It has been quite an unusual year. We have had good rainfall and few pest and disease issues thus far this growing season. But now we are beginning to encounter a pest that we do not normally pay any attention to in our area of the state. Whiteflies! They are small insects the size of a gnat. Their nymphs attach to the backs of cotton leaves and suck juice from the plant. Eggs laid by these flies are the size of a pin point and are football shaped when examined with a hand lens.
To scout for this pest examine the fifth leaf down from the top of the plant that is attached directly to the main stem. Slowly flip it over and count adults as they fly off. Then pull the leaf off and check for nymphs and eggs. If you have 3 adults per leaf checked and 5 nymphs you are at threshold. Standard for scouting whiteflies is to check 30 plants per field at random.
SLWF adults and immatures feed with sucking mouthparts. Damage ranges from reduced plant growth and vigor, general leaf decline, honeydew deposits on leaves and open cotton (honeydew accumulation on lint will negatively impact quality), and premature defoliation. Yield reductions can be serious. Adult whiteflies are not hard to kill but the nymphs are and they can multiply like crazy over a two week span. This time of year farmers are spraying for stink bugs as well. When using organophosphates you can flare the population of whiteflies because they will eliminate any beneficial insects present. Keep this in mind as you go to the field and consider using bifinthrin or other beneficial friendly products when you must spray for stink bugs. Whiteflies are best controlled with timely applications of Insect Growth Regulators like Knack and Courier.
For more information on the whitefly outbreak you can visit: http://www.ugacotton.com/2017/07/whitefly-alert/
For a UGA handout of Scouting and Managing Silverleaf Whiteflies in Cotton drop by our office.