Scout for Tarnished Plant Bugs (Phillip Roberts, UGA Extension Entomologist) Yes, we too have some selected areas of plant bug issues. Brandon Phillips Crop Consultant shared his plant bug numbers from previous sweep net counts above threshold and a 65% square retention (85% square retention or better is desired). Unlike cotton production areas in the Mid-South, tarnished plant bug is an uncommon and sporadic pest of Georgia cotton. However, tarnished plant bug populations must be scouted as economic infestations occur in some fields each and every year. Only treat tarnished plant bugs if threshold levels are exceeded.
Tarnished plant bug sprays are disruptive to beneficial insect establishment. Our primary method for scouting plant bugs is square retention. Our goal is to retain 80 percent of all first positions as we enter bloom. The square retention technique works well in pre-bloom cotton but is not as a reliable technique in blooming cotton as physiological shed confounds counts. More scouts are using sweep nets to monitor plant bugs. Sweep nets are an excellent tool for monitoring adult plant bug populations, but the drop cloth (especially a black drop cloth) is more effective for monitoring immature plant bugs.
Adult tarnished plant bug (left) and immature tarnished plant bug in bloom (right). Images by Russ Ottens, University of Georgia and Ron Smith, Auburn University, Bugwood.org. Effective use of the sweep net becomes difficult after bloom due in part to plant size and more emphasis should be placed on use of a drop cloth.
Also, be observant for both adult and immature plant bugs when making visual plant inspections; examine terminals and inside the bracts of squares, blooms, and small bolls. Also, be observant for “dirty blooms”, blooms in which many of the anthers are dried and brown. Dirty blooms are an indication that plant bug (especially nymphs) are feeding on larger squares which the plant did not shed. “Dirty Blooms”. Images by Ron Smith and Barry Freeman, Auburn University, Bugwood.org. Clouded plant bug adult (left) and immature (right). Images by Ron Smith, Auburn University, Bugwood.org.
Tarnished plant bug thresholds can be used for clouded plant bugs, but clouded plant bugs should be counted 1.5 times when using a sweep net. Note that the threshold is higher during the third week squaring and bloom compared with the first two weeks of squaring. Sweep Net and Drop Cloth Thresholds: Third week of squaring through bloom: Drop Cloth: 3 plant bugs/6 row feet, Sweep Net: 15 plant bugs/100 sweeps First 2 weeks of squaring: Drop Cloth: 1 plant bug/6 row feet, Sweep Net: 8 plant bugs/100 sweeps