Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2010
Publication Date: August 1, 2010
Citation: Hanson, B.D., Gerik, J.S., Schneider, S.M. 2010. Effects of reduced-rate methyl bromide applications under conventional and virtually impermeable plastic film in perennial crop field nurseries. Pest Management Science. 66:892-899. Interpretive Summary: Soil fumigation with methyl bromide + chloropicrin is routinely used in perennial tree nurseries to meet the state phytosanitary requirements. Currently the use of methyl bromide is allowed under provisions of the Montreal Protocol dealing with quarantine and pre-shipment and critical use. The introduction of low permeability plastic tarps may allow for the reduction in application rates of fumigants without the loss of efficacy. Two field trials were conducted in commercial perennial crop nurseries, a garden rose nursery site near Wasco, CA, in 2005–2007and a fruit tree nursery site near Visalia, CA, in 2006–2007. Methyl bromide + chloropicrin were applied at reduced rates from 100 kg/ha under low permeability tarps and compared to the industry standard rate of 392 kg/ha under standard tarps. The primary alternative fumigants containing 1-3 dichloropropene were also tested. The reduced rates of methyl bromide + chloropicrin with the low permeability tarps provided as good weed and pest control as did the conventional treatment. The alternative fumigants provided poorer pest control compared to the standard treatment. If regulators approve the use of the low permeability tarps, the rates of methyl bromide could be reduced.
Technical Abstract: BACKGROUND: Producers of perennial crop nursery stock in California use preplant soil fumigation to meet state phytosanitary requirements. Although methyl bromide (MB) has been phased out in many agricultural industries, it is still the preferred treatment in the perennial nursery industry and is used under Critical Use Exemptions and Quarantine/Preshipment provisions of the Montreal Protocol. The present research was conducted to evaluate reduced-rate MB applications sealed with conventional and low-permeability plastic films compared with the primary alternative material. RESULTS: Reduced rates (100–260 kg ha-1) of MB applied in combination with chloropicrin (Pic) and sealed with a low permeability plastic film provided weed and nematode control similar to the industry standard rate of 392 kg ha-1 MB: Pic (98 : 2) sealed with high-density polyethylene (HDPE) film. However, the primary alternative chemical, 1,3-dichloropropene (1,3-D), tended to provide slightly lower pest control even on sites with relatively low plant parasitic nematode, soil-borne pathogen and weed pest pressure. CONCLUSION: If California regulations change to allow the use of low-permeability films in broadcast fumigant applications, the results of this research suggest that reduced rates of MB in perennial crop nurseries could serve as a bridge strategy until more technically, economically and environmentally acceptable alternatives are developed.