Low aphid pressure meant minimal incidences of cotton leafroll dwarf virus (CLRDV) this year in Alabama, according to Amanda Strayer-Scherer, Extension plant pathologist and Assistant Professor at Auburn University.
“This year, mainly, I think the biggest thing was at least for us in terms of Alabama, we had very light aphid pressure. That’s what vectors the disease and what it comes in on,” Strayer-Scherer said.
“What we did see was it varied in terms of incidences throughout the state. The southwest part of Alabama, in our trials near Fairhope and Brewton, we saw the greatest incidences from it. Then as you move toward the central part of the state it decreased in the Pratville/Headland area to where it virtually was non-existent in the Tennessee Valley. We only had three confirmed positives the whole season in our sentinel plot up there; very light aphid pressure, especially in the northern part of the state.”
Colder Weather Impacts Aphid Pressure
She believes the harsher winter and harder freezes contributed to the lack of aphids this year.
Symptoms from early season infections of the virus include stunting or dwarfing of the plants, compacted terminal growth, upward-cupped leaves, red discoloration of petioles and stems, distorted growth with yellowing around leaf edges and crinkled leaves.
Research specialists in Alabama have been monitoring the aphid-transmitted disease since its appearance in cotton fields during the fall of 2017.
“But I would say out of all the states, Alabama has seen it the most. I know in Georgia’s it’s occurred more sporadically and hasn’t really caused too many issues yet,” she added.
CLRDV is known to cause cotton blue disease (CBD). It can reduce yields up to 80% in cotton fields infected in early growth stages. Symptoms include leaf curling and reddening and drooping leaves.
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