Handling Plant Bugs Post Bloom

Plant bugs are still being found and treated, even farther into the Coastal Plain than usual.  It seems like a lot of our fields treated for plant bugs in the past have experienced pressure once cotton blooms and corn dries down.  With that in mind, it will pay to be vigilant, although not over reactive, to plant bugs.

Hopefully you’ve been monitoring both square retention and sweeping for plant bugs in squaring cotton (see previous article here and here).  Once blooming has been under way for one to two weeks, square retention is a less reliable indicator of possible plant bug feeding, due to natural square loss for mostly weather-related reasons.  In blooming cotton, the presence of plant bugs and their damage is best assessed by continuing fruit examinations, evaluating dirty blooms, and by the use of a black beat sheet (also called a ground cloth, drop cloth or shake sheet).  Plant bug feeding on large squares damages their pollen anthers which subsequently show up as easy-to-spot brownish to black anthers when the flower opens.  Although we do not recommend the use of a dirty bloom threshold, dirty blooms are easy to spot and may indicate plant bug activity. So you can use these dirty blooms as a method to identify when a field should be scouted more intensively.

During the bloom period, the black beat cloth (also called a ground cloth, drop cloth or shake sheet) mentioned previously is probably the best tool to access live plant bug levels. This video covers the proper use of the black beat cloth. Because plants bug may be active, they should be counted quickly. Researchers have found that the small plant bug nymphs are much easier to identify on a black beat cloth than older standard white beat cloth. Scouts should be aware that plant bugs may be more common at field edges or in rank areas. These trends should be noted by scouts, as they are sometimes taken into consideration in making treatment decisions. However, this occurrence also points out the need to sample randomly from throughout the cotton field.

Finally, once threshold has been met (two to three plant bugs per beat cloth sample (equal to 5 feet of row)), a treatment action can be made.  Please use this previous article as a starting point for insecticide choice.  Note that our goal is to get to a point where we can manage stink bugs and plant bugs in tandem (generally somewhere in the third to fifth week of bloom).

Written By

Dr. Dominic ReisigAssociate Professor and Extension Specialist (252) 793-4428 Entomology and Plant Pathology - NC State University

Posted on Jul 16, 2014

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