CHAMPAIGN, Ill. -- With the goal of improving the natural biological control of flies, scientists have scoured Illinois feedlots. After three years of study, they say that two parasitic wasps known as Spalangia endius and Spalangia nigoraenea are especially important in the Midwest and actually could emerge as weapons.
Such is the finding of a study of parasites that feed on stable and house flies in Illinois. Both types of flies are well-known pests. Stable flies feed on the blood of cattle, annoy other livestock and adversely affect production, and, like house flies, are a public health problem among humans.
Researchers from the University of Illinois collected fly pupae from manure, spilled feed, along fence lines, near water sources and waste piles of straw and hay at feedlots. The scientists then looked for the presence of either emerging flies or the parasites that kill them.
The predominant parasites that kill flies are tiny wasps. As in the movie "Alien," the wasps lay their eggs inside a host, in this case within a fly pupa, killing the host from within. The egg hatches and the parasite larva feeds on the dead fly's pupa before emerging as an adult about a month later.
Spalangia endius wasps, although rare or absent in similar studies in Kansas and Nebraska, were common in southern Illinois. Because these wasps already are reared and sold as a biological control, mostly for use in California and Northeast dairies, they may be worth a closer look as a biological control in Illinois, said U. of I. agricultural entomologist Richard Weinzierl.
The findings were published in the April issue of Environmental Entomology. Working with Weinzierl on the project, which was funded by the USDA and the U. of I., was Carl J. Jones, a U. of I. veterinary pathobiologist.
"In general, endius had been written off as ineffective and
unimportant in the Midwest, where we have harsh summers and
Contact: Jim Barlow
University of Illinois at Urbana-Champaign