By Clint Thompson
Cotton growers in Georgia and Alabama need to be mindful of high whitefly populations. University of Georgia Cooperative Extension cotton entomologist Phillip Roberts said silverleaf whitefly populations have increased rapidly in some Georgia fields in the past 10 days. Since cotton is susceptible, producers need to scout and take appropriate action.
“It’s extremely important that you know if whiteflies are present. When whiteflies are present, this insect must be a part of every insect management decision,” Roberts said. “What we mean by that is we only want to spray other insects when absolutely necessary, based on scouting and the use of thresholds. We need to conserve beneficial insects as much as possible to moderate and suppress whitefly populations.
“Now, when and if whiteflies exceed thresholds, it is extremely important that applications for whiteflies are made in a timely manner. Our experiences have taught us that it is very difficult and expensive if we get behind and have to play catch up with whiteflies.”
According to UGA Worth County Extension Coordinator Scott Carlson, as of July there was a field in Worth County, Georgia that reached the threshold for whitefly treatment. The same can be said for Colquitt County, Georgia.
Scouting remains the best course of action against whiteflies, which are sucking insects that feed on the underside of leaves and excrete a sugary substance called “honeydew.” This serves as a host for sooty mold fungus. The accumulation of honeydew and sooty mold leads to quality problems on open cotton bolls. When uncontrolled, whiteflies can reduce cotton yields and affect cotton quality.
Whiteflies migrate from winter vegetables to spring vegetables to agronomic crops, like cotton, to fall vegetables and back to winter vegetables. If producers do not adequately scout for these insects, they could face a whitefly epidemic, much like 2017.
Whiteflies are difficult to control because of their prolific reproductive cycle. A female can lay between 150 and 200 eggs, and it only takes those whiteflies two to four weeks to mature into the adult stage and begin reproducing.
While colder temperatures do not eliminate whiteflies, they do kill many of their wild hosts. They also slow population development in cultivated hosts. Warmer temperatures this winter allowed for larger whitefly populations to overwinter and become mobile earlier.