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United States Department of Agriculture

Agricultural Research Service

Research Project: Alternatives to methyl bromide soil fumigation for vegetable and floriculture production

Location: Subtropical Plant Pathology Research

Title: Alternatives to methyl bromide for nematode control in ornamental crops

Authors
item Burelle, Nancy
item Rosskopf, Erin

Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: September 29, 2012
Publication Date: N/A

Interpretive Summary: Nematode control options for production of in-ground ornamental crops are extremely limited. Ornamental production has different obstacles to nematode control and chemical application than raised-bed vegetable production. Challenges include a need for flat fumigation, lack of labeled herbicides, fixed structures such as shade houses, unknown levels of nematode susceptibility of ornamental varieties, and proximity to highly populated areas which impacts fumigant buffer zone requirements. Research was conducted in cooperation with ornamental growers in East and Central Florida, and at the USDA, ARS experimental farm in Ft. Pierce on Celosia, Delphinium, Snapdragon, Dianthus, and Caladium. Trials assessed alternative chemical fumigants, non-fumigant methods, biological control, and plant varieties for effects on parasitic nematode populations and disease. Fumigants tested were methyl iodide, and dimethyl disulfide. Physical control methods investigated were steam and anaerobic soil disinfestation. New research on nonchemical options includes newly developed formulations and application methods of the nematode biological control agent Pasteuria penetrans. In addition to chemical and physical nematode control measures, assessment of caladium varieties for susceptibility to infestation by common and new species of root-knot nematodes is being conducted. A better understanding of the ability of nematodes to reproduce on weeds will also become increasingly important as growers transition from broad-spectrum fumigants. Observations from field trials on soil fumigants resulted in isolation of M. arenaria from cheeseweed mallow, a newly reported natural host for M. arenaria. Studies were undertaken to determine the host status of several weeds to the three predominant species of root-knot nematodes in Florida, Meloidogyne incognita, M. arenaria, and M. javanica.

Technical Abstract: Nematode control options for production of in-ground ornamental crops are extremely limited. Ornamental production has different obstacles to nematode control and chemical application than raised-bed vegetable production. These challenges include a need for flat fumigation, lack of labeled herbicides, fixed structures such as shade houses, unknown levels of susceptibility of ornamental varieties to common and new species of root-knot nematodes (Meloidogyne), and proximity to developed areas which impacts fumigant buffer zone requirements. Research was conducted in cooperation with ornamental growers in East and Central Florida, and at the USDA, ARS experimental farm in Ft. Pierce, FL beginning in 2007. Ornamental crops include Celosia, Delphinium, Snapdragon, Dianthus, and Caladium. Trials assessed the effects of alternative chemical fumigants, non-fumigant methods, biological control, and plant varieties on parasitic nematode populations and disease. Fumigants tested were methyl iodide (98:2 and 50:50 formulations), and dimethyl disulfide (79:21 formulation), while physical control methods investigated were steam and anaerobic soil disinfestation (ASD). Fumigants and physical control methods were compared to methyl bromide. New research on nonchemical options includes newly developed formulations and application methods of the nematode biological control agent Pasteuria penetrans. Application methods being investigated include transplant, seed treatment, and drip applications. In addition to chemical and physical nematode control measures, assessment of caladium varieties for susceptibility to infestation by common and new species of root-knot nematodes is being conducted. A better understanding of the ability of nematodes to reproduce on weeds will also become increasingly important as growers transition from broad-spectrum fumigants. Observations from field trials on soil fumigants resulted in isolation of M. arenaria from cheeseweed mallow (Malva parviflora), a newly reported natural host for M. arenaria. Studies were undertaken to determine the host status of several weeds to the three predominant species of root-knot nematodes in Florida, Meloidogyne incognita, M. arenaria, and M. javanica. Portulaca oleracea and Amaranthus americana were found to support the most juveniles (J2) of all three Meloidogyne species, and also had the highest number of eggs/g root for all three species. Although P. oleracea supported very high numbers of J2 in roots, galling was moderate to low for all three species. Low levels of apparent galling combined with high egg production, may increase the potential for P. oleracea to affect populations of these nematode species to an unexpected degree.

Last Modified: 9/1/2014
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