Evaluation of non-fumigant pesticides as methyl bromide alternatives for managing weeds in vegetables

Authors: GREY, T - University Of Georgia; Webster, Theodore

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 6/11/2015
Publication Date: 11/26/2015
Citation: Grey, T.L., Webster, T.M. 2015. Evaluation of non-fumigant pesticides as methyl bromide alternatives for managing weeds in vegetables. Book Chapter. In: Price, A., Kelton, J., editors. Herbicides, Agronomic Crops and Weed Biology. InTech. DOI:10.5772/61635.

Interpretive Summary: With the elimination of methyl bromide as a weed management component in high-value vegetable crop production, there has been the search for various potential replacements. While methyl bromide had efficacy against many types of pests (e.g. plant pathogens, arthropods, nematodes, and weeds), many of the alternatives focus on a narrower spectrum of pests. Nutsedges, both purple nutsedge and yellow nutsedge, are among the most difficult to control and widespread pests of vegetable production systems in the southern USA. The complexity and difficulty of managing nutsedge species in vegetable crops have increased with the elimination of methyl bromide. Successful management of nutsedge will require diligent control programs that combines low density polyethylene (LDPE) mulches and residual herbicides. Herbicides can be applied prior to crop planting, during the cropping season, and between spring and autumn crops, to minimize weed interference and extend the utility LDPE mulches beyond a single cropping season, which reduces costs. In the current study, combining multiple herbicides controlled purple nutsedge in bell pepper and cucumber LDPE mulch systems. However, variability in purple nutsedge control occurred. Spring and autumn applications to the soil prior to laying LDPE mulch did not reduce bell pepper growth, and bell pepper was tolerant of herbicide combinations not previously evaluated for use in this system. However, cucumber injury from s-metolachlor was not acceptable. To optimize this potential methyl bromide alternative, future research will need to further evaluate the causes for the observed variability in purple nutsedge control.

Technical Abstract: The phase out of methyl bromide challenged vegetable growers’ abilities to control weeds in low-density polyethylene (LDPE) mulch production systems. The herbicides halosulfuron, fomesafen, s-metolachlor, and clomazone are needed as part of the pesticide program in LDP vegetable production to control weeds, including Cyperus species. Experiments were conducted during the spring and autumn of 2012, evaluating Cyperus rotundus (purple nutsedge), bell pepper, and cucumber response to these herbicides applied to soil immediately prior to laying LDPE. The herbicides applied under LDPE did not negatively affect crop density and growth of bell pepper in the spring or autumn, or cucumber in the spring trials. However, there was significantly less growth in the autumn experiment, with halosulfuron, s-metolachlor plus clomazone plus halosulfuron or fomesafen reduced vine length. Cyperus rotundus suppression and control were achieved with halosulfuron alone and when used in combination with of s-metolachlor plus clomazone both with and without fomesafen. These herbicides provided weed control that were comparable to methyl bromide plus chloropicrin. Using herbicides for control and suppression of Cyperus rotundus in combination with safety for bell pepper and cucumber will allow growers to implement new control strategies into their vegetable production systems.