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Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/27/1996 Publication Date: N/A Citation: N/A Interpretive Summary: The application of biocontrol to reduce diseases caused by soilborne plant pathogens depends upon the development of appropriate formulation delivery systems. This report describes the production of a novel extruded granular product containing rice flour, gluten, Pyrax, vermiculite, canola oil, and fermentor-produced biomass of isolates of Gliocladium virens (Gl-3, Gl-21, Gl-32), Trichoderma hamatum (TRI-4, 31-3), T. harzianum (Th-32, Th-87), an T. viride (Tv-101). The granules were evaluated for their ability to reduce eggplant damping-off caused by Rhizoctonia solani and pathogen inoculum, as well as to encourage proliferation of the isolates in a soilless mix. Most products, applied at a rate of 0.5%, reduced damping-off and yielded stands comparable to that (90%) of the noninfested control. Granules with isolates Gl-21 and TRI-4 were the most effective in reducing saprophytic growth of R. solani. Isolate propagules proliferated at least 1000 fold in soilless mix 6 wk after granule addition. Granules o Gl-21 and TRI-4 also significantly prevented the spread of R. solani in flats of eggplant seedlings. These results indicate the feasibility of formulating biocontrol products by industry which can be applied in commercial greenhouses to reduce soilborne diseases of ornamental and vegetable bedding transplants. With biocontrol, growers and consumers benefit from use of fewer pesticides and an increase in commodity quality. Adaptation of this technology for use in high-value, low acreage crops may also result in a reduction of methyl bromide use in field application. Technical Abstract: Extruded granular formulations containing rice flour, gluten, Pyrax, vermiculite, canola oil,and biomass of Gliocladium virens (Gl-3, Gl-21, Gl-32), Trichoderma hamatum (TRI-4, 31-3), T. harzianum (Th-32, Th-87), and T. viride (Tv-101) were evaluated for their effect on reduction of eggplant damping-off caused by Rhizoctonia solani, reduction of pathogen inoculum, and proliferation of the isolates in a soilless mix. Granules with all isolates except 31-3 reduced damping-off, and granules with Gl-3, Gl-21, Gl-32, TRI-4 and Th-87 yielded stands comparable to that (90%) of the noninfested control. Granules with isolates Gl-21 and TRI-4 were the most effective in the reduction of saprophytic growth of R. solani. Isolate propagules proliferated about 1000 fold in soilless mix after a 6-wk incubation, but there was no correlation between cfu and eggplant stand or reduction in saprophytic growth of the pathogen. Granules with Gl-21 and TRI-4 amended to pathogen-infested soilless mix at a rate as low as 0.06% significantly reduced damping-off and pathogen saprophytic growth and a rate of 0.25% of Gl-21 granules resulted in an eggplant stand comparable to that of the noninfested control. There was no significant correlation between rate of granule amendment and proliferation of Gl-21 and TRI-4. Granules of Gl-21 and TRI-4 also significantly prevented the spread of R. solani in flats of eggplant seedlings when the biocontrol granules were applied to the soilless mix 1 day before the pathogen inoculum. |
