Effectiveness and residual activity of four common insecticides used in the Mississippi Delta to Control Tarnished Plant Bugs in Cotton

Authors: Portilla, Maribel; Little, Nathan; Allen, Clint; Zhu, Yu Cheng

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2024
Publication Date: 6/4/2024
Citation: Portilla, M., Little, N., Allen, K.C., Zhu, Y. 2024. Effectiveness and residual activity of four common insecticides used in the Mississippi Delta to Control Tarnished Plant Bugs in Cotton. PLOS ONE. 19(6)01-20. https://doi.org/10.1371/journal.pone.0290858.
DOI: https://doi.org/10.1371/journal.pone.0290858

Interpretive Summary: The tarnished plant bug, (TPB), is the most common phytophagous species of the genus Lygus in North America and is widely distributed from Mexico to Alaska. TPB is a pest of economic importance in various agronomic crops across the United States. This insect became one of the most yield limiting pests of cotton in the mid-southern U.S production system following the eradication of the boll weevil, and the subsequent introduction and widespread adoption of the genetically modified cotton varieties to control heliothines. Prior to the eradication program and the introduction of transgenic cotton varieties, boll weevils and heliothines were primarily controlled with large-scale applications of organophosphates and pyrethroids. Repeated exposure to these broad-spectrum insecticides likely contributed to the development of insecticide resistance in TPB to several pyrethroids and some organophosphates including acephate. Today, regardless of inherent resistance levels, organophosphates and pyrethroids are the most common contact insecticides used for TPB control. However, during the last decade newer insecticides have been introduced, including neonicotinoids and sufolxamines. Therefore, this study was conducted to evaluate the efficacy and residual activity of four potential insecticides (one per class) used in Mississippi Delta. The results for this study will provide a better understanding of selecting insecticide used based in residual activity and mode of action to control TPB as an integrated pest management strategy.

Technical Abstract: The tarnished plant bug, (TPB) Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae) is a key pest of cotton in the midsouth region and some areas of the eastern United States. Its control methods have been solely based on chemical insecticides which has contributed to insecticidal resistance and shortened residual periods for control of this insect pest. This study was conducted over a two-year period and examined the efficacy and residual effect of four commercial insecticides including lambda-cyhalothrin (pyrethroid), acephate (organophosphate), imidacloprid (neonicotinoid), and sulfoxaflor (sulfoxamine). The effectiveness and residual effects of these insecticides were determined by application on cotton field plots on four different dates during each season using three different concentrations (high: highest labeled commercial dose (CD), medium: 1/10 of the CD, low: 1/100 of the CD) on field cotton plots. Four groups of cotton leaves were randomly pulled from each treated plot and control 0-, 2-, 4-, 7-, and 9-days post treatment (DPT) and exposed to a lab colony of TPB adults. One extra leaf sample/ plot/ spray /DPT interval (0-2-4-7-9-11) during 2016 was randomly collected from the high concentration plots and sent to Mississippi State Chemical Laboratory for residual analysis. Mortality of TPB adults was greatest for those placed on leaves sprayed with the organophosphate insecticide with mortalities (%) of 81.7'23.4 and 63.3'28.8 (SE) 1-day after exposure (DAE) on leaves 0-DPT with the high concentration for 2016 and 2017, respectively, reaching 94.5'9.5 and 95.4'7.6 6-DAE each year. Mortality to all insecticides continued until 9 and 4-DPT for high and medium concentrations, respectively. However, organophosphate (39.4'28.6) and pyrethroid (24.4'9.9) exhibited higher mortality than sulfoxamine (10.6'6.6) and the neonicotinoid (4.0'1.5) 7-DAE on 9-DPT leaves with the high concentration. Based on our results using the current assay procedure, TPB adults were significantly more susceptible to contact than systemic insecticides and due to its residual effect, organophosphate could kill over 80% of the TPB population 7-DPT.