Scorching temperatures and dry conditions could make an already tough whitefly season even worse for cotton growers, according to Phillip Roberts, University of Georgia Cooperative Extension cotton entomologist in Tifton, Georgia.
“In cotton, populations can build so rapidly. Whiteflies really thrive in hot, dry conditions. They’ve just exploded in some localized areas in the last 10 days. The last 10 days, we’ve seen numbers go from moderate to really high,” Roberts said. “These whiteflies will turn a generation every 14 days. We need some rains, not only for the crop, but we also need those rains to help us suppress these whitefly numbers.”
Whiteflies Worse Than Normal
Roberts said populations are above average or worse than normal. Farmers started treating for whiteflies two weeks ago. It is unusually early since treatments have generally started in August in previous years. It is especially important for farmers to scout and manage whiteflies accordingly since cotton is at such a vulnerable stage in the growing season.
“The younger the cotton is when whiteflies infest the cotton, the greater the potential yield loss is. We can manage them, we just need to know that they’re there. We just need to make good decisions and do what we need to do,” Roberts said.
When uncontrolled, whiteflies can reduce cotton yields and affect cotton quality. Whiteflies are sucking insects that feed similarly to aphids. When they feed on a plant, they excrete a sugary substance called “honeydew,” which serves as a host for the sooty mold fungus. The accumulation of honeydew and sooty mold leads to quality problems on open cotton bolls.
“Right now, we’re dealing with them here, but the question is how much is this going to mushroom or spread outside of our area where we typically deal with them? That’s like the million-dollar question. We don’t know the answer but what we can say is that wherever you are, that you need to be scouting your cotton for whiteflies.
“One of the things that I try to stress, once you know you have whiteflies at any level in a cotton field, they should influence every decision you make for insects the rest of the year. What we mean by that, once you have whiteflies, we need to only spray other pests like stinkbugs; only spray when absolutely necessary based on good scouting and use of thresholds. You need to conserve beneficial insects. Whitefly control, if we have to intervene with insecticides, it’s very expensive. It’s a pest we just don’t have in our budget.”
Why Such a Problem?
Whiteflies are a greater problem this year due in large part to the mild winter. While colder temperatures do not eliminate whiteflies, they do kill off many of their wild hosts and slow population development in cultivated hosts. Warmer temperatures allowed for larger whitefly populations to overwinter and become mobile earlier this summer.