In a promising development in the battle against the invasive Spotted Wing Drosophila (SWD), two ancient adversaries of the fruit fly, Ganaspis brasiliensis (Samba wasp) and Leptopilina japonica (Ronin wasp), have made their way to North America. These natural enemies, long acquainted with SWD in their native habitats of Asia, are showing early signs of success in parasitizing and controlling SWD populations in U.S. fruit regions.
Entomologists, recognizing the potential of these wasps in managing SWD, have initiated efforts to encourage their proliferation. Michigan State University entomology professor, Julianna Wilson, expresses to the site Good Fruit Growers that, “It’s really exciting, because the more natural enemies we have, the better chance they will start to suppress this pest.”
Recent studies have revealed promising outcomes. In Michigan, researchers released 39,000 samba wasps across 30 fruit sites in 2023, marking the first large-scale rearing of these parasitoids. Subsequent recoveries of samba wasps in several sites indicate their survival and successful parasitization of SWD larvae. This achievement, as noted by MSU entomology professor Rufus Isaacs, marks a significant milestone in the battle against SWD.
Further investigations by graduate student Andrew Jones have examined the samba wasp’s ability to withstand Michigan winters, showing promising survival rates even in underground containers. These studies, funded by a combination of federal, state, and industry sources, highlight the collaborative effort to combat SWD infestations.
While native parasitoids exist in North America, none have evolved to effectively prey on SWD. The introduction of samba and ronin wasps from Asia presents a novel solution to this challenge. Kent Daane from the University of California, Berkeley, underscores the importance of these natural enemies, emphasizing their coevolution with SWD and their unique ability to parasitize the fruit fly.
Although initial releases have shown varying degrees of success across different regions, researchers remain optimistic about the long-term impact of samba and ronin wasps in controlling SWD populations. Efforts are underway to establish these parasitoids in refuge areas outside of crops, aiming to reduce SWD numbers and mitigate outbreaks later in the season.
As research continues and the presence of samba and ronin wasps expands in North America, hopes are high for a sustainable solution to the SWD menace, offering newfound resilience to berry and cherry farmers against this invasive pest.
Source: Good Fruit Growers
