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Title: Status of tachinaephagus zealandicus (Hymenoptera:Encyrtidae), a larval parasitoid of muscoid flies, in the U.S. and Denmark

Author
item Geden, Christopher - Chris
item SKOVGARD, HENRIK - Aarhus University

Submitted to: Journal of Vector Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2014
Publication Date: 12/1/2014
Citation: Geden, C.J., Skovgard, H. 2014. Status of tachinaephagus zealandicus (Hymenoptera:Encyrtidae), a larval parasitoid of muscoid flies, in the U.S. and Denmark. Journal of Vector Ecology. 39(2):453-456.

Interpretive Summary: House flies and stable flies are important pests associated with animals and humans and transmit a wide array of disease organisms. Biological control is an important element in successful fly management. In the 1960’s there was an effort to import exotic biological control agents into the U.S. to assist with fly control. One of these agents was Tachinaephagus zealandicus, a parasitic wasp that attacks fly larvae and is native to the Southern Hemishpere. It was imported from Australia and released on farms in the U.S. and Denmark in 1967-1970 but no follow-up studies were done to see whether it had become established. This study, conducted by scientists at USDA’s Center for Medical, Agricultural, and Veterinary Entomology and Aarhus University (in Denmark), set about to document the distribution of the wasp 40 years after the releases had been made. No wasps were found in any of the Danish collections. In the U.S., however, T. zealandicus was found in every state that was sampled, and the collections represent new records for Florida, Georgia, North Carolina, Tennessee, Kentucky, Illinois, Indiana, Missouri, Kansas, and New York.

Technical Abstract: A survey was conducted to determine the status of the muscoid fly parasitoid Tachinaephagus zealandicus in the U.S. and Denmark 40 years after this species was introduced from Australia as a classical biological control agent. No T. zealandicus were recovered from any of the collections made in Denmark. In the U.S. survey, 57 of the 118 samples (48%) included at least some parasitism by this species. Percent parasitism of host larvae was highest in New York, Florida, and Georgia (>10% of hosts parasitized), and comparatively lower in the other states. The collections represent new records for T. zealandicus in Florida, Georgia, North Carolina, Tennessee, Kentucky, Illinois, Indiana, Missouri, Kansas, and New York. Most (74-94%) of the emerged parasitoids were females. Gregariousness ranged from an average of 9 to 14 parasitoids produced per parasitized host. Between-sample variation in this parameter was high, however, and ranged from 3 (Sept 28, 2008, Dyar Wildlife Management Area, Georgia) to 40 (also on Sept 28, 2008, Stephens State Park, Georgia) parasitoids per parasitized host. Although the survey was not designed to examine seasonality in a systematic way, the data set was large enough to partition the results into different times of year, enabling an examination of broad trends. The percent of samples with at least some parasitism from Florida and Georgia was highest (>75%) in May, September and December, and lowest (0) in August. Percent parasitism of host larvae, however, was highest in March (25%). There was no clear trend in the seasonality of gregariousness.