Strategies for Minimizing Emissions From Soil Fumigation in Perennial Nurseries.

California tree and grapevine field nurseries must meet the requirements of the CDFA’s Nursery Stock Nematode Control Program, which is intended to ensure delivery of healthy and nematode-free crops.  This has been achieved primarily by preplant soil fumigation with methyl bromide (MeBr) which was officially phased out.  The industry faces a number of challenges in transition from MeBr to alternative fumigants because of efficacy concerns as well as stringent environment regulations that require low emissions of the alternative chemicals. The objective of this research was to identify effective emission reduction methods that also provide good efficacy. We conducted two field trials to evaluate the effects of two application shanks and several surface sealing treatments on emission flux and fumigant distribution and concentration in soil following an application of Telone C35 (mixture of 1,3-dichloropropene and chloropicrin). Data indicated that there was little difference in emissions between two different shank designs used for fumigant application. Among the soil surface treatments, total emission loss was the highest from bare soils (>60%), reduced ~30% by water seals, 50% by HDPE tarp, and >90% by VIF tarp. Water seals (irrigation with sprinklers after fumigation) showed some negative impacts on pest control. Use of VIF film resulted in the highest fumigant concentration under the tarp and the lowest emissions which suggests that low permeable film can be the most promising technique to meet the sometimes contradictory goals of low emissions and effective pest control.