Submitted to: Bulletin of Entomological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2003
Publication Date: 8/20/2003
Citation: Bulletin of Entomological Research (2003) 93, 561-567
Interpretive Summary: Several species of pest beetles, popularly known as leaf beetles, corn rootworms, or cucumber beetles, in the family Chrysomelidae, subfamily Galerucinae, tribe Luperini, represent enormous damage and control costs to agriculture throughout the Americas. Since the pest genera are of South American origin, where the greatest species richness is found, the USDA/ARS South American Biological Control Laboratory (SABCL), was appointed to carry out explorations in South America in search of potential biocontrol agents. Of the two parasitoids found so far a braconid wasp, Centistes gasseni Shaw, has attracted great attention for being abundant and the only Hymenoptera (wasp and bee order) parasitizing Diabrotica. The objectives of this work are to report field observations, and results of experiments on the reproductive biology and ecology of C. gasseni, including their host range, distribution, and environmental constraints. C. gasseni has been found in northeast Argentina, and southern Brazil and Paraguay. Three Diabrotica species were found to host the parasitoid, D. limitata (Sahlberg), D. speciosa (Germar), and D. viridula (F.). Laboratory experiments with field beetles and cocoons reared in the laboratory, indicate C. gasseni overwinters obligatorily in overwintering adult host beetles, remaining quiescent in its live host below developmental temperatures. Based on the known climatic range of this parasitoid, and its requirement of adult overwintering hosts, a potential distribution in North America is proposed.
Technical Abstract: The genus Diabrotica (Coleoptera: Chrysomelidae) includes a large number of pest species, including some of the most important crops pests of the Americas. The parasitoid Centistes gasseni Shaw is the first braconid to be described parasitizing Diabrotica in South America, and high natural infestations are reported. Field and experimental observations on the host range, distribution, and biology of this parasitoid are described. Centistes gasseni was collected in southern Brazil, eastern Paraguay, and northeastern Argentina, in a region comprising humid lowlands and highlands, and cool temperate to warm subtropical climates, with regular rainfall in excess of 1300 mm. Three Diabrotica species, D. limitata (Sahlberg), D. speciosa (Germar), and D. viridula (F.) were found to host the parasitoid, with mean percent parasitism of 5.4, 2.0, and 1.0%, respectively. Diabrotica speciosa and D. viridula are the two most important pest Diabrotica species in South America. Laboratory experiments with field-collected beetles and parasitoid cocoons, indicated that C. gasseni overwinters in adult host beetles, remaining dormant in its live host below developmental temperatures. A potential distribution in North America is suggested for C. gasseni based on its known climatic range and the distribution of the main pest species of adult overwintering North American Diabrotica.