Cotton Blue Disease in Georgia Cotton and it’s Implications on Production for 2019

This information is from the University of Georgia Extension Cotton Team

In the fall of 2018, Cotton leafroll dwarf virus (CLRDV) was confirmed to infect cotton plants in 14 South Georgia counties. During the winter of 2019, this virus has already been confirmed to infect cotton regrowth from ratooned cotton stalks and several weeds; even though screening has just begun. This virus is associated to cause cotton blue disease (CBD) with symptoms that include leaf curling, reddening and drooping of leaves, subsequent distortion of leaf growth above the nodes where reddened leaves were first observed, and shortening of upper internodes and their discoloration to deep green along with subsequent lack of fruit retention. Some view the symptomology to resemble that often observed with drift from phenoxy herbicides such as 2,4-D, 2,4-DB, and dicamba.

Cotton blue disease, caused by the aphid-transmitted Cotton leafroll dwarf virus, is newly detected in Georgia cotton but has been previously observed in Argentina, Brazil and some regions of Asia and Africa. Although resistance has been bred into cotton cultivars in areas with history of CBD, there are currently no known resistant varieties being planted in the United States. Efforts to bring resistance to varieties which are commercially viable are underway, yet it is clear that introduction will take years. The presence of CBD in the Southeastern US is potentially alarming because of three particular concerns: (1) susceptibility of our cotton crop, (2) size and importance of the crop in Georgia and (3) the widespread presence of aphids which vector the virus. Although it would seem logical to more aggressively control aphids to manage this issue, it just is not that simple as aphids are dynamic infesting a vast array of plant species in varying landscapes. Thus, chemical control methods could actually increase pest management issues (i.e. treating for aphids would likely flare other more nefarious insect populations) without reducing impact from the virus; much more research is needed to better understand this scenario before providing aphid management recommendations.

Although the impact from this virus to the 2019 Georgia cotton crop cannot be scientifically determined, it is important to discuss the situation. Science does not currently support increased insecticide use to control aphids. However, there may be two approaches that could benefit overall farm sustainability while also possibly reducing impact for CBD including (1) removing cotton stalks from 2018 and (2) controlling winter weeds well in advance of planting.

Ultimately what producers in Georgia should know is that there is a new virus that COULD attack our cotton crop. The UGA Cotton Team is working diligently to obtain as much information as possible and is currently developing research strategies for 2019. At this point we know that the virus is present in living cotton stalks and henbit. Therefore, one could consider it prudent to consider trying to eliminate a source of the virus, especially considering the practices are already endorsed and encouraged anyway. If you have any questions, feel free to contact your local county extension agent and visit the UGA cotton webpage at www.ugacotton.com  for more information.

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