Background Information
- Sclerotinia is a major disease pest affecting many crops, and farmers rely on genetics and fungicides for control.
- Sclerotinia head and stem infections occur when apothecia release ascospores, which land on plant tissue.
- There is concern about timing and efficacy of fungicide applications to control sclerotinia head rot in sunflower, specifically.
- All fungicides were aerial-applied at R5 stage.
Summary
Fungicides registered in Manitoba for sclerotinia head rot in Sunflower are Acapela, boscalid products (Lance, used in 2024), prothioconazole products (Proline, used in 2024), and Quash. Also available for soil-applied applications is LALSTOP Contans WG.
Zero out of 10 site years have shown statistically significant yield differences between treatments in the Sunflower Fungicide Treatment trial. Test weights in all 10 site years were extremely consistent, so fungicide treatments appeared to have no effect on seed fill.
Disease assessments were performed for sclerotinia head rot, head and stalk rot combined, and sunflower rust. Assessments were done on 100 plants per replicate in each treatment for every site. Across the 10 site years, no disease patterns were observed between treatments. Six sites had lower or the same number of head rot infections in the untreated check versus the fungicide treatment. Three sites had more head rot infections in the treated replicates, and one location was not assessed. Full plant infections were assessed as well to determine if fungicide treatments were impacting the movement of sclerotinia, but results were inconclusive and varied from site to site.
Sunflower rust was also assessed in 2024 and 2025. At the time of assessments (R9), very minor rust infections were observed on the top four leaves of each plant and these were inconsistent among treatments. Proline 480 SC and Quash SC fungicides were used in several treatments and do claim to have strong effects on rust infections, but no promising results were viewed in these trials.
Weather
