Combining Irradiation and Biological Control against Brown Marmorated Stink Bug: Are Sterile Eggs a Suitable Substrate for the Egg Parasitoid Trissolcus japonicus?

Simple Summary Halyomorpha halys is an alien stink bug species native to south-eastern Asia, and is now widely distributed and very invasive worldwide. Management of this pest by chemical insecticides is not very effective because of the high mobility of the pest species and its innate ability to develop resistance to most of the synthetic insecticides applied. For this reason, classical biological control has been considered, with attention focused on co-evolved egg parasitoids, which oviposit and complete their larval development within a single egg of the host. The detection and collection of the egg parasitoid species is often conducted by exposing newly oviposited egg-masses of the stink bug pest in the field for a few days as sentinels, which can then be parasitized by the egg parasitoids. In newly invaded areas, limiting factors in the use of sentinel eggs include the short amount of time that they are a suitable substrate for the oviposition of the egg parasitoid and the risk of the unintentional release of additional pests from unparasitized eggs. A valid potential alternative is to use sterile sentinel eggs of the pest species. This study focused on the evaluation of the performance of three types of sterile sentinel eggs for the oviposition and the larval development of the egg parasitoid Trissolcus japonicus. The brown marmorated stink bug (BMSB), Halyomorpha halys, is a phytophagous invasive pest native to south-eastern Asia, and it is now distributed worldwide. This species is considered to be one of the most damaging insect pests in North America and in Europe. In agriculture, the predominant approach to managing BMSB is based on the use of insecticides, specifically pyrethroids and neonicotinoids. Unfortunately, the biology of the species and its facility to develop mechanisms of resistance to available pesticides has induced farmers and scientists to develop different, least-toxic, and more effective strategies of control. In a territorial area-wide approach, the use of a classical biological control program in combination with other least-toxic strategies has been given prominent consideration. Following exploratory surveys in the native range, attention has focused on Trissolcus japonicus, a small scelionid egg parasitoid wasp that is able to oviposit and complete its larval development in a single egg of H. halys. A common method for detecting egg parasitoids in the native range involves the placement of so-called 'sentinel' egg masses of the pest in the environment for a short period, which are then returned to the laboratory to determine if any of them are parasitized. Outside of the area of origin, the use of fertile sentinel eggs of the alien species may lead to the further release of the pest species; an alternative is to use sterile sentinel eggs to record the presence of new indigenous egg parasitoids or to detect the dispersal of alien species (in this case, T. japonicus) released in a new environment to control the target insect pest species. This study evaluated the performance of three types of sterile sentinel eggs as a suitable substrate for the oviposition and larval development of the egg parasitoid T. japonicus in a context of combining classical biological control with a Sterile Insect Technique (SIT) approach.

Automated summary

The brown marmorated stink bug is a invasive pest species that is widely distributed and highly aggressive. Chemical insecticides are not effective in managing this pest due to its high mobility and ability to develop resistance. Classical biological control, specifically egg parasitoids, is being considered as an alternative approach. The study evaluated the performance of three types of sterile sentinel eggs as a suitable substrate for the oviposition and larval development of the egg parasitoid Trissolcus japonicus.