Location: Sunflower Research
2012 Annual Report
This is a new project that builds on accomplishments from a project previously funded by the Sclerotinia Initiative wherein we evaluated five chemical fungicides applied alone or in combinations - two fungicides at a time and three biological fungicides - for control of Sclerotinia stem rot (SSR) of canola and developed sensitivity data to thiophanate methyl and metconazole for 96 SSR isolates collected from 14 states in North central U.S. Analyses are currently underway regarding SSR sensitivity to boscalid and pyraclostrobin. Efficacy of fungicides for disease control was evaluated in field trials whereas fungicide sensitivity was assessed in laboratory. In field trials, compounds were applied alone or in combinations of two compounds at a time each at 50% of the field doses. Efficacy of control vary from year to year, but most treatments, either applied alone or in tank mixes with other compounds, but on average they reduced disease incidence by almost 40% when compared to the non-protected plots although in some years a few mixes reduced incidence by up to 80%.Since several important new fungicides were recently introduced to the market, we are including these new compounds in tank mix trials in an effort to fine tune the combinations we identified previously as the most effective and consistent, i.e. thiophanate methyl and boscalid. Tank mixes with concentrations >50% of the doses of some of the compounds will also be evaluated. A regional data base on sensitivity to thiophanate methyl and metconazole was developed using 96 SSR isolates collected from 14 states in the North Central U.S. Information on sensitivity to boscalid is in preparation. Most isolates were sensitive to thiophanate methyl, but a few of them, collected from Minnesota and Nebraska, were identified as having EC50 values > 2 ppm, which is considered the resistance threshold.
We intend to characterize the fitness of these isolates to determine whether the resistance imposed a penalty on their ability to affect plants, estimate the effect of currently recommended field doses on disease caused by these isolates and to determine the genetic changes that are responsible for this increased resistance. Because this fungicide is also used in dry bean and soybean for control of S. sclerotiorum, the results generated by this project will have immediate impact on multiple cropping systems.