Surveillance d'insectes ravageurs des cultures par piégeage sexuel des mâles dans les départements de la Guadeloupe et de la Guyane

Abstract

Three noctuid moths are particularly harmful to cultivated Graminaceae in French West Indies and Guyana : Spodoptera frugiperda J.E. Smith (the grass worm), Heliothis zea Boddie (the cotton boll worm) and Mocis latipes Guénée. All the three species have multicomponent sex phermones where minority components play an important role for male attraction. Synthetic sex attractants have been developed recently for these insects and have been used for population monitoring. In French Guyana, sexual trapping of M. latipes and S. frugiperda males, in artificial grass lands, has been extensively used to predict caterpillar swarms and to adjust insecticide applications. In the case of S. frugiperda, for example, there are good relationships between the number of males caught in a sexual trap and the number of caterpillars that can be found in the grassland one week later. It has also been found, for the same species, that there are 3 flights for the adults during the year, separated by 4–5 week periods. A similar correlation can be predicted for M. latipes, but owing to the very low populations present during the experiments it was difficult to show conclusively. Advertisements concerning swarming risks for S. frugiperda are now broadcasted by radio and T.V. for the growers of the coastal range of Guyana. In the French West Indies (Guadeloupe) sexual trapping of both S. frugiperda and H. zea has been used to study the spatial repartition of the insects on all the island and to discover relationships between the population levels and nature of the crops in a given area. It has been found that S. frugiperda is present in all locations and during all the year with a maximum during the rainy season. On the other hand, H. zea is present only when a favourable host plant grows in the same area. The species can disappear for several months if host plants are not present. These experiments, conducted for the first time in these two geographical areas, clearly demonstrate the usefulness of sex attractants for monitoring insect pest populations in tropical countries.