Journal of the American Mosquito Control Association, 15(3):4O0-4O6,1999 Copyright O 1999 by the American Mosquito Control Association,Inc. DEVELOPMENT OF THE FIRST BLACK FLY (DIPTERA: SIMULIIDAE) MANAGEMENT PROGRAM IN ARGENTINA AND COMPARISON WITH OTHER PROGRAMS ELMER W. GRAY,' PETER H. ADLER,I CECILIA COSCARON-ARIAS.' SIXTO COSCARON3 EIO RAYMOND NOBLET4 ABSTRACT. In response to increasing pest populations of black flies, the government of Argentina initiated a pilot program to evaluate the effectiveness of larval control in the irrigation system of the Negro River Valley, an 18,240-km' area in Patagonia. The extensive system of irrigation canals, drainage ditches, and natural wa- terways not only provides water for agriculture and general habitation but also affords habitat for immature black flies. Three species (Simulium bonaerense, Simulium wolffiuegeli, and. Simulium nigristrigatum) are pri- mary pests of humans and animals in this area. Trials were conducted using Vectobac@ AS in representative irrigation canals, a drainage ditch, and a medium-sized river. Most trials resulted in effective larval mortality and insecticide carry. Based on a comparison with I I black fly suppression programs throughout the world, a suppression program for the Negro River Valley has a projected cost of approximately $1,623,360/year. This study represents the initial steps in development of the lst areawide black fly suppression program in Argentina. KEY WOR-DS Black flies, management program, Argentina, Bacillus thuringiensis var. israelensis INTRODUCTION In 1991, the government of Argentina initiated a program to investigate the ecology and manage- ment of black fly populations in the Negro River Valley. This valley includes the Limay (721 m3/sec) and Neuquen (302 m3/sec) rivers that converge to form the Negro River (1,023 m3lsec). The Negro River Valley is in Patagonia, which is characterized as desert, receiving an average of only 20O mm of rain per year. The valley has about 700,000 inhab- itants, encompasses approximately 18,240 km2, and is surrounded by desert plains. In the early 19OOs, an extensive canal system was constructed to pro- vide irrigation for farming. The Negro River Valley has approximately 87,316 ha of fruit and vegetable production. Substantial numbers of livestock, in- cluding cattle, sheep, horses, and poultry, also are raised in the valley. While providing the water nec- essary for agriculture and general habitation of this region, the canal system also provides ideal habitat for larval black flies. The system incorporates 2'79 krn of canal in the middle valley. The area considered the upper valley contains a similar canal structure. Each valley also has about 150 km of drainage ditches to remove excess irrigation water. The majority (>9OVo) of the canal system provides suitable black fly habitat. However, the drainage system has slower water ve- I Clemson University, Department of Entomology, Long Hall, Box 340365, Clemson, SC 29634-0365. 2 Facultad de Ciencias Agrarias, Universidad Nacional Del Comahue, CC 85, 8303 Cinco Saltos, Rio Negro, Ar- gentina. 3 Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata, Argentina. a University of Georgia, Department of Entomology, 413 Biological Sciences Bldg., Athens, GA30602-2603. locities and larval habitat of lower quality, with only about 6OVoofthe system producing black flies. Initial studies identified 3 pestiferous species in the Negro River Valley: Simulium bonaerense Cos- car6n and Wygodzinsky, Simulium wolffiuegeli (Enderlein), and Simulium nigristrigatum (Ender- Iein) (Coscar6n-Arias 1997). These species are bit- ing and nuisance pests of residents, workers, and livestock. The purpose of our study is to provide information on a pilot-management program for black flies in the Negro River Valley and to com- pare projected costs with those of similar programs in other parts of the world. The establishment of an areawide black fly management program in this valley would constitute the lst black fly suppres- sion program in Argentina. MATERIALS AND METHODS Study sites: Five field evaluations, using Bacillus thuringiensis Berliner var. israelensis (B.r.i.), were conducted February 18-26, 1997 (late surnmer in southern hemisphere): 3 in irrigation canals, I in a medium-sized river channel, and 1 in a drainage ditch (Table 1). Irrigation canals in the Negro River Valley are typically steep-sided, flat-bottomed, and straight. Drainage channels have gradually sloped banks and slower velocities and lower discharges than canals. Canal VI had a flow of 3.23 m3/sec and was straight, with the exception of 2 45" bends in the evaluation area. Canal VII had a flow of 3.49 rlr3/ sec and was evaluated over a straight, 3,0O0-m sec- tion. This canal supports dense beds ofaquatic veg- etation (Potamogeton sp.) and is typical of many of the irrigation canals in the Negro River Valley. Ca- nal VIII had a flow of 11.5 m3/sec and originated at the same water-control structure as Canal VI. Ca- nal VII originated 50 m downstream of the water- control structure that created Canal VI[. All of 400