Location: Subtropical Plant Pathology Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop new management strategies for control of pests and pathogens currently controlled by methyl bromide in vegetable and ornamental cropping systems. • Sub-objective 1.A. Evaluate new and alternative chemistries singly and in combinations for their efficacy, spectrum of activity, and feasibility under controlled and field conditions. • Subobjective 1.B. Ascertain the effectiveness of individual and combined biological and cultural pest control tactics on the incidence and severity of soilborne pests under controlled and field conditions. Objective 2: Develop and test novel application technologies and methods for chemical fumigants to optimize their efficacy, reduce their environmental impact, and minimize exposure to workers in the field. Objective 3: Integrate cultural, biological, and chemical control tactics into technically feasible pest management programs for soilborne pests under field conditions.
1b. Approach (from AD-416):
A rational and sustainable approach to finding viable alternatives to methyl bromide is to utilize integrated pest management (IPM) programs where combinations of tactics are used to maintain economic damage from key pests below a tolerable threshold. Another approach is to redesign production systems minimizing the potential for outbreaks of soilborne pests. Availability of biologically-based pest management tactics must be increased for successful IPM programs for soilborne pests to be implemented. Growers must have the option of choosing tactics that fit the needs and constraints of their individual programs. Deployment of multiple or companion tactics is essential to alleviate selection pressure and manage potential increases in resistant pest populations. Synergistic effects from combinations of pest management tactics need to be determined. Specific research methodology will include combinations of cultural practices, biotechnology, biological, and conventional control methods.
3. Progress Report:
This is a bridging project which replaced old parent project #6618-22000-036-00D, and which will be replaced by a new parent project #6618-22000-040-00D. Progress reported here is on objectives for the old parent project #6618-22000-036-00D. Research continued in cooperation with University of Florida to evaluate a reduced-risk compound for control of weeds, plant pathogenic fungi and bacteria, and plant parasitic nematodes. Research continued on anaerobic soil disinfestations (ASD) for weed and nematode control. Additional field trials have been conducted on ASD in cooperation with private crop consultants and a commercial caladium grower. Further nematode host range studies were conducted to assess galling and egg production of three common root-knot nematode species, M. incognita, M. arenaria, and M. javanica on weeds, cover crops, and floriculture crops common in Florida production. Research was conducted on new formulations and applications methods for the nematode biological control agent Pasteuria penetrans.
1. Reduced risk chemicals for weed, nematode, and pathogen control. Crop protection materials are needed that provide broad-spectrum control of pests, but do not pose a risk to workers or the environment. Research was continued in cooperation with University of Florida to evaluate a novel, reduced-risk compound for control of weeds, plant pathogenic fungi and bacteria, and plant parasitic nematodes. The compound’s broad-spectrum pest control activity was further defined in field trials. Significant findings of this research include the effects of the reduced-risk chemical on populations of beneficial fungi. Populations of Trichoderma were found to increase significantly with application of the experimental compound. Weed control is improved with drip application of the material when compared to in-bed shank applications. In addition, the experimental compound does not produce any volatile organic compounds, thereby limiting potential by-stander risks as well as increasing its potential for use between crops.
2. Anaerobic soil disinfestation as an alternative to methyl bromide fumigation. A cooperative research project between ARS in Fort Pierce, FL, the University of Tennessee, Knoxville, and the University of California, Santa Cruz has generated new information on Anaerobic Soil Disinfestation (ASD), a technique that utilizes the combination of a nitrogen source, such as composted broiler litter, and a carbon source, such as molasses, with soil saturation and heating to create an anaerobic condition that induces weed, nematode, and soilborne plant pathogen control. Control of yellow nutsedge emerging though the plastic early in the season with ASD was equivalent to methyl bromide in one field trial. Root-knot nematode control was influenced by initial irrigation, molasses addition, and by the incorporation of composted broiler litter. Several plant pathogenic fungi were found to be controlled by the application of litter alone. ASD was found to be more effective in the control of the strawberry charcoal rot pathogen, Macrophomina phaseolina, than were the commercial standard or other experimental control measures. Populations of potentially beneficial fungi, belonging to the genus Trichoderma, as well as populations of the bacteria Bacillus and Paenibacillus, were found to increase significantly with the application of ASD. Successful crop production using this method is influenced by the nematode-susceptibility of the crop.
3. Susceptibility of weeds, floriculture crops, and cover crops common in Florida to Meloidogyne spp. Greenhouse trials were conducted to assess galling and egg production of three common root-knot nematode species, M. incognita, M. arenaria, and M. javanica on weeds, floriculture crops and cover crops common in Florida production. Portulaca oleracea (purslane), Eleusine indica (goosegrass), Aeschynomene americana (American jointvetch), Solanum americanum (American black nightshade), Cyperus esculentus (yellow nutsedge), and Amaranthus retroflexus (redroot pigweed) were the weeds evaluated. Floral crops evaluated were Celosia argentea (cockscomb), Delphinium elatum (larkspur), Antirrhinum latifolium (snapdragon), and Helianthus annuus (sunflower). Although recommended as a cover crop in the southern U.S., A. americana was evaluated as a weed following a heavy volunteer infestation of an experimental field in southeastern Florida where galling was observed on roots. Most of the floral crops tested were highly susceptible to all three species of root-knot nematodes. Delphinium was not tested for susceptibility to M. arenaria but was consistently less susceptible to M. incognita and M. javanica than the other floral crops tested with those nematode species. Results of these greenhouse trials are consistent with observations from field trials on alternative fumigants conducted in Florida in which low levels of galling by root-knot nematodes were consistently observed on Delphinium. Cover crops evaluated were Eruca sativa (Arugula ’Nemat’), Vigna unguiculata (Cowpea ’Iron clay’), Canavalia ensiformis (Jackbean), Brassica juncea & Sinapsis alba (Mustard ‘Caliente 61’), Brassica juncea & Sinapsis alba (Mustard ‘Caliente 99’), Pennisetum glaucum (Pearl Millet), Sorghum bicolor L. Moench × Sorghum sudanense P. Stapf (Sorghum Sudangrass hybrid), Helianthus annuus (Sunflower ‘545A’), Helianthus annuus (Sunflower ‘Nusun 5672’), Helianthus annuus (Sunflower ‘Nusun 660CL’).
4. Evaluating new application methods for nematode biocontrol. Research was undertaken to evaluate new formulations and applications methods for the nematode biological control agent Pasteuria penetrans. Greenhouse and field microplot trials to evaluate granular and liquid formulations applied as seed treatments, transplant amendments, and post plant applications for control of Meloidogyne incognita on tomato and cucumber, and Meloidogyne arenaria on snapdragon are underway and data are being collected.
5. Vegetable grafting for plant pathogen control. During this reporting period, field experiments were conducted and repeated in Florida in cooperation with commercial growers. A field experiment evaluating grafted heirloom tomato was performed in cooperation with an organic grower in St. Lucie, County FL, and a sustainable grower in Palm Beach, County FL. Also microplot, greenhouse, and growth chamber experiments were conducted to evaluated grafting techniques, virus resistance, and nematode susceptibility of rootstocks. In field trials evaluating root-stock virus resistance, heirloom tomatoes with no Tomato Yellow Leaf Curl Virus (TYLCV) resistance produced greater yields when grafted than when non-grafted. USDA, ARS researchers are active in Executive and Advisory Team meetings, and commodity (tomato and cucurbit) Working Groups.