Weed Management in No-Till Zucchini Squash

Abstract

Weed control in no-tillage (NT) zucchini squash (Cucurbita pepo L.) was determined for various preemergence (PRE) herbicide combinations in herbicide-killed ‘Wheeler’ winter rye (Secale cereale L.) or bare soil. Winter rye provided 65% and 75% control of redroot pigweed (Amaranthus retroflexus L.) and smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.], respectively, in the absence of herbicides compared with no control in the bare soil system. Tank mixing dimethenamid [2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)-acetamide], halosulfuron [methyl 3-chloro-5-(4,6-dimethoxy-2-pyrimidinylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate], or imazamox [2-(4,5-dihydro-4-methyl-4-(methylethyl)-5-oxo-1H-imidazol-2-yl)-5-(methoxy-methyl)-3-pyridine-carboxylic acid] with clomazone [2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone] and ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl) benzenamine] increased redroot pigweed control compared with clomazone and ethalfluralin alone, and the presence of winter rye did not affect redroot pigweed control from any herbicide treatment except the no herbicide control. Squash plants were injured by treatments containing halosulfuron regardless of winter rye residues. Clomazone and ethalfluralin + imazamox and clomazone and ethalfluralin + dimethenamid provided some minor stunting to squash plants early in the growing season. Marketable squash yields were influenced by herbicide but not cover crop, and halosulfuron alone and clomazone and ethalfluralin + halosulfuron resulted in lower marketable yields compared to most other herbicide combinations. However, clomazone and ethalfluralin + imazamox was the only herbicide combination with similar high yields as the weed-free control; early season squash injury caused by this herbicide combination did not result in yield reductions. The lack of season-long weed control using small grain cover crops and PRE herbicides in NT squash continues to be a major impediment to the widespread implementation for this type of production system.