Development of a physiological age-grading system for Nezara viridula (L.) (Hemiptera: Pentatomidae)

Authors: Grodowitz, Michael; ELLIOTT, ROBERT - Former ARS Employee; Evans, Richard; Rojas, Maria - Guadalupe; Morales Ramos, Juan

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2020
Publication Date: 9/22/2020
Citation: Grodowitz, M.J., Elliott, R.B., Evans, R.M., Rojas, M.G., Morales Ramos, J.A. 2020. Development of a physiological age-grading system for Nezara viridula (L.) (Hemiptera: Pentatomidae). Journal of Insect Science. 20(5):1-8. https://doi.org/10.1093/jisesa/ieaa092.
DOI: https://doi.org/10.1093/jisesa/ieaa092

Interpretive Summary: Southern green stink bug is a major pest on many economically important agricultural crops. The reproductive system of females was described in detail and a physiological age-grading system developed based on changes in morphology in relation to number of eggs produced and egg masses laid. Three stages were described for the period prior to egg laying and three stages described for the active egg-laying period based on follicle changes, deposition of material during ovulation (i.e., follicular relics), and eggs present in the reproductive system. Such information can be used to assess past, present and to some extent future reproductive performance.

Technical Abstract: The southern green stink bug (SGSB), Nezara viridula (L.), is an important agricultural pest in the U.S. Limited information is available on the morphology of the female’s reproductive system in relation to morphological changes associated with the number of eggs produced and egg masses oviposited. The ability to assess reproductive health and reproductive status based on ovarian morphology (i.e., physiological age-grading) can be an important tool for evaluating field populations and laboratory colonies intended for the application of different management strategies and experimental trials. Thus, the goal of this study was to develop a physiological age-grading system for SGSB. Females aged from 0 to 79 days chronologically randomly selected from laboratory colonies and dissected to assess ovarian morphology. Specific morphological differences in ovarian structures including differentiation of the ovarioles, deposition of yolk in the most proximal follicle, quantity and appearance of follicular relics, expansion of the lateral oviducts, and number of developing follicles per ovariole were related to chronological age, the number of eggs produced and number of egg masses. Based on specific combinations of these morphological characteristics, the continuum of ovarian development was divided into three nulliparous (i.e., “no eggs”; N1, N2, and N3) and three parous stages (i.e., “with eggs”; P1, P2, and P3). Direct relationships were noted between number of eggs produced and physiological age with over 7-fold higher number of eggs and 14-fold higher number of egg masses associated with the P2 and P3 stages, respectively.