As cotton matures this growing season, Alabama farmers could battle a new strain of cotton blue disease (CBD) that reduced yields by nearly 50,000 bales in 2018.
Cotton leaf roll dwarf virus (CLRDV-AL) is an aphid-transmitted disease that diminishes blooms and bolls in the upper canopy, resulting in lower yields — particularly in late-planted cotton, according to the Alabama Cooperative Extension System (ACES).
The Alabama Farmers Federation’s Carla Hornady highlighted the importance of checking fields for initial signs of CLRDV-AL.
“The most obvious sign that aphids spread CLRDV-AL to your field is a reduction in bolls,” said Hornady, the Federation’s Cotton Division director. “However, farmers should stay vigilant and look for early symptoms like red leaf veins and cupped leaves. Severely damaged plants also grow taller and may look healthy from far away.”
CLRDV-AL symptoms include stunting due to internodal shortening, leaf rolling, distorted new growth, reduced flowers, decreased boll size and sterility.
This new strain of virus was first observed in Brazilian fields of CBD-resistant cotton in 2006. Researchers identified the virus in Alabama in 2017 before discovering CLRDV-AL in Florida, Georgia and Mississippi.
ACES experts report symptoms are most severe in June-planted cotton, a concern for farmers delayed by a wet-then-rainless planting season. Signs of CLRDV-AL appeared in August and September the last two years, though mild winter weather and aphid overwintering in wheat and live cotton stalks could lead to earlier onset symptoms in 2019.
Hornady said the best defense against CLRDV-AL will be new, resistant cotton cultivars, which could take years to develop, test and get to market. Report signs of CLRDV-AL to your local Extension agent or contact Hornady at email@example.com.
Cotton is Alabama’s largest row crop, with state farmers expected to plant 510,000 acres this year.