Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2005
Publication Date: 2/5/2006
Citation: Rendon, P., Sivinski, J.M., Holler, T., Bloem, K., Lopez, M., Martinez, A., Aluja, M. 2006. The effects of sterile males and two braconid parasitoids, Fopius arisanus and Diachasmimorpha krausii, on caged populations of Mediterranean fruit flies, Ceratitus capitata at various sites in Guatemala.Biological Control. 36:224-231. Interpretive Summary: The Mediterranean fruit fly (medfly) attacks over 250 species of fruits and vegetables and causes trade barriers wherever it occurs. It is abundant in Central America and is kept from spreading northward into the USA by an insecticide and Sterile Insect Technique barrier (SIT) established along the Mexico / Guatemala border. However, this barrier is increasingly porous and new controls are required. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida in collaboration with USDA-APHIS and MOSCAMED examined the effect of combining mass-reared parasitoids with SIT in large field cages. The addition of parasitoids always resulted in higher medfly mortality; in some instances suppression was over one hundred times greater than SIT alone. Large scale field tests of combined releases are planned.
Technical Abstract: Areawide control of the Mediterranean fruit fly (= medfly), Ceratitis capitata (Wiedemann), typically involves sterile insect technique (= SIT), and at present the 'Temperature Sensitive Lethal' (= TSL) strain is commonly mass-reared for such releases. In theory, and with some experimental support, the augmentative addition of parasitoids to sterile releases can suppress pest populations to a greater extent than either technique alone. The efficacies of TSL males, parasitoids, and TSL males and parasitoids were compared in large field cages erected over coffee grown at four locations and three altitudes (relatively high, medium and low for the crop) in Guatemala. Two species of opiine braconid parasitoids, the larval-pupal parasitoid Diachasmimorpha krausii (Fullaway) and the egg-pupal parasitoid Fopius arisanus (Sonan), were released either alone or in combination with sterile males into cages along with fertile medflies. Results of this evaluation were assessed by comparing the number of pupae and adult insects that completed development (F1 generation) as a result of the reproduction of a parental generation released into each field cage. The TSL males alone gave mixed results and significantly suppressed F1 fly populations at a single site. However, the inclusion of F. arisanus, and to a lesser extent D. krausii, always improved the control provided by sterile males and this improvement was frequently substantial. Neither parasitoids nor sterile TSL males were equally effective in all environments. While the site and/or timing of the experiments clearly played a role in the efficacy of the various control agents, it is unclear what environmental factors, if any, were responsible for the differences. The only correlations of relative effectiveness with temperature suggested that the inclusion of F. arisanus to sterile releases was most beneficial compared to sterile males alone at lower minimum and maximum temperatures. There was no overall pattern of suppression related to either the numbers of fruit or hosts in any of the treatments. These results suggest that mass-reared sterile medflies and biological control agents should be tested for quality in the various environments in which they will be released.