Dissipation of fomesafen in fumigated, anaerobic soil disinfestation-treated, and organic-amended soil in Florida tomato production systems

Authors: LI, ZHOUNA - University Of Florida; DI GIOIA, FRANCESCO - Pennsylvania State University; HWANG, JEONG-IN - University Of Florida; Hong, Jason; OZORES-HAMPTON, MONICA - University Of Florida; ZHAO, XIN - University Of Florida; Pisani, Cristina; Rosskopf, Erin; WILSON, PATRICK - University Of Florida

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2019
Publication Date: 8/27/2019
Citation: Li, Z., Di Gioia, F., Hwang, J., Hong, J.C., Ozores-Hampton, M., Zhao, X., Pisani, C., Rosskopf, E.N., Wilson, P.C. 2019. Dissipation of fomesafen in fumigated, anaerobic soil disinfestation-treated, and organic-amended soil in Florida tomato production systems. Pest Management Science. 10.1002/ps.5558.
DOI: https://doi.org/10.1002/ps.5558

Interpretive Summary: New management strategies for soilborne pests are in development as a result of the loss of the soil fumigant methyl bromide. Alternative fumigants and systems that involve the application of organic amendments may require coupling with herbicides to improve weed control, particularly in locations in which nutsedge is a significant problem. In Florida, one alternative to fumigation is the use of anaerobic soil disinfestation (ASD) in which composted poultry litter and molasses are applied to raised beds and soil is saturated to achieve anaerobic conditions for a short period of time. A field trial was conducted in which ASD was compared to the a commercial organic amendment system, Soil Symphony (SSA), and an application of composted yard waste (CYW). These applications of organic amendments were compared to soil fumigation using the a combination of chloropicrin and 1,3-dichloropropene (CSF). The herbicide fomesafen was included as an addition to each treatment. CSF resulted in the longest and greatest herbicide retention and ASD resulted in the shortest. Results correlate the level of anaerobicity as well as the organic matter content with the degradation of the herbicide. Herbicides that are not impacted by anaerobic conditions and high organic matter will need to be tested for compatibility with ASD.

Technical Abstract: Fumigated and organic-amended soil management strategies have been investigated as potential methyl bromide (MBr) alternatives for controlling diseases, nematodes, and weeds in soil. Nutsedge and broadleaf weed control using fomesafen has been reported to be comparable to MBr. Information on the fate of fomesafen using these alternative practices do not exist. A modified QuEChERS method coupled with LC/MS-MS was developed for investigating the dissipation of fomesafen. Results indicated the DT50 values for fomesafen in the top 15 cm soil in this study were generally higher than those reported in previous studies performed at different locations. For three treatments using organic amendments, reductions in concentrations were positively correlated with lower redox potentials and organic matter content. Due to increased losses of the herbicide and subsequent reduction in weed control, fomesafen would not be recommended for weed control using anaerobic soil disinfestation (ASD) technique, which utilizes composted poultry litter with molasses as the carbon source. Fomesafen combined with composted yard waste and Soil Symphony Amendment (SSA) resulted in longer herbicide retention times. Some leaching of fomesafen into the 16-30 cm zone was found for all of the treatments. Given that the soil is very sandy and the pH is higher than the pKa for the soil at Immokalee, fomesafen might leach deeper than 30 cm, particularly with the use of chemical soil fumigation.