Alternatives to MEBR for California Cropping Systems
Location: Water Management Research
Title: Efficacy of 1,3-dichloropropene plus chloropicrin reduced rates under two different tarps against nematodes, pathogens and weeds
Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: September 19, 2011
Publication Date: October 30, 2011
Citation: Cabrera, A., Hanson, B., Abit, M., Gerik, J.S., Gao, S., Qin, R., Wang, D. 2011. Efficacy of 1,3-dichloropropene plus chloropicrin reduced rates under two different tarps against nematodes, pathogens and weeds. International Conference on Methyl Bromide Alternatives and Emissions Reductions. San Diego, California, October 31-November 2, 2011. p. 75.1-75.3.
Interpretive Summary: Telone C35 is a mixture of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) currently registered in California as a pre-plant soil fumigant to control nematodes, soilborne pathogens and weeds. Field trials were conducted to evaluate the efficacy of reduced Telone C35 rates followed by covering the field with a standard high density polyethylene tarp (PE) or a totally impermeable film (TIF) on plant parasitic nematodes, soilborne pathogens and weeds. Results showed that both PE and TIF did not affect the efficacy of reduced 1,3-D and CP rates against nematodes and weeds. Telone C35 reduced rates were highly effective against plant parasitic nematodes resulting generally in a control that would comply with current California phytosanitary regulations for nursery stock production. However, higher soilborne pathogen incidence was encountered in the reduced rate treatments compared to full rates under both tarp types. This situation suggests that fumigant concentrations at reduced rates may be sufficient for adequate nematode control in sandy soil conditions but is not enough for the control of some soilborne pathogens.
One of the major concerns in tree nursery production is the control of parasitic nematodes. The susceptibility of some nursery stocks to soilborne pathogens and vulnerability to weed competition are other important problems that need to be addressed. The use of fumigant 1,3-D and CP is restricted by township caps and buffer zone requirements because of their volatile organic compound emissions. Thus, there is a pressing need to investigate alternative methods that would reduce emissions with reduced rates while still providing effective pest control. Field experiments were conducted in 2009 and 2010 at the San Joaquin Valley Agricultural Sciences Center, near Parlier, CA. Plots were randomly assigned to receive Telone C35 (1,3-D and CP) treatments at full rate (605 kg/ha), ¾ rate (454 kg/ha), or ½ rate (303 kg/ha). A non-fumigated control was included for comparison. Bags containing citrus nematodes (Tylenchulus semipenetrans) were buried at 15, 30, 60, and 90 cm soil depth prior to fumigation. Immediately after fumigation, PE or TIF was installed to each Telone C35 application rate. Two weeks after fumigation (WAF) the tarps were removed and soil samples were taken for nematode and pathogen evaluations. Bags containing citrus nematodes that were buried before fumigation were recovered and nematode survival was evaluated. Weed emergence and biomass production were also determined several months after fumigation. Results showed that citrus nematodes were controlled 100% at 15, 30, 60 and 90 cm soil depths in both trials (2009 and 2010) with all rates and both tarps with one exception where living citrus nematodes were detected at 15 cm soil depth in the 2010 trial where ¼ rate was applied under PE. Full rate and ¾ rate of Telone C35 provided 100% control of pin nematodes (Paratylenchus spp.) at 30, 60, 90 and 120 cm soil depths when evaluated 2 WAF with both tarp types tested. The Telone C35 ½ rate provided 100% pin nematode control at 30, 60 and 90 cm soil depth whereas 96 and 98% at 120 cm soil depth with PE and TIF tarp, respectively. Additionally, there were no pin nematodes detected 0 to 60 cm soil depth 16 WAF in all three rates tested and two different tarps. In the 2010 trial, all root-knot nematodes (Meloidogyne incognita) inside the tomato roots that were buried at 90 cm soil depth were controlled 100% by all treatments. There were no differences at 15 cm soil depth in the efficacy of Telone C35 at any rate with both tarps against all the soilborne pathogens. However, Telone C35 was more effective against Pythium spp. and Verticillium spp. than Fusarium spp. For example, full and half rate of Telone C35 provided 100% control of Pythium spp. and Verticillium spp. under both tarps whereas only around 20% control for Fusarium spp. A total of six and nine broadleaf weed species were observed in 2009 and 2010, respectively. Total broadleaf and grass weed populations were reduced in all Telone C35 treatments in both years. Further, PE and TIF tarps significantly reduced weed density in both years but no differences were observed between PE and TIF. These results indicate that reduced fumigation rates may be used under TIF without significantly compromising the efficacy.