Submitted to: Crop Protection Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 22, 2010
Publication Date: February 1, 2011
Citation: Hanson, B., Gao, S., Gerik, J.S., Shrestha, A., Qin, R., Mc Donnald, J.A. 2011. Effects of emission reduction surface seal treatments on pest control with shank-injected 1,3-dichloropropene and chloropicrin. Crop Protection Journal. 30(2):203-207. Interpretive Summary: Volatile organic compounds (VOC) are becoming more regulated in California. Methyl bromide alternatives such as 1,3 dichloropropene and chloropicrin are VOC's. Several techniques can be used to reduce VOC emissions. Little is know about the interaction of emission reduction techniques and pest control efficacy. Test were conducted to study this interaction. Surface seal treatments included 1) Control; 2) Composted manure (12.4 Mg/ha) + HDPE film; 3) Potassium thiosulfate + HDPE film; 4) Pre-irrigation; 5) Intermittent water seals; and 6) Intermittent potassium thiosulfate seals. Overall, it is clear that emission reduction techniques will have an impact on pest control, especially near the soil surface or at greater soil depths where fumigant concentrations may already be marginal. These experiments were conducted with a high rate of 1,3-D:Pic in a well-prepared sandy soil with no recent deep-rooted crops; additional efficacy weakness could become apparent in situations with lower rates, high pest pressure, heavy soils, or substantial amounts of old tree or vine roots. Emission strategies such as intermittent water seals may be useful in situations where pest control thresholds are higher but in highly regulated situations such as nursery stock production, the risk of nematode survival is too great with these techniques. These results strongly support the inclusion of pest control assays in emission reduction research to ensure that the primary goal of soil fumigation is not compromised on either a short or long-term basis. Additional research is needed to determine the long-term effects of these surface seal treatments on establishment, early growth, and economics of the subsequently planted crop.
Technical Abstract: The phase out of methyl bromide for preplant soil fumigation has resulted in an increased reliance on combinations of 1,3-dichloropropene and chloropicrin in many annual and perennial cropping systems in California. Unlike methyl bromide, these fumigants are not classified as stratospheric ozone depleting substances; however, they are classified as volatile organic compounds which contribute to ground-level air pollution and can have negative environmental and human health consequences. In order to meet regulatory requirements designed to protect human health and the environment, considerable research has been conducted on methods to minimize fumigant emission from the soil to the atmosphere. To ensure that pest control efficacy is not compromised by emission reduction techniques, this research was conducted to simultaneously evaluate the effects of several surface seal techniques on fumigant emissions and soil-borne pest control efficacy with 1,3-dichloropropene:chloropicrin. Results indicated that the interaction between emission reduction techniques and pest control efficacy can be complicated. For example in the 2006 trial, nematodes survival was observed in plots with high cumulative 1,3-D emission (manure plus HDPE film) and with intermediate 1,3-D emission (pre-irrigation). Weed control also was reduced when soil was pre-irrigated to 60% of field capacity but was affected less than expected by intermittent water seals. Substantial differences in nematode and weed control was observed between the two trials that could not be explained solely by surface seals which underlines the complex interactions among soil moisture and other environmental factors, application techniques, and emission reducing surface seal treatments. Future research on fumigant emission reduction techniques should include pest control efficacy evaluations before such practices are implemented by regulators and growers.