Collection of D. suzukii's parasitoids in Japan

Collection of D. suzukii's parasitoids in China

Collection of D. suzukii's parasitoids in China

Ganaspis cf. brasiliensis ovipositing in D. suzukii larvae in blueberry

Female Ganaspis cf. brasiliensis

D.suzukii on cherry

Asobara japonica ovipositing in larvae of D. suzukii in blueberry

Damage symptoms ©Dr Gevork Arakelian

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Project Overview

So, what’s the problem

In contrast to the majority of Drosophila species that feed on rotting fruits and other organic matter, D. suzukii is only able to lay eggs in fresh fruit. In fact, it can attack and develop in over 150 wild and cultivated fruits as well as in fruits of ornamental plants.

Since 2008, this Asian fruit fly has invaded several continents and has become a very serious pest and major problem for fruit growers around the world. Its larvae feed on developing fruit, causing rapid degradation and reducing crop yields. In the USA alone, losses are estimated to be over $500 million per year. In Switzerland, significant losses have already occurred in the high stem stone fruit industry.

The pest occurs throughout the majority of the year, in a wide variety of habitats, so we need to develop an area-wide management approach that will control the fly in both cultivated and wild habitats.

What is this project doing?

Current methods of controlling D. suzukii rely on chemical insecticides or expensive and labour-intensive cultural practices.

Our approach is to develop a classical biological control programme which would introduce Asian parasitoids that have co-evolved with the pest. This will provide a sustainable solution, as long as the parasitoids are sufficiently specific to the pest to avoid any non-target effects to local biodiversity.

To this end, we have been collecting possible candidates in China and Japan since 2015. These parasitoids (belonging to the genera Asobara, Leptopilina and Ganaspis) have been imported to our quarantine facilities at CABI in Switzerland. In the beginning, little was known about the collected species, so we have studied various aspects of their biology and ecology, including their life cycle, habitat preference (fresh fruits, artificial diet, decaying matter) and specificity compared to other fruit flies. We are also sorting out important taxonomic issues.