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Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/5/2003 Publication Date: 3/1/2003 Citation: Larkin, R.P. 2003. Effect of green sprouting and biocontrol products on soilborne diseases of potato 2002. Biological and Cultural Tests for Control of Plant Diseases. 18: PT011 Interpretive Summary: Soilborne diseases of potato are persistent and recurrent problems causing substantial yield losses and reductions in tuber quality. These diseases are caused by soilborne fungal pathogens, and two of the most important are Rhizoctonia solani, causing stem and stolon canker and black scurf on tubers, and Streptomyces scabies, causing common scab of tubers. These diseases are very difficult to control. Chemical pesticides are often not very effective or economically feasible, and alternative approaches are needed. Cultural and biological control, may provide comparable or superior disease control without the use of pesticides. Promoting rapid and early emergence, in particular, can greatly reduce losses to many soilborne diseases, including Rhizoctonia. In this study, green sprouting, a technique that pre-sprouts potato seedpieces prior to planting to promote early and improved emergence, was found to decrease the time to emergence by 7 to 9 days, reduce emergence problems, and reduce disease symptoms by R. solani and S. scabies. A bacterial biocontrol product also reduced disease symptoms of R. solani and improved yield relative to the pathogen control. Thus, although no treatments effectively controlled black scurf, two bacterial biocontrol treatments controlled stem canker and resulted in greater overall yield and yield of larger potatoes. 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: Green sprouting (GS) of potato seedpieces to enhance rapid and early emergence was used in combination with a bacterial and fungal biocontrol product and compared with non-sprouted seed (NS)and pathogen-treated and nontreated controls for their effects on symptoms of Rhizoctonia and other soilborne diseases of potato in the field. Green sprouted seed reached 95% emergence 7-9 days earlier than nonsprouted seed and showed fewer emergence problems (represented by missing and stunted plants). The nontreated control (No pathogen added)also showed greater emergence and had fewer emergence-related problems than all pathogen and biocontrol treatments. Overall, GS reduced the incidence and severity of stem and stolon canker, black scurf, and common scab, as well as the total incidence and severity of all diseases combined compared to NS plants. The bacterial biocontrol treatment (Burkholderia cepacia)reduced stem and stolon canker and black scurf symptoms relative to the pathogen control. Biocontrol treatments had no effect on the levels of common scab observed. The fungal biocontrol treatment (Trichoderma virens) reduced the total incidence of all diseases together compared to the pathogen control. Despite effects on diseases, total and marketable yields were not different for GS and NS treatments. The bacterial biocontrol treatments showed higher yields than the pathogen control and fungal biocontrol treatments. Interactions between the sprouting and biocontrol factors were not significant for any parameter, indicating there were no additive effects of the combination of green sprouting with biocontrol treatments. |
