The Sterile Insect Technique (SIT) and Parasitoid releases are two methods of biological control which are successfully applied against diverse pest species, reducing the need for pesticides. For the SIT, sterile males of the pest species are produced which outcompete the wild males but produce no offspring, and for parasitoid releases a host is needed to produce parasitoid wasps which attack the pest in the field. Both methods are therefore relying on mass rearing of large numbers of high quality insects.
Olive fruit flies (Bactrocera oleae) cause substantial damage to the olive industry by laying their eggs in the olives, which are then destroyed their larva. The olive fruit fly can be sterilized for SIT applications and several parasitoids are promising candidates for biological control; however, these techniques are not currently applied because the olive fruit fly cannot be mass-reared cost-effectively. The bottleneck to mass-rearing is the larval diet, which is expensive and does not yield enough pupae.
I am working on the characterization and potential use of symbiotic bacteria to enhance the rearing efficiency of olive fruit flies. In nature, these specialist animals rely on their bacterial symbionts which they, like other fruit fly species, need in order to digest their fruit. In a mass rearing environment olive fruit flies lose their associated bacteria and they also have to rely on an artificial diet. Recently there have been several successful experiments with the Mediterranian fruit fly, and one in olive fruit fly where bacteria were added to the diet as probiotics. Giving them back their bacteria could increase their production and enhance their quality. My goal is to see if we can increase olive fruit fly production by giving them larval probiotics.
So far I have used Next Generation Sequencing (NGS) approaches to characterize the composition of the bacterial community in the gut of the olive fruit fly. In this way, we got to know which bacterial species are present and their relative abundance. To our surprise, the wild pupae, which ESR Manolis Lyrakis brought from Crete, also harboured parasitoid wasps, which I was able to rear in the lab. These parasitoids were also analysed with NGS approaches to see which bacterial species they may be sharing with their host and might be important for them. Besides looking at the whole gut-associated bacterial community, I also isolated different species from the guts of wild flies by cultivation on growth media. This will bring me to the next step of my research, where I will test these isolates as probiotics in the larval diet.