With cotton moving along throughout North Louisiana, tarnished plant bugs have begun to migrate into fields. As a result, Dr. Kerns and I been receiving more calls relating to TPB thresholds and treatments in early bloom cotton.
Tarnished plant bugs are ¼ inch long insects that vary in color from yellowish brown to green with black markings and a conspicuous triangle located on the dorsal (back) side. Nymphs resemble the adults in general body shape and color but do not have wings. Tarnished plant bugs damage cotton from pinhead square to final boll set. Larger square damage affecting anthers, stigma, and styles can cause fertilization problems and fruit shed.
The Louisiana threshold for bloom to harvest is 2-3 TPB per 5 ft of black drop cloth, 10 TPB per 100 or sweeps or 10% dirty squares. Pre-bloom threshold levels are 10 -25 TPB per 100 sweeps. Tarnished plant bugs are a difficult pest to control with constant insecticide rotation essential to attaining satisfactory control and prolonging the life of our current insecticide chemistries. An initial application of imidacloprid, at high label rates, gives suppression of TPB. If cotton is beginning to bloom, an application of Diamond tank mixed with a neonicotinoid should be strongly considered. Diamond is an insect growth regulator and will not control adult TPB, an adulticide needs to be added in with the application to control adults. Diamond has excellent activity on large nymphs while also causing egg sterility. Additionally, Diamond offers good residual activity and nymphal populations may be suppressed 7-14 days after application.
Once an initial Diamond application has been used, producers should rotate away from Diamond and rely on its residual activity for eggs and hatching nymphs. However, producers should also target migrating adults with something that will offer good adult control. Insecticide choice at this time may likely be dictated by the presence of aphids, mites or bollworms. Diamond may be good for a follow up after this application.
If you have questions or concerns feel free to contact Dr. David Kerns or Sebe Brown for more information.
Dr. David Kerns Cell: 318-439-4844 Office: 318-435-2157
Sebe Brown Cell: 318-498-1283 Office: 318-435-2903