Sclerotinia is a soil-borne fungal pathogen, which can remain viable in the soil for up to 8 years. A single sclerotium produces 10 – 14 apothecia which in turn produce 10 – 14 million spores and it can affect many crops, including: oilseed rape, peas, beans, lucerne, carrots and potatoes (>400 host species).
Sclerotinia is usually the main disease to impact OSR at the important flowering stage and in severe infections the yield impact can be over 50%! Although epidemics are uncommon, localised infections occur most years and the inoculum burden continue to build if infections are not controlled.
There are three main factors required for the infection cycle to take hold in OSR, as illustrated in the graphic below:
1. Presence of sclerotinia fungal resting bodies (Sclerotia) in the soil which germinate when soils are moist and >10°C
2. Favourable weather conditions, long periods (>23hrs) of relative humidity >80% & air temperatures >7°C (day & night)
3. Crops to be in flower, providing spores with external nutrients needed for germination
Traditional management of Sclerotinia involves monitoring crop and weather conditions, as well as fungicide strategies, managing susceptible weeds and crop rotation. Timing is key as existing chemical controls are protective not curative! Once you see the infection it is too late and identifying presence of the disease can be done based on the scoring system below.
Most sprays offer approximately three weeks control; therefore, two sprays are often required to cover most of the flowering period. (Although flowering can last circa 8 weeks). Fungicide efficacy may be limited as new flowers will form during the flowering period that will not be protected by previous applications.
PT303 has a unique native multi-genic sclerotinia tolerance trait. By sowing PT303 growers can incorporate a level of tolerance to sclerotinia for the first time into their crop management planning.