Assessment of the toxicity of four formulated pyrethroid-containing binary insecticides in susceptible and resistant adult tarnished plant bug, Lygus Lineolaris

Authors: Du, Yuzhe - Cathy; Zhu, Yu Cheng; Portilla, Maribel

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2023
Publication Date: 9/13/2023
Citation: Du, Y., Zhu, Y., Portilla, M. 2023. Assessment of the toxicity of four formulated pyrethroid-containing binary insecticides in susceptible and resistant adult tarnished plant bug, Lygus Lineolaris. Insects. https://doi.org/10.3390/insects14090761.
DOI: https://doi.org/10.3390/insects14090761

Interpretive Summary: During the past several decades, intensive use of pyrethroids has led to the development of resistance in many insect populations, such as the tarnished plant bug (TPB), Lygus lineolaris (Palison de Beauvois) (Hemiptera: Meridae), a serious and major damaging pest in cotton. Several formulated mixtures of individual pyrethroids with neonicotinoids or avermectin are currently recommended for TPB control and resistance management in the mid-south United States. In this study, we evaluated the toxicity and resistance risks of four formulated pyrethroid-containing binary mixtures, Endigo, Leverage, Athena, and Hero, as well as their corresponding individual components in susceptible and resistant TPB using modified Potter spray tower. Based on LC50 values, the resistant strain showed variable tolerance to all formulated mixtures and individual pesticides, with the highest resistance to Hero and lowest resistance to abamectin. Based on co-toxicity coefficient (CTC), all four formulated mixtures, Endigo, Leverage, Hero, and Athena, exhibited the synergistic effects compared to the corresponding individual components in the susceptible strains. The mixtures, except Leverage, also revealed synergistic effects against the resistant populations. Endigo and Hero showed lower synergistic effect in resistant population than in the susceptible strain. Athena exhibited the similar synergistic interaction in both susceptible and resistant TPB populations. Considering Hero is the mixture of two pyrethroids, to which TPB may develop resistance easily, Endigo and Athena are more effective and good choices for managing resistant TPB populations. Taken together, this study provides useful information for choosing best mixtures or individual insecticides to achieve better control of TPB through synergistic toxicity or to reduce control cost and risks to environment and resistance development in the insect pest.

Technical Abstract: During the past several decades, intensive use of pyrethroids has led to the development of resistance in many insect populations, such as the tarnished plant bug (TPB),a serious and major damaging pest in cotton. Several formulated mixtures of individual pyrethroids with neonicotinoids or avermectin are currently recommended for TPB control and resistance management in the mid-south United States. In this study, we evaluated the toxicity and resistance risks of four formulated pyrethroid-containing binary mixtures, Endigo, Leverage, Athena, and Hero, and their corresponding individual components in susceptible and resistant TPB. Based on LC50 values, the resistant strain showed variable resistance to all formulated mixtures and individual pesticides, with the highest resistance to Hero and lowest resistance to abamectin. Also, all four formulated mixtures, Endigo, Leverage, Hero, and Athena, exhibited the synergistic effects compared to the corresponding individual components in the susceptible strains. The mixtures, except Leverage, also revealed synergistic effects against the resistant populations. Considering Hero is the mixture of two pyrethroids, to which TPB may develop resistance easily, Endigo and Athena are more effective and good choices for managing resistant TPB populations. Taken together, this study provides useful information for choosing best mixtures to achieve better control of resistant TPB, and to reduce control cost and risks to environment and resistance development in the insect pest.