While it isn’t a concern that affects the entire service area of Central Valley Ag, white mold affects enough of us—and with such impact—that I’d be more than remiss not to address it here. Historically, there aren’t a lot of options to deal with it, but, friends, take heart, whether it is your fields that are affected, or your neighbors, or your uncles: there are steps that we can take to manage it from this point forward, and we at CVA are pledged to continue to bring you solutions as they come to light.
We might not be able to technically beat Sclerotinia, the pathogen that causes white mold, at this point in time, but we can use a combination of cultural and chemical approaches to manage it better than ever before.
I’m going to skip telling you how to recognize the signs of white mold, because you already know if you have it. The approach I’ll lay out here takes the perspective that we should treat problem fields as problem fields for the rest of time and be proactive in our treatment of them rather than reactive. So, if you’ve got a field with soybeans and a history of white mold, go out and tackle it. You, friend, have two of the three points of the disease triangle—host and pathogen. Don’t wait for the third—conditions—to manifest because the conditions are certainly coming, as soon as you start irrigating.
So just go take it on instead of letting history repeat itself.
At this point in the season, management options are all chemical. Sclerotinia invades soybean stems via dead flowers, so we can delay infection of the stem if we soak those flowers with a fungicide application while the plants are still small. This won’t prevent infection eventually, but it will delay it and thus lessen the considerable damage that white mold can cause. Then, later on during R2-R3, we can make a subsequent fungicide application to help your plants pull through until the end, not unscathed, but faring so much better than if we just accepted white mold as fate.
Once we shepherd our plants through to harvest this year, we can then start to institute cultural practices that will further lessen the blow of white mold in future years by reducing its spread and disallowing it opportunities to splash out of the soil and infect our plants.
During harvest, the cultural practices are as simple as harvesting the fields with the worst infections last and washing your combine afterward to lessen the spread of the spores.
Outside of harvest, changing your cultural practices to disturb your soil as little as possible will help contain the pathogen to the soil. The use of cover crops assists to this end as plant residue left on problem fields will act as a lid of sorts, inhibiting the ability of the ascospore to splash onto future plants and cause an infection.
The reality of this situation is that no one management practice will solve the problem, but the combination approach of chemical and cultural practices will mitigate the effects of a problem that up until now has evaded our efforts. The message that is implicit in this, but that I want to make explicit here, is that you can’t be discouraged. The improvements these practices bring might not be as immediate or as profound as you would like, but they will gain and build and each year we at CVA will mine the yield data to continue to bring you additional strategies to combat this difficult disease.