Spot river trials of new anti-blackfly larvicides: I. effects of carbsosulfan or marshall on the non-target fauna

ocP/vcu/HYBro/86 .2 ORIGINAL FRENCH SPOT RIVER TRIALS OF NEW ANTI-BLACKFLY LARVICIDES r. Effects of carbsosulfan or Marshall on the non-target fauna L. Yam6ogo, B. Cou1lbaly INTRODUCTION 1' The serious and harmful consequences of onchocerclasls for the health of the peopleLlvlng Ln vast areas of tr'lesE AfrLca and for the socloeconomlc development of the infested zones led the seven most affected countrLes to joln together in a programme to flght thescourge, lrith financlal assistance from 19 countries and lnstitutlons. 2' To attain its obJectives, the onchocercLasls Control programme in the Volta RlverBasln Area (ocP) chose chemicaL control of the aquatLc l-arvai stages of the vecror,Slnullum damnosum s.1. Thls choice is explalned by the fact that the appllcatlon of@sscampa1gnsw111poseprob1ensveryd1fficu1ttoso1ve(amoreor1esslong duratLon of the course of treatment which will Lncrease the rlsks of absenteelsm, theneed for sufflclent speclalLzed personnel for a strict check-up during and after thetreatment, etc.). 3' The appearance a few years ago of resLstance to Abate and then to chlorphoxim lncertain cytotypes of the vector revived the search for "ne!r" possible replacenentlarvlcides. In order to ninlmize the rlsks of cross-reslstante, the trials are dlrectedtowards chemi.caL familles which are dlfferent from that of the organophosphorus compounds.Thus, some carbamates lncludlng Marshall (carbosulfan) have been tested. This documentglves the results of a spot triaL of carbosulfan as part of thls search. GENERAL 4' Marshall or carbosulfan is a carbamate produced by the flrn F.l,l.c. The formulation isa 252 emulsifLable concentrate known as pL g3-237 or ous 3022. 5' When pure, carbosulfan or 2.3-Dihydto-2.2 dimethyl-7-benzofuranyl ((dibutylarnino) thlo) methyl carbamate is a brown-coloured vlscuous J.lquid wlth density between 1.056 and1'083 9/n1 at 2o degrees c. rt is soLuble ln water (up to 0.3 ppm), and stable in neutralor slightly alkaline conditions. Furthermore, carbo"rlf.., is non-corroslve, non-exprosiveand non-infIammable. Experiments carrled out on mice and rats (De prospo et al.19g5) (1)dld not reveal any effect of injection of carbosul"fan at a dose of 2o ppm. 6' The spot trlal of carbosulfan took place on 29 March 19g5 at DjodJi, on the wawa lnTogo' The larvlciding was carrLed out at about 2oo metres upstream from the sampring zoneusing the "Hudson X-pert sprayer., at a dose of 0.05 ppn/10 ni.nutes. (1) De Prospo J.R, l'Ieiner M., Mc Carty J.Dr. Geiger L.E.; Nowell M.J. and Fletcher M.J,(1985) : twenty-four dietary toxlcity and oncogenlcity studles wlth carbosulfan ln mlceand rats. The roxlcologlst 1985, 5 (1) ocP/vcu/HYBTO/86.2 Page 2 7. The effect on the invertebrates rras evaLuated by the sinple gutter systeu (Dejoux,1975) (1). 8. The fauna which was lnstalled on the eve of the larvlcidlng rras left to rest 24 hoursln order to have a good colonlzation. The drlft col-lections whlch rtrere started a fewhours before the larvl.clding were cont.inued up to the next d.ay. RESULTS 9' The raw results_of the experiment show that the gutter fauna was composed mainly ofEpheneroptera (42.L7"), Diptera-Chironornldae (30.12), Trichoptera (4.2y.) and other Dlptera(L6'6%)' The other organisms (Coleoptera, Pieeoptera, Ilydracarians, odonata, etc.) represent.ed only 6.9'l of the fauna tested. a) Epheneroptera The Epheueroptera (Figure la) were greatly affected by carbosulfan (96.6"1 detachment).Among them, the Trlcorythidae and the rBaetldae were more affected than the Caenldae (Tabler). Specles Remainder Total D* Total T % Drc Leprophlebiidae Heptageniidae Trlcorythidae Baetidae Caenldae Total Epherneroptera 9 9 43 13 34 108 LL4 22L 2001 66L 110 3107 L23 230 2044 674 L44 32ts 92.69 96.08 97 .gg 98 .07 76.39 96.6 Table 1 : Gutter effect of carbosulfan on Djodji/wawa (Togo) - 29-30 March the Ephemeroptera. 1985. * Tot. Tot. 7"D D = Total fauna that drifted T = Total- fauna tested = Percentage of detachment. There was a detachment of nearl-y 38 .7"1 of the chlronomidae (Diprera). The Tanytarslnlseem to be less suscePtible than the lndlvlduals of the other trtbls (Table rr). on thewhoLe, the chironomLdae were, relatively, not very much affected Uy ttre p.""rg" of thepestlcide (Flgure lb). (1) Dejoux C., (1975) : Nouvelle technlque pour tester in sltu lrlmpact des pestlcLdes surla faune aquatlque non-cible. oRsroM, Entomologlcal, ueatciTEdEl[EtologicaL series No2 : 75-80. Species Remalnder Total D. Total T. .A D. Chironomini Tanypodilnae Tanytarsinl Orthocladiinae Total Chirononidae 324 52 279 7s6 t_411 236 32 83 s3B 889 560 84 362 L294 2300 42.L4 38.09 22.92 4L.s7 38.7 ocP/vcu/HYBTo/ 86 .2 Page 3 Table II : Gutter effecE of carbosulfan on the Chironomidae. Djodji/Wawa (Togo) - 29-30 March L985. c) Trichoptera The detachment of the Trichoptera was about 682. The Philopotamidae were quite greaEly affected by carbosulfan. The same applies to the Hydropsychidae (Table III). The relatively suall number of Trichoptera had, however, only a linlted lncldence on the trend of the overall drift of the organlsms (Flgures lc and 1d). Specles Remainder Tot. D Tot. T %D C. falclfera C. copiosa C. digltata A. senegalensis C. spII Chimarra sp. Protomacronema Iiydropsyche Leptocerl,dae Total Trlchoptera L2 1 o o 12 19 3 L2 46 105 51 18 6 1 34 77 1 I_3 L8 2L9 63 19 6 1 46 96 4 25 64 324 80.95 94.73 73.9L 80.20 52 28.L2 67 .6 Table III : Short-term gutter effects of carbosulfan on the TrLchoptera. Djodji/wawa (Togo) ' 29-30 March 1985. 10. It should be poLnt.ed out that the product was almost on the target fauna. In fact, there was a 997. detachment whlch survived were all moribund. ocP lYcu/HYBTO/86.2 Page 4 completely effective in gutter of S. damnosum. The lndividuals 11. The lntensity of the drift was relatively low before the larvicidlng. There was apeak only a few mlnutes after the sprayl:rg. An Lrregular fal1 began after that but became stable around 18hOO (Flgure Ld). The so-called biological acrlvity drifr (night-timedrift) was not perceptible. Thus, the relatlvely conslderable long-duration detachment whlch occurred just after the Larviclding resulted in a certaln dlsruptlon of thebiological rhythms and a reduction in the total fauna comparable to that recorded wlthpermethrin at 0.015 ppn/10 nlnutes (paugy et a1. 1984). Ilowever, no flsh nor macrocrustacean mortality was observed. L2. It should be noted that a spot trial had been carrled out at 0.2 ng/l for an exposure tlme of 1O minutes. The results revealed a greater effect of carbosulfan on Ehe non- target aquatic fauna with an efficacy on the target fauna that was almost similar to that recorded at a dose four times less. During that trlal whlch was carried out in November 1984 at Ntcanbeto on the Mono (Togo), abnorrnal behaviours of the fish and shrimps were observed ln sltu. Individuals were therefore caught wlth dip-net and observed in unpollute?ffi f,or 24 hours. They reeovered and were alrlady behaving normally after 3o ELnutes of observatlon. It is important to note that these studies were carried out on a "virgin" fauna during the low-water period (4 rn3/sec.), and therefore under condltions where the effect of larvicides on the aquatlc fauna is generally at a maximum. CONCLUSIONS 13. Carbosulfan is a carbamate whlch, at o.O5 ppu/lo mlnutes, resulted in a considerable detachment of the aquatic lnvertebrate fauna (74%) ln the short term, under low-water condiEions. L4. The Ephemeroptera were quite severely affected. The Chironomidae (Diptera) seem to be the least susceptlble among the most important farnilies concerned wlth the test.. 15. Generally speaking, carbosulfan at 0.05 ppn/10 minutes has an effect on the non- target fauna which is comparable to that of Talcord permethrln utllized at 0.O15 ppu/lo mlnutes, and therefore greater than that of temephos. '16. Since the naxlutum exposure to carbosulfan did not cause, ln the short term, any ellnination of Ehe main taxonomic groups or fish or macrocust.acean mortality, operational hlgh-water trlals wl11 be carried out ln order to evaluate lts medium-term effects. A revlsed protocol w111 be enployed by taking into account the experience gained during thetrlals of Talcord permethrin. Tests wlLl also be carried out at different concentratlons so as to have a good understanding of the level of toxicity of the product on the fish and macrocrustaceans. c) Square root (total .kLchoptera) N(,ttoooo a) square root (tota1 Ephemeroptera) -Nu5oooc_) b) Square rost, (tot. Chironmitiae) oo88B o I II I l.-----=1r'1t1/)/ _rl)/ )) 1(l\ 1)It l/ v I I 17 I I I L 1l o u v UI \l u LNi, I(, a) Square root (total far:na) !,(^ !u !,, UI I(n N !" tn N(,