By Katie Nichols
Extension professionals have already confirmed the presence of Cotton leafroll dwarf virus (CLRDV)—the causal agent of Cotton Blue Disease—on multiple research substations across Alabama. The aphid transmitted disease has been monitored closely since its appearance in cotton fields during the fall of 2017.
Kassie Conner, an Alabama Extension plant pathologist, said the virus was confirmed in samples taken since July 1, 2019. The first diagnostic test was not available for the virus until October 2018, which made it difficult to identify plants with symptoms during the 2018 growing season.
“This does not mean the virus was not present earlier, it only means we did not have the capability to test for the virus until then,” Conner said. “Last summer, symptomatic plants were found at substations as early as mid-September, with the worst damage recorded in June-planted cotton in fields in Baldwin County.”
Conner, who is also the director of the Auburn University plant diagnostic lab, said specialists have also identified several weed species that are alternate hosts for CLRDV. The most alarming hosts are white clover and henbit—common weeds found all over Alabama. This confirms a heavy virus presence in the environment.
CLRDV Symptoms
Symptoms from early season infections include:CLRDV
- stunting/dwarfing
- compacted terminal growth
- upward-cupped leaves
- red discoloration of petioles and stems
- distorted growth with yellowing around leaf edges
- crinkled leaves
Submitting Plant Samples
Conner said the data will help researchers better understand the development and distribution of the disease.
Follow these steps when collecting samples:
- Collect five samples from symptomatic plants and non-symptomatic plants at each location (one sample = top 6 inches of plant).
- Place samples in a sealable plastic bag with no other material (no paper towels).
- Keep sample cool—place in a cooler, refrigerate until shipped and ship overnight with an icepack in a styrofoam cooler.
- If aphids are present, collect and send them on the plant material.
- Include a submission form and shipping permit in a separate sealed bag in the package. Shipping permits are only necessary if samples originate outside of Alabama.
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