Evaluation in troughs on S.damnosum s.l. larvae of a formulation of Bioresmethrin (OMS 3043)

-a EVALUATION IN TROUG}IS ON 5i. DA'IN(BIN S. L LARUAE oF'A NEI{ FORilULATION oF BI0RESIIETHRII{ ((IlS 3O431 Technical Report OCP/IRU 90.01 Insecticide Research Unit Onchocerciasis Control Programme Programme de Lutte Contre l'Onchocer@se World Health Organisation Organisation Mondiale de la Sant6 Bouak6 - January !990 a Rok ? i 1 Cr -5n l I a i,torld Health Organization - Onchocerciasis Control Programme - Insecticido Research Unit ocP,zIRU,z90. ot ERRATUM TABLE 1. COMPARATIVE RESULTS OF BIOASSAYS WITH BIORESMETHRIN AND PERMETHRIN. Column 3. Permethrin (OMS 1821) 20% EC Lot 0019 (FMC). For LC50 read 1.54 lnstead of 15.4. a aTABLE 1 - COMPARAT]VE RESULTS OF BIOASSAYS wlTH BIORESMETHRIN AND PERMETHRIN FORMULATpN TEST @DE % MORTALITY FOR MATURE LAM/AE (Nl LC50 tolL ($.16c.,.) LCr95 /g,IL ($tbc.t.l LC19g ttglL ($%c.t.l Nbr of TestsCoteiltgtlott lor pllat 0' et@EE,ue 0.6 1.2 2.8 5.0 !0.0 Bioresmethrin (oMs 3o4{l) 20% EC Lot 1.7x1 1 13 (Roussel-Uclaf) T90{1 T9043 T90{5 13.2 (ffi) 42.O (1(t9) 66.6 (e{F) 93.5 (t&1) 95.0 (1374 1.5 (1.u2.0) 7.4 (6.0-t t.o) 14 (to.a-21.o) 3 Bioreemethrin (oMs 3043) 10% EC Lor 15U0310 (Roussel-Uclaf) T9042 T9046 34.5 (2u) 52.1 (@t 57.3 (ffi) s.4 (t5tl) 99.4 (fi@) 1.4 (t.o-2.o1 6.9 (5.0-r.1) 13.5 (8-Csr-o) 2 Permethrin (oMs 1821) 20% EC Lot 0019 (FMc) T904 7.6 (12t 58.9 (178) 67.5 (3e3) 82.5 (154 1.54(-, 8.4(-l 17 ( -, 1 Temp. Water =21 -2'C pH =7.5 -7.8 Turbidity = 5 JTU @nductivity= 9t.6 ri6 - 100.1 ,6 a Fig. 1 SUtvlt\,'lAR'f OF TROUGH RESULTS Er.iFI:r/,rETHRlll 10z Ec F -)FMlJLATl,.|tl t,) o a. or oro I I I I !1 ar (J I I I t-) roo 10 c. 1 BIORESMETHFII.i 2OZ EC PERMEIHRII.T 2OZ EC worlct Health Organization - Onchocerciasis Control Programme - Ins€cticide Research Unit ocP/IRu/90.0r Page 2 ABSTRACT EVALUATION OF BIORESMETHRIN 2OT EC IN TROUGHS ON S. DAMNOSUM S.L. Authors: M. Ocran, C. Back Bioassays of the new 20% EC formulation of bioresmethrin supplied by Roussel-Uclaf were performed on Simulium damnosum s./. at the IRU/OCP field station at Soubrd using the trough or closed-circuit system and the standard OCP protocol (refer to annex for method). Tests were carried out in parallel with bioresmethrin 10% EC, also from Roussel-Uclaf (1988), permethrin 20% EC, the pyrethroid currently in use in OCP.'Results obtained showed that bioresmethrin 29g EC was as active on the target species as the 10% EC formulation. For example, the calculated LC99 values for bioresmethrin 20% and the 10% EC were 14 UglLx1O min (0.014 m9,/Lx10 min) and 13.5 ugllx1O min respectively. The 2 were only slightly more active than permethrin 20% EC for which the LC99 was 17.0 UglL.xlO min. The 20% EC formulation does not appear to be significantly different from the 10% EC and, for that matter, from the 20xi EC permethrin. It is, however, quite stable in comparison with the others. The emulsion remained stable 48h after preparation with only slight creaming on the surface compared to the 10% emulsion. RESUME EVALUATION EN TROUGH SUR LARVES DE S. DAMNOSUM D'UNE NOUVELLE FORMULATION DE BIORESMETHRINE 2OX CE Auteurs: M. Ocran, C. Back Des bioessais de la nouvelle formulation de Bioresmethrine A,20% CE ont 6t6 effectu6s dans le systEme de circuit ferm6 (troughs), utilisant le protocole standard d'OCP (ref. Annexe pour m6thode) sur des larves de Simulium damnosum s./. au laboratoire de l'IRU e Soubr6. Pour pouvoir comparer son efficacit6, la bioresmethrine a 10% CE et la permethrine d 20% CE ont 6t6 test6es en paralldle. Les r$sultats obtenus indiquent que la bioresmethrine e 20% CE est aussi efficace que la 10% CE. Les valeurs de la CL99 par exemple pour les 2 formulations 6taient respectivement de 14.0 UglLx1O min et 13.5 UglLxlO min, et elles sont l6gErement sup6rieures A la permethrine A 20% CE dont la valeur CL99 6tait de 17.0 ugllx1O min. Ces r6sultats montrent que les deux formulations de bioresmethrine ont une activit6 6quivalente. tl faut noter cependant que la 20% CE avait une meilleure stabilit6 que la 10% CE 48h aprds la pr6paration de l'6mulsion. A la surface, un l6ger ddp6t de crdme 6tait plus marqu6 avec la formulation A 10%. a World t{ealth Organization - Onchocerciasis Control Programme - Insecticide Ree€arch Unit ocP/IRu,/90.01 Pag€ 3 EVALUATION ON S. DAMNOSUM S.L. LARVAE OF A NEW FORMULATION OF BIORESMETHRIN 2OT EC (PYR) INTRODUCTION Bioresmethrin from Roussel-Uclafr is a potent contact insecticide composed of a mixture of stereoisomers (cismethrin and resmethrin), a group which has already been evaluated by IRU/OCP as a 10% EC formulation, (Ocran & Kurtak 1988). The 20% EC formulation was furnished by Roussel-Uclaf, with an increased active ingredient content whlch means less volume per cubic meter of river discharge compared to the 10x EC. Permethrin 20% EC is the only pyrethroid used operationally in OCP. It is employed only at high river discharge and against larvae resistant to organophosphates and only for a few treatment cycles. As permethrin has a strong environmental impact and as the possibility of resis.tance to it cannot be ignored, the search continues for other pyrethroids with different structure-activity relationship and with less harmful effects on non-target aquatic organisms. Such formulations could be used for longer periods, at lower discharges (Kurtak et al. 1987). MATERIALS AND METHODS The following sample was supplied by Roussel-Uclaf: - Bioresmethrin 20% EC (OMS 3043). Batch N' 1.7 x 1113 (50 litres) (Rec'd Bouak6 01/90) Evaluation of bioresmethrin 20% EC together with thA lOX EC formulation supplied in 1988 was carried out at the IRU Research Station at Soubr6 with the trough (closed-circuit) system, using the standard OCP protocol (24-26/01/9O(refer to Annex for method). Permethrin 20% EC was also tested in parallel wlth bioresmethrin 20% for purposes of comparison. The larvae used in the bioassays were' mostly S. sanctipauli cyto-species collected from the untreated lower section of the Sassandra River, Southern C6te d'Ivoire. They are known to have normal susceptibility to all insecticides in operational use in OCP. "ROUSS€L UCLAF 35, boulevaro des Invalides, Borte postale 12O.O7, 75323 Paris Cedex 07, France world ttealth organization - onchocerciasis contro'l Programme - Insecticioe Research unit ocP/IRu,/90.01 ' Pege a 3. RESULTS The bioresmethrin 20% EC sample was supplied as a pale very fluid emulsifiable concentrate. It mixed readily in water to form a white homogenous emulsion which remained stable 48h later, but produced a slight creaming on the surface. The 10% EC formulation and the 20% EC permethrin produced slightly higher proportion of creaming on the surface by comparison. Activity of larvae increased with concentration and exposure time. In general within 3 minutes of exposure, most larvae were strongly affected. There were marked increases in detachment of larvae of all stages between 6 and 10 min, especially at the higher concentrations. Almost all larvae thus detached died within 3 hours. The results of 6 trough tests are presented in Table 1, and in Fig. 1 levels of efficacy of bioresmethrin 20% EC, 10% EC and permethrin 2095 EC are summarised. Figs 2 to 4 give detailed probit analyses results of all tests. Probit analysis of results shows that the 3 formulations had the same level of activity, with LC50s of 1.5 UglLx10 min (bioresmethrin 2O%), 1.4 UglLxl0 min (bioresmethrin 10%) and 1.54 ug,/Lx10 min (permethrin 2O%). In the standard prot6col al! detached larvae are classified as dead, while in fact a variable proportion is usually alive for some time. It was noted that the proportion of dead drifting larvae was higher with bioresmethrin than with permethrin. 4. DISCUSSION The new 20% EC formulation of bioresmethrin is an effective Simulium larvicide. It also has good stability. Its activity is as good as that of the 10% EC formulation and compares favourably with permethrin to which bdth formulations are slightly superior. The product appears to act mostly by contact, provoking a strong agitation and detachment during exposure. Presuftlably larvae must be ingesting toxic material for them to die within 3h after exposure. Susceptibility tests with technical grade solution in alcohol was observed to cause higher mortalities with bioresmethrin 20% than with permethrin 20% at similar concentrations. This observation suggests that irrespective of formulation, bioresmethrin may have a different mode of action and this could in itself be of interest in the event that larvae developed resistance to permethrin. 5. CONCLUSIONS & RECOMMENDATIONS Bioresmethrin 20% EC is an effective Simulium larvicide and a potential good candidate for operational use since it could be used at the same dosage as permethrin, if it became operational. It is however important that its effect on the non-target aquatic organisms be fully evaluated. It is recommended ttrat in the course of a river trial full aquatic monitoring should be undertaken. On the other harrd multiple gutter tests with non-target h,orld Health organization - onchocerciasis control Programoe - In6ecticide Re3€arch unit insects and separate evaluation on fish and f reshwater prawns could be performed to ensure its safety before it can be considered for operational use. 6. LITERATURE CTTED Ocran, M. H. and D. Kurtak. 1988. Evaluation of larvicide against larvae of Simulium damnosum s./. in West Africa. Technical Report OCP/IRU 23/8. Kurtak D., H. Jamnback, R. Meyer, M. Ocran and P. Renaud. 1987. Evaluation of Larvicides for the Control of Simulium damnosum s,l. (Diptera: Simuliidae) in West Africa. Journal of the American Mosquito Control Association. 3: 2O1' 210. . ocP/IRu/90. ol . p.ge .5 a TABLE 1 - @MPARATIVE RESULTS OF BTOAS{}AYS WITH BIORESMETHRIN AND PERIIETHRIN FORMUI.ATION TEST @DE % MORTAL]TY FOR MATURE T.ARVAE (N) LC50 ttglL (lsoic.t.) LCgs l!{,IL ($%c.t.t LG:9O tolL (t}stb c-t.) Nbr of TeetsCorpaarefbtr lot pfixt A' etqrcuo 0.6 1.2 2-8 5.0 10.0 Bioresmethrin (oMS 3@13) 20% EC Lot 1.7x1113 (Houssel-Ucla't) T90-O1 T9043 T90-Os 13.2 &nt 42.0 66.6 (ffi)(t(tet qt.5 95.0 (ts72l(t asq 1.5 (t.uz.o) 7.4 (6.O-t r.ol 14 (to.o-21.o) 3 Bioresmethrin(oMsMI) 10% EC Lot 15U0310 (Fouesel{Jclaf) T9042 T9046 34.5 ("u) 52.1 (@ol 57.3 (ffi) 9e.4 (t5t1) s.4 (flt2) 1.4 (t.o-2.o) 6.9 (s.o-t.q 13.5 (8.Ht -01 2 Permethrin (oMs 1821) ?o9/o EC Lot 0019 (FMc) T90-O4 7.6 (@) 58.9 Knt 67.5 (3t}3) 82.5 (s7) 15.4(-) 8.4(-, 17(-) 1 Tcmp. tYater =21 -ZoC pH =7.5-7.8 Turbidity = SJTU Conductivity= 94.6 16 - 100.1 ,6 Fis. 1 SUI/MARY OF TROUGH RESULTS e,'_ ef :.'.tfTr{Fltl IQZ Ei .ne!\lr-rIJATt._tl I a <\o x oi. €rlIJ I I I I tt ol c)) I I I I 3 100 ro I I .l I 1 I .l I 1^,. r i-- 3.iPt:r,(E!--r ', -cI 5: F E;rriTHRill 20; E'- RESULTS OF PROBIT ANALYSIS 5 it€rationa CHI-2 CRITERION =HETEROGENOUgloc LO99 = -1.84820 -2.0OS < < -1.62t- LO99 = O.01rl18rt 0.O1O ( < O.O24 0.1 OATA CORR. PREO. CHI.SQ PROBIT PROBIT CONTRIB. .955 .955 .955 .2t8 .218 .218 . a81 .48t .48r . ?43 .743 .7a3 .006 . 006 Fig.2 T-VALUE= GFAC = TITLE: C9O0 t 248 SUBTITLE: 2Ox EC OoBe units:l{c/LControl : O.O I OOSE TE9TEO -2.213 < < -1.9630.006 < < 0.011 -2.877 < < -2.727 o.ool < < 0.oo2 S.E.b = 0.055 SMETHRIN (ROUSSEL-UCLAF )7 X 1 1 13 (Ol,lS 3043 ) OATA TRANSFORMS log LO95 = -2.1265,1LD95 = O.OO7a72 lo9 LDsO = -2.79833LOSO = O.OO1591 intercapt alope --b= I 1 .852 2.118 OEGF CHI.2 Probabi I ity HETER 12 196.871 oo0 406 180 040 0. 16. 2. 0. BIORE LOT 1. DEAO x oB9 LOG 00sE CORR OEAD CORR. PERC. 23 49 10 21 2a 09 25 o6 38 oo 1a 26 94 12 90.5 97. O 99.8 94.5 87.9 97.2 62. O 73. I 66.7 39. 9 46. 3 38. 2 12.1 1{.8 0 0 5 0 o o o o o 0 o 0 o o 10 C , 1 3 OATAt I 2 3 1 5 6 ?I 9 to 4 -2.000 -2. 000 -2. OOO -2.301 -2.301 -2.301 -2.602 -2.602 -2.4O2 -2. 903 -2. 903 -2. 903 -3. zoa -3. 2O't 0. 01 o.01 0. ol o.005 o.005 o. oo5 o. o025 0.oo25 o. o025 o. ool 25 o.001 25 0.00125 o. 000625 0.000625 600 460 3r2 850 290 211 132 305 258 670 529 220 611 385 543 446 312 803 255 208 268 223 172 267 245 84 74 57 90.5 97. O roo. o 9,t. 5 87.9 97.2 62. O 73.1 66.7 39. 9 46. 3 38. 2 12. 1 14. 8 208. 268. 223. 1?2. 267. 215. 84. 71. 57. 6.311 66.874 67.917 66.596 66.172 66.910 65.306 55.616 5 5. a31 54.743 1 a.907 14.699 a3.83r 13.955 1 118 0 7 27 o 15 8 3 o 0 9 o 6 0 sis 4{6 31t 803 255 1t 12 13 14 I 7 C98OI21B BIGRESfIETHRIN (ROIESEL{'CLAF) 2OZ EC LoT r.7 X il13 (fiS EX3) -, LOC DOSE ( rn llC/L ) ao E l!q, c, s urc 6 I ,2 2 20 o RESULTS OF PROBIT ANALYSIS Fi8.3 5 iterationa loq LD99 = -1.868?8- LO99 = O.O13527 lo9 LO95 = -2.16095LO95 = O.006903 loq LD5O = -2.86614 - LOSO = O.O01361 CHI-2 CRITERION = 0.1IIETEROGENOUg OATA Probabi I itY HETER ((( -2.320 < < -1.8590.oo5 < < 0.01t -3.O98 ( ( -2.730 o.ool ( < 0.002 3.8.b = 0.075 N (OMS 3O{3) 1988) TRANSFORMS L(x! coRR.00sE 0EA0 -2.0930.008 < -1. a04o.039 i ntercept 6lOpe I 1 .685 2.332 a-b= OEGF r-2CH T-VALUE= GFAC 7 1 75. 5a5 o. oo0 25. O78 2.360 o. t4t TrrLE : cgoo I zfl aronesuerxRtSUBTITLE: lOI EC LOT 15UO31O ( Ooee unit€:MG/LControl : O.5 : OATA OOSE TESTEO OEAO (ROUSSEL-UCLAF ) CORR. PREO. CHI.SQ. PROBIT PROBIT CONTRIB. T oBs CORR. PERC.OATAI t 2 3 1 5 6 7II o. ol o. ol o. oo5 o. o05 0. oo25 0.o025 0. oor 25 0.o0125 0. eoo625 -2.000 -2. 000 -2. 301 -2. 301 -2.602 -2.602 -2. 903 -2.903 -3. 204 718 354 993 521 a54 401 357 323 238 711 35{ 912 502 261 226 189 165 82 99. 1 100. o 91 .8 96. 4 58. I 56. 4 52. 9 51. r 3,1. 5 7a1.O 353. 5 911 .6 501 .9 263. O 225.1 186.2 16a. 2 8r .2 I 7 6 6 5 5 5 5 1 57. 9 56. r 52.7 50. I3{. I . 351 .986 99. 1 99. 9 91 .8 96. 3 392 791 5. 35 6.85 I .56 19.87 53. 17 58. 73 5. 43 2.37 22.31 ?.o20 ?.020 6.318 6.3r 8 5.6r6 5.616t3.9ta a.91tl 1.212 .200 154 o68 021 591 Gmta6"'o,,Ei1'J1'Jlt-gf*1'.'ilrf.3"sEL{ELAF) I 7 6 , 1 F ao e,o u,o 6oo LJa 10 3 3 .) 2 -6 4 -2 LOC OGE ( in rlC/L ) 20 4.,lug {t 2 101.789 GFAC = TXXTE TESTEO OEAD iffiRESULTS OF PROBIT. ANALYSIS5 {terrtlons ctrl-, .*rIE$t88oEn*loo LO99 = -1.?6881 -2.439 ( < -4.909LO99 = O.017O29 0.004 ( ( O.OO0 loc LD95 ='2.07152 -2.598 ( ( -4.20it - LO95 = 0.O08423 O.0O3 ( ( 0.000 loc LOSO = -2.8t238 ERR - LOSO = O.O0154O ERR int.roaot a = 11.2693lopb b= 2.229 s.E.b= 0.106 +i;,,.. {r PERT.TETHRIN (ot{g 182r) (Fr{C) LOT O0t9 OATA TRANSFORI{s o.t OATA CORR. OORR. PREO. CHI.SQ. OEAD PROBIT PROEIT OO{TRIB. o 5.93a ,3 5. 't556 5.2252 3.570 DEGF =Ctll-z =ProbebllltY =HETER =T-VALUE= 0.oo0 50.895 a.300 2.121 TITLE: T9OOl 258 SUETITLE: 2OT EC Dose units:[O,/LControl ! 1.2 : t o83 LOG DGE r.301 .602 .903 .2O,1 CORR. PERC.OATA a I 2 3 1 o.005 o. oo25 o. o01 25 o.000625 457 393 178 122 3?8 267 281 37 6. tao 5. a69 4. ?98 1.127 5 5 9 6 82 67 58 7 9.44 o.05 56.21 36. 05 377 265 28t 32 -2 -2 -2 -3 82.7 6?.9 59. a8.8 T9@1258 PENfiENIRTil (qls2e EC LOT S €41) (Ftf)t9 i " ,r iI E ; R E TEg I ? 6 J 4 3 5 ' t',. ' . .;r ,|,"6i . -' -.lLilr' . 'iti..Im:,i ! illi ,r. , ...'i:!l,' .--r*:, 2 2 -6 { -2 tOC DGSE ( in rl6/L ) 20 o a t I!t a ANNEX OCP PROTOCOL FOR CLOSED-CIRCUIT TROUGH TESTS BRIEF DESCRIPTION. Thie method, rhich wa8 d€vslop€d for OCP by Or. H. Jarnnback, ia bas€d on a systsm that he and Mr. R. Gaugler us€d cxtensively in Ner York State. ft has been furth€r modifi€d by the OCP Ins€cticide R€- Bearch Team in Lo6€, To9o. Lerva€ coll€cted in the field are ailored to attach on e removablo Plate lylng in the bottor of r trouEh rhere natsr ia recirculated by r Puop. Thc plate iE transferred to a sccond trough rhere th€ inracticid€ has alr€ady been mixed into th€ r€circulating rat€r. Aftcr 10 oinutes the plat6 is tranBferred to e third trough xith clean uat€r. llortality i. count€d sfter 2'l hours. TECHNICAL DETAILS. Th€ trough3 uscd are construct€d of aluminiuo and patntcd uhitc. Thc troughs ere 80 cn long, 15 co Hide and 6 cm d6ep. Thgy are cloBed et th€ upp€r €nd. At th€ lower end, e conatrictlon or liP, i5 cm'long, E.8 cn xlde and 2 co dc€p iB attech€d. A r€rlovabl€ octal plate rests in the bottoo of thls lip. t{atcr ie pump€d lnto th€ cloaed cnd of the trough and flows ov€r thc pletc ln the lip into e reBervoir, to b€ aepiratad by the pt.irlp 8gain. Snall €lectric centrlfugal ptmpa rlth r dlBcharg€ of about 22 L/min erc u8ed, .nd th€ vcloclty of Hater over the attactm€nt plate ia about 70 cm/3. For the attach0tent and obE€rvation ayateo3, the reservoir is a plastic raste-bucket holding 60 L of water. For the cxposur€ ayat€lr, a 10 L €nannelware pot is usad aB a reaervoir to reduce ths anount of ins.cticide n€ed€d. Riv€r Hrter ie used at aII sta968 for routinc tests. Ite charact€ristics(t6operatur€, pH, turbictity end conductivity) are m€a6ur€d and noted. L$vee are oollccted by removing thelr natural Bupports froo the river. They arc transported in plastic bage pl.c€d ln en lcebox. Care ie tak€n to aeperat€ the lervae froo the icc by a layer of freati lervei or greaa. AlthouEh the equlpDent can be uaed rt the rivcr8icle uilng t portrblc genera- tor, thi8 type of test lB usually donc ln r laboratory rhich rey b€ at some diatance from th€ col- lcctlng point. The vcgetatlon xith th€ ittach.d lrva€ iB placed ln thc rttachoent trouEh. Thc larvac netu- ralty leave th€ vegetrtlon to ac€k e Etronger curr€nt and thus att.ch to the plrtc of the liP, Hhlch haB thc highc8t velocity in th€ trough. The larvae are left Cor 21 h to gnsurc flf{0 rttachmcnt. Lrr- vae xhlch pupate clurlng this p.riod are .liminated just b€forc expoaurc. The plrto usually contalna about 100 ilature lcrvee .nd a€voral hundred young larvae. The lrrvicldc forauletlon8 rrc appropri.tely cllluted rith dt.til to the test. The qusntlty ncccB€ary for the loreEt conc€ntr.t{on lE addcd of the cxposqrc trouEh rlth thc punp runnlng. Thc insecticide is ellorcd to run for 5 nin to obtaln r uniform diepersrl. Ad<litioml ln8ecticid€ iB added to thc aam€ 6y6t€m to obtrln th€ htghcr cotrcentrs- tionB in e te3ts scrica. The pleto fro tho sttactnent trouEh le now carefully lifted out and placed ln the €xpoaura trough for a deflncd pcriod, uauelly lO rln. Larva€ detaching during the expoaur. period are cought in a nct attached to th€ llp of th€ trough. Aft€r the expoBur€ pcriod th. plat€ and th€ n€t are tranEferrcd to e holding trough. At th. end of e 24 h obecrvation p6riod, the detsched larvae in the n€t, 13 Hcll rB .ny d€rd ones Etill rt- tach€d to the plate tre prea.rv€d ln elcohol for countinE. A first collectlon ie Eenerelly mad,e.2 h aftcr cxposurc 6incc ooBt lrrvae det.ch ln thie period and th€ larvao oay d€cqnpoBe lf l€ft deacl too long. Thcl living larvae arc kllled iith hot uater and also preserv€d ln rlcohol^-for--countlng. The nunbcr of gxpgFed, livlngr rnd dead larvte iB establishect separately for mture (6Ltr-7urr instarB) rnd young 1lraE-sEn) 'larvac. Lrv.e cxpos€d to insecticid€ and pupatlng durlnE the t€sts are not counted except for the control nherc thay erc includ6d in the nuober aurvivlng. Tho uBual conforoation of a tc6tB is a range of 5 conc€ntretlonS rnd an untrcrted control rith 2 repllcatos rt aach corrcgntretion. Percent nortality is calculeted at each concentratlon rnd th€ concentmtion./mortality r€lation is establlshecl by probit analyele. ll ledtv ratcr {nodlatcly prlorplp€tto to the r€Ecrvolr