Effets of treatment with propoxur (0.05 ppm/10 min) on benthic invertebrate drift in the Wawa

a.#h\N woRLD HEALrrr oRGANrzATroN W o*t^,,orloN M.NDIALE DE LA 'ANTE ocefva:fmtof at.s ORIGINAL: FRENG EFFECTS or TREAI}{ENT }IITII PRoPoXUR (0.05 ppm/Io min) ON BEIMEIC INVERTEBBATE DRIFT IN fiIE I{AI{A by D. Paugy and B. Coulibaly (Ouagadougou, 1 July 1982) We shall here describe the impact o;r the non-target invertebrate fauna of the release of propoxur in a concentration of O.O5 pp./tO ,oi.rr,. This test was carried out on the Warra near Badou (Togo-Ghana frontier) on 2O May L982. In order to eval-uate the impact of this larvicide, we worked out a drift profile of the organisms over a period of 48 hours centred around the release (L9-21 I'Iay 1982): Collections were made with two twin nets, each having an aperture measuring 0.06 m2 and a 25O np mesh bag. Durtng the day before treatment, the sanpling time \ras two minutes, which was shotrtened to one minute during the night and returned to two minutes on the morning before release. Frqn the time of release until the end of the experinent, the sanpling tirne was rnaintained at one mi.nute. Heavy rain during the evening of. L,9 May changed the flow rate, which increased from O.8 il" at the start of the experiment to 1 n/s on 21 May. Because of this, and of the different sampling times, the voltrne filtered tas not the sameforeach sampling (range from 12.8 to 27.0 EJ). This leads us to give only the curve corresponding to the drift indices, disregarding the tabl-e of crude data, which in fact have no meaning. Lastly, with the exception of the samples taken between 19hOO and 24hOO on 19 May, whidr had to be taken in another place because of the abrupt rise in rilater Ievel, all samples rsere taken at the same place, approximately 40 m downstream from the treatment point. In terts of the taxa collected during the drift cycle, no si.gnificant gualitative differences are to be noted between the samples taken before and after treatment (Table 1). This indicates that the effect of treatment is revealed through an i.ncrease in the drift of organisms that drift naturally (Fig. 1). From the point of view of the whole of the fauna sa,mpled, an imredi.ate effect of the action of the pesticide is to be noted, since the drift index was maximum a quarter of an hour after release (Fig. 1). However, the ratio of instantaneous increase was low at 9.7. For purposes of cornparison,. the following are some vaLues obtained with other insecticides: 43 for Abate 2oo Ec (o.os ppa/10 min) z L52 to 186 for chlorphoxin (0.o2 s ppn/to min) ; 46t for methoxychlor (0.3 ppm/lO min). The apparent toxic effects of propoxur on the non-target fauna may therefore be regarded as negligible at this concentration. Of all the products thus far tested, only B.t. HL4 is of Lower toxicity. Comparison of the maximum diurnal drift indices reveals an increase of 887. for the fauna as a whole (Table 2). Although this value is considerable, it sti1l does not reach the usual figures, which are of the order of 95-1OO%. The percentage increase in the night drift i-s Lower, no more than 287" overall. Consequently, although the pesticide does affect the night drift, the effect is modest. Ce document ne constitue pas une publication. ll ne doit faire l'objet d'aucun compte rendu ou rdsum6 ni d'aucune citation sans l'autorisation de l'Organisation mondiale de la Santd. Les opinions exprimdes dans les articles signds n'engagent que leurs auteurs. The variation of the ratio uof maxr/ool max is of the usual type, and although there is a reduction, it is moderate. The issue of this document does not constitute formal publication. lt should not be reviewed. abstracted or quoted without the agreement of the World Health Organization. Authors alone are responsible for views expressed in signed articles. oce/van/wto/as.s page 2 Some cotments are ca11ed for on the study of the impact of propoxur on the m4in taxocoenoses coll-ected. The flrst thing that will be noted is the apparent lack of any i"umediate impact on Tricorythidae and the weakness of the impact on Tanypodiinae and Tanytarsini. However, although there is little or no increase in night drift for Chironomidae, there is a noticeable increase for Tricorythidae. ftre other taxa experience a relatively considerableimediate effect, since the increase in the maximtrm day drif t index is between 77 and 94%.Simuliidae, among which S. darnnos,'m s.lat. is the most represented, Ilydropsychidae, orthocladiinae and tti"niffii,"Tleneral experience the strongest irrnediate impact. Never-theless, as regards the Last two groups, the increase in the night drift, which is between2.1 and 3.4%, Ls very modest. After every proviso has been rnade, particularly because of thesnall nurnbers of organisms collected, it nay be conceded that this "right repercussion stemsdirectly frorn the heavy initial impact that had a considerable effect on the organisms in situ.rf this hypothesis is adopted, it also implles that, despire the initial toxiclty of tnf-product, Ilydropsychidae and simuliidae remained reLatively plentiful. To suunarize, i-t emerges quite clearly that propoxur, in the concentration employed, onthe one hand has a weakly harmful effect on the ,orr-i..g"t fauna and, on the other hand, onlya limited carry and a non-drasti.c effect at least imnediately on the target fauna. TABLE 1. QI]ALITATIVE CCD{POSITION OT DRIFT BEFORX AND AFTER PROPOXUR TREATI,TENT (0.05 ppno/lo min). r.IAwA NEAR BADOU Taxocoenoses Beforetreatment After treatment Nematoda Baetidae Caenidae Leptophlebiidae Heptageniidae Tricorythidae PJ-ecopteridae Go'urphidae Libellulidae ZygoptEres Hydropsychidae Hydroptilidae Leptoceridae Philopotamidae Polycentropodidae Notonectidae Pleidae Ceratopogonidae Simuliidae Chironomini Tanytarsini Orthocladiinae Tanypodiinae Tipulidae Syrphidae Rtragionidae Iabanidae Elmidae Gyrinidae Pyralidae Hydracarina Collenbola + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + owfvcufwwrof at.s page 3 TASLE 2. VARIATIONS OF },IMIUI'}l DRIFT INDICES BET'ORE AND AI'IER ltsEAlYENT CORRESPO}IDING PERCENTAGE INCREASES AID VARIATIONS IN IIIE RATIOS OF fiIE INDICES. }IAI{A AT BADOU TROM 19 TO 2L MAY 1982 DDI uax: l.laxlmun diurnal drift index NDI rnax: Maximum nocturnal drift lndex Taxocoenoses Before treatment After treatEent loincrease NDI max DDL max DDI uax NDI Eax DDI max NDL nax DDI NDI Before After Tricorythidae Baetidae Tanypodiinae Tanytarsini Orthocladiinae Simuliidae llydropsychidae Other Trichoptera Total of Organisms 1_.88 2.LL 0.33 o.44 o.27 o.15 o.22 o.3 5 3. 59 3. 59 4.L4 L.64 o.63 o.94 o.16 0.39 0.86 12.81 1.7 8 9.04 1.04 1.11 4.44 2.67 2.30 5.26 29.!L 4.59 5.33 0.30 o.67 o.96 o.30 1.04 o.89 17.85 0 7 6.7 68.3 60.4 93.9 94.o 90.4 93.3 87 .7 2L.8 22.3 o 6.o 2.L 46.7 62.5 3.4 28.2 1.91 r..96 4.97 t.43 3.49 L.o7 L.77 2.46 3.57 2.58 o.59 o.29 o.60 o.22 o.11 o.45 o.17 o.6l_ f o - N @ lr) e N (\l '- @ 60 ,r>- E? S-EsNF N@ 33 o) o ocv/vcu/wtto/at.z page 4 3 E o Eo o- lr)of oO -oF<ZcD[!. =kF uJ= a.Q F= EU)-xto' Aci .. Etr e 1[r!J ZtO9 6{JUJ(,(E= t-oZ-Ui Frlr- o E. oJ r<o(r .fO r! lt o ln(J F UJz n 54 3 2 1 oce/vw/tttrc/as.z page 5 FIG. 2 K|NET|CS OF 48H. DR]FT CENTRED ON A PROPOXUB TREATMENT (0.05 ppm/10 min) FOR THE PRINCIPAL TAXOCOENOSES. THE WAWA AT BADOU 10 I 6 4 2 RSINI 5 4 3 2 1 5 4 3 2 't 12 18 24 1Sl05l82 t 41218 20106182 24612 t 21l05l82 *) 12 18 1SlO5l82 Treatmant 61218 201o5182 612 21tO5182 24 I 24 I TRICORYTHIDAE TANYPODIINAE TR ICHOPTE RA. HYDROPSYCHI DAE OTHER TRICHOPTEBA