Cotton root rot (CRR), aka Texas root rot, occurs on wine grapes in the calcareous soils of Central, South, and West Texas where soil pH is well above 7. The most common symptom of CRR in grapes is a sudden wilt and death of the infected vine. All of the leaves on the vine usually turn yellow and quickly become brown and dry. Vines often die in groups as the fungus advances underground along trellises to adjacent vines. Taproot, crown, and lower stem tissues appear dark brown and decayed after the dead bark is removed with a pocket knife. The symptoms become most obvious during the mid-to-late summer months, or when soil temperatures exceed 82 degrees Fahrenheit.
TOPGUARD® Terra Fungicide
As a result of four years of research on control of CRR in wine grapes, the TOPGUARD® Terra Fungicide has been found to reduce losses caused by this deadly disease. It is now available for wine grape growers to use in their vineyards.
In order to use the fungicide on wine grapes, a special copy of the TOPGUARD® Terra label must be in hand in order to apply it in vineyards. A copy of the label for downloading can be found below. Remember – you MUST have this additional label on hand when applying TOPGUARD® Terra on wine grapes in order to comply with pesticide regulations. Also, a bulletin prepared by FMC Corporation can be found. This bulletin contains some background information on how to use the product as well as some expectations for control when properly applied. The fungicide may be purchased from most local agricultural retail outlets.