Low-input management of weeds in vegetable fields

Abstract

Field trials were conducted at the University of California's Five Points and Davis Research Farms in 1988-89 to evaluate the effects of weed removal by hand hoeing 0-10 weeks after crop emergence (WACE) in cucumbers cv. Perfecto Verde 14, bell peppers [Capsicum spp.] cv. Jupiter, cauliflowers cv. White Cloud and lettuces cv. Fame (Empire type) and cv. Coolguard. Weed seeds were broadcast into the soil prior to crop sowing, redroot pigweed [Amaranthus retroflexus], barnyardgrass [Echinochloa crus-galli], black nightshade [Solanum nigrum], common purslane [Portulaca oleracea] and lambsquarters [Chenopodium spp.] in cucumbers and bell peppers, and annual bluegrass [Poa annua], chickweed [Stellaria/Cerastium spp.], London rocket [Sisymbrium irio] and shepherd's purse [Capsella bursa-pastoris] in cauliflowers and lettuces. The following herbicides were also applied at standard and half-standard rates: naptalam + bensulide in cucumbers, napropamide in bell peppers, DCPA [chlorthal-dimethyl] in cauliflowers and pronamide [propyzamide] in lettuces. Cucumbers yielded 99% of their control value (resulting from biweekly hand hoeing for the entire season) after treatment with 2 + 2 lb/acre naptalam + bensulide + hoeing at 3 WACE, whereas weed-free periods of _6 weeks reduced bell pepper yields by _40%. Weed competition did not significantly affect yields of cauliflowers and lettuces (unless competition was season-long), yields of 98 and 110% of control values resulting from the use of 6 lb DCPA and 1 lb pronamide + hoeing at 6 WACE in the resp. crops.