Integrated management and causes of damping off disease of chickpea (Cicer arietinum L.) in Montana
Leisso, Rachel Sue
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Chickpea is a minor crop in Montana with great potential for increase in both the conventional and organic sector. The semi-arid climate of much of Montana is well-suited to organic chickpea production, which commands a higher market price than conventional chickpea. Ranking third in the nation for certified organic cropland acres, many operations in Montana are already capable of organic chickpea production. There is a need for rotational crops such as chickpea that are compatible with organic wheat production. In addition to their profit potential, chickpea can perform valuable functions in wheat rotations such as fixing nitrogen and breaking insect pest and disease cycles. Damping-off of chickpea is one of the critical concerns of producers raising organic chickpea. Little was known about the pathogens causing damping off in Montana prior to this research. To determine the organisms responsible for damping off, pathogens were isolated from chickpeas affected by damping off at three field sites and identified to genera. Pythium spp. and Fusarium spp. are the predominate causes of damping off in Montana. Fusarium spp. have not been previously reported in association with damping off of chickpea. To determine if the Fusarium isolates were pathogenic or facultatively pathogenic, eight isolates of Fusarium were indentified to species and pathogenicity tests were performed under controlled conditions. All isolates caused damping off of chickpea. Damping off incidence and severity increased with increasing moisture levels for the majority of the Fusarium isolates. Seed treatments are the most common method of preventing damping off, and biological seed treatments are a control option for organic and conventional growers. The potential for control of chickpea damping off using biological and fungicide seed treatments was tested in greenhouse trials and at three field locations in Montana in 2007. Biological seed treatments Bacillus pumilus GB34 (Yield Shield), B. subtilis GB03 (Kodiak), and Trichoderma harzianum Rifai strain KRL-AG2 (T-22 Planter Box) were compared with conventional seed treatments fluidoxonil (Maxim) and mefenoxam (Apron XL LS) and combinations of biological and fungicide seed treatments in field trials. Treatments containing the chemical fungicide mefenoxam, which targets oomycete pathogens, were most effective for controlling damping off. Biological seed treatments were not effective at controlling damping off.