A seed dressing formulation of metalaxyl was evaluated under greenhouse and field conditions for the control of pigeonpea blight caused by Phytophthora drechsleri f. sp. cajani . Significant control of the blight (over 90 per cent) was achieved with metalaxyl (1.75 g a. i./kg seed) in a greenhouse trial for 30 days after planting. However, the fungicide was found ineffective against the disease in field tests

Kannaiyan, J

Nene, Y L

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EFFICACY OF METALAXYL FOR CONTROL OF PHYTOPHTHORA BLIGHT OF PIGEONPEA J. KANNAIYAN A D Y. L. NINE WEICACYOFMETALAXYL FOR COETROL OF PHTTOPHTHORA BWGHT OF PIGEONPEA J.  K A L ~ A I Y A N  N D Y. L. N ~ h 6  Pulsor 111rpronntcnr Programme, Inrernorronol Crops Res~orch Insrirore for rhc Srmi-Arrd Tropics. P .  0. Paranchrru 502 324 A w r ~ . v r  A l a d  am$%,?& brrndl.i!l.ml . f nrlalar) r.$ e,. valsd unlc. grccnn, urs and field mnd t on, f.,r Ire :an rdl .,I p.prorpca h1.n ;JJS?.!  b, Pn r .  pl,rn..r. urr nr r , ,  I rp <.,,an Sirr *#:int : I",:. . l r  I lr PI PII* ~ \ ( r  911 P. CCP was 1 ~ 1  e . , d  n tr. mec4..x: I I - 5  r s 8 r l  r e d l  lr. 2 W n ?  ) L V  I I I R  1111 (1, d a \ l  l f l~ l  pldnllrg HOYIIII. the I Y P ~ .  c.dc *IS h,unl :ncRtcl Sr npllnr' lac alscarr n nr 1 aan. Phytophthora blight or  pigeonpea (C'ujunw ru1an [L.] M~llsp.), caused by P l~yrg / t~hora  dr<'chslerr Tucker f, sp. cokni is a serious disease In lndia (Kanna~yan cr ol., 1980). The blight is particularly severe durlng Ihc early crop growth uhlch normally coincides 8 1 t h  rainy season (June to September). Somc of fhc bl~ght resistant genotypes ident~ficd at ICRISATCentre (Kannatyan 6.r ril., 19811 are now bc~tfe used In brecdlng programmes to  devclop bltghr.resisfant cultivars (Sharma 6.1 "I., 1982) However, most of thrse res~avant genotypes are susceptible to  anothcr iiolatc of [he pathogen from Kanpur in northcrn lndia (Sharma er 01.. 1982). Wc havc alrcady ln~tiatcd a search fur reslatant sourcc to this ~solatc. Meanwhile, wc arc uslng the aynemic fungicide melalaxyl [methyl D. L-N-(2. 6-dimcthyl-phenyll-N.(!.methoxy- acctyl).alaninatc). which has been Found etTectlve against Phyrophihf~ru spp. (Fcrrim and Mellinger, 1978. Mitchell c/ el., 1977; Papaviras et a / . ,  1979: Urcch cr "I., 1977: and Zentmyer and Ohr. 1978~, to  control pigeunpea blight. In t h ~ s  study wc report on the efficacy of a seed dressins formulation of metalaxyl agsinsl pigeonpea blight. S ~ < T E R I & L S  A\D .\lt-THo~s . A bl ghr % IS:;;IIIIII: p1gcOn;lc3 ''-11 \dr. H I  .?Cand Fh)roptrhorc dromilcr: f. -p Cajuns ~h.,lat.d trt m bl g2tcrl P gu.~rpcaat ICRISAT Centre tP: .solatc) and nl Ksrp~r  (P3 ~ ~ o l r l e i  ue-r u\cd thrc ~ g h o u t  he eap::lxnts. Thr  e c d  Cress rp uas a 35 per L.:nt nctalsa)l  I..rrrdlat .r:. 4p~:n 3.' SD, pr.,Jucra by thc C bd.Gclg) Corpnrat .~n Dr) secd cr:S.lng uas  uone h) ~ 1 x 1 - p  the . e q ~  r ~ d  quant t )  o i  the funp.c.d: utth the seed and shak~ng t h o r ~ ~ g t l !  In c .~n~ca l  f asks t~ obtain uniformly coated seeds. Lobororory resr :To  evaluate the cfect of fungicide on secd germination metalaxyl.treated (0 35, 1.05, 1.75, 3.50. 700,  and 10.'0 g a .  ilkgsecdl and nowtreated pigeonpea seeds wcrc plated on moist hlotter paper at the rate of 10 seeds/plnte and incubated in thc dark a t  28' $ 20°C. Each treatment had 4 replications (SO seeds/ replication), Germination counts were recorded after 9 days of incubation. Greenhouse resrs : Pigconpea see& werc treated with mclalaxyl(0.35,0.70, 1 05, 1.40, nnd 1.75 g a ,  i./kg seed), with four replications or each treatment (25 a&/ Submttled u lovrrul Anlelc No 271 dslcd 25 O M k r  1982 by the ICRISAT, P O. ma- m 321. Rauvd lor puMlutron J s n w  29, 198) KANNAIYAN AND NENE : CONTROL OF PHYTOPHTHORA BLIGHT OP PlGWNPU 507 replication). A soil drench technique (Ncne er al., 1981) waa followed for  inoculations (P2 isolate). Mycelial suspension of the pathogcn waa poured around the base of aecdl~ngs whcn they were 5 to 10 d a y  old and again after 15 days. Observations o n  blight Incidence were recorded I5 days after each inoculation. The experiment was repeated once. In another experiment, we also testcd the efficacy of  metalyx)] as  seed drcsscr (only 1.75 g a ,  i./kg seed) w ~ t h  P2 and P3 isolates by following the soil drench tcchn~que. A spray inoculation (Nene rr a/.. 1981) was used to  confirm the results. Seeds were treated wich meta1ax)l a t  1.75 and 3 50 g a .  i./kg. A mycelial suspensfon of the P2 isolate was rpraycd on the foliage of two sets of 15. and 30 dayold plants which wcre thcn covered with pnlythcne bags to ensure high humidty for 48 hrs. The final observat~ons were taken 15 days after inoculation: Similar study was also conducted with P3 i,olatc. Field Irsls : Field tests were conducted during the 1979, 1980, and 1981 rainy seasons a t  lCRlSAT Centre. In the 1979 and 1980 ralny seasons, only P? isolzte was present in the expe~imental fields. But In the 1981 rainy season onwards P3 isolate was also present. Metalaxyl treated and non-trcaled seeds were sown in plols of 4 m rows spaced 75 cm apart In naturally infested Alfisol and Vertisol fiulds where blight disease appears in the ralny season. In preliminaiy ficld (Alfiaol) test in 1976, metalaxyl treated seeds (1.75 g a. )./kg) were tested along w ~ t h  non-treated seeds. In 1980 season, four races of  metalaxyl (1.75, 3.50, 7.00 and 10.50 g a.  i.,kg seed) wcre tested in both Alfisal and I'ertisol fields. In 1981 wc deleted the phytotoxic race of metalaxy! (10 50 p a. i./kg seed) and ncluded a spray treatment of metalaxyl 25 WP (at the rate of 500 ppm) 30 day, aftcr planting (DAP) in addition to seed dressing treatments (1.75, 3.50, and 7.M g a i./kg seed). The test was carr~ed out In the AIfisol field only. The trials wcrc of randomized block design w ~ t h  four replications. The bli&ht incidence was recorded 30 and 60 DAP. R s s v ~ t s  AuD DISCUSSION : Lubora~ary resl : In the blotter test, metalaxyl a t  0.35. 1.05, 1.75 and 3.50 g a i./kg seed had no sign~ficant effect on germination in comparison to  the check (Table I j, but a t  7.00 and 10.50 glkg rate, the germmation was adversely affeclcd. TABLE I : Omlnation of piponpa wed treslcd wifh six rats  of melaiaxyl as dctsrmincd in I blotter 1511 - - Metalaxyl (s a I /kg wd) = A w I g e  of lour rsplicrriom (SO wds wen kepl plmpljat im).  rOsrminallm rcmrdcd a h  9 day8 or i rmbt~oa .  'Sauut mot (x t I) vuulomution uud. Trutmmt with the am kclw ut not ligniE-anfly diflpont (0.0S.0.01). Grro~ho~uc  icsrr : The blight [PZ isoletc) was cITccttvcly rcduccd (i I 0  pcr cent blight) wi th rnctalxa\l seed dreas~np at 0.70. 105, 1.40 and 1.75 c a.i ,kg seed (Tnblc 2). After the sccond inbculatioo, eirecti\,r conlrol n a r  achlercd oniy at thc hiphcr rates of mclalaxyl ( I  05. 1.40 and 1.75 g a i kg hcrd). S:itlbractory control (.. 10 pcr cent blight) o f  thc dlseas; was also achic\,cd with n i c ta l :~x~ l  sccd trcatmcnt uhcn  lnoculatcd w i th  the P3 isolnte (Table 3).  Houcvcr ,  aftcr thc sccond inoculation. 26 pcr ccnt blight was recorded with the P3 as comporcd to  onl! 6 per ccnt wi th the P2 isolntc. I'cf ccn! bl~ghl. Meral?xyl - . -- -. - -- - - - - . . - fg a. 8 /kg seed) 1st l n i l e ~ l ~ f l n n ~ ~  2nd ~nocul i l l ion~r~ ... .- . ~~ 0 15 203 40h 0 70 7' 22. 1.05 so 126 140 I?"  1.75 qa hon-treated 99. 100. -,&wrage of 2 lcrts and in each tcst 4 replicrrions wcre krptJlrcnlmcnl. .The seedlings wcrc ~noculatcd v l lh  lhc fungus by sod drench ~noculslton. Obscrviltions on the direare wrrc rrcordcd after I5 days of inoculurlon. rlnsiudn per sent plnnlh bii~hled I" 1st inocuIrt8on. *Square roo1 f r  i 1) tranriormrtion u5ed. Trratmcnt u l lh  the snmc lcller ilre not s~gnifi- cantiy dllrerent (0.05, 0.01). TABLL 3 : Fllicacy o imet~lary l  seed trealmcnt in conlrollingP/r~Iophihuru bllghl fP? and P3 ~rolatol) a i  plreilnpw under prccnhauccwnd~t~ons Pcr cent bllghIw M~lalaxyl ------ --- ( ~ a .  ~ . / k g  P2 ~ m l n ~ c  P3 ilolatc - rcedr - .- 171 inocu- 2nd inocu tat inoeu- 2nd ianeu. i~llon'l '  lati<m'r" i i l t l ~ n ~ ~  latlon'w .Avflaac 0 i 4  replications. *Scedlmp rwrs inoculated with the fungus by mil  drench inoculallon. Obmvntionl on the d i  were recorded afla I5 days of lnoculalion. rlnclude~ wr ~ c n t  ~ lan t r  blighted In Irt inosulalion. 'Sqwc root fx 4 1) transiormslioa uacd. Treatment uith (be lam letter an MI sipni- 6sally dalTsrmt (0.05. 0.01 1. A good control (< 10 per cent blight) of the d i r cax  (with P2 end P3 isolates) was a l w  achicvcd wi th rnctalaxyl at  1.75 and 3.50 ga.i./kg seed by following spray inoculation technique in IS- and %day-old plants. The rcsultr show that mnalaxyl at the higher rates was effective in protecting pigeonpea seedlings from the blight for over a month undcr greenhouse conditions. Firld t a t s  : The mctalaxyl treatment a t  1.75 g a i.jkg e e d ,  which was effective in greenhouse tes!s (Table 21, failed to control the blight ln preliminary field test in 1979 season. Therefore, in 1980 seaaon, we tried higher rates of mctalaxyl both in Alliaol and Vertisol fields. The bl~ght inc~dence was recorded 60 DAP when the non- treated check plots showcd abore 80 per cent disease iTabie 4). Metalaxyl failed to  control the d~sease in the Alfisol ficld even at iO.50 g a.i.lkp seed, while a moderate control (25 per cent bltpht only) was accomplished at this rate in the Venisol field. Generally, more blight occurs in pipeonpea grown in Alfisol than in Vertisol, which may explain the lower level of control in the Alfisol. However, melalaxyl at 10 50 g a.i.;kg x e d ,  rcduced seed germination to about 50 per cent and produud phytotox~c symptoms such as stuntlng and chlorosis liuring early crop powth.  During the 1981 season. the natural disease incidence was 47 pcr cent and 99 per cent in non-treated plots at 30 and 60 DAP, respectively (Table 5). Satisfactory control cf blight wa, achieved with 7 00 p a.t./kg seed treatment without spray at 30 DAP. However. ail the freatmcnts with and without spray f-itled to control the blight at 60 DAP. Else- where good control of soybean root rot and damp~ng off IPapavizas r l  a/., 1979) and tobacco black shank (Kannwischer and Mitchell. 1978) was achieved wtth melalaxyl in the greenhnuse and plant growth room. but thefuneicide waq lneffect~ve in field tests. The poss~ble reason for the h ~ l u r c  of metalaayl in controlling the disease undcr ficld condit~ons may be accounted for by the followini: (ii insufficietit persi.itcm,ce ( I5  days) o f  tho fung~cide applied to  the seed (Kotwal cr a1.. 1981) and (iii reduction in efficacy of the fungicide over time or changes in the physiology of the plant (Kannwischer and Milchell, 1978). TABLE 4 : Efficacy of rnetaluxyl recd ricslrnsnl in controlling Phgfoph,horu hlight ofpigeonpa under held wndnlonr dvtin~ 1980 rsiny MaSon Pcr Pnt bilphl. Metalsxy lp  a. idkg aced) Alfifoll Vertlsol' 1.75 76 67' 3 50 93 6' 7.00 77 55. 10 501 67 2 9  Non.trcal? 93 82. :Awravof 4 replilionl. Biipht insiden- rsmrdd60 d ~ y s  rpri plantln~. .Modens permination with mild taiidly. rThcm is no lignifimt diReMo k t k  my of tbe atow -. 6 u n l l ; ~ ~ r , m ; ~ ~ ~ t  I )  ~~larformadoa ued. Trcsrmmt vilh tbe umc kt la  we mt ipai- t h n k  M r r  Y. K. 6nd Mr. T. N Raju for the 510 MDUN PUITU?AMoUKIY pol. 37, 1 9 y  RmEmNcar m. D. U ud n c Muys 1978) Contml of Phymphrhom wilt rith ffiA 48988. Pmr. F k  SOl, HM*. b~ eO : 3 \ f  31k J.. O L I1L.h. D. C. En* ud Y. L. N m  (1980). Ph?loplUID~o M i a t  of dwonp .  m ~ n d i c  M ) c D & ~ ~ :  16g181. U r n  J. Y L )rr* T. N. R.1m a d  V, L 6Wlm (1981). S a a d n p  for d m ~  lo Phyloplc I& d i g i t  of plsomp.. PI. Dlr. e : 61-62 I(lr0rr. M. E d D. J. M l W  (1918). Tk innuenm of a fungicide on thc cpidcmiolow of black h k  ef tohuso.  P h ~ r o w h d w  6) : 17-1165. I M W .  kdh., 8.,C V m  R. L VIP. ud A, C. Jab (1981). T z a m I ~ ~ ~ c i ~ n  and praitteass of Awlon in pyooap.. Indm Phyromrh. 24 : 492493. uw+ D. J+ m E. uunb ur C. E ~ u d r  (19n). Control of black ,hank of t o h w  wlth an w h b i n o  mabyuc. Ablu. No. C.23. Ploc. Am. Phytopllrhol. Sm. 4 : 179-180. Nao. Y. L., J. Wlu 1.1 M. V. Pldd7 (1981). P i p o p .  di lc lu t  : ruillao,m-ainp Ischniquo : lnfornm~~on bullrrb No. 9 .  Rtambcru. A. P.. Indts; Istrrnauoml Crop ROY.rcb Inatilu~e for IhO M M d  Tmpia. I4 pp. P.LI1..., 0. C.. P. W. &4& J. C b& ad J. A. Lnb (1979). Sfllemio funpisidea Lr mnfmllingPhytoph1bra mot mt and dampinpal  of Soyban. PI. DIE. 63 : 708-711. SLM.. D., J. h d w  ud L.J. W (1982). Inhrritmm olra i l t lnec  to blight in piwsonp.. PI. Dir. 66 : .2-25. Lbd, ?. A,. F. J. B c h w i ~  ud T. SM (I Pm. CUA-48988 a now1 luaplcidc for mnlrol of late blipbC d o v q  mildm and d a t e d  lolhbarnc dl-. Prm. Br. Crop. Pmr. CoM., 623-631. -a C. A. ud H. D Obr(1978). S f l W k  mil An d a  lor mnuol of Phyro hlhora coot m<md ,Urn ankcr'of lr- (Abrtr. No. 70). &opothol. New, 11 : 142-14f. 

Efficacy of metalaxyl for control of Phytophthora blight of pigeonpea

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