Last season there was some talk about “blue disease” or “cotton leaf roll dwarf virus”. Katie & I have been in several trainings this year where this disease has been discussed. I do not believe we know enough about it currently to predict whether it’s a problem for us. I do believe, however, that you need to be aware of this virus. The following are a few thought that Dr. Kemerait shared:
- Based on research by Dr. Sudeep Bag and the UGA Cotton Team, this virus was found LATE in the 2018 season in cotton in 14 counties across the Coastal Plain of Georgia. It has also been found in Alabama (2017), South Carolina (2018) and Mississippi (2018).
- This virus is spread/vectored by aphids. Dr. Philip Roberts will offer insights into those implications; however and “all out war on aphids from day one of the cotton season” is not the answer.
- Yield losses in Georgia last year, and elsewhere were negligible, though some late-late planted cotton fields in Lower Alabama did suffer significant losses.
- All of our current cotton varieties are likely susceptible; our only suggested management strategy is to avoid planting late.
- IMPORTANT: The 2018-2019 winter has NOT been cold enough to kill all of the cotton remaining in the field from last year’s disaster of a season and with warmer temperatures some (not all) is showing signs of regrowth.
- IMPORTANT: Cotton stalks surviving through the winter and into the spring could serve as a “green-bridge” for the virus (Dr. Bag has confirmed the virus in some of the cotton regrowth samples) and for overwintering nematodes.
- IMPORTANT: the virus may also survive in specific winter weeds (Dr. Bag has found it in hen bit)
- IMPORTANT: While we do NOT have any research to show the full impact of this reservoir of virus in the surviving cotton or winter weeds, it is certainly not a good thing.
- Given the potential threat from a reservoir of virus that exists now, it could be helpful to destroy the cotton and winter weeds well ahead of planting to try and break the life cycles of the virus and the nematodes.
- Though we do not know the full impact of this practice on the severity of Blue Disease in 2019, as Dr. Culpepper stated to me, “our (general) recommendations of pulling stalks and killing weeds are principles based upon decades of sound science and it may be beneficial with this new virus issue. But even if not, these practices are among our “best management practices” anyway and for other important reason.
If you have specific questions, please let us know. Here is a link for more detailed information: Cotton Blue Disease