By: Dr. Bob Kemerait
Here are some comments:
- Finding white mold in a field in August is not necessarily a “BAD” thing for me. It demonstrates that A) SOMEONE cares enough to look, and B) SOMEONE knows what white mold looks like.
- White mold is likely to be found now in most every field EXCEPT after A) long rotations with non-host crops or, perhaps, where Georgia-12Y is planted.
- No fungicide program, no matter how good it is, can eliminate ALL of the white mold in a field. Individual plants affected by white mold is often times inevitable.
- The mark of an EFFECTIVE fungicide program for white mold is that A) the disease is contained to individual plants, not spreading along a row, and B) the fungus is not strongly active on the plants are are affected (yes the plants may die, but the fungal growth is restricted).
- Spreading white mold in a field is an obvious sign for concern, but may not be the fault of the fungicide. Other factors that affect efficacy of a program include: A) good timing for fungicide applications- don’t get behind, B) Effective use of rainfall/irrigation to move the fungicide from the foliage to the crown of the plant where it is needed, C) rainfall or irrigation within 24 hours after application.
- Clearly, some fungicides are better than others, but simply finding “some white mold” in a field is not necessarily and indication that the fungicide program failed or that the grower needs to “switch up” and change fungicide programs. The grower should maintain realistic expectations for success.
- Some fungicides are CERTAINLY better than others for management of white mold. For example, tebuconazole is cheap and effective, but other products such as Elatus, Fontelis, Convoy, Umbra, and Provost Silver are better. Yes they cost more, but white mold that is not effectively controlled can steal much more value from the grower than the difference in cost.
- When is the field “safe”? Growers should consider protecting their field from white mold to within 2 weeks of digging. Where white mold is scarce in a field, I do not believe that a grower needs apply additional fungicides for white mold (leaf spot may be a different story) within 3 week of digging.