Aphids update March 2017
BIOCOMES partner Viridaxis is specialized in the mass production of parasitic wasps for aphid control. These parasitoids are already massively used in some covered crops (vegetables, soft fruits, ornamentals). In the past, Viridaxis developed several specific cocktails of parasitoids for different protected crops. The aim of the BIOCOMES project is to enlarge the experience of Viridaxis to outdoor fruit tree crops.
4 new parasitoid species for production scaling-up
During the first 2 years of the project, an intensive sampling campaign was carried out with the collaboration of BIOCOMES partner pcfruit in the field. The main objective of this campaign was to collect specimens of each of the 10 parasitoid species previously identified as potential biological control agents for aphids in commercial fruit tree crops.
Specimens from 7 species out of the 10 targeted species were found and tested in the lab for production efficiency with Viridaxis proprietary technology. Among them, 4 species appeared to be fully compatible with our rearing method and were selected to go through a scaling-up process:
- Ephedrus plagiator
- Diaeretiella rapae
- Binodoxys angelicae
- Praon abjectum
Efficient mass production required
The scaling-up process aimed at establishing an efficient mass production of these species at low costs to allow a massive adoption of the new biological control agent by open field crop growers. The production of Binodoxys angelicae could not be stabilized and this species was eventually abandoned. For Ephedrus plagiator and Diaeretiella rapae, the best production parameters were determined and both species could now be produced at a big scale. The parasitoids produced had a good quality in terms of emergence rate (>80%) and fecundity. The sex ratio can however still be improved to gain in efficiency in the field (only females parasitize aphids and are then the most important for biological control). Moreover, the production efficiency remains rather low (<50%). For these two species, although it is now possible to mass rear them at the facilities of Viridaxis, the production costs remain high and the application costs, related among other things to the sex ratio could be reduced. Further work is thus still needed in order to establish a cost effective production.
The last species, Praon abjectum, is still in an early stage of the scaling-up process. However, preliminary results are very promising concerning a future scaling-up of the production of the species.
Cherry field trial results in Belgium
In 2015, after the good efficiency results obtained under controlled conditions in cage trials with the collaboration of BIOCOMES partner pcfruit, we carried out field trials in Belgium in cherry tree orchards with pcfruit. These trials aimed at testing a strategy of biocontrol of cherry aphids (mainly Myzus cerasi) based on preventive releases of a cocktail of different parasitoid species. Interesting results were obtained. Indeed, parasitoid dispersed efficiently in outdoor conditions and mummies were found in abundance through the orchards. However, full control of aphid infestations has not been reached. It appeared that this situation was mainly due to external factors such as adverse climatic conditions in outdoor conditions at the beginning of the trials which could have impaired the early parasitism of the wasps.
Peach field trial results in Spain
In order to avoid such climatic conditions at the time of the first releases, we decided to perform new trials in a warmer climate during the 2016 season. The Mediterranean climate of Spain appeared to be the good candidate and trials were organized in peach tree orchards in the Lleida’s area (Catalonia) with pcfruit and the help of the local company and BIOCOMES partner OpenNatur. 5 releases of a cocktail composed with 3 parasitoid species were carried out over 4 hectares of peach trees. The main target aphid species for these releases was Myzus persicae, the most problematic aphids for peach production.
Results in the peach tree orchards were very encouraging. Indeed, parasitoid mummies were observed regularly in all the fields where releases had been performed. Thus, up to 50% of the followed trees were sheltering mummies in several of the trial orchards. The use of parasitoids helped reducing considerably the aphid infestation level compared to control plots (without parasitoid releases). Consequently, the use of chemical insecticide treatments was reduced in all the plots concerned by the parasitoid releases, with at least 2 treatments avoided during the season, compared to control plots.
In 2017, the total surface of orchards concerned by the parasitoid releases will be doubled to check with the collaboration of BIOCOMES partner pcfruit if the 2016 results will be confirmed.
Read more about our activities on aphids
Picture: Parasitoid wasps lay their eggs in aphids. Parasitized aphids eventually die and the parasitoid host forms its cocoon inside. The parasitoid pupae in the skin of the dead aphid is called a mummy. Here you see mummies that were found in one of our trial cherry orchards.