White Mold In Peanuts

We are having really conducive conditions now for white mold (Sclerotium rolfsii). It is very hot and having more showers across the county. This field has had a good fungicide program and has been nearly 7 years without peanuts, still white mold is showing up in spots. There may also be some underground white mold which is the same pathogen as above white mold. Often with underground white mold, the top of the plant look okay. We see damaged pods and pod rot. In hot weather, we often see the underground type. We are going to have to tighten up on our spray intervals and use good chemistries. Below is an up close of white mold. You can see the white mycelium growth and round BB’s, which are sclerotium.

Cottony mycelium and sclerotium (BB’s) of white mold

Pod rot and mycelium of underground white mold

Here are some tips from UGA Extension Pathologist Dr. Bob Kemerait as we continue to fight this disease with conducive conditions:

1.  REMEMBER:  In a season like this, the perfect storm of a season, even our BEST fungicide programs for white mold may only provide ~70% control.  No program will stop all initial “hits” of white mold where a plant here, there and across the field wilts.  BUT a fungicide program MUST prevent the disease from spreading from that plant to other plants within the row and down the row.
2.  Though most most growers will not adopt this practice, spraying the peanut field at night or in the darkness of early morning when the leaves are folded is a GREAT way to get the fungicide where it needs to be (the crown of the plant).  
3.  Where a grower is not satisfied, he may consider using a more aggressive fungicide.  For example, Tebuconazole/Bravo is good but not the best.  If problems are developing, he may shift to a more effective (an more expensive) program.
4.  Consider extending the white mold schedule.  Even if the grower has completed a “traditional” white mold program, he may extend the program, perhaps using the Tebuconazole/Bravo program mentioned above.
5.  Use anticipated rain events and irrigation to move the fungicide to the limbs and to the crown of the plant.