Helicoverpa armigera

Bombyx mori

Insects are in competition with human agro-industry. Every day, 1/6 of the world’s agricultural production is consumed by insects (the majority by lepidopteran larvae), especially in those countries which are the most dependent on agriculture for their subsistance or for the revenue it generates for health and development expenses.

The Lepidoptera are the most diverse group of animals in the world (>160,000 species) after the Coleoptera, and they are practically all herbivores (compared with Drosophila and Anopheles).

Helicoverpa armigera (Photo from the website http://www.sindominio.net/)

The diversification of the Lepidoptera followed that of the angiosperms, about 130 million years ago. The noctuid family (Noctuidae) is the largest in the order (>50,000 species), and includes the most devastating pests on the planet. Helicoverpa armigera (Helicoverpa zea in America) is found in all the major crops (corn, sorghum, cotton soja, dry legumes) and Spodoptera frugiperda is also found in rice, corn and cotton. The distribution of species from these two genera (Helicoverpa and Spodoptera) covers all the continents.

Helicoverpa armigera larvae (Photo from the website http://www.sindominio.net/)

Genetically-modified plants (GMOs) protected against the lepidopterans (cotton and Bt-corn) can reduce the use of these neurotoxic pesticides by 80% (Huang et al., Science 295:674; 2002). However, opposition to GMOs is increasing (Gahan et al., Science 293: 857: 2001), and may lead to serious consequences (return to pesticide use, ruin of the agrarian sector, etc.). It is therefore urgent to clearly understand the molecular mechanisms of resistance to Bt and classic pesticides, as well as the biology of the Lepidoptera and their interactions with plants and pathogens.

Spodoptera frugiperda

A model insect, for which substantial genetic and genomic resources are available, is needed for this type of research - Bombyx. But despite phylogenetic proximity (60-90 million years) between Bombyx and the noctuids (compared to Drosophila/Anopheles - 250 million years; D. melanogaster/D. pseudoobscura—46 million years), it must be shown that Bombyx, which has been domesticated for more than 6,000 years, can serve as a model for insect pests.