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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Nosema Disease on Fitness of the Parasitoid Tachinaephagus Zealandicus (Hymenoptera: Encyrtidae).

item Geden, Christopher
item Almeida, Maria - INSTITUTO DE BIOLOGIA
item Pires Do Prado, Angelo - INSTITUTO DE BIOLOGIA

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2003
Publication Date: October 1, 2003

Interpretive Summary: Biological control is an important component of integrated management systems for flies associated with livestock, poultry and horses. Parasitic wasps are among the most important biocontrol agents for flies, and there are several commercial insectaries that provide these wasps to farmers. Because the species of wasps native to US attack the fly in the pupal stage, there is interest in finding other species that attack the fly while they are still larvae. Tachinaephagous zealandicus is an exotic species common in the Southern Hemisphere that is an attractive candidate for use in the U.S. This wasp attacks flies in the larval stage, has a high attack rate, is easily reared, attacks several species of pest flies (house fly, horn fly, stable fly), and produces many new wasps from each fly that it kills. Recently T. zealandicus has been found to be infected with a protozoan parasite in the genus Nosema. Similar diseases are known in native wasp species and methods to manage the diseases have been implemented. In this study, a scientist at USDA's Center for Medical, Veterinary and Agricultural Entomology worked with colleagues in Brazil to determine the impact of this disease on T. zealandicus. Infected wasps were found to live about half as long and produce less than half as many progeny as uninfected wasps. Colonies of infected wasps also produced higher proportions of males than uninfected colonies. Male wasps do not attack host larvae. Eliminating the disease from colonies of T. zealandicus is advised so that wasps that are imported and released in the US are of high quality and can achieve the greatest impact on populations of pest species of flies.

Technical Abstract: The effects of an undetermined species of Nosema on fitness of the muscoid fly parasitoid Tachinaephagus zealandicus were examined in the laboratory. Infected female parasitoids that were given honey and water lived about half as long as uninfected parasitoids under these feeding conditions. Effects of infection on longevity were strongest at 30oC; infected and uninfected females lived 2.8 and 8.7 days, respectively. Infected and uninfected parasitoids that were given only water had similar longevities, but water-only fed parasitoids had much shorter lifespans than honey-fed parasitoids at all temperatures. Infection did not result in significant lengthening of development times of immature stages, with male and female parasitoids completing development from egg to adult in approximately 23, 33, and 60 days at 25, 20 and 15oC. Overall emergence of uninfected parasitoid adults was 16 times greater than infected parasitoids at 15oC. Emergence of uninfected parasitoids was 11- and 3-times greater than infected parasitoids at 20 and 25oC, respectively, and sex ratios of emerged adults were significantly more male-biased in infected parasitoids at these temperatures than among uninfected parasitoids. Dissections of uneclosed puparia revealed that many infected parasitoids completed development to the adult stage but did not successfully emerge from host puparia. Infected and uninfected females killed similar numbers of hosts (70-75 house fly or Sarcophaga bullata larvae killed per group of 5 females in 24 h). Effects of infection on fecundity were modulated by host species. Uninfected females parasitized significantly more house fly larvae (59.7) and produced more than twice as many adult progeny (311.1) as uninfected females (34.1 hosts parasitized, 138.3 progeny produced). Infected females parasitized about as many S. bullata hosts as uninfected females and produced slightly fewer adult progeny (588.2 and 460.1 progeny per group of 5 uninfected and infected females, respectively). In tests with individual females given house fly hosts daily throughout life, uninfected and infected parasitoids had similar longevities (3.9 and 3.7 days respectively), but uninfected parasitoids produced 2- to 5 times as many adult progeny.

Last Modified: 4/20/2015
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