ABSTRACT

A field experiment was conducted on a Taloka silt loan soil at Fayetteville, AR, to compare efficacy of bromoxynil at 0.25, 0.38, 0.5, 0.75, 1.0, and 1.5 lb ai A^-1 when broadleaf weeds were in the 1- to 2-inch (early timing) , 3- to 5-inch (mid timing), and 6- to 8-inch (late timing) stages of growth. Weed species were planted in rows one foot apart and included entireleaf morningglory (Ipomoea hederacea var. integriuscula Gray), pitted morningglory (Ipomoea lacunosa L.), palmleaf morningglory (Ipomoea wrightii Gray), hemp sesbania (Sesbania exaltata (Raf.)Rybd. ex A.W. Hill], velvetleaf [Abutilon theophrasti (L.) Medicus], smooth pigweed (Amaranthus hybridus L.), prickly sida (Sida spinosa L.), jimsonweed (Datura stratnonium L.), and sicklepod (Cassia obtusifolia L.). Smooth pigweed, jimsonweed, and sicklepod were not present at the early timing. Treatments were applied in 10 gpa at 30 psi. The experimental design was a split plot with three replications. The lowest rate of bromoxynil needed to obtain approximately 85% control is provided.

Approximately 0.25 lb ai A^-1 of bromoxynil was necessary to provide 85% control of entireleaf morningglory, pitted morningglory, hemp sesbania, and velvetleaf when weeds were 1 to 2 inches tall. At this timing 0.5 lb ai A^-1 was required to control 85% of palmleaf morningglory. To control 85% of entireleaf morningglory, pitted morningglory, palmleaf morningglory, hemp sesbania, velvetleaf, prickly sida, and smooth pigweed required 1.5, 1.5, 0.75, 0.25, 0.75, 0.75, and 1.5 lb ai A^-1, respectively, of bromoxynil when applied to 3- to 5-inch weeds. Entire leaf morningglory, pitted morningglory, palmleaf morningglory, velvetleaf, smooth pigweed, and prickly sida required greater than 1.5 lb ai A^-1 of bromoxynil to obtain 85% control when applied to 6- to 8-inch weeds. Hemp sesbania was controlled 85% with 0.75 lb ai A^-1 at this growth stage. Sicklepod control was less than 20% regardless of the rate or timing of application.

DPX-PE350 at 0.1 lb ai A^-1 provided 85% control of entireleaf morningglory, pitted morningglory, palmleaf morningglory, velvetleaf, and hemp sesbania at the early timing. At the mid timing, DPX-PE350 provided 85% control of entireleaf morningglory, smooth pigweed, prickly sida, hemp sesbania, velvetleaf, and jimsonweed. At the late timing, DPX-PE350 provided 85% control of entireleaf morningglory, smooth pigweed, velvetleaf, hemp sesbania, and jimsonweed. Pitted morningglory and palmleaf morningglory were less susceptible to DPX-PE350 than entireleaf morningglory at both the mid and late timings.