Managing Soil-Borne Fungal Pathogens

January 8, 2024

Soil-borne diseases such as phytophthora, rhizoctonia, dampening off, pythium, verticillium, fusarium, timber rot, white mold, and others can cause significant challenges and yield loss in crop production.

As in all cases of disease and insect pressure, there are particular areas of nutrition and biology that have to balanced so that the symptoms of the problem disappear.

An exceptionally effective treatment is sowing a mustard cover crop and letting it grow till it has been blooming for 5-7 days. During this time, the mustard sends out chemical compounds that have a bio-fumigant effect on these soil-borne pathogens, as well as on root rot nematodes. Terminate and incorporate 2 weeks before planting the next crop. This is especially successful on vine crops, such as watermelon, cantaloupe, squash, zucchini, cucumber, and pumpkin.

Cole crops need to be treated differently – mustard should be avoided just before these crops. These crops, which are broccoli, brussel sprouts, cauliflower, cabbage, and kale, are in the same general family as mustard and therefore should not be sowed just prior to these cash crops.

Rhizoctonia and dampening off are two diseases that are known to be a challenge in cole crops within the first week or two right after planting. This can be avoided by shifting the profile of bacteria and fungi that are in the soil. Many time, this is on freshly-tilled soil and the biology has not been rebuilt yet. We have seen very successful results from drip irrigating 4 qt. Rejuvenate and 4 qt. SeaShield per acre to help rebuild this biology. Ideally, this application would be applied 1-2 weeks before planting, but we have seen it successful even at planting.

Another newer tool in the toolbox is to use Serenade ASO, which is a strain of Bacillus Subtillus. This particular strain has been well-documented to shift the soil environment so that these soil-borne pathogens do not thrive. It is registered OMRI listed fungicide, but it very different from many of the fungicides that are out there, in that it actually has a very beneficial impact on the soil biology we desire.

In addition, James White from Rutgers University has determined through testing that this product actually enhances the rhizophagy cycle, which is where soil microbes are providing an increasing amount of the plant’s nutrition. It has also been determined that Serenade ASO will enhance the root system. How awesome is it that you can manage diseases while also enhancing root development?

We will have Serenade ASO available this year for those of you who want to try it.

Finally, we come to plant nutrition. While all minerals have an effect on these diseases, trace minerals especially so. Manganese, Copper, Zinc, Boron, and Molybdenum all play major roles in these diseases. And they need to be balanced to have the best effect.

In summary, to manage these diseases, I would first of all look at utilizing cover crops and especially mustard. This is the foundational piece. Next, use Rejuvenate and SeaShield to enhance the biology. These two are the most important because they give you advanced support. Next step could be to try Serenade ASO in the transplant solution, if that is an option – drip irrigating it if it is not. Then utilize sap tests throughout the season to manage the nutrition more closely.