As we enter the flowering period for winter oilseed rape - with some forward crops potentially approaching the mid flowering stage - the risk of sclerotinia stem rot begins to rise.
Typically, winter OSR is at the highest risk from this disease at mid flowering, but if the conditions are right, infection can set in much earlier, during early flowering.
Identifying the risk of sclerotinia stem rot
There are two key factors which facilitate the emergence of the disease.
The first is the presence of sclerotinia in the soil, which may have been dormant for many years.
The second is favourable weather conditions - specifically - relative humidity above 80% and temperatures warmer than 7℃ for more than 23 hours.
The AHDB website has a helpful, weather-based risk tool you can use to help you identify the threat from sclerotinia.
The disease can be difficult to spot, often going unnoticed until the summer. Early signs include empty pods on bleached stems. Open any that are cracked, and look for the tell-tale indications of sclerotinia - white fungal growth and black fungal bodies inside.
Acting early to prevent infection
Where crops are at risk of sclerotinia, it’s important to act early. The oilseed rape fungicides that target this disease are protectants, which means they need to be applied before infection.
As per the AHDB risk tool, that means spraying your crops now, while the risk is low. Now is a good time to act to protect crops and optimise yield.
If you have OSR that might be at risk, there are a couple of disease control options to consider.
1. STOCKHOLM EC
From early to full flowering, STOCKHOLM EC (prothioconazole+tebuconazole) can be applied at up to 1.0 L/ha in any preventative scenario. Apply a maximum of two times per crop, leaving at least 21 days between applications.
2. EVITO-T
EVITO-T (tebuconazole+fluoxastrobin) can also be used preventatively, from early to full flowering. Its combined formulation works more effectively than either active used alone, with high systemicity and good mobility. This results in excellent rainfastness and even distribution.
Apply up to 0.8 L/Ha, with the best results coming from a full dose spray between GS 61-65. Do not apply before 10% of flowers on main raceme open, main raceme elongating (GS61) or May 1 if this occurs after GS61 in the year of harvest.
For more details about these preventative fungicides, head over to the STOCKHOLM EC and EVITO-T product pages.
