by Sebe Brown and Dr. David Kerns, LSU AgCenter Entomologists, and Dr. John Kruse, Cotton and Feedgrains Specialist
With most of the cotton in Louisiana at or reaching bloom, producers and consultants have options when sampling for tarnished plant bugs. Sweep net, drop cloth and visual inspections are sampling methods that help aid in application decision making. However, each method has its advantages and disadvantages. Drop cloths and sweep nets are not intended for all types of insects. Sweep nets work best for sampling adults while drop cloths for immature insects, and visual inspection is subject to variability from person to person and is not standardized.
Drop cloth sampling has typically been regarded as the best way of accurately measuring the amount of tarnished plant bugs present in a field. A typical drop cloth is 2.5 X 3 ft in area and black in color. However, pest managers and consultants are often reluctant to use drop cloths because of effort and timed required for sampling. Drop cloth efficiency is dictated by crop size, weather conditions and row spacing. Dr. Roger Leonard, in the link below, demonstrates how to effectively use a drop cloth.
Sweep net sampling employs the use of a canvas net fitted to a standardized 15 inch metal hoop attached to a handle. Sweep net sampling allows the user to scout large areas with increased efficiency and mobility. However, due to the sweep nets limited sampling area, sweeps may miss insects in the lower portion of the plant canopy. Dr. Roger Leonard, in the link below, demonstrates how to effectively use a sweep net.
Visual inspections base recommendations on perceived damage and fruit retention by cotton plants. However, these visual methods are not standardized and considerable variability exists between individuals. Also, accurate thresholds have not been established for visual damage and often rely on experience rather than research.
With corn beginning to dry down across Louisiana and tarnished plant bugs migrating into fields, utilizing sweep nets for continued scouting would a prudent choice for detecting adults. It is not uncommon to find tarnished plants bugs above threshold near corn, but 20 or 30 rows into the field have numbers drop off. In these situations, strip treatments may be an economical way for producers to save money and control migrating adults.
For more information concerning insect pest management, contact your local LSU AgCenter parish agent, LSU AgCenter specialist, or Louisiana independent agricultural consultant.