Dealing With Plant Bugs During Early Bloom
DR. SCOTT STEWART
JACKSON, TENN.
Tarnished plant bug infestations in pre-flowering cotton have been pretty typical thus far … sporadic infestations with many but not all fields requiring at least one treatment. Realistically, I expect more consistent problems as we move through July. Below are a few thoughts about the best management practices for plant bugs over the next two weeks.
• Consider using a sweep net and a drop cloth in tandem during early bloom. As we progress further into bloom, I prefer the drop cloth because the population often shifts primarily to immatures. However, the 14 days just before and after bloom is a time where we might see mixed populations of nymphs and adults knock off squares and feeding on small bolls.
• Continue monitoring square retention in the top five nodes for 10-14 days after first bloom. Monitoring square retention after this point is generally not suggested for a couple of reasons. Later squares will not contribute much to yield. You can also get a ‘bad read’ as squares will naturally shed as the plant develops a fruit load.
• Treat for plant bugs when infestation levels average 15 or more plant bugs per 25 sweeps or when 3 or more plant bugs per drop cloth. It is very likely a second spray will be needed at a 4-5 day interval if infestations are several times threshold, particularly when the population is composed mostly of immatures.
• Use the right insecticide! We have several excellent treatment choices for cotton just prior to flowering and during the first two weeks of bloom. This is an good window for the use of 1.5 oz of Transform (1.5 oz/a) or Diamond (4-6 oz/a and usually tank mixed with Orthene/Acephate or Bidrin). Transform and Diamond provide unique modes of action. This is also a time where Acephate (0.67 – 0.75 lb/a) or Bidrin (5-8 oz/a) work well by themselves, although many will reserve the use of these products as tank mix partners with pyrethroids until later in the season when stink bugs and bollworms are a bigger part of the equation.
• Don’t use the wrong insecticides. Pyrethroid insecticides applied alone will provide little or no control of tarnished plant bug. Also, I suggest laying off neonicotinoid insecticides such as Centric or the imidacloprid products once past first bloom, in part for resistance management but also because they just don’t work as well in this window as immature plant bugs are a growing part of the population.
Note - Bidrin is not labeled for use during the interval of first square to first bloom. Please follow the label restrictions for this and other insecticides. ∆
DR. SCOTT STEWART: IPM Extension Specialist, University of Tennessee
