Location: Subtropical Plant Pathology Research
2013 Annual Report
2. Develop, adopt, and use training materials and conduct educational programs based on outcomes of the Area-Wide demonstration trials and in accordance with the new fumigation regulations established by the USEPA Fumigant Re-registration Eligibility Decision.
3. Conduct economic analysis on assimilated data emerging from Area-Wide field demonstration trials and assess the economic impacts of new fumigation regulations.
Over the course of 3 years, 7 different soil fumigants were tested using 7 different rates, under 4 different plastic types in 36 different experimental trials in 6 forest-tree nurseries in 3 southern states. By far the best MBr alternatives tested were Pic+, Chloropicrin, Chlor 60, and DMDS/Chloropicrin mixtures. This is based on seedling quality data, seedling root morphology, soilborne pathogen control and minimal nematode and weed pressures. Of those soil fumigants tested, Midas® (methyl iodide and chloropicrin), was removed from the US market by its’ distributor due to market and environmental concerns. New Pic+ (chloropicrin and solvent) was tested only once as this compound did not control weeds that became an issue in production quality. Chlor 60 (60% chloropicrin and 40% 1,3-dichloropropene) performed comparatively well to MBr. However, nutsedge control with this compound is lacking and nursery managers may choose this alternative if soilborne nematodes are more of a problem than nutsedge. The unpleasant odor of DMDS (dimethyl disulfide) may limit this compounds acceptance as an MBr alternative by some nursery managers even though it consistently perfomed well. As far as application rates under the 2012 soil fumigant REDs, a good starting point with high barrier plastics (TIF & VIF) in broadcast applications would be: New Rate with VIF or TIF = One half of Old Rate under HDPE or LDPE. Also, an MBr alternative becomes more effective when chloropicrin (>20%) is included. For example DMDS & Chloropicrin (Paladin®) performed better than DMDS alone and Telone & Chloropicrin (Chlor 60) performs better than Telone alone. The final decision when selecting an MBr alternative needs to take into consideration the ability of the soil fumigant to work under individual nursery soil conditions and the impact of the new soil fumigation rules have on each individual nursery. Any choice of current alternatives will likely require an increased use of pesticides to compensate for alternative short falls. Nearly all alternative research has been done on land that has been fumigated with methyl bromide exclusively. Therefore, the long term effects of the best alternatives are unknown. In addition, an alternative that works well in one nursery may not be as effective in another nursery. While none of these soil fumigants are the perfect replacement, seedling production is still possible without MBr if compounds such as chloropicrin are used and the reduced rates of 250 and 168 kg/ha under high barrier plastics such as TIF or VIF.