Survival and fecundity parameters of two Drosophila suzukii (Diptera: Drosophilidae) morphs on variable diet under suboptimal temperatures

Authors: RENDON, DALILA - Oregon State University; BUSER, JESSICA - Oregon State University; TAIT, GABRIELLA - Fondazione Edmund Mach; Lee, Jana; WALTON, VAUGHN - Oregon State University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2018
Publication Date: 11/15/2018
Citation: Rendon, D., Buser, J., Tait, G., Lee, J.C., Walton, V. 2018. Survival and fecundity parameters of two Drosophila suzukii (Diptera: Drosophilidae) morphs on variable diet under suboptimal temperatures. Journal of Insect Science. 18(6):1–7. https://doi.org/10.1093/jisesa/iey113.
DOI: https://doi.org/10.1093/jisesa/iey113

Interpretive Summary: Understanding the time it takes for an insect to develop from egg to adult is important for pest control to help predict population growth. Spotted wing drosophila (SWD) is an invasive agricultural pest and previous studies have estimated it reproductive rate (Ro), generation time (T), and rate of population increase (rm). However, these estimates were measured under relatively favorable settings at room temperature, and do not reflect colder conditions, did not test diets variable in protein to carbohydrate rations nor test the winter-type fly. Often a certain protein:carbohydrate ratio is optimal for insects; SWD has both a winter and summer morphotype. Therefore, this study investigated the impacts of 1) low temperatures and 2) dietary protein: carbohydrate ratios on both survival and and egg laying by SWD summer morphs and winter morphs that have undergone a simulated overwintering period. Reproductive rates were higher and lifespan was longer when flies were exposed to low protein or carbohydrate-only diets compared to high protein diets, and in post-overwintering winter morphs compared to summer morphs on an optimal 1:4 diet. Flies in lower temperatures had longer lifespan, but lower reproductive rates. Egg laying among flies receiving 1:4 diet commenced from 0 to 100 DD, and peak fecundity occurred from 400 to 500 DD. Peak fecundity happened earlier in flies receiving 1:1 diet, and later in flies receiving 0:1 diet, suggesting that dietary protein has a crucial role in early egg development. The parameters developed here reflect the population dynamics of SWD before and after the crop growing season, an essential time for population build-up, survival, and early and late host infestation.

Technical Abstract: Life history parameters are used to estimate population dynamics, mortality, and reproduction in insects relative to their surrounding environment. For Drosophila suzukii, an invasive agricultural pest, previous studies have estimated net reproductive rate (Ro), generation time (T), and intrinsic rate of population increase (rm). A main limitation is that these estimates were measured under relatively favorable settings, and do not reflect environmental conditions and physiological states encountered during dormancy periods. Therefore, this study investigated the impacts of 1) low temperatures and 2) dietary protein: carbohydrate ratios (P:C) on both survival and fecundity parameters of D. suzukii summer morphs (SM) and post-overwintering winter morphs (WM) over physiological age (degree-days, DD). Reproductive rates were higher and lifespan was longer when flies were exposed to low protein (P:C 1:4) or carbohydrate-only diets (P:C 0:1) compared to high protein diets (P:C 1:1), and in post-overwintering WM compared to SM on optimal 1:4 diet. Flies in lower temperatures (9 °C compared to 14 and 17°C) had longer lifespan, but lower reproductive rates. Oviposition for SM and WM receiving 1:4 diet commenced from 0 to 100 DD, and peak fecundity occurred from 400 to 500 DD. Peak fecundity happened earlier in flies receiving 1:1 diet, and later in flies receiving 0:1 diet, suggesting that dietary protein has a crucial role in early oogenesis. The parameters developed here reflect the population dynamics of D. suzukii before and after the crop growing season, an essential time for population build-up, survival, and early and late host infestation.