Submitted to: Crop Protection Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 1997
Publication Date: N/A
Interpretive Summary: Studies were conducted to assess potential for utilizing metolachlor herbicide to reduce the losses caused by weeds in direct-seeded collard and kale. The relatively slow early growth of the small-seeded crops makes them particularly sensitive to early weed competition when direct-seeded. Metolachlor herbicide controls many of the weed species common in collard, and research required to register metolachlor for cole crops is currently being conducted by the IR-4 project. Most cultivars were sufficiently tolerant to allow safe use of the herbicide, but metolachlor at normal use rates reduced the yields of the most susceptible cultivars. Cole crop cultivars should be tested for metolachlor tolerance in order to avoid the crop losses that could result from using the herbicide on a susceptible cultivar. Metolachlor can facilitate direct-seeded production which would save growers up to $300 per acre in direct costs when compared to producing the crops from transplants. It also provides weed control in no-till and ridge tillage systems and allows cole crop growers to utilize these soil conservation tactics.
Technical Abstract: To assess the feasibility of using preemergence application of metolachlor for weed control in direct-seeded collard and kale, responses of eight collard and three kale cultivars were evaluated in greenhouse and field experiments. The lower rates, 0.75 and 1.5 kg ha-1 caused significant injury and reduced seedling weights in the greenhouse and field; however, yields were reduced in the field at rates of 3.0 and 6.0 kg ha-1 only when seedling injury and seedling weight reduction were severe. There were differences between cultivars in injury ratings and plant weights in the greenhouse and field. Shoot weights of the most tolerant cultivar, Flash were not reduced at metolachlor rates that reduced the weights of the least tolerant cultivar, Georgia. These studies indicate that metolachlor at rates of 1.5 kg ha-1 or lower can be used safely for weed control in direct-seeded collard and kale if susceptible cultivars are avoided.