A cold storage strategy for parasitized hosts significantly improves the probability of parasitoid eclosion

Abstract

Parasitoids, as effective biological control agents, have been extensively applied to reduce the population size of pest species. However, important limitations of biological control programmes are often related to difficulties in synchronizing parasitoid and host life cycles and failure to obtain sufficient numbers of parasitoids when they are required for release. To address these issues, cold storage for parasitized hosts is considered a valuable method. Anastatus disparis Ruschka (Hymenoptera: Eupelmidae) is an important egg parasitoid and is considered a potential biological control agent for several species of lepidopteran forest pests, including Lymantria dispar Linnaeus (Lepidoptera: Lymantriidae). Thus, to synchronize parasitoid and pest host life cycles and obtain an abundance of parasitoids before release, the strategy of cold storage of the parasitized host was studied for A. disparis. Our results suggest immediate refrigeration of the host after parasitization is severely detrimental to the development of the parasitoid A. disparis. More than half of the A. disparis offspring failed to successfully eclose even after a short period of refrigeration, and none eclosed after 60 days. However, when immature A. disparis offspring developed in the host for a period, reaching the larval stage and pupal stage, and were then refrigerated, the eclosion ratio could be significantly improved after long-term refrigeration. In addition, the sex ratio of the offspring was also evaluated and did not change, although the body size of the offspring decreased in the parasitized host after refrigeration. In summary, our study explored an effective strategy for parasitoid preservation under long-term cold storage.