With the current weather trend we are in considerable risk for white mould infection in soybeans again this year. Daytime temperatures between 20-25C and night time temperatures below 15C with regular rainfall, heavy dew and high humidity points to high risk. Below are some of the risk factors that possibly lead to white mould infection. Fields in wider row spacing and later planting often have lower risk. A hot, dry spell will cancel the risk for white mould. Spores will not survive without free moisture at the soil and in the canopy.
Soys on soys
Cool, wet weather, high humidity
Lush early canopy
Alternate susceptible hosts
The first line of defence is rotation, wider rows and reduced seeding rates. In crop the final option is fungicide applications. These will help reduce white mould infection but are far from perfect. 4-7 bu/ac protection from losses due to white mould is a common response. Soybeans are continuously flowering making timing of application very difficult. High risk farms should consider 2 passes. Timings at R1 and R3 are ideal for the 2 pass plan. If the risk is more moderate and you are choosing to apply once the timing is at R2-R2.5. The reproductive stages are attached for soybeans and we are happy to help you stage your fields for application timing. Many fields are entering R1 stage currently and you can expect R2 in approx. 7 days. The target of the white mould spray is the flower petals. They are the host for the initial infection. There are low and high rates for some of these products based on your perceived risk for white mould infection. High water volume and excellent coverage within the canopy are critical for the success of these products.
Fungicide options include:
*white mould rate
Many agchem suppliers have rebate programs that support price discounts for fungicides. Be sure to check with your retailer for details.
***If your soybeans are destined for a specialty IP market, be sure to check with your contract provider to know which products are approved for the destined export market.***