Significant reductions of seven species of flies breeding in poultry manure were attained over a 20-month period through procedures that favored the natural increase of predatory and scavenger arthropods and by periodic inoculative releases of four parasitic Hymenoptera. Parasite releases during springtime had an apparently greater direct effect on fly reduction than did similar releases in the summer. Autumn releases were not evaluated. A minimum manure height of 8–12 inches (20–30 cm) was considered essential for minimum fly production. The importance of manure stability and importations of additional beneficial species are also discussed.

The authors are grateful for the assistance of R. F. Hobza, formerly with Cooperative Extension, U.C., Riverside; T. V. Hartle, Agricultural Field Assistant, San Bernardino County; the Department of Public Health, San Bernardino County; and the Rincon-Vitova Insectaries, Inc., Riverside.