buctril provided > 90% control of weed species evaluated. The standard herbicide treatment provided 98 to 100% control of weed species evaluated except for prostrate spurge which was controlled 89%.

Seed cotton yield ranged from 2343 to 2678 lb/A for all treatments except the Treflan + Zorial PPI fb Cotoran PRE fb Cotoran + MSMA PDS fb Bladex + MSMA PDS treatment which yielded 1986 lb/A. This treatment, 31 days after the last herbicide application resulted in 18% visual injury while none of the other treatments showed injury symptoms.