Alabama: Cotton Blue Disease On Ratoon Cotton? Does It Matter?

Cotton leaf blue on ratoon cotton plant in Georgia, 2020. Photo: Bob Kemerait

The image above is from Dr. Bob Kemeriat, UGA Extension Plant Pathologist. It is ratoon cotton and displays symptoms of cotton blue disease, which is caused by cotton leafroll dwarf virus (CLRDV),.

Most likely, this cotton crown survived the winter infected with the CLRDV and the reddening and bronzing often associated with blue disease in cotton are on full display.

It is hard to say what this might mean for cotton for 2020. In Brazil, ratoon cotton is a major source for the virus and certainly can result in early movement of the virus into cotton and increased risk of sizable yield losses. Before COVID-19 hit, sampling showed that cotton crowns succumbed to the hard freeze in November, so ratoon cotton is not going to be a virus source in Alabama.

However, the virus was detected in several weed hosts, mainly henbit and Carolina geranium, in mid- to late winter.  Unfortunately, the weed sampling program was suspended in March due to issues relating to COVID-19.

Sentinel plots, with planting date as a variable, were established in early May at the Brewton Agricultural Research Unit and Prattville Agricultural Research Unit. Additional sentinel plots will be planted at several additional AAES outlying units later this month. Dr. Alana Jacobson will be monitoring aphid populations and their relationship with cotton blue disease incidence as well.

The trial will be monitored for the appearance of symptomatic plants and information will be distributed as we receive it. If you see symptomatic plants, particularly in early cotton, please notify Drs. Amanda Scherer, Austin Hagan, or Kassie Conner.




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