Evaluating Insecticide Efficacy Against Tarnished Plant Bugs in Cotton

Introduction

In Mississippi and across the Midsouth, the tarnished plant bug (TPB) is consistently the most economically important insect pest of cotton. TPBs typically cause the most damage from first square to the early flowering growth stages. Depending upon the growth stage, tarnished plant bug sampling techniques and thresholds vary. Adult TPBs are often most abundant during the preflowering stage, while nymphs are more common during the flowering period. TPBs prefer to feed on squares compared to small or medium bolls. Abscission or square loss directly impacts yield and can occur through fruit set. High square loss during the preblooming window has the greatest potential to negatively impact yield, but square loss can occur throughout the season. Damaged squares that do not abscise often develop into flowers that have malformed anthers. Anther damage of greater than 30 percent can result in pollination issues and subsequently lower yield.

There are several insecticide options available to manage TPBs in Midsouth cotton, including products from the organophosphate, carbamate, neonicotinoid, pyridinecarboxamide, pyrethroid, insect growth regulator, and sulfoximine classes. Currently, there is confirmed TPB resistance to organophosphates, carbamates, pyrethroids, and neonicotinoids, and this resistance has led to increased input costs. Current recommendations across the Midsouth are to rotate insecticide modes of action and to tank mix compatible insecticides to achieve satisfactory control of TPBs.

The objective of this study was to assess the relative efficacy and crop protection provided by the multiple insecticides commonly used in Midsouth cotton production to control TPBs.

Methods

Field experiments were conducted from 2017 through 2021 at nine locations across Arkansas, Louisiana, Mississippi, and Tennessee. Treatments were applied at the labeled rate during the blooming window when TPB nymph populations reached or exceeded each state’s respective economic threshold insecticide.

Results

• Tarnished plant bug nymph numbers were significantly reduced by all insecticide treatments (Figure 1).
• Admire Pro provided the least control (Figure 1), while Transform, Diamond, and Orthene provided the best control.
• No insecticide provided greater than 70 percent control of nymphs with a single application (Figure 1).
• All insecticide treatments resulted in significantly higher yields than untreated control (Figure 2).

Conclusion

For Midsouth cotton producers to effectively manage TPB, multiple insecticide applications at shorter application intervals will continue to be necessary to achieve acceptable control. Cultural practices such as optimized fertility, management of alternate host plants, early planting dates, and selected placement of cotton fields within the landscape should also be utilized to reduce TPB populations in cotton. Rotating among different insecticide classes and avoiding repeated use of the same insecticide class against multiple generations is discouraged when possible.

All treatments controlled TPB nymphs to varying levels and increased yield. The best sustained control was provided by Transform, Diamond, and Orthene. These products applied along or in combination with other insecticides are the backbone of current TPB insecticide management programs in the Midsouth. Sequential application of insecticide will be needed when TPB pressure is high or persists over time. Selection of insecticides and potential tank-mix partners will at least partly depend on other pests that may be present.

Treatments

Tarnished plant bug means by treatment at 4, 7, and 14 days after treatment.

Mean lint yield by treatment.

Funding for this research was provided by Cotton Incorporated – Core Program as part of the Midsouth Entomology Working Group.

The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.

Publication 3757 (POD-04-22)

Mary Jane Lytle, PhD Student, Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology; Jacob Smith, Extension Associate I, Delta Research and Extension Center; Whitney Crow, PhD, Assistant Professor, Delta R&E Center; Angus Catchot, PhD, Professor, Biochemistry, Molecular Biology, Entomology, and Plant Pathology; Jeff Gore, PhD, Interim Head, Delta R&E Center; Don Cook, PhD, Associate Research Professor, Biochemistry, Molecular Biology, Entomology, and Plant Pathology; Tyler Towles, Louisiana State University AgCenter; Nick Bateman, Ben Thrash, Glenn Studebaker, and Gus Lorenz, University of Arkansas; Sebe Brown and Scott Stewart, University of Tennessee; and David Kerns, Texas A&M University.