Location: Subtropical Plant Pathology Research
Title: Anaerobic Soil Disinfestation (ASD) and Steam As Alternatives For Parasitic Nematode Control In Florida Floriculture Authors
Submitted to: Society of Nematologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2013
Publication Date: N/A
Technical Abstract: Anaerobic soil disinfestation (ASD) and steam are being investigated for controlling a broad spectrum of pests, including parasitic nematodes and weeds. ASD is a biologically-based method that combines organic amendments and solar heat with water saturated soil to create oxygen-depleted soil conditions that favor growth of facultative and obligate anaerobic bacteria. Often, these bacteria produce antimicrobial compounds and acids as secondary metabolites that, in conjunction with anaerobic conditions, can control many pathogens including nematodes. A previous experiment on snapdragon (Antirrhinum majus) which compared soil solarization to steam and methyl bromide (MeBr) application established that soil solarization alone does not provide acceptable control of root-knot nematodes (RKN), Meloidogyne arenaria, in Florida. However, ASD provided superior control of nematodes and weeds which was not achieved with soil solarization alone. Steam directly affects nematodes, killing them through a combination of moisture and heat. Both ASD and steam can be applied in ornamental and vegetable production. Results from a commercial-grower field trial that included both ASD and steam treatments on naturally-occurring populations of RKN are presented. ASD was accomplished using molasses as an easily-decomposable soil amendment to stimulate microbial activity. Composted poultry litter (CPL) was used as a nitrogen source and to increase bacterial diversity. Amendments were incorporated into the upper 20 cm of soil. The soil was covered with clear, UV-stabilized polyethylene and saturated with water to create conditions favorable for anaerobic bacterial growth. The polyethylene tarp was left in place for approximately 3 weeks, until the soil temperature was elevated and anaerobic conditions were established, based on measurements using oxidation-reduction probes. Steam treatments were applied using standard 7.6 cm perforated tile (steam 1), and custom-drilled drain tile with 1.6 mm holes spaced every 3.8 cm approximately 120° from the center line of the tile (steam 2). Drain tile was buried at 35.5 cm depth and four tiles were installed in each plot. MeBr was included as a control and was applied under metalized film at 225 kg/ha (MeBr: chloropicrin 67:33). All plots were 30.5 m long and 1.8 m wide. The floriculture crops Sweet William (Dianthus barbatus), larkspur (Delphinium x belladonna), and snapdragon were produced according to standard commercial practices during winter 2011-2012. Both ASD and steam provided RKN control in soil at the end of the season comparable to, or exceeding that of MeBr. ASD and steam also reduced RKN populations in snapdragon roots comparable to, or exceeding control with MeBr. MeBr and ASD increased plant growth compared with both steam treatments for larkspur and snapdragon. Although steam provided excellent control of nematodes in this study, plant growth was reduced, indicating a possible deleterious effect of steam on beneficial soil microorganisms. Additional research on different organic amendments for use in ASD, and on supplementing or enhancing natural populations of beneficial soil microorganisms to improve plant growth following steam treatments is currently underway.