Alternatives to MEBR for California Cropping Systems
Location: Water Management Research
Title: Effects of surface seals and application shanks on nematode, pathogen and weed control with 1,3-dichloropropene
Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2011
Publication Date: February 20, 2012
Citation: Jhada, A., Gao, S., Gerik, J.S., Qin, R., Hanson, B. 2012. Effects of surface seals and application shanks on nematode, pathogen and weed control with 1,3-dichloropropene. Pest Management Science. 68(2):225-230.
Interpretive Summary: Two field trials were conducted to test different surface seals and application shanks on pest control using 1,3 dichloropropene (1-3D) as an alternative to methyl bromide for pre-plant soil fumigation. Surface seals tested included high density polyethylene film, virtually impermeable film, water and water amended with metam sodium. Overall results suggested that the surface seals after an application of 373 kg ha-1 of 1,3-D had little impact on the control of nematodes and Fusarium spp., but it may have a greater impact on weed and Pythium spp. control. For example, 1,3-D sealed with HDPE and VIF were consistently superior for controlling broadleaf and grass weeds at both the sites. Under most conditions, surface seals like VIF are very effective; however, potential damage to the VIF during installation and sheet joint gluing issues can impact pest control and emission reduction efficacy. Emerging multi-layer films such as the so called totally impermeable film (TIF) may overcome these issues and lead to increased pest control and emission reduction performance. Under the conditions of this study, 1,3-D provided nematode control comparable with a standard MeBr treatment in a nematode bioassay. However, because no data from resident plant parasitic nematode populations were available from these fields and no nursery crop was grown after the treatments, interpretation of the nematode treatment efficacy is limited. Although intermittent water seals has been reported as one of the 1,3-D emission reducing techniques, it cannot be recommended in all cases because of poor weed and Pythium spp. control observed in this study. Several reports indicated that 1,3-D is among the most promising pre-plant fumigant alternatives to MeBr. However, the commercial adoption of 1,3-D in California is limited because of the safety concerns related to worker, bystander and air quality; buffer zone requirements; limitations on the amount of 1,3-D used annually in local areas (township caps); special soil preparation and moisture management requirements, and inability to use in nurseries with fine textured soils. Therefore, more research is required to reduce the limitations of 1,3-D to improve its efficacy to use in California tree nurseries.
Pre-plant soil fumigation with methyl bromide (MeBr) has been used for decades for controlling plant parasitic nematodes, soilborne pathogens and weeds in many high value annual, perennial and nursery crops. However, MeBr was identified as an ozone depleting substance and its availability was restricted under the US Clean Air Act and Montreal Protocol. Most California perennial crop nursery growers are currently using MeBr under critical use exemption (CUE) and quarantine/preshipment (QPS) provisions in order to meet California phytosanitary criteria. Currently, 1,3-dichloropropene (1,3-D) is the only registered alternative fumigant accepted by the California Department of Food and Agriculture’s (CDFA) Nursery Stock Nematode Certification Program; however, this fumigant also has air quality issues related to its release of volatile organic compounds (VOC). Research is under way to develop application strategies such as improved shank designs and surface sealing techniques to reduce VOC emissions but little information is available on the effect of these techniques on pest control efficacy. In 2007 and 2008, research trials were conducted to evaluate the effects of five or four surface seals and two application shanks on pest control with 1,3-D.
All 1,3-D treatments were comparable with MeBr for control of citrus and non-parasitic nematodes at both the sites. The soilborne pathogen analysis revealed that 1,3-D with virtually impermeable film (VIF) was effective for reducing Fusarium oxysporum propagules compared to unfumigated plots, but was not as effective as MeBr. Applications of 1,3-D with VIF or 1,3-D followed by metam sodium were as effective as MeBr for reducing Pythium spp. propagules. In contrast, Pythium spp. in plots treated with 1,3-D followed by intermittent water seals was comparable to the untreated plots. When sealed with high-density polyethylene (HDPE) film or VIF, 1,3-D was usually as effective as MeBr for reducing broadleaf and grass weed density and total weed biomass. Intermittent water seals and the dual application of 1,3-D with no surface seal did not provide any measurable weed control. In this research, sealed applications of 1,3-D controlled nematodes and pathogens similar to MeBr. However, Pythium spp. and weed control with 1,3-D was poor in plots treated with intermittent water seals. Future research on fumigant emission reduction techniques should include pest control evaluations as pre-assessment criteria before commercial recommendation of these techniques to nursery growers.