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United States Department of Agriculture

Agricultural Research Service

Title: A Cellulose Granule Formulation of Trichoderma and Gliocladium to Reduce Damping-off Caused by Rhizoctonia Solani and Saprophytic Growth of the Pathogen in Soilless Mix

Authors
item Lewis, Jack
item Larkin, Robert
item Lopez, Dawn

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 1998
Publication Date: N/A

Interpretive Summary: The implementation of biocontrol for the reduction of soilborne plant pathogens depends upon the development of effective and commercially-produced formulations for the application of microbials in delivery systems. The results of this report address this problem. An industrial grade cellulose granule was mixed with a sticker and fermentor-produced biomass of isolates of the biocontrol fungi Trichoderma and Gliocladium. The chlamydospores in the biomass were treated with dilute acid to produce actively growing hyphae of the biocontrol fungi within a 2 to 3 day period. This product inactivated propagules of the soilborne pathogen Rhizoctonia solani (R-23) in soilless mix. Granules with acid-treated biomass of isolates Gl-3, Gl-21, and Gl-32 of G. virens and isolate TRI-4 of T. hamatum applied to soilless mix at a rate of 1.5% reduced damping-off of eggplant caused by R-23 and resulted in stands comparable to that (88%) in the nonpathogen check. Saprophytic growth of the pathogen was also reduced. Populations of all isolates increased about 1000-fold. Granules of Gl-3 reduced the spread of R-23 in soilless mix when the pathogen was applied at specific foci rather than when evenly distributed. The inhibition of the spread of the pathogen significantly reduced the postemergence damping-off of cucumber, eggplant, and pepper seedlings. This information benefits greenhouse production by demonstrating the use of a disease control approach as an alternative to chemicals, especially the application of methyl bromide. The environment and commodity quality are improved because of reduced pesticide use.

Technical Abstract: A formulation system was developed in which a commercially-manufactured cellulose granule was mixed with a sticker and fermentor-produced biomass of isolates of the biocontrol fungi Trichoderma spp. and Gliocladium virens. The novel aspect of this approach involved the "activation" of the chlamydospores in the biomass with dilute acid to produce young, actively-growing hyphae of the biocontrol fungi within a 2 to 3 day period under no special aseptic conditions. This product inactivated propagules of the soilborne pathogen Rhizoctonia solani (R-23) in soilless mix. Activated granules with biomass of Gl-3, Gl-21, and Gl-32 of G. virens and isolate TRI-4 of T. hamatum applied to soilless mix at a rate of 1.5% (w/w) reduced damping-off of eggplant caused by R-23 and resulted in stands comparable to that (88%) in the nonpathogen-infested control. Activated granules added at a rate of 1.5% with as little as 0.13 g of biomass of Gl-3 or TRI-4 or activated granules added at a rate of 0.2% with 0.1 g of biomass (both preparations containing the same amount of biomass) reduced disease as well as saprophytic growth of R-23. All isolates on activated granules gave about 1000-fold population increase compared to the initial amounts added with the granules. Activated granules with Gl-3 also reduced the spread of R-23 in soilless mix when the pathogen was applied at specific foci rather than when evenly distributed. The inhibition of pathogen spread significantly reduced the postemergence damping-off of cucumber, eggplant, and pepper seedlings.

Last Modified: 12/21/2014