~The susceptibility of cocoa to mealybugs

Transcription

1 Bllltin f Entmlgil Rsarch (1990) 80, Th suscptibility f c t mybugs (Psudcccida) and thr hnydwprducing Hmptra in Ghana / C.A.M. Campbll C Rsarch nstitut, P.. Bx 8, Nw Taf, Ghana Abstra Ppulatin dnsitis f mybugs and thr hnydwprducing Hmptra wr assssd in six cc a (Thbrma Linnaus) tris by insping trs frm grund t y lvl, and s by dissing sampls f trmin buds. A tt f 68 c prgnis was xamind, mainly intrcrsss f six clns. Prgnis diffrd in thir lvls f infstatin with tt mybugs, Plancccids njnsis (Laing), Plancccus citri (Riss), Phnacccus hargravsi (Laing), (Psudcccida), Txptra lrantii (Byr d Fnsclmb) (Aphidida), and Mshmtma tssmanni (Aulmann) (Psylida). Crsss with Amlnad r T63/971 wr gnry mr dnsly infstd with mybugs than ths fr xampl f NA34 and T63/967. Trs f T7/524 parntag wr sparsly infstd with mybugs. Rankings f prgnis by infstatin with mybugs frm th tw diffrnt sampling prcdurs wr psitivly crrlatd, but th rlativ abundancs f individu mybug spcis n th trunk and in th npy diffrd. Svr spcis f mybug fund in buds wr ithr rar r nvr fund by insping trs up t y lvl. Crrlatins btwn rankings f prgnis by rdr f abundanc f Plancccids njnsis and PlanccClls citri wr psitiv and statistily signifint, as wr ths btwn mybugs and infstatin f buds by T. aurantii r M. tssmanni. Th aby rankings wr ngativly crrlatd with ths by aphid and psylid abundanc assssd frm insping trs up t y lvl. Th tw sampling prcdurs wr cmplmntary but, fr cnmy, sampls f buds gav th clarst inditin f a prgny's suitability fr mybugs. nlrduin Mybugs (Psudcccida) ar imprtant psts f c (Thbrma Linnaus) in Wst Afri bus at last 18 spcis ar vrs f c swllnsht virus (CSSV) (Rivainn, 1976). n Ghana, up t th nd f 1988,. 190 millin c trs had bn flld in ffici raditin mpaigns aimd at cntaining th sprad f swlln sht disas, a tt.that mits trs killd by th disas itslf (Thrsh t., 1988). Th brding f varitis f c mr rsistant t CSSV infin Crrspndnc: Dr C.A.M. Campbl, nstitut f Hrticultur Rsarch, East Ming, Maidstn, Knt ME1Y 6BJ, LK than ths currntly grwn ffrs an pprtunity far rducing disas sprad (rviwd by Thrsh t., 1988). C prgnis s vary in thir suitability fr, and clnizatin by, mybugs (Biggr, 1975a, 1975b; Firmpng, 1982, 1984), which ffrs th pssibility f incrprating hst plant rsistanc t th vr as a furthr slin critrin fr plant brdrs attmpting t xpand swlln sht disas cntrl stratgis. Althugh mybugs as ptnti vrs f CSSV ar th ky psts, th ppulatin dnsitis f thr sucking inss may rfl clsly a prgny's rlativ suitability far mybugs (Biggr, 1975a). Amng Hmptra, svra l taxa, including aphids, psyllids, margardids and sticccids, ar mr cnspicuus than mybugs

2 138 C.A.M. Campbll n c and culd prv mr cnvnint t mnitr in scrning prgramms. Tw prcdurs fr assssing mybugs and thr hnydwprducing Hmptra in diffrnt strata f th trs wr cmpard in th prsnt study. Matris and mthds Fiv cntiguus c plantings ttling 5.5 ha at th C Rsarch nstitut, Taf, Ghana, wr assssd fr Hmptra n tw t six csins btwn March 1976 and January Ths tris wr plantd t tst CSSV rsistanc in prgnis f six clns (Lgg & Lckwd, 1981; Lckwd, 1981a), and wr stablishd undr frsttr shad as randmizd blck dsigns, rplitd 10fld (tris B6, B7a, B7b, B8 and B) r 11 fld (tri B9). Tw standard prgnis wr includd in ach tri and wr duplitd in ach blck f ah tris xcpt B6. Plts cnsistd f thr rws f fiv, six and fiv trs. Th trs wr spacd 1.52 m apart in a triangular grid. Lgg & Lckwd (1981) illustrat th plt layut. Plts wr sparatd by rws f guard trs with additin rws f guard trs at xpsd bundaris. Tris B6, B7 and B8 wr plantd in May 1972, and B9 and Bl in May Trs in th cntr rws f B6, B7 and B8 wr graftinculatd with CSSV in April (B6 and B7) and Nvmbr (B8) 1975, aftr th npy had clsd. Nn f th xprimnt trs in B9 and Bl was inculatd with CSSV. Tri B6 was xamind fr Hmptra thr tims and B7 twic, bfr ths tris wr cppicd in Sptmbr Tri B8 was xamind n fur csins; B9 and Bl n 6 csins. Tris B8, B9 and Bl wr nt cppicd during th prid f this study.. Critria fr prgny slin wr rviwd by Lckwd (1981a). Crsss in B6 wr f uppr Amazn clns, sld fr rsistanc t virus infin, with Amlnad. Similarly, in B7a, B7b, B8 and B9, uppr Amazn clns, sld fr virus rsistanc, wr crssd with T63/967, T79/467, T63/967 and T63/971, rspivly. Th thr namd ar ah uppr Amazn clns frm sd gardns plantd btwn 1959 and 1962 t prduc Sris 11 hybrids (uppr Amazn x Amlnad r Trinitari). Crsss in Bl wr f virus rsistant slins with MC76 and NA34, bth strng surcs f rsistanc t CSSV (Lckwd, 1981b). Tris B7a, B7b, B8, B9 and Bl includd hybrids btwn th main uppr Amazn parnt(s) and Amlnad. Th tw standard prgnis wr a hydrid (T85/799 x Amlnad), and an intruppr Amazn crss (T85/799 x T79/501). Prgnis wr idntifid by th cds (prsntd in standard rdr in figs 16) usd in 311 prvius publitins n ths tris. Th cds and thir rspiv prgnis ar givn in tabl 1. Th abundanc f spcis f Hmptra was assssd by indpndnt tams f wrkrs. n tam xamind l surviving trs in ach plt frm grund t y lv!. (A vry fw trs did bfr assssmnt.) Thy scrd th abundanc f individu spcis f Hmptra n ach tr using a lgarithmic sl (Biggr, 1975a), whr 0= nn fund, 1 = n individu. 2 = tw t tn indi\'idus, 3 = tn t 100, and 4 = mr than 100. n 86, B7 and B8 nlv trunks and lwr branchs wr.1ccssibl, whras, in B9 and Bl, whs trs wr tw yars yungr, much f th npy was accssibl t. An avrag scr was thn btaind fr ach spcis fr ach plt. Anthr tam chd a sampl unit f 16 branch tips ('buds') frm ach plt, usuahy n tip/tr unlss dad trs ncssitatd taking mr than n tip frm survivrs. Th apil buds wr dissd in th labratry undr a strmicrscp. Hmptra wr idntifid and a tt cunt fr ach spcis was btaind fr ach plt. nspins wr rpatd vr a tw yar prid in rdr t incras th prcisin f th ppulatin stimats, s th variats statistihy anysd fr ach spcis wr 'f.i.' ('fild inspins'), i.. avrag plt scrs avragd vr inspins, and 'buds', i.. pltbyplt tt cunts (x) transfrmd t lg (x + 1) and thn avragd vr inspins. Fr tris B6, B7 and B8, angularly transfrmd prprtins f trs infd with CSSV wr usd as a cvariat in th anyss f varianc. Diffrncs btwn mans wr assssd by last signifint diffrnc tsts (LSDs), du lwanc bing mad fr th xtra rplitin f th cmmn standard prgnis in mst f th tris. Cmparisns wr rstrid t ths with th tw cmmn standard prgnis thugh, fr cnvninc, LSDs ar prsntd fr ah withintri cmparisns (figs 1 6). Th rlativ abundanc f Hmptra n th tw cmmn standards was usd t cmbin rsults frm th sparat tris (Pimntl Gms, 1970). Furthr paramtric anyss n th cmbind rsults wr nt justifid as variancs wr htrgnus wing t variatin in th numbr f csins n which ach tri was assssd. nstad, prgnis wr rankd by th adjustd man abundanc f th varius Hmptra. Sparman's cfficint f rank crrlatin (rh) (Cnvr, 1980) was lculatd fr l cmbinatins f pairs f varia ts and usd as a tst statistic fr agrmnt btwn rankings. Rsults Psudcccida Plancccids njnsis (Laing) was th cmmnst mybug ncuntrd, with a tt f 18,252 individus frm 58,848 vgtativ buds xamind, and an avrag scr f 0.266/tr frm f.i. Bth sampling prcdurs inditd that P. njnsis was mr abundant in B8, B9 and Bl than in B6, B7a and B7b (fig. 1). Signifint diffrncs btwn prgnis wr rcrdd frm buds in Bl (P = 0.018), and frm fj. in B9 (P = 0.014). N tst prgnis diffrd signifintly frm ithr standard in B6, but in th rmaining fiv tris th abundanc f P. njllsis n srn prgnis diffrd frm that n n r thr f th standards. Nin prgnis, including T85/799 x T79/ 501 (882) in B7a, had signifintly fwr P. ljllsis in buds than had T85/799 x Amlnad (881). Tn prgnis, including T85/799 x T79/501 (882) in B9 and Bl, had lwr scrs frm fj. By cntrast, just n prgny (lmc76 x SCA9 (1554) in Bl) was signifintly lss infstd' than T85/799 x T79/501 (882) frm bud sampls, and nn frm f.i. Fur prgnis frm buds, and tn frm f.i., wr signifintly mr havily infstd than T85/799 x T79/501 (882). Th T85/799 x Amlnad (881) standard rankd as 23rd and 16th mst infstd prgny fr P. /jl.'l/sis frm

3 Tabl 1. Suscptibility f c t Hmptra 139. Classifitin by rankings f 68 c prgnis frm mst t last infstd by Hmptra. 'sudcccida Aphidida 'syllida Pllcccidc,; Pll1lh'C(Cl P'Ct1((l(C:; Tx >/m Mt'í'("'(Jf()111t1 Tt l;cl,;i,; ci/ri ha rgrt.'t1pi /mll/ii fcssmmllli lf(lgllny Cd Bud f.i. Bud ti. Bud f.i Bud Bud f.i. Bud f.i. T7<i/467 x T42/1615 /<i R T7<i/467 x T61/1313 /lr / T6:l/967 x Amlnad Amlnad x lmc R \.JC76 xsca T63/971 x NA Amlnad x lmc Amlnad x MC / T63/971 x Amlnad T63/971 x Tll / T3/971 xt17/ \ia34 x MC :> T79/467 x T90/ T63/971 x T72/ T79/467 xtl7/ T79/467 x T85/ Amlnad x T87/ Amlnad x T85/ T79/467 x MC T85/799 x Amlnad 881' T63/971 x MC T79/467 x MC T63/971 x MC T63/967 x T65/ T79/467 x T87/ T63/967 x MC MC76 x 'A T79/467 x MC T63/971 x MC T63/971 x T85/ T63/971 x T73/ Amlnad x T65/ T63/971 x T65/ MC76 x T60/ T63/971 x T87/ NA34 x T6/ T79/467 x NA T63/971 x T65/ Amlnad x T79/ NA34 x 'A T85/799 x T79/ ' NA34 x MC S T63/967 x T73/ \:A34 x MC T63/967 x Tll / T79/467 x Tll / T63/971 x T60/ T63/967 xt85/ T63/967 xga T63/967 x T79/ T63/967 x T87/ \:A34 xsca T3/967 x T6/ lylc76 x NA \1C76 x Tl7/ Th3/967 x Amlnad /467 x MC Th3/967 x T79/ S \K76 xsca S T79/467 x T65/ Th3/967 x MC '\A34 x T17 / T79/467 x Amlnad i Th3/967 x T65/ S li T63/967 x MC Th3/967 x MC ,A34 x SCA6 11 :tj_ i , 1" fh3/967 x T7 /524 8 :>, 6/ 'Cmmn standards.

4 140 CA.M. Campbll c: ;: u A.5 'i " :;. U 1/) as A.1: Amlnad prgnis UJL&&..u. ft" CC CC :::& 0.2 " as 1/) " ;:, J: 1/) as ;:, " > ". + C as G :::& 87b: T79/467 prgni. a b c 0.0 L.L.J,uu.&LL.J&.L.&LJa.Lu.&L&.&L&La.uL E ""." ft""c"(,,) CCC CC CJ)CJ)CJ)CJ)CJ)CJ)CJ) CJ) CCCCCCCCCCCCCCCJ)CJ) 89: T63/971 prgnis a b c B D F 87a: T63/967 prgnis a b c lll 88: T83/987 prgni. a b c l!jl [1 ",,".C" CC " CC.. 810: NA and M prgnis a b c [].t)ccj) (")"""(")t)c CC t) ftlt) t) cc. Prgny C.ft C CC ftftftftt) CC 1t)1ft1t)1ft1ft1t)1t)1t) ftlt) t)ft 1ft 1ft.. cd Fig. 1. AbundK ni Plilll[ll[lll[lidc, ljcllsi, in six tris AF. Vrtil bars ar 57< LSD's: a, 881 v 882; b, 881 r 882 v ny thr; c, l cmp<lrislms in Bó, and cmparisns xcluding 881 and 882 in thr tris. #, duplitd in ach blck. Fr xplanatln f prgny cds, s tabl 1.

5 .' p ' :D n 3 " 111 D ' id fh QJ :D ;: 111 ;;:. c:r L..; n 1 ". ' ' fh fjl (1) "Q. [.. 8' :r: 3 '" :. "T] '!» tr ::1 Q. :>J ::1 n r 'lj r r 10 'J,. '<, S' <> 'X', n j' r;; D» :n '., Q. (1)!ir r;; <> r r g: :' !''". r Man lg(x + 1) ndivldus/16 buds () and Man scr/tr fr flld insplns (.) p. p p Gt C»." 1\) 1\) 1\) ;:: 111 ;:: =: n >;::: 111 ;=:n :D 1 ".. ' ' fh." :D.!? Z 111 D i: ' ' fh "" P ""'. "'" P" ;::: n ;:: 111.:: ;::::: n :D. 1. " '. ' fh :D C» 1 ". ' ' fh "'" ::::::

6 p. U1 )la ;::::::n D :3 ' :::11. " :::11 n QJ D., m H c:r!?.: n 4 ) (.,) U) " )., :::s ' n. *'" N n );. n 3 '" cr" " " rr.;' 1454 ',,", ; ir 1459 ::l c 1460 ::l '" 1461 r, 11) :::. 1472, '::., 1473, ::: :::s 1478 '< '"' '!: 5' 'f> X' n :::l.. ;:;: ; ; :n 1548 '., 1549 c ;:;: 1551 \F> 11) ) :' ? P 111 Man lg(x + 1) indlvldus/16 buds () and Man scr/tr fr flld nsptlns (.) U1 p. p. U1 m : r:r ;:! n m. c:r ;:::: n lt1 D U) 4 ) C) " U)., " :::s ' n "" D. g Z m :::11. i " :::11 ' n P P.. N U1 U1 D CT n l H m CT n D.,., 4 U) """ )., " :::s ' n t D Q) 4 ) (.,) U) " )., ". :::s ' n g p. U1

7 ...::.=::: n 1 tt 1». t < :. :D l> 3 " : 1» Q. 't:j c : ;" r Q:J :D ' n 1 CJ). CJ) 't:j c : id" r rj) r:: 'J; r; r "Q. :. s r; r; :» :r: 3 '" r., :». :. \J.l "Tl ciq ); 1458 'T r:: 1459 ::l 1460 :» ::l r; 1461 r r <F> r r:: "ti r; c r; 1476 r; 1478 c.: '< :» r 5. " n., ;;. Q, ':J: ); 1547,"Tl , 1549 r r 1551 Vi <F> 1552 r r => Man lg(x + 1) ndlvidus/16 buds () and Man scr/tr tr fild inspins (.)!=>!=>!=>!=>.. N. :. CJ) Q N 1'11 t;:::::::::::. ';:::::::l :D 1» +881 ' t;:::::::::::: n CJ) """ 't:j 892 c 893 : 894 ;" r " :D. :::::::: 1» ;:::::::: '!=? +882 >;:::::::::: n Z 1209 l> » : 1211 Q, ! 1221 't:j c 1226 : 1228 ;" r 1233 ;., :,. c",.!=>. Q i i _ ' 1» :D ':::::n 1.. :. CJ) "= 1» >;::::=: ' 't:j c : ;" r 1:) :D Q 1 t;:::::::=: n CJ). CJ) 't:j c : ;" r ;., :,. c" m!"'""'

8 Man lg(x + 1) indlvldus/16 buds () and Man scr/tr fr flld nsplns (.1 " J t 'Tl 'J 1459» a" 1460 c: :l 1461 '" 1463 :l f) r 1464 Q., 1467 ;' 1472 '"' 1473 : '" " 1475 l '< 5 <J> ;;;:.. ;j. n (Ji Q.» :n 1547, 1548 r 1549?J. (Ji 1550 <J> r r 1551 :::::! 1552 q<l N.", rt r:t r. r:t r=. t=:l t::::::=l,,,, L"1 r,, r, 1570 n 1571 t" h 1578 t="1 DJ ;:::::: 1» 1 n n ' 892 l ". N c",. N =::::: DJ 1» 881 ;:=:; n DJ. n!::=::: 882,... n n 1». 916 Q. 920 ' ' 922. DJ t» +881.:::::: +882,. 1» 1210 >;:::::: n Z Q i 1221 ' l l 923 l tj Q) DJ 1» +881 h c». DJ +882.===:!! 1 n n 857 n 1 n. 860,. n 863.., 864 n. ' 866, ' 872 l l 877 (j > (j '" 3 " a"

9 :b ) > 3 ' 111 Q. ' f/) QJ. 111 t ) (.,) " c ). ' f/) g> < g,,. :c ª8" 3 ".,., 'iq' (]' ; r:r c: ::l l. '"' ::l r. ft.!::: :;: 1 ::: :;, 5' '!: x ;.. 'ir. ;,"" Q.. l. : '" '" '"., " '< (') l. Man lg(x + 1) individus/16 buds () and Man scr/tr tr tild nsplns (.) C'."» c "";::!c:r t 1454 t;:::(') ) (.,) 1455 " c ' f/) , """;::::1». ;:::c:r 1547 ;::::::::: (') z 1548 > Q : ' f/) "r C' 1» c:r ;:::::::::: (').. t t c:r (') 1» C'. c:r ;::::: (') t 907 t:::::::::. c 912, " 915 ). 916 ' f/) Q) t >;::::::! 1» ==== a' ) 857 (') (.,) " 860 c ) ' n

10 146 CA.M. Campbdl Tabl 2. Cfficints f rank crrlatin (Sparman's rh) btwn rankings f 68 c prgnis by abundanc f Hmptra. 2 3 Tt Psudcccida Bud f.i. 2 01,1 Plilllcccid, /lfillcl"i, Bud 3. f.i. 4.. Plillcccl/S cilri Bud 5. f.i. 6 n. n PzCllilCCCltS }wrsrl!ilpl!si Bud 7 n n Txplcra ill/ra/ll;i Bud 8 n. f.i. 9 MC50} l1lll/lil cssl/llllí Bud 10 n n f.i. 11 n n n n n n n n n n n n n n n n n n 0.15 n n n n n n " ", Signifint at P<0.05, P<.01 and 1'<0.001, rspivly. n Nt signifint (P>.S). buds and f.i., rspivly, whras T85/799 x T79/501 (882) rankd as 43rd and 55th mst infstd by ths mthds (tabl 1). vrl, MC76 x SCA9 (1554) was th prgny last infstd by P. njnsis, ranking as 68th frm buds and 64th frm f.i., rspivly. thr prgnis with lw infstatins by bth sampling mthds wr T63/967 x T65/238 (860), NA34 x T7/524 (1548), MC76 x NA33 (567) and T63/967 x T7/524 (857). Backtransfrming man cunts and scrs gav diffrncs btwn th gmtric man dnsitis frm mst and last infstd prgnis f 16fld frm buds and 20 fld frm f.i. Dspit csin wid disparitis in rankings f prgnis by th tw sampling mthds (.g. MC76 x SCA6 (1551», a psitiv crrlatin f 0.43 (P<.1) was fund btwn th tw sts f rankings (tabl 2), inditing that prgnis wr gnrly cnsistnt in th rlativ ppulatin dnsitis f P. njnsis sustaind. Plancccus citri (Riss), with a tt f 17,259 individus, was nly slightly lss cmmn in buds than Plancccids njnsis. Hwvr, with an vrl avrag scr f 0.064/tr, it was abut nsixth as cmmn frm f.i. Lik P. njnsis, Plancccus citri was mst numrus in B9 and B0, and fairly cnsistntly lss numrus in th thr tris (fig. 2). A signifint diffrnc fr prgnis (P=0.048) was fund frm just n f th 12 sts f rsults, th f.i. f B9. Svn prgnis had signifintly fwr P. citri in buds than had T85/799 x Amlnad (881), thugh th lwr infstatin f T85/ 799 x T79/ 501 (882) was nt signifintly diffrnt frm that hybrid. N prgnis wr signifintly mr dnsly infstd than T85/799 x Amlnad (881). Tw prgnis had signifintly mr P. citri in buds than had T85/799 x T79 / 501 (882), but nn had signifintly lss. Dspit th lw vrl scrs fr P. citri frm f.i., fiv prgnis had signifintly lwr avrag scrs than had T85/799 x Amlnad (881), and fur (163/967 x T7/524 (857), T63/967 x T87/1312 (866), T63/971 x T65/238 (1458) and T63/971 x MC76 (1475», had signifintly lwr scrs than had th intruppr Amazn standard T85/799 x T79/501 (882). Rankings f th tw standards fr P. citri wr bradly similar t ths fr Pllcccids ja/hsis (tabl 1\, with T8S/799 x Amlnad (881) (ranking 19th by bth assssmnts) mf havilv infstd than T85/799 x T79/ Sl (882). Takn tgthr, th rankings frm bth s.1mplmg pwcdurs inditd that MC76 x T7/524 (547), NA34 x T60/887 (1550) and MC76 x NA33 (1567), l frm B0, wr th prgnis last infstd by Plancccls citri. Th diffrnc in dnsity btwn th mst and last infstd prgnis was 5fld frm buds, but was indtrminat frm f.i. as n P. citri was fund n srn prgnis. Th crrlatin cfficint btwn prgnis rankd by th tw sampling mthds, thugh psitiv and signifint (P<0.05), was ls s than than fr Plancccids njnsis (tabl 2). Cmparisn f rank crrlatin cfficints btwn prgnis fr P. ljnsis and fr Plancccus citri indi ts that in gnr a prgny's rlativ infstatin by Plancccids njllsis was as accurat an inditr f its likly infstatin by Plancccls citri as was sampling fr P. citri itslf by th trnativ mthd. A tt f 1521 individus (an avrag f n individu pr 39 buds), wr fund f Phnacccus hargra1.'si (Laing), th third cmmnst mybug. P. hargra1.'si was vn rarr by f.i. (fig. 3), prducing an vrl avrag scr f 0.003/tr (apprximatly n individu pr 144 trs). Prgny diffrncs wr nt signifint frm any f th twlv anyss f varianc. F.i. scrs shwd that n prgnis diffrd signifintly frm ithr standard, s th f.i. data wr nt cnsidrd furthr. n B0, fwr P. hargra1.'si wr fund in buds f NA34 x MC60 (1577) than in ths f T85/799 x Amlnad (881) (P<0.05). n B7a, P. hargravsi was absnt frm buds f T63/ 967 x T79/378 (863). Unusuly, in B7a, bud infstatin f th T85/799 x T79 / 501 standard (882) was signifintly gratr (P<0.05) than that f th T85/799 x Amlnad standard (881), thugh in B0 th ppsit pattrn f abundanc was bsrvd with th sam lvl f signifinc. Such incnsistncy btwn tris, dspit th dubld rplitin f th standards in l but B6, wakns cnfidnc rgarding th prgnis' rlativ suitability fr P. hargravsi. n abnrmly high cunt frm a plt f T63/967 x Amlnad (1233) accuntd fr vr hf th man vu n that prgny as illustratd in fig. 3D. That cunt was mittd frm th anysis f varianc. vrl, th tw standards rankd c\sly by infstatin f P. hargraz'si, and nar th avrag f th 68 prgnis (tabl 1). Rank cfficints crrlating prgny infstatin with P. llrgrl.'csi with that fr th tw cmmnr mybugs wr psitiv, but nt signifint (tabl 2). Likwis, Kndl's nnparamtric tst f cncrdanc (Cnvr, 1980) f

11 Suscptibility f c t Hmptra 147: prgny rkings fr th t mybug spis frm bud infstatln was nt slgmflnt (W == 0.355; x == 71.36). Ntwithstanding th lack f signifinc f crrlatins invlving P. 117rgn:m.>l'si and th thr mybug spcis, th psitiv crlatins?twn rankings f prgnis fr P/lcccuil's, ja/l'ls.ls and fr /lcccls citri Sllggst that a prgny s rlatlv sultablh.ty.?",ay b t l mybug spcis as a grllp. That psslbll ty,:"as xplrd by anyss f varianc fr tt psudcclds. A furthr fur spcis, PSl'ldcvccls cllvcram Jams, MaCll'llicccls l,\ld' (Laing), P. lclari' (Maskll) and Fcrrisia virgata (Cckrll), tgthr ttling 719 individus, wr rcrdd frm buds. nly th thr spcis cnsidrd in figs 3 wr rcrd f!"m f.i. As th scr intrvs frm f.1. wr a lganthmlc prgrssin, th tt psudcccid scr/tr (t) fr ach plt was stimatd frm th individu spcis scrs (n, c and h, rspivly) frm th xprssin: t == lg (10" + 1 0< + l h 2) Fig. 4 summarizs rsults frm th 12 ana.lyss. As with P/ancccids nja/nsis n, prgny dlffrncs wr signifint fr buds in B0 (P==0.038), and fj. f B9 (P == 0.015). n nn f th six tris was any prgny signifintly lss infstd than th standard T85/799 x T79/501 (882). Thr prgnis frm buds, and svn frm f.i., wr mr infstd by mybugs (P<0.05) than th standard T85/799 x Amlnad (881), whras six and nin prgnis, rspivly, wr lss dnsly infstd than that standard. Th lattr list frm fj. includd th standard T85/799 x T79/501 (882) in tw tris (Bl, P<.; B9, P<0.05). Th diffrncs in gmtric man dnsitis btwn mst and last suitabl prgnis was 5fld fr buds, and 12fld fr fj., a narrwing f bth rangs frm ths rcrdd fr P. nja/nsis. As xpd frm th prdminanc f P. nja/ls1s, prgny rankings frm f.i. fr tta Ps.udccClda wr mst idntil t ths fr P. njnsls n, and that is rfld by a vry highly signifint rank crrlatín cfficint f 0.96 (tabl 2). n l but a fw instancs th additin f gmtric man scrs fr Planccclls citri and Phnacccls hargravsi trd prgny rankings by at mst tw frm ths fr P/ncccids nja/nsis n. Th mst ntabl xcphns wr Amlnad x T87/1312 (916) and T79/467 x T90/ 344 (893), which wr displacd 12 psitins, largly as a rsult f disparity in thir rankings fr P. nja/nsis and fr P/G//CCCllS citri. Gratr rrdring ccurrd amng prgny rankings frm th bud data, a rspns t t.h mst gu abundanc f th tw cmmnst s'pcls (cmprising 48'70 and 46% f tt psudccclds n buds, rspivly).th crrlatin cfficint f 0.33 btwn rankings f prgnis fr Phllacvccls hargra> i and fr tt psudcccids (P<.l) cntrasts wlth th nnsignifint rank cfficints fr P. ha rgra vsl and th thr tw psudcccids, sparatly. t suggsts that th abundanc f P. 117r,\ra,'csi n th varius prgl'nis (4'1c f tt mybgs) was gvrnd by thir uitability fr ithr f th thr spcis. vrl, T63/ %7 x T17/ 524 (857) mrgd as last infstd with mah"bugs, whras with t\\" xcptins prgnis having.\mlnad as a parnt \Vr gnrly amng th mst havily infstd. Aphidida A tt f 5679 individus f th aphid Txptra lrantii (Byr d Fnsclmb) ccurrd in buds, and it was s cmmn frm f.i. with an vrl avrag scr f 0.453/tr. F.i. inditd that T. lrantii was mst abundant in B7a and B7b. Bud sampls shwd n such variatin btwn tris (fig. 4). Signifint diffrncs wr fund btwn prgnis frm buds in B8 (P==0.030) and frm f.i. in bth B9 (P=0.038) and B0 (P==0.022). N prgnis diffrd signifintly frm ithr standard in B6. Th bud data lackd cnsistncy rgarding rspnss t th tw standards. Fr xampl, in B7a mr aphids wr prsnt n T85/799 x T79/501 (882) than n T85/799 x Amlnad (881) (P<0.05), whras in B8, with a similar lvl f signifinc, th rdr f suitability was rvrsd. By cntrast, in f.i. f B8, scrs wr signifintly highr n T85/799 x T79/501 (882) than n T85/799 x Amlnad (881) (P<0.05). This pattm was rpatd in B9 (P<.1), and similarly, but nt signifintly, in B7a, B7b ad. B10. an.numbrs f aphids in buds f six prgms n B8, ncludmg th standard T85/799 x T79/501 (882) wr lss (P<0.05) than that n th standard T85/799 x Amlnad (881). A tt f 19 prgnis, S, 7, 5 and 3 frm B7a, B7b, B8, B9 and Bl, rspivly), including th standard T85/799 x T79/501 (882) in bth B8 and B9, had signifintly highr avrag scrs than did th standard T85/799 x Amlnad (881), and nn had a signifintly lwr scr than that standard. Frm f.i., 61 prgnis including T85/799 x T79/501 (882) rankd mr suitabl fr T. aurantii than did T85/799 x Amlnad (881). Frm buds, hwvr, th standards tid (tgthr with T63/971 x MC60 (473» at 35th mst suitabl. Thr was pr agrmnt in th apparnt suitability f prgnis as assssd by th tw mthds (tabl 2). Hwvr, thr was a larg psitiv crrlatin f 0.42 (P<.l) btn :'rg.nis rankd fr T. lrantii and fr Planccc/ds njnsls n buds a crrlatin that was waknd by th inclusin f thr spcis f mybugs. By cntrast, th ngativ crrlatins btwn prgny rankings fr T. auyant/l frm fj. with ths fr P. njnsis (bth sampling prcdurs) r fr Planccclls citri frm buds wr highly signifint (tabl 2). Psyllida Th psyllid Ml'shmtma tssmanni (Aulmann) was th mst abundant hmptran in th six tri aras. Th tt f 45,779 individus cuntd frm buds utnumbrd th cmbind tts f l thr Hmptra. Th avrag scr frm fj. f 0.495/tr was s highr than that f any thr hmptran. Thr wr signifint diffrncs btwn prgnis frm fur f th twlv anyss f varianc (Buds: Bl, P== Fj:: B7b, ==0.042; B8, P<.l; B9, P==0.044). With th xcphn f tn B7b, psvllids wr mr abundant in buds f th standard T85/799 x Amlnad (881) than in th intruppr Amazn standard T85/799 x T79 / 501 (882) (fig. 6), but in i10n f th tris \Nas th diffrnc signifint. Th ppsit pattrn was vidnt frm fj., and in B8 and B9 signifintly mr psyllids wr rcrdd n T85/799 x T79/501 (882) than n T85/799 x Amlnad (881) (B8, P<.l; B9, P<0.05). n cmmn with th thr Hmptra, psyllid dnsitis n tst prgnis did nt diffr

12 . H8 Tabl 3. C.A.M. Campbll Avrag rankings by Hmptran abundanc fr prgnis f th six cmmnst parnts (N. f prgnis in parnthss). Amlnad T63/971 T79/467 lmc76 NA34 T63/967 (12) (14) (14) (12) (10) (17) Man+ Man Man Man Man Man rank rank rank rank rank rank Psudcccida Plmlcccids bud /jl/sis f.i Plmlcccus bud citr; f.i PhrlllccCs Jllrgravsi bud Tt bud f.i Aphidida Txptm bud auml/ti; f.i Psyllida Mshmtma bud tssmamlí f.i t Th xpd man rank is Th pssibl man ranks rang frm , and 609 fr parnts rprsntd by 1017 prgnis, rspivly. signifintly frm ithr standard in B6. n B7a, nly T63/967 x T17/524 (857) mrgd as signifintly diffrnt frm a standard (P<0.05), with a highr avrag scr frm f.i. than that fr T85/799 x Amlnad (881). Frm buds, a tt f lvn prgnis was lss infstd with M. tssmanni and nn mr infstd than th standard T85/799 x Amlnad (881), whras just tw B7b prgnis wr ls s infstd than T85/799 x T79/501 (882), th thr standard. Th standard T85/799 x Amlnad (881) was rankd amng th last infstd prgnis by M. tssmanní frm f.i. (tabl 1). N prgnis wr signifintly lss infstd than it in any f th six tris; hwvr, 13, including th standard T85/799 x T79/501 (882) in bth B8 and B9, wr signifintly mr infstd. Th intruppr Amazn standard, T85/799 x T79/501 (882), rankd abut avrag fr abundanc f M. tssmanni, svn prgnis wr signifintly lss, and fur signifintly mr infstd than it in th six tris. As with T. aurantíi, th prgny rankings fr M. tssmanní frm th tw sampling mthds wr cntradiry (tabl 1). Cnsquntly, th rank crrlatin cfficint fr prgny infstatin btwn th tw mthds was nt signifint (tabl 2). Hwvr, th crrlatin f prgny rankings fr M. tssmanni and tt Psudcccida in buds was psitiv and signifint, whras nn f ths with individu spcis f mybug was signifint (fr P=0.05, rh=0.24 with 66 d.f.). Prgny rankings frm f.i. fr M. tssmanni shwd a similar pattrn t that fr T. aurantii whn crrlatd with prgny rankings fr mybugs, bing mstly ngativ (tabl 2), thugh nly th ngativ crrlatin with that fr Plzrzaccclls hargravsi was signifint (P<.l). StiClJccidac a/lli Margardidac T\\' spcis f sticccid sls (SticCCl/S sjstdti Cckrll and Plrl1sticCClS 1lltltispillSl/S (Nwstad» wr ncuntrd, but fr cnvninc thy wr tratd as a singl taxnmic ntity. Althugh lhy abundant in th trritris f crtain cccidphilic ants, nithr Sticccida, nr a spcis f Gasrdia nr G. znata (Nwstad), was widsprad. Nithr taxn was fund in buds. Diffrncs btwn prgnis wr nt signifint in any f th 12 anyss f varianc f th f.i. data. Thr prgnis (T63/971 x MC60 (1473), NA34 x SCA9 (1555) and NA34 x MC47 (1561» wr lss infstd by Gasrdia sp. than th standard T85/799 x Amlnad (881), and nn was mr infstd than that standard. Similarly, th standard T85/799 x T79/501 (882) was lss suitabl fr Gasrdía sp. than was Amlnad x T87/1312 (916). Diffrncs btwn prgnis in dnsitis f Sticccida wr nt signifint. Bus f thir llizd distributins, nithr taxn culd b cnsidrd a suitabl prxy fr assssing mybug dnsity indirly. Parnt ffs Prgnis in ach f th tris wr crsss with Amlnad r n f fiv uppr Amazn parnts, plus th tw standards. Fr ah f ths parnts thr was grat variatin in th ranking s f thir individu prgnis fr th svr Hmptra (tabl 1). Hwvr, sm inditin f parnt influnc n prgnis may b drawn by cmparing th avrag rank fr l prgnis sharing a cmmn parnt with th man scr f 34.5 xpd if parnts xrtd n influnc n thir prgnis' suscptibility t Hmptra (tabl 3). Th rsults shuld b intrprtd with utin, hwvr, as in ach tri diffrnt slins wr crssd with th six main parnts.. Amlnad x uppr Amazn hybrids wr plantd in ah tris, and gnrahy th Amlnad x T85/799 standard (881) was amng ths prgnis mst havily infstd with mybugs. Amlnad prgnis had th lwst avrag rank fr mybugs f any f th parnts, inditing that thy wr th mst havily infstd by

13 Suscptibility f c t Hmptra 149 " mybugs (tabl 3). Th avrag ranks by bth sampling mthds wr rmarkably cnsistnt fr th cmmnst t\v spcis f mybug and, cnsquntly, f tt Psudcccida s. Similarly, T63/971 prgnis supprtd aby avrag ppulatins f mybugs, particularly P//cccids /ja/l/sis. Bth Amlnad and T63/ 971 prgnis shwd similar pattrns f infstatin by T. i1l1ml/tii with buds aby avrag and f.i. blw avrag infstatin. Prgnis f T63/971 supprtd fw M. tss/li1//li by f.i., but that was nt rfld in th buds sampls. Prgnis f bth NA34 and T63/967 wr blw avrag in infstatin by mybugs, but th spati distributin f mybugs within trs diffrd. Vry fw mybugs wr fund by f.i. n prgnis f NA34, whras, mybugs wr lss cmmn in buds n prgnis ft63/967. Discussin Many bitic and abitic fars aff th abundanc and withintr distributins f Hmptra n c. f ths fars, nly th rspnss t diffrnt c prgnis was spcifilly cnsidrd in th prsnt study. Th rlativ cntributins f uncntrlld fars rlativ t prgny ffs n b gaugd frm th btwn tri variatin in ppulatin mans fr individu spcis f Hmptra n th cmmn standard prgnis. Similar ffs ccurring within tris cntribut t th unxplaind varianc which was rfld in th siz f LSDs. n rdr t cmpar hmptran rspnss t prgnis plantd in diffrnt tris it is ncssary t us a cmmn rfrnc pint. Th mthd f Pimntl Cms (1970) prvids such a rfrnc pint by wighting th rspnss f Hmptra t tst prgnis rlativ t thir rspnss t th cmmn standards. Whn th 68 c prgnis wr rankd by thir, dgr f hmptran infstatin rlativ t that n th tw cmmn standards, thy shwd cntinuus gradatins in ppulatin dnsitis fr a h hmptran taxn. N prgnis wr immun t infstatin by mybugs, aphids r psyllids. Svr intruppr Amazn prgnis wr signifintly lss infstd with mybugs than was th uppr Amazn x Amlnad standard (881), whras fw prgnis wr signifintly mr sparsly infstd than was th intruppr Amazn standard (882). Prgny T63/967 x T17/524 (857) rankd amng th last infstd prgnis fr l thr spcis f mybug by bth assssmnt mthds (tabl 1). P/mlcccids jll/llsis had a signifintly shrtr avrag ifspan n hat prgny than n T85/799 x Amlnad (Firmpng, 1 Y82). n th prsnt study, signifintly fwr (P<.01) individus f P. lji1/llsis wr fund in buds f T63/967 \ T17/524 than in ths f T85/799 x Amlnad (881),,lnd variatin in mybug lngvity cmbind with a cllrrspnding rduin in fcundity culd hav cn ributd t diffrncs in mybug ppulatin dnsitis <1 mng prgnis. vr th fiv T17/ 52+ crsss plantd in th six (ri,lis, th avrag ranks fr tt psudcccids wr 422 frm buds and 54.4 frm f.i., th lattr inditing th,'wst avrag mybug cunt fr any parnt rprsntl'd in svr tris. Althugh th uppr Amazn parnts, érll'isd with th six main parnts, \Vr sld fr virus rsistanc in sd inculatin tsts (Lckwd, 1981b), Attafuah & Clndinning (1965) fund n vidnc f rsistanc t virus infin in cuttings f T17/524. Hwvr, thy did idntify it as th mst tlrant f CSSV infin amng th 50 T17 clns thy tstd. dly, fr swlln sht disas managmnt, a c varity shuld cmbin rsistanc t and tlranc f CSSV, and rsistanc t infstatin by th virus vrs; prgnis f T17/ 524 parntag currntly cm clsst t that ida!. n prvius studis, diffrncs f abut twfld wr fund btwn mst and last infstd c prgnis (Biggr, 1975b; Firmpng, 1984). Th vr diffrnc bsrvd in th prsnt study was fivfld fr tt mybugs in buds, and twlvfld frm f.i. t y lv!. Th widr rang hr cmbins ffs frm bth th gratr numbr f prgnis studid, and thir gratr gntic variatin. Firmpng (1982) suggstd that Amlnad was mr suitabl fr mybugs than wr Amlnad x (uppr) Amazn hybrids, with intr (uppr) Amazn crsss last suitabl. That pattrn rsta ts th mr fuly dcumntd rlativ rdr f suscptibility f c typs t infin with CSSV (rviwd by Thrsh t., 1988). Althugh pur Amlnad was nt plantd in th prsnt study ara, Amlnad x uppr Amazn hybrids wr plantd in l six tris. Dspit wid variatin in individu rankings (tabl 1), th avrag rankings f such hybrids prvd rmarkably stabl acrss spcis and assssmnt prcdurs (tabl 3), and cnfirmd that prgnis f Amlnad wr indd th mst infstd by mybugs f th parnts tstd. Hwvr, prgnis f T63/971 wr nly slightly lss infstd than ths f Amlnad. Amng parnts rprsntd by tn r mr prgnis, NA34 and T63/967 prvidd th mst cnsistnt vidnc fr inhritabl 'rsistanc' t mybug clnizatin. D Mir (1975) dmnstratd hritabl rsistanc t M. tssmanni amng c prgnis in Camrn, but nn f th parnts studid by d Mir was rprsntd in th prsnt study. Biggr (1975a) bsrvd that Pl1ccclls citri smd lss influncd by hst gntyp than was P/1 cccids 1jnsis and this was cnfirmd in th prsnt study. Fr P. njnsis, th diffrnc btwn bud infstatins n mst and last infstd prgnis was sixtnfld, whras fr Planccclls citri th crrspnding diffrnc was fivfld. Similarly, dspit th dminanc f Plancccids njnsis in f.i., th rang f gmtric mans was 20:1 fr P. njllsis n, cmpard with 12:1 fr tt psudcccids. PllnaccCl/s largrm'si was t infrquntly ncuntrd in f.i. t matrily influnc that rati. As Biggr (1975a) warnd, th incrasd prpndranc f PlanccCl/s citri n c in Chana (.g. s Campbll, 1984) lssns th pssibility that th sprad f swlln sht disas will b rducd by a cc a varity that is partily rsistant t mybugs. n a lngtrm study f c prgnis T85/799 x T17/359 and Sris lb (a ll Trinitari x T17/359), Biggr 0975a) fund that th ltr was cnsistntly mr infstd by l Hmptra cmmn t his and th prsnt studis. f th spcis cnsidrd hr, nly M. tsslli1l/l/i was nt rcrdd by Biggr. A similar cnsistncy t that fund by Biggr \Vas shwn by cunts f

14 , 150 CA.M. Campbll Hmptra in buds, but nt frm f.i. scrs. That cnsistncy is vidnt frm th crrlatin cfficints btwn rankings f prgnis fr ach taxn, which, with tw nnsignifint xcptins, wr l psitiv (tabl 2). Likwis, th psitiv and signifint crrlatins f prgny rankings fr mybug taxa btwn assssmnt prcdurs (indpndnt tams sampling diffrnt strata, using dissimilar mthds) indits that th rspiv rdrings f prgnis wr in brad agrmnt. Th crrspndnc btwn rankings f individu prgnis fr diffrnt taxa was smtims wid (tabl 1). Hwvr, in a fild study, uncntrllabl fars wuld cntribut t such variability. Th patchy spati distributins vr th 5.5 ha f th tris f th varius Hmptra, and thir attndant ants, was prbably a majr cntributing far. By cntrast t th cnsistncy fund by Biggr (1975a), and t that f th bud data, prgny rankings fr T. lrantii frm f.i., and hr M. tssmllli s, wr mstly ngativly crrlatd with ths fr th sam spcis in buds, and fr mybug taxa assssd by ithr mthd. Dzy (1979) rprtd that numbrs f M. tssmanni n flush tissu varid indpndntly f ths n thr plant rgans. Antagnism frm ants that slicit hnydw frm mybugs r thr cccids prvids a pssibl xplanatin fr th ngativ crr latins. Biggr (1981a) bsrvd that l truly 'dminant' spcis f ants n c wr cccidphilic. H suggstd that intr and intraspcific cmptitin by ants fr hnydw was imprtant fr maintaining th trritri msaics f ths ants n c. Sticccid sls, and th spcis f Gasrdia, ar invariably attndd by ants. Likwis, th ftn larg and prsistnt clnis f Pllcccids njllsis and Plancccls citri, n pds and in fissurs in th bark, ar mstly attndd by ants (Strickland, 1951), as ar clnis f T. lrm tii. Althugh M. tssmanni is rary if vr attndd by ants, bus f th ants' ubiquity, it usuly ccurs n trs whr cccidphilic ants ar prsnt (Dzy, 1979). Hwvr, as bth T. aurl tii and M. tsslllan/li principly xpit nnwdy and immatur tissus such as flwrs and flush grwth (Dzy, 1979), ppulatin fluuatins clsly fllw th sasn cycls f af flushing. Trs with larg ppulatins f hnydwprducing cccids and psudcccids ar liky t xprinc gratr rganizd ant aivity than trs with sparsr ppulatins f ths Hmptra. Expsd clnis f aphids and psyllids might suffr frm prdatin by fraging ants assciatd with mr cnsistnt prvidrs f hnydw narby. n buds, maybugs ar physilly islatd frm attndant ants, and this shard islatin may nab psyllids and aphids t multipy in rspns t th quity f th hst's sap Whatvr th us f th ngativ crrlatins, thy prclud th us f f.i. fr ithr T. aurltii r M. tssm1 l1i as an indx t a prgny's suitabiity fr maybugs. Lv\' ppulatins, r th absnc f a spcis, nnt b rliably attributd t a singl us. Simiarly, Sticccida, which wr amng th mst numrus Hmptra by t.i. t matur c in prvius studis (C1mpbll,!ll8l; Strickland, 1951), wr nithr numrus nr \\"idsprad. Thy, and Gasrdi sp. nr G. :l1t, \'n if thl'\' rl'spndd t c prgnis similarly t mybugs, clnizd c t slwly t b usful fr indiry assssing mybug ppulatins in plant brding tris. M. tcss/t1lll1i and T. aur1tii, assssd frm bud samps, wr signifintly psitivly crrlatd with maybug ppulatin dnsitis (tab 2), but th crrlatins wr nt sufficintly cls t n anthr t prvid a rliab indx Thrfr, nn f th mr cnspicuus Hmptra was a substitut fr assssing maybug ppulatin dnsitis dirly. F.i. was th simplst f th tw mthds usd fr assssing mybug ppulatin dnsitis in th prsnt study. Prgny rankings by fj. and by buds sampls fr mybugs wr mstly highly crrlatd (tabl 2). Hwvr, f.í. prvidd an inaccurat stimat f th spcis cmpsitin in th npy. Biggr (1981b) dmnstratd that rarity might bli th ptnti imprtanc f a spcis as a vr f CSSV, bus th rlativ mbility f th individu spcis must s b cnsidrd. Althugh th tw sampling mthds usd in th prsnt study wr cmplmntary, sampl units f buds prvid th mr usful infrmatin, and that wuld b th prfrrd ptin if assssmnt prcdurs wr simplifid. Acknwldgmnts 1 am indbtd t my tams f assssrs fr thir xcllnt tchnil assistanc. This papr is publishd with th prmissin f th Excutiv Dirr f th C Rsarch nstitut f Ghana. Th wrk was spns rd by th vrsas Dvlpmnt Administratin, Unitd Kingdm. Rfrncs Attafuah, A. & Glndinning, D.R. (1965) Studis n rsistanc and tlranc t c viruss in Chana. Allllllls af Applicd Biagy 56, Biggr, M. (1975a) Varit suscptibility t attack by c inss, pp ill: Kumar, R. (Ed.) Pracdillgs f th 4tll Cllfrllc f Wst AfriClll CCl Elltamlgists, 913th Dcmbr, Lgn, Chana, Zlgy Dpartmnt, Univrsity f Chana. Biggr, M. (1975b) Suscptibility f tw c prgnis t attack by ins spcis. l. Effs f npy siz n numbrs f mybugs. Expri/llllt AsriCllltllr 11, Biggr, M. (1981a) bsrvatins n th ins fauna f shadd and unshadd Amlnad c. Bl//ti/l af Ellt/lllSiCll Rst'llrc/171, Biggr, M. (1981b) Th rlativ abundanc f th mybug vrs (Hmiptra: Cccida and Psudcccida) l c swlln sht disas in Chana. Bl//ill f E/ltllllSiCll Rcsarc/l 71, 4354J,8. Campbll, CA.M. (198J,) Th influnc f vrhad shad and frtilizrs n th Hmptra f matur UpprAmazn c trs in Chana. Bl//i/l f E/lt(l/lllsil RÓl'llrcll 74, 16317J,. Cnvr, W.J. (1980) PraiCll11(1/l"lril/lll'tric stlltistics 2nd Editin J,93 pp. [\;w Yrk, Wily. Dzy, B. (1979) :"\jt prliminair sur 'clgi du psvll du célyr: Tl/0rtl tcss/lltl/lzi (Aulm.) (Hmptr Psyllida), pp i11: Mbndji, M. & Dzy, B. (Eds) Rlll'l'(lrt d 51/11t"sl' 1,/'"'' C(llltác11c ds E11t(lll/"Sist'S dll C,lC,lt'./C/" d

15 Suscptibility f c t Hmptra rlll:stafriil/, 1318 D ccllllm', narst, B.P. Yaundé, Camrun. D Mir, P.B. (1975) Cmprtmnt d cultivars d yrs a 'égard ds attaqus d'hmptrs, pp ill: Kumar, R. (Ed.) Pnl(dil/gs f tir 4tlr Clfmlc f Wst Afril/ C E/tlll%gists, 913tlr DcClbcr, Lgn, Ghana, Zlgy Dpartmnt, Univrsity f Ghana. Firmpng, S. (1982) Th prfrmanc f P//cccids /ja/l/sis (Hmptra: Psudcccida) n srn c cultivars, pp il/: Tsts f agrchllli/s /d cllltimrs, 3. A/a/s f App/id Bi%gy 100 (suppl.), 112 pp. Firmpng, S. (1984) Labratry and fild vuatin f c prgnis fr rsistanc t mybug vrs (Hmiptra: Psudcccida) f swln sht virus. Bll/il/ f E/tlllp/agi/ Rsarch 74, Lgg, 1.T. & Lckwd, G. (1981) Rsistanc f c t swlnsht virus in Ghana. 1. Fild tris. Allra/s af App/id Bi%!:,'Y 97, Lckwd, C. (1981a) Rsistanc f c t swlnsht virus in Ghana.. Assssmnt f sd inculatin xprimnts. Alllra/s f Applid Bi/agy 97, Lckwd, C. (1981b) C brding in Ghana with rfrnc t swlnsht disas, pp ill: d Laffrst, J.' (Ed.) Prcdillgs f tir 7tlr llltcmati/la/ C Rcsarcll C {amc, Dlla/a, Ca1l/a01l1l 712tlr NPclllbcr, Dua, Camrun. Pimntl Cms, F. (1970) An xtnsin f th mthd f jint anysis f xprimnts in cmplt randmisd blcks. Billltrics 26, Rivainn,. (1976) Transmissin f c viruss by mybugs (Hmptra: Psudcccida). lma/ f th Scicl/tific Agricllltllra/ Saciy af Fill/ld 48, Strickland, A.H. (1951) Th ntmlgy f swln sht f. 1Th ins spcis invlvd, with nts n thir bilgy. Bulltill af Elltllllagil Rsrh 41, Thrsh, l. M., wusu, C.K., Bamah, A. & Lckwd, C. (1988) Ghanaian c varitis and swln sht virus. (rp Prttin 7, CA B ntrnatina, 1990