Silverleaf whiteflies seem to make an appearance in cotton south of us every couple of years. However, normally treatment is unwarranted until late in the cotton season when we have already set a good crop. Unfortunately, last winter was so mild that many populations of whiteflies that were already large, never fully crashed, and therefore gave rise to a new population that has continued to drift north… into our cotton early this season.
Silverleaf whiteflies suck juice from plant tissues much like aphids, and in severe infestations can defoliate entire stands of cotton. Even worse than this leading to yield loss, their excrement can lead to sooty mold infesting cotton lint, and honeydew accumulating for a sticky mess on a cotton picker. This leads to deductions of price and quality at the gin, and a sad day for a farmer.
When do we know we have a problem? The whitefly adults are small, white, flying insects the size of a gnat. They lay tiny eggs on the undersides of leaves and have nymphs that hatch and look like tiny football shaped scales when viewed under a hand lens. They are approximately the size of a ball in a pen. In massive infestations, the adults can be seen flying when the canopy is disturbed as you walk through the field. The threshold is reached when the 5th leaf from the top of the plant has greater than 5 immatures on half of the leaves that you sample in a field. I have already found several fields in Terrell County with whiteflies, but to date none have been above threshold and warrant treatment. However, this could change in the coming weeks. For Treatment options contact your local extension office.