Submitted to: Western Society of Weed Science Research Reports
Publication Type: Research Notes
Publication Acceptance Date: December 1, 2006
Publication Date: July 7, 2007
Citation: Boydston RA. 2007. Broadleaf weed control in lima beans. Western Society of Weed Science Research Reports. Pg. 36-37. Technical Abstract: Broadleaf weeds are particularly troublesome in lima beans due to the long growing season which extends beyond the period in which soil residual herbicides provide control. Weeds reduce yield and quality of lima beans, reduce harvest efficiency, and increase incidence of white mold. A study was conducted at Paterson, WA in 2006 to evaluate preemergence (PRE) and postemergence (POST) herbicide options for broadleaf weed control in lima beans. The trial was conducted on a Quincy sand, pH 6.8, 0.4% O.M. under center pivot sprinkler irrigation. Lima beans, var. ‘M15’ were planted May 26, 2006 in 22 inch rows. POST treatments were applied June 26, 2006 when lima beans had three trifoliate leaves and were 5 to 8 inches tall. All POST treatments followed s-metolachlor applied PRE at 1 lb ai/acre and included nonionic surfactant at 0.25% (v/v) spray solution. PRE treatments of dimethenamid-p at 0.66 lb ai/acre or s-metolachlor at 1.3 lb ai/acre did not injure lima beans appreciably. Both herbicides controlled black nightshade and pigweed 93% or more. Hairy nightshade and common lambsquarters control with dimethenamid-p or s-metolachlor ranged from 89 to 93% and escape weeds were enough to reduce lima bean yield in dimethenamid-p treated plots compared to weed free checks. Imazmox plus bentazon or bentazon alone applied POST gave excellent control of all broadleaf weeds with little or no injury to lima beans. Cloransulam-methyl controlled all broadleaf weeds 98% or more except common lambsquarters and did not injure lima beans. Fomesafen injured lima beans at all rates tested and stunted the beans season long. Fomesafen controlled black nightshade, hairy nightshade, and pigweed well, but control of common lambsquarters was only 87 to 91% at 4 WAT. Uncontrolled weeds in nontreated checks reduced lima bean yield by 95% compared to weed free checks and averaged only 0.12 ton/acre. Among POST herbicide treatments, lima bean yield was greatest and similar to weed free checks with imazamox plus bentazon or bentazon alone. Lima bean yield was slightly lower in plots treated with cloransulam-methyl, probably due to common lambsquarters escapes. Lima bean yield in plots treated with fomesafen was lowest and similar to that of nontreated weedy checks due to excessive herbicide injury and stunting.