Biocontrol against Sesamia nonagrioides using the larval parasitoide Cotesia typhae – BIOCOSMA

The Mediterranean corn borer, Sesamia nonagrioides, is the second aerial pest of maize in France after the European corn borer. It attacks grain and seed maize crops in the South and West of France where it can cause significant yield losses. It is a species native to sub-Saharan Africa, where its larvae are naturally parasitized by the parasitoid wasp Cotesia typhae, which is specialized on this Sesamia. This parasitoid, not present in Europe, constitutes a biological control agent with high potential, thanks to its specificity, its reproductive success on European populations of S. nonagrioides and its low environmental impact.
The BIOCOSMA project proposes to develop a biological control solution against S. nonagrioides using inundative releases of C. typhae in the field. It is the continuation of the ANR project Cotebio, which made it possible to carry out the biological studies necessary for asking the authorization to introduce this biocontrol agent in France, as well as, for its mass production in the laboratory. In addition, experiments carried out under controlled conditions in greenhouses using French S. nonagrioides have shown a high parasitic potential and an ability to persist on 2 generations of the pest.
Each year around 300,000 ha of maize are damaged by S. nonagrioides in France with up to 11% yield loss. In addition, attacks at the end of the maize cycle increase the risk of development of Fusarium, which produce mycotoxins impacting the quality of the harvest. Currently, no effective biocontrol solution is available to control the 2nd generation of this pest. Crops are protected mainly by chemical insecticides. Having C. typhae solution would have two major advantages for producers: 1/ applying the parasitoid during the first generation of S. nonagrioides should allow to control the second generation which economic and health impacts are the most important; 2/ this solution is complementary to the effective Trichogramma use against the European corn borer and the combination of both represents a strategy of biocontrol of the two main aerial pests of maize which often co-occur.
The key stages of maturation, so that C. typhae can be used by farmers, are the change in scale of the parasitoid production, and the performance of field trials, which will be guided by the development of a mathematical model. The main tasks proposed must lead, at the end of the project, to the development of a control strategy that is effective, practical, economically acceptable to maize growers, and respectful of the environment. In particular, we propose to 1/ optimize the mass production of the parasitoid in order to have it available in quantity and quality for the experiments planned over 3 campaigns; 2/ carry out releases in the field, according to different methods to estimate their effectiveness on the reduction of S. nonagrioides population and its crop damage, compared to untreated plots. These field trials will be assisted by modelling the pest-parasitoid system in order to determine the optimal period of introduction of C. typhae, according to the biology of the 2 species and the environmental conditions. They will also make it possible to verify the absence of adverse effects for the environment.
To ensure every chances of success for the project, a multidisciplinary consortium bringing together private and public partners, specialists in each theme, has been formed. It gathers Bioline Agrosciences, a major actor in biocontrol for project management and field trials; Arvalis, the centre of applied research and agronomic development also for field studies; EGCE for mass breeding and complementary biological studies; and GQE for modelling.