Laboratory evaluation of Ooencyrtus obscurus (Mercet) (Hymenoptera: Encyrtidae) on Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) eggs

Abstract

Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae), known as the western conifer seed bug (WCSB), is a significant pest of the Pinus pinea L. kernel sector in the Mediterranean basin. The egg parasitoid species Ooencyrtus obscurus (Mercet) (Hymenoptera: Encyrtidae) has been recently recorded on WCSB eggs in Central Spain. This study defines the influence of the egg cluster size on the parasitism rate of O. obscurus, its reproductive and demographic parameters with the goal of defining the potential of this species to be a biological control agent. Ooencyrtus obscurus is weakly synovigenic, with the parasitism period concentrating in the first two weeks, reaching its maximum level of intensity on the 1st day (30.2 %). The mean oviposition period was 2.3 days, with the mean female longevity being 16.9 days. The mean rate of pre-imaginal survival was high (96.7 %), with the mean pre-imaginal development time being significantly higher for females than for males. The sex ratio (% females) was 41.2 %, while the reproductive strategy was defined as being pseudo-arrhenotokous parthenogenesis after comparing mated and unmated female offspring. Regarding demographic parameters, a single O. obscurus female was able to produce more than 3 female offspring (R0) in a generation time (T) of 23.96 days, multiply its population 1.05 times a day (λ), and double it in 14.34 days (Td). The comparison between these results and those established for the main egg parasitoid of the WCSB in its native area could allow for decisions to be made on the type of biological control program to be applied in Europe.