Novaluron prevents oogenesis and oviposition by inducing ultrastructural changes in ovarian tissue of young adult Lygus lineolaris

Authors: CATCHOT, BEVERLY - Mississippi State University; ANDERSON, CHANCE - Mississippi State University; GORE, JEFF - Mississippi State University; JACKSON, RYAN - Syngenta; RAKSHIT, KUNTOL - Mayo Clinic College Of Medicine; MUSSER, FRED - Mississippi State University; KRISHNAN, N. - Mississippi State University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2020
Publication Date: 7/13/2020
Citation: Catchot, B.D., Anderson, C., Gore, J., Jackson, R., Rakshit, K., Musser, F., Krishnan, N. 2020. Novaluron prevents oogenesis and oviposition by inducing ultrastructural changes in ovarian tissue of young adult Lygus lineolaris. Pest Management Science. 76:4057-4063. https://doi.org/10.1002/ps.5960.
DOI: https://doi.org/10.1002/ps.5960

Interpretive Summary: The tarnished plant bug is the most important insect pest of cotton in Arkansas, Louisiana, Mississippi, Missouri, and Tennessee. In the early 1990s, tarnished plant bug populations developed resistance to several classes of insecticides, increasing the need for insecticides with alternative means of targeting different sites within the insect, such as insect growth regulators (IGRs) for integrated pest management (IPM). The IGRs act by disrupting the growth and development of immature stages of insects, but little is known about its impact on adult stages. One of these insecticides, novaluron, was investigated on adult female tarnished plant bugs. Treatment of 1-day-old adults with novaluron in diet prevented egg lay, while treatment of older females had no impact on egg lay. Oral novaluron exposure of adults of all ages reduced the viability of eggs laid. Novaluron treatment caused ultrastructural changes in the ovaries of 1-day-old adults (48 hours post exposure). Additionally,the novaluron treatment decreased the chitin content in ovarian tissue. Our results suggest that chitin or chitin-like components in the developing ovaries of adult tarnished plant bugs are a target of IGRs such as novaluron, but its activity is specific to a critical time during development. This enhances our understanding of the effects of some IGRs on adult insects and could lead to incorporation of IGRs in IPM for controlling adult insect pest popula-tions in the field.

Technical Abstract: The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has emerged as a major pest of cotton ,Gossypium hirsutum L, in the mid-southern USA. In the early 1990s L. lineolaris populations developed resistance to several classesof conventional insecticides, increasing the need for insecticides with alternative modes of action such as insect growth regulators (IGRs) for integrated pest management (IPM). The benzoylphenyl urea (BPU) class of IGRs acts by disrupting the growth and development of immature stages of insects, but little is known about its impact on adult stages. The effect of novaluron (Diamond™0.83EC), a BPU with known chitin synthesis inhibitor activity, was investigated on adult females of L. lineolaris. Treatment of 1-day-old adults with 600 ppm of novaluron in the diet prevented oviposition,while treatment of older females had no impact on oviposition. Oral novaluron exposure of adults of all ages reduced the viability ofeggs laid. Novaluron treatment caused ultrastructural changes in the ovaries of 1-day-old adults (48 h post exposure), distorting the follicular epithelial cell architecture of developing oocytes. Additionally, novaluron treatment decreased the chitin content in ovarian tissue. Our results suggest that chitin or chitin-like components in the developing ovaries of adult L. lineolaris are a target of IGRs such as novaluron, but its activity is specific to a critical time during development. This enhances our understanding of the effects of BPUs on adult insects and could lead to incorporation of IGRs in IPM for controlling adult insect pest popula-tions in the field.