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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Optimizing Management of Sclerotinia Diseases Through Fungicide Use

Location: Sunflower Research

2012 Annual Report


1a.Objectives (from AD-416):
The overall objective of this proposal is to optimize management of sclerotinia stem rot (SSR) on canola. Specific objectives will be.
1)develop a regional base line of fungicide sensitivity to common fungicides used for control of S. sclerotiorum in the north central region;.
2)identify fungicide mixtures that provide improved SSR control on canola; and.
3)characterize the value of new biological control compounds available in the U.S. market.


1b.Approach (from AD-416):
To achieve the objectives we propose to conduct replicated laboratory and field trials. Laboratory trials will be conducted to develop base-line information on fungicide sensitivity to fungicides currently registered for use to control SSR in canola, soybean, and dry bean. The information generated by these studies will serve in the detection of isolates with increased fungicide resistance. Laboratory trials will also be used to calculate 50% lethal doses (LD50) for mixtures that will be evaluted in the field as well as to evalute the probability of development of resistance. Field trials will be used to optimize concentrations of fungicides in mixtures. Special attention will be made to the analysis of the economic aspect of disease control. Field trials will also be used to identify the relative value of new biological compounds that are getting into the U.S. market, as well as of others that have not been previously evaluated for use in canola. Efforts will be made to create high disease pressure by inoculating ascospores twice on flowering canola plants. The research proposed here is included as one objective in the Strategic plan of the Sclerotinia Initiative. Results from these sutdies will be available for growers in a short period of time since we plan on presenting this information at field days and other growers meetings.


3.Progress Report:

This project was initiated on July 1, 2011, research is ongoing, and the overall objective is to optimize the fungicide management of Sclerotinia diseases in canola.

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.


Last Modified: 7/31/2014
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