Bemisia tabaci biotype B (Hemiptera : Aleyrodidae) and its parasitoids : Guadeloupe Island as a representative site of the Carribean

Over the past decade, the whitefly Bemisia tabaci Gennadius has caused extensive damage to cucumber, melon and tomato on the Caribbean island of Guadeloupe (Lesser Antilles). Recent collaborations have led to the characterization by RAPID, with primers H9, H16 and F12, of B. tabaci from Puerto Rico, Guadeloupe, Martinique and Trinidad. We have observed the population dynamics of B. tabaci, on experimental plots of squash (Cucurbita moschata), and we have also identified their parasitoids. The study areas were located at two sites on Guadeloupe: Petit-Bourg (INRA-Duclos) exhibits acidic oxisols with low fertility, humid tropical climate; annual rainfall 2.8 m, annual PET 1.3 m, average temperature 23.5°C, while Petit-Canal (INRA-Godet) is characterized by neutral swelling clay soils, humid tropical climate with a marked dry season; annual rainfall 1.6 m, annual PET 1.5 m, average temperature 26°C. Both sites are surrounded by a mosaic of sugarcane, food crop parcels and natural forest at less than one kilometer. It is of special value to perform such studies on Guadeloupe, because this one island exhibits a suite of vegetation, climatic and geographic conditions that are more often found individually on the other Caribbean islands. Our RAPD results show that Bemisia from Puerto Rico, Guadeloupe, Martinique and Trinidad is biotype B - the same as that found in Australia, Colombia, France and the USA. The observation of population dynamics revealed that the Bemisia populations at Duclos are small throughout the year - less than five adults per leaf. At Godet, however population sizes were generally larger, particularly during July, when as many as 20 adults per leaf could he found. Eight species of parasitoids were found at Duclos (Encarsia transvena, E. formosa, E. tabacivora, E. strenua group, E. parvella, E. aff. hispida, E. aff. basicincia and Amitus bennetti) and only three at Godet (E. transvena, E. labacivora and E. nigricephala). At Duclos, E. transvena is the most abundant species throughout the year, and thus seems to be better adapted to humid conditions. From January to July, E. aff. basicincta and E. tabacivora are present and competing with E. transvena. The others are quite rare. Studies such as these will aid in developing a biological control component in a management strategy which will limit direct damages due to B. tabaci biotype B on cucurbitaceae or to minimize impact of begomovirus on tomatoes in Lesser Antilles and other world regions as well. (Résumé d'auteur)