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 JH - Mississippi State University; GORE, JEFFERY - Mississippi State University; JACKSON, RYAN - Syngenta; RAKSHIT, KUNTOL - Mayo Clinic; MUSSER, FRED - Mississippi State University; KRISHNAN, NATRAJ - 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., 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: Chitin is a critical component of not only the arthropod cuticular exoskeleton and peritrophic matrix of the gut but can also be an important component of developing ovaries and eggshells. Many chemicals have been developed to target chitin biosynthesis, among which BPUs are the oldest and the best known. The general application of the benzoylphenyl urea (BPU) can reduce chitin biosynthesis, leading to hatching defects and abortive molting in immature insects of various insect orders. However, much less is known of its effects on adult insects. In this study, we demonstrated that novaluron, a BPU, can impact oviposition by affecting ovarian maturation in the tarnished plant bug and hatching by a yet unclear mechanism. The effect on oviposition is very specific to the age at which the insect is exposed to the novaluron. Egg viability, on the other hand, was uniformly affected regardless of the age of the treated adults.

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 classes of 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 of eggs 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 populations in the field.