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 locities and larval habitat of lower quality, with only about 6OVoofthe system producing black flies. In 1991, the government of Argentina initiated a Initial studies identified 3 pestiferous species in program to investigate the ecology and manage- the Negro River Valley: Simulium bonaerense Cos- ment of black fly populations in the Negro River car6n and Wygodzinsky, Simulium wolffiuegeli Valley. This valley includes the Limay (721 m3/sec) (Enderlein), and Simulium nigristrigatum (Ender- and Neuquen (302 m3/sec) rivers that converge to Iein) (Coscar6n-Arias 1997). These species are bit- form the Negro River (1,023 m3lsec). The Negro ing and nuisance pests of residents, workers, and River Valley is in Patagonia, which is characterized livestock. The purpose of our study is to provide as desert, receiving an average of only 20O mm of information on a pilot-management program for rain per year. The valley has about 700,000 inhab- black flies in the Negro River Valley and to com- itants, encompasses approximately 18,240 km2, and pare projected costs with those of similar programs is surrounded by desert plains. In the early 19OOs, in other parts of the world. The establishment of an an extensive canal system was constructed to pro- areawide black fly management program in this vide irrigation for farming. The Negro River Valley valley would constitute the lst black fly suppres- has approximately 87,316 ha of fruit and vegetable sion program in Argentina. production. Substantial numbers of livestock, in- cluding cattle, sheep, horses, and poultry, also are MATERIALS AND METHODS raised in the valley. While providing the water nec- essary for agriculture and general habitation of this Study sites: Five field evaluations, using Bacillus region, the canal system also provides ideal habitat thuringiensis Berliner var. israelensis (B.r.i.), were for larval black flies. conducted February 18-26, 1997 (late surnmer in The system incorporates 2'79 krn of canal in the southern hemisphere): 3 in irrigation canals, I in a middle valley. The area considered the upper valley medium-sized river channel, and 1 in a drainage contains a similar canal structure. Each valley also ditch (Table 1). Irrigation canals in the Negro River has about 150 km of drainage ditches to remove Valley are typically steep-sided, flat-bottomed, and excess irrigation water. The majority (>9OVo) of the straight. Drainage channels have gradually sloped canal system provides suitable black fly habitat. banks and slower velocities and lower discharges However, the drainage system has slower water ve- than canals. Canal VI had a flow of 3.23 m3/sec and was straight, with the exception of 2 45" bends in the I Clemson University, Department of Entomology, evaluation area. Canal VII had a flow of 3.49 rlr3/ Long Hall, Box 340365, Clemson, SC 29634-0365. sec and was evaluated over a straight, 3,0O0-m sec- 2 Facultad de Ciencias Agrarias, Universidad Nacional tion. This canal supports dense beds ofaquatic veg- Del Comahue, CC 85, 8303 Cinco Saltos, Rio Negro, Ar- etation (Potamogeton sp.) and is typical of many of gentina. the irrigation canals in the Negro River Valley. Ca- 3 Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La nal VIII had a flow of 11.5 m3/sec and originated Plata, Argentina. at the same water-control structure as Canal VI. Ca- a University of Georgia, Department of Entomology, nal VII originated 50 m downstream of the water- 413 Biological Sciences Bldg., Athens, GA30602-2603. control structure that created Canal VI[. All of 400 Snprsi\assn1999 Ble,cr Flv MaNecsN4BNr n AncrNrtNe 401 these canals are in the Lamarque farms area in the middle valley of the Rio Negro province. The Rio Salado is a medium-sized river extend- e Nn$nr) o C.I N ing from the town of Chimpay to the town of Choe- le Choel. This area also is located in the middle valley of the Rio Negro province. The Rio Salado had a flow of 5.58 m3/sec on the date measured. Its flow, however, is directly related to the level of the tr- Negro River and is typically higher than measured during this study. The Negro River Valley was ex- ?l o^- o\ t'..F r) o ol cl c'.1N c.) periencing a dry period, and all rivers were lower 6 -. O than normal during our study. Flow in the Rio Sal- o ado was relatively uniform through the first 1,50O lJ. m. Beyond 1,500 m, no suitable larval habitat was present untll 2,2OO m below the treatment site. The d I area between these 2 sites had slow water, with a \oooor) o -€ u^v 100-m stretch of dense aquatic vegetation. o0 e A-- H N ti c'.1 c.l Drainage Plottier (Neuquen province) represent- 0 * ed a typical drainage channel in the valley region. C) It had a flow of 0.31 m3/sec at the treatment site and 0.40 m3/sec at the most distant evaluation site (2,300 o m). The area betweeh 1,200 m and 2,300 m was virtually inaccessible. A 20O- to 300-m stretch afF-nc.ii of slow flow followed r;+oi+r; the l,2OO-m site. c.l Application and evaluation: a TIte lst field trial z (Canal VI) was conducted with a Vectobac@ AS q F (600 ITU-Abbott Laboratories, N. Chicago, IL) .B.r.1.product (lot no. O9-244-SL) that was produced in September 1995 and had a use-by date of Sep- tember 1996. This product had been stored at room ' iOhr+\O 0) v?\q9q temperature since receipt by the Universidad Na- 20. B cional Del Comahue in Cinco Saltos, Argentina. Vectobac AS (lot no. 2O-628-51) rhat was manu- factured in August 1996 was used in all subsequent a trials. Flow measurements were conducted following the recommendations of Horosko :.; 3 ol \o t-.. \o 00 and Noblet :: €ONoC.l (1986), with the following exception. Velocity mea- zutre-i* -; ...i.: ci d 6l surements on February 18 and 20 were conducted with a Fisons Scientific Equipment velocity meter q)l (MJP-Geopacks, Cornwall, Trinidad). We used corks and a stopwatch to calculate velocity on the remaining treatment days. Surface velocities were 4l 0l multiplied by 0.8 to adjusr for flow velocities ! 0) tsl .E throughout the water column (Colbo 1985, Molloy OI 6 and Struble 1989). ol ; HI o Larval mortality was evaluated using techniques >>>S yo similar to those of Gray et al. (1996). B Mortality evaluations were conducted at various distances :!:o!E I downstream from (Table (.)| udd;t6 the treatment site 2), de- pending on individual waterway characteristics, lar- -l val substrates, and the dose. A minimum of 100 I larvae were collected approximately 5 h posttreat- I I ment by removing pieces of substrate and returning I I them to the laboratory in ice chests. Samples were aerated with aquarium pumps. At approximately 24 ooooV)\o I i N Ol a'.1c.l h posttreatment I each sample was poured in a white I >'>>'>>. EE!EH pan I enamel and the percent mortality was deter- I I ELLHT mined. I Adult monitoring was conducted on I ,9 ,9 .9 ,9 ,9 9 occasions from February 18 to 27,1997, following the pro- 402 JounNer-or rnn AuentcAN MoseulTo CoNrnol AssocrnrroN Vor-. 15, No. 3 Table 2. Larval mortality evaluations in 5 waterways in the Negro River Valley, Argentina, February 1997. Percent mortality (r?) Site m down- Drainage stream Canal VI Canal VII Canal VIII Rio Salado Plottier Control (0) 0.3 (307) o.o(127) 0.3(361) 2.4(295) 0.0(158) 500-1,000 100.0(202) 100.0(150x 99.r (2r3) l,000-1,500 99.6 (264)l q{ I /l {7\4 91.s(236) I,500-2,000 71.6(278) 8O.4(224) 9s.2(210) 2,000-2,500 99.s (222) 62.9(3o7) 60.s(778) s.6(199) 2,500-3,000 89.9(139)' 4O.2(r37) 87.9 (2oo) 3,000-3,500 92.7 (42s) 88.8(295)3 3.9(383) 3,500-4,000 61.5(191) 88.7(363)3 4,000-4,700 74.3 (288) rAdditional mortality evaluations were made at 2 sites in a side channel downstream of a water-control structure located 1,100 m below the treatment site: 1,300 m, mortality :98.2Vo (n: 327);1,880 m, mortality -- 92.4E" (a : 238).