Evaluation of the Sustainability of Methyl Bromide Alternatives in a Double Crop System

Non-Technical Summary: Methyl bromide has been an effective tool for managing multiple pests since the early 1900's, with extensive use in vegetable and fruit crops since the 1950's (Ragsdale and Wheeler 1995). Methyl bromide has been the foundation for pest management in many of these crops, as it has provided effective broad spectrum pest control. The Montreal Protocol of 1991 defined methyl bromide as a chemical that contributes to the depletion of the Earth's ozone layer (USDA, 1999). Accordingly, based on scientific data, the manufacturing and importation of methyl bromide to developed countries is currently being phased out. Under-developed countries have a significant advantage as methyl bromide will be phased out slowly and complete phase out will not occur prior to 2015. Unless viable alternatives are found, US farmers will be at a disadvantage when competing in the global agricultural market (Ragsdale and Wheeler 1995). Fruiting vegetable and cucurbit crops account for the majority of plasticulture acres that utilize methyl bromide for pest control in Florida and Georgia. Nutsedge species are the most troublesome and among the most common weeds infesting Florida and Georgia fruiting vegetable and cucurbit crops (Webster, 2006). Yellow nutsedge growth and reproduction is reduced by polyethylene mulches (Majek and Neary 1991; Webster 2005a). However, another study demonstrated black polyethylene mulch promoted growth of purple nutsedge plants relative to non-mulched plots (Webster 2005b). A single nutsedge tuber was capable of producing 3,400 new shoots in black low density polyethylene mulch plots after 60 weeks of growth, nearly double the number of shoots in the non-mulched plots. Black low density polyethylene mulch also promoted lateral expansion of purple nutsedge patches (22.1 m2 after 60 weeks) compared to the non-mulched plots (11.6 m2 after 60 weeks). Though yellow nutsedge is typically more common in agronomic fields, purple nutsedge has been observed to be more tolerant of many of the methyl bromide alternatives (Culpepper and Langston 2004b, Stall 2000). This increased tolerance to fumigant alternatives coupled with the ability to thrive in black polyethylene mulch systems makes purple nutsedge a formidable pest. Re-use of polyethylene mulch often occurs in an effort to distribute the significant capital investments of the mulch and the drip irrigation over several crops. This use pattern raises at least two issues. First, excessive nutsedge piercing of the mulch barrier will reduce the stability and integrity of the mulch. Mulch that does not tightly adhere to the soil bed may allow for crop lodging if wind gets between the soil bed and the mulch. Second, black polyethylene will moderate cool autumn and winter temperatures and allow for earlier soil warming in the spring. The use of black polyethylene mulch may alter the environmental characteristics of the cropping system (i.e. extend growing seasons because of increased soil temperatures) to the benefit of purple nutsedge. Objective 1. Determine the sustainability of possible methyl bromide alternatives applied in sequential years on the same production land. One large scale plot experiment will be conducted each year over a period of three years on the same piece of crop production land. This land has been used for tomato production the last three years with methyl bromide plus chloropicrin (67:33 year one and two, 50:50 year three) used as the fumigant during the production seasons. Full plot size will be 3 beds wide by 300 ft long. Sub plot size will by one bed by 300 ft in length. Treatments will be replicated four times. Tomato and bell pepper will be planted as the first crop followed by squash as a second crop. Crop growth, weed emergence, soil borne disease, and nematode measurements will be taken. Data collected will include: 1) Crop Growth Measurements 2) Yield Measurements 3) Weed Response Measurements 4) Soilborne Disease Measurements 5) Nematode Measurements Objective 2. Compare the economic validity of each fumigant /plastic systems for potential adoption by Southeastern vegetable producers. In order for an alternative to be acceptable at the farm level, it must be economical. Thus, cost benefit analyses will be evaluated for all cropping systems. All the explicit and implicit cost components of each crop sequence will be captured and analyzed using both quantitative and qualitative models. The economic analysis will be vital to determine whether the results of this research will provide superior pareto-optimality to the farmers from economic, welfare, ecological and environmental perspective concomitantly. The economic analysis will be conducted using the primary data collected by each collaborating scientist in this project. Objective 3. Distribute results on the adoption of methyl bromide alternatives to growers and other interested parties. Distribution of information will be conducted using: 1) Extension County Meetings 2) Field Tours 3) State Meetings 4) Education/Professional Meetings