Methyl Bromide (MBr) was widely used for controlling diseases, nematodes, and weeds in soil for tomato production in Florida since the late 1970’s. After it was banned due to the ozone-depleting effects, chemical and non-chemical soil management strategies have been explored as potential alternatives. Fomesafen has been reported as an effective herbicide for nutsedge and broadleaf weed control. So far, information on the fate of fomeafen with fumigated and organic-amended soil management strategies is not available. In this study, a modified QuEChERS - LC/MS-MS method was developed for exploring the fate of fomesafen in the soil of a tomato production system. Results showed the half-life (DT50) of fomesafen in the fumigated treatment was higher than in organic-amended soil. Overall, half-life values of fomesafen in the top 15 cm soil were higher than those reported in other studies. Dissipation rates for all treatments were positively correlated with organic matter content and redox potentials. Considering the fast dissipation rate and poor weed control results, fomesafen would not be recommended for weed control using the anaerobic soil disinfestation (ASD) technique utilizing composted poultry litter with molasses as the carbon source. Leaching of fomesafen was also observed in the 16-30 cm soil depth interval for all treatments. Considering that the soil was very sandy and the soil pH was higher than the p<i>K</i>a of fomesafen, fomesafen might leach deeper than 30 cm, especially for the fumigated treatment (combining fomesafen with a chemical fumigant).<br/>

Dissipation of fomesafen in fumigated and organic-amended soil in Florida tomato systems

2019 Fall National Meeting

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