Aphid endosymbionts and parasitoid wasp biocontrol

Background

Biological control of crop pests is becoming more important with the stricter regulations on pesticide use. Aphids are serious pests in greenhouses, and laboratory studies have shown that parasitoid biocontrol, which is considered particularly effective against aphids, can be seriously affected by defensive symbiosis. In defensive symbiosis, secondary bacterial endosymbionts protect its host, the aphid in this case, against natural enemies. Since facultative symbionts have been found in almost all pest aphid species studied so far, this could pose an underestimated threat to biocontrol efficiency. Unfortunately, studies on endosymbiont-conferred resistance in aphids have been limited to the laboratory, with only a few studies on effects in the field. Information on the effects of symbiont-conferred resistance in greenhouses is lacking entirely, and this information is needed for the biocontrol industry.

Project description

The aim of this project is to study the dynamics between endosymbionts, aphids and parasitoids in greenhouses and the field, and to use our findings to improve the efficiency of biological control. Part of this project is focused on studying which endosymbionts are present in which aphid species, both in the field and in crop systems. The first year was focused on bell pepper greenhouses (see publication below), and we are currently focusing on strawberry greenhouses and the field. 

Another part of this project involves parasitism assays to see whether aphid strain and endosymbiont presence affects the success of biocontrol parasitoids. 

We are also looking at the effects of common endosymbionts on insect community dynamics on strawberry plants. Here we are looking at parasitoids but also predators and the presence of other aphid species. 

Lastly, we are working on visualizing aphid endosymbionts with fluorescence microscopy (FISH).

Results

We have found that secondary endosymbionts are uncommon in bell pepper greenhouses in the Netherlands, and that the variation in different aphid lines of the same species in their resistance against common biocontrol parasitoids is low.