ARS | Publication request: Comparative susceptibilities of different life stages of the tarnished plant bug (Hemiptera: miridae) to three classes of insecticide

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 20, 2012
Publication Date: September 1, 2012
Citation: Allen, K.C., Jackson, R.E., Snodgrass, G.L., Musser, F.R. 2012. Comparative susceptibilities of different life stages of the tarnished plant bug (Hemiptera: miridae) to three classes of insecticide. Southwestern Entomologist. 37(3):271-280.

Interpretive Summary: The tarnished plant bug is one of the most serious insect pests of cotton in the southern United States. It prefers to feed on developing fruit, causing it to abort from the cotton plant. Some insecticides that have, historically, been used for its control have become less efficacious due to develop of resistance in some populations. Efforts to monitor for insecticide resistance in populations of this insect pest have predominantly used the adult stage, although insecticide applications are targeted at both adult and immature stages. This insect goes through five different molts before it becomes an adult with each stage between molts referred to as an “instar”. The comparative susceptibilities of each of these instars and the adult stage to the various insecticides used for its control are largely unknown. Laboratory studies were used to examine the susceptibilities of each instar and the adult stage of tarnished plant bug to three common classes of insecticides used for its control. For all but one population of tarnished plant bugs tested, the tolerance to the various insecticides ranked from lowest to greatest was: 1st instars, 2nd instars, 3rd instars, adults, 4th instars, and 5th instars. The tolerance of 5th versus 1st instars was much greater when tarnished plant bugs were tested with an insecticide in the class of the “pyrethroid” insecticides than insecticides in the organophosphate or neonicotinoid classes. Overall, the results of this study indicated that the effectiveness of an insecticide application for the control of tarnished plant bugs depends on the age-structure of the population being treated.

Technical Abstract: Insecticidal control of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is targeted at the adult and nymphal stages, but there is little information on relative susceptibilities of these insects to insecticides. Tarnished plant bug adults were collected from various locations in Mississippi during 2008-2009, and different life stages of their progeny were tested for susceptibilities to three classes of insecticides. A glass vial bioassay was used to evaluate four populations of tarnished plant bugs for susceptibility to the pyrethroid insecticide, permethrin, and two populations to the organophosphate insecticide, methamidophos. Additionally, a diet-incorporated bioassay was used to evaluate the susceptibility of the various life stages of a single population of tarnished plant bugs to a neonicotinoid insecticide, thiamethoxam. For all but one population and insecticide combination, the estimated LC50 values ranked from least to greatest were: 1st instars, 2nd instars, 3rd instars, adults, 4th instars, and 5th instars. The tolerances of 5th versus 1st instars were greater for populations of tarnished plant bugs exposed to permethrin compared to methamidophos or thiamethoxam. The results of this study indicated that the effectiveness of an insecticide application for the control of tarnished plant bugs depends on the age-structure of the population being treated.