|Larkin, Robert - bob|
Submitted to: Crop Protection Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/21/2005
Publication Date: 9/12/2005
Citation: Brewer, M.T., Larkin, R.P. 2005. Efficacy of several potential biocontrol organisms against rhizoctonia solani on potato. Crop Protection Journal. 24: 939-950 Interpretive Summary: Rhizoctonia solani, a common soilborne fungal pathogen that results in substantial disease losses of numerous food crops, causes two distinct disease problems on potato: 1) stem, root, and stolon lesions (or canker) which affect growth of the plant, and 2) dark spotting of the potato tuber, called black scurf. Each phase of the disease can seriously reduce potato production and tuber quality, respectively. Currently, cultural and chemical control practices provide only limited control of this pathogen, and alternative approaches, such as biological control, may provide comparable or superior disease control without the use of pesticides. In this study, several bacterial and fungal organisms were found to reduce the development of stem canker and black scurf in greenhouse trials, with control comparable to that of a standard chemical treatment. However, no treatments, including the chemical treatment, effectively controlled stem canker and black scurf in all trials. Combinations of selected biocontrol organisms provided some improvement in control for some combinations, indicating that this approach may provide improved efficacy. This information can be used by scientists, extension agents, and ultimately growers for the development of effective and environmentally friendly approaches to disease control.
Technical Abstract: Twenty-eight potential biocontrol organisms were tested for efficacy against R. solani on potato in a series of greenhouse trials. Organisms tested consisted of field isolates of Paenibacillus polymyxa, Pseudomonas fluorescens, Penicillium sp., Trichoderma sp., and Rhizoctonia zeae; known biocontrol isolates including Laetisaria arvalis, Verticillium biguttatum, Cladorrhinum foecundissimum, and Stilbella aciculosa; and commercial products of Bacillus subtilis, Trichoderma virens, and T. harzianum. Different formulations and rates of several fungal isolates and the efficacy of combinations of effective antagonists were also investigated. None of the treatments, including a chemical control (azoxystrobin), effectively controlled stem canker and black scurf in all trials. However, B. subtilis GB03, R. zeae LRNE17E, S. aciculosa 112-B, and the chemical control were most effective in reducing stem canker severity (40 to 49 % reduction) relative to the infested controls over all trials. L. arvalis ZH-1, R. zeae LRNE17E, and the chemical control reduced black scurf 54 to 60 % relative to the infested control. Other treatments also significantly reduced stem canker and black scurf, however they were slightly less effective. Different rates of biocontrol organisms provided varying disease reductions with higher rates usually providing the best control. One combination of biocontrol organisms, B. subtilis and T. virens, demonstrated somewhat better control of stem canker than each organism alone, suggesting that this approach may provide improved biocontrol efficacy.