New biological insecticides, which make use of “entomopathogenic” viruses that are harmful to insects, have emerged in recent years. The big advantage versus regular pesticides is that they are innocuous to man, vertebrae and plants, and environmental activists have not heard of them yet. Each viral strain attacks a very limited number of insect species.

The baculovirus is frequently studied and to identify the virus in this family that will most effectively control the Guatemalan potato moth, a French-Ecuadorian research team from Institut de Recherche pour le Développement (IRD) has analyzed the pathogens among moths from all over the world.  

The granulosis virus, or granulovirus, appears to be the most widespread. The researchers detected it in moths from twelve different countries and it also has the widest activity spectrum: it also attacks five other tuber pests. The researchers then did a laboratory test of a formula based on this virus. The result was as efficient as chemical products: it produces a mortality rate among Guatemalan potato moth larvae of more than 98%.

Pulverized on the surface of potatoes or the eggs of the invasive species, the granulovirus contaminates the larvae through ingestion. It then spreads through the digestive tract and to the entire organism of the host, causing a lethal infection within two or three days.


Credit: IRD / O. Dangles

The action is therefore relatively slow compared to chemical insecticides that have an immediate effect upon contact. Its use also requires expert knowledge and detailed monitoring of the moth’s biological cycle, ecology and behavior, which could hold back its deployment for biological control.

This kind of biopesticide has many advantages and is a worthwhile alternative to chemical insecticides which are still the primary method used by farmers in Ecuador. Phytosanitary products are toxic for the environment and potentially for the user as well. Using biological pesticides that rapidly degrade in the environment would reduce the risks of pollution.

Host specificity means that the Guatemalan potato moth can be targeted while preserving the ecosystem, in particular useful insects like pollinators. Lastly, unlike the molecules in chemical plant-protection products, viruses are able to mutate, which limits the development of resistance in their host.

For efficient control of the Guatemalan potato moth, the use of this viral pesticide must therefore necessarily form part of an integrated control strategy. To this end, the team has been doing genetic, agronomic and ecological studies: molecular analyses to describe the genetic structure of the pests, a study of the impact of temperatures on their ecology by means of drones with thermal cameras.

The aim is to get a better understanding of the insects’ population dynamics and define good practices to limit their proliferation. In this respect, the researchers have developed methods like role-playing games to raise awareness among farmers.

Recent surveys have shown their efficiency on a regional scale (Ecuador, Peru and Bolivia). Training remains a key element in efficient crop-pest management.

References:

Carpio C., Dangles Olivier, Dupas Stéphane, Léry Xavier, Lopez-Ferber M., Orbe K., Paez D., Rebaudo François, Santillan A., Yangari B., Zeddam Jean-Louis. Development of a viral biopesticide for the control of the Guatemala potato tuber moth Tecia solanivora. Journal of Invertebrate Pathology, 2013, 112 (2), p. 184-191. ISSN 0022-2011 fdi:010058973

Rebaudo François, Carpio F.C., Crespo-Pérez V., Herrera M., Mayer de Scurrah M., Ccanto R., Montañez A.G., Bonifacio A., Mamani M., Saravia R., Dangles Olivier. Agent-based models and Integrated Pest Management diffusion in small scale farmer communities. In: Experiences with Extension and Farmer Adoption of IPM. Peshin R., Litsinger J., Eds. (Springer), 2013, in press.