Submitted to: Trade Journal Publication
Publication Type: Trade Journal
Publication Acceptance Date: 1/16/2010
Publication Date: 1/21/2010
Citation: Spokas, K.A., Jacobson, B. 2010. Impacts of Strobilurin Fungicides on Yield and Soil Microbial Processes for Minnesota Strawberry Production. Minnesota Fruit and Vegetable Growers Association. January 21-22, 2010. St. Cloud, MN. pp. 25-29. Interpretive Summary:
Technical Abstract: This article will describe the preliminary results of the ongoing research into the impacts of strobilurin fungicides both on yield as well as soil microbial processes for strawberry production in Minnesota. The research is being conducted with an on-farm collaborator. This article will present the preliminary data from the first two years. We have not observed consistent trends in the first two years of the project. For example, in 2008 we observed a significant increase in strawberry yield (64% increase), but there were non-significant increases observed in 2009. We have seen some minor impacts on the distribution of the soil microbial community as a consequence of pyraclostrobin application with decreases in the number of yeasts and molds (37% reduction) and a corresponding increase in pseudomonads (240%) in the fungicide treated plots. No significant differences were observed in the heterotrophic bacteria, anaerobic bacteria, actinomycetes, or nitrogen-fixing bacteria as a consequence of the fungicide treatment. There has been no detectable leaching of the fungicide into the soil system, despite the supplemental irrigation for the strawberry production and the sandy soil texture. The only detectable quantity of pyraclostrobin was observed in the straw mulch covering (~1.5 ug/gstraw), and this dropped to undetectable levels 2 weeks after application (<1.0 ug/gstraw) in both years. In the second year, we did monitor greenhouse gas fluxes biweekly to examine the impacts of the fungicide application on the trace gas exchange. Initially there is a decrease in the flux of carbon dioxide immediately following fungicide application, but this quickly returns to control levels 1 week after application. There were no significant differences noted for methane or nitrous oxide flux or soil gas concentrations as a result of the fungicide application. To date, we have observed no long-term negative impacts on the soil or strawberry production as a consequence of pyraclostrobin application. In addition, there was no data that indicated any leaching risk of the fungicide into the soil system. The yield increase that was observed in the initial year was not observed in the second year, which could indicate the importance of climate or a synergy between the fertilizer and pyraclostrobin applications. These interrelationships are planned to be evaluated in the final year of the project.