Examining Disease In Taraxacum officinale by Sclerotinia minor From the Bioherbicide Sarritor™.

Broadleaf weeds such as dandelion (Taraxacum officinale Wigg.) are major pests of low input turfgrass. Conventionally, chemical pesticides such as 2,4-D, mecoprop and dicamba have been used to manage these weeds within a turfgrass stand. However, in 2009, the province of Ontario implemented a cosmetic use pesticide ban restricting the use of pesticides on turf and landscape plants in urban settings. Several products are being developed and evaluated to meet the increased demand for alternative weed management strategies. One of the alternatives available for use on home lawns is Sarritor^™ Granular Biological Herbicide containing the plant pathogen Sclerotinia minor Jagger. Living organisms such as S. minor require specific conditions to thrive. Thus, their efficacy is often variable as the ideal conditions can be unclear. Growth chamber studies are being conducted to examine the optimal temperature and leaf wetness duration for infection of S. minor from Sarritor^™ on dandelions. Treatments include five temperatures: 12^oC, 16^oC, 20^oC, 24^oC, & 28^oC and thirteen leaf wetness durations: 0 to 96 hours, in 8-hours increments. Once treatments have been applied, disease severity on dandelions is measured using a scale from 0 to 10. The disease severity at each of the temperatures will be analyzed using ANOVA, while the relationship between temperature and leaf wetness duration will be analyzed using non-linear regression. All statistical analyses will be performed using SAS 9.2 (SAS Institute Inc.). Preliminary results suggest that temperature has a significant effect on growth of S. minor from Sarritor^™. The greatest initial incidence and severity occurs at 16^oC while little to no disease occurs at 12^oC.  Leaf wetness duration does not appear to play a major role in disease severity at this time. This study will be repeated twice.