ENVIRONMENTAL FATORS AFFETING SPITTLEBUG EGG SURVIVAL DURING THE DRY SEASON IN ENTRAL BRAZIL 1 GEORGE BERLVN HEWITT 2 ABSTRAT - Spittlebug egg survivl nd hthing ws mpred in pstures where differenes urred in vegettive hrteristis nd grzing intensity. Egg smples were pled in pstures t the strt f the dry sesn nd revered befre hthing begn. Signifintly (P < 0.05) mre eggs were revered frm rs where litter ws present thn frm bte sl! rs. Mrtlity frm predtrs nd svengers ws estimted t 73%. An dditinl 34% f the eggs were desited nd 35% were nnvible. Egg survivl ws estimted t be 8.5% nd ws greter in pstures with the fliwing hrteristis: 1) npy height > 30 m; 2) bundnt litter; 3) plnt ver > 50%; 4) miniml rn grzing. Mre predtrs, espeilly spiders (Arneid) were ls lleted frm these types f pstures. At ne site mre eggs hhed In high grss psture (74%) thn in mw grss psture (59%). Althugh high grss my reeive less dmge frm spittlebug feeding the disdvntges f mintining grss > 30 m pper t utweigh the dvntges. Index terms: spider-,arneid, Zuli entrerin, JJeis flvpit, Brhirk deuinhens. FATORES AMBIENTAIS QUE AFETAM A SOBREVIVÊNIA DE OVOS DAS IGARRINHAS-DAS-PASTAGENS DURANTE A ESTAÇÃO SEA, NO BRASIL ENTRAL RESUMO - Frm mprds sbrevivêni de vs ds igrrinhs-ds-pstgens e elsã de ninfs em pstgens m diferentes rterístis vegettivs e intensiddes de pstej. Amstrs de vs frm lds n interir de pstgens, n in(i d estçã se, e reuperds ntes de se iniirem s els6es. O númer de vs reuperds ns áres que presentvm plh em dempsiçã fi signifitivmente mir (P - 0,05) d que ns áres desberts. O (ndie de mrtlidde pr preddres fi estimd em 73%. Ds vs reuperds, 34% estiverm resseds e 35% inviáveis. A sbrevivêni de vs fi estimd m send de 8,5% e fi mir ns pstgens m s seguintes rterístis: 1) ltur d pim > 30 m; 2) bundâni de plh em dempsiçã; 3) áre bert pel frrgeir > 50%; e 4) pstej m(nim u usente. Mis preddres, prtiulrmente rnhs (Ar,,eid), tmbém frm letds neste tip de pstgem. Em um ds lis huve mir perentul de elsões (74%) ns vs mntids n pst lt, em mprçã pst bix (59%). Embr pst lt sej mens dnifid pr igrrinhs, s desvntgens de mntê-l m ltur superir 30m preem sbrepujr s eventuis vntgens. Terms pr indexçã: rnh, Arneid, Zuli entrei-ln, Deis flvpit, Brhiri deumbens INTRODUTION Tw spittlebug speies, Zuli entrerin (Berg) nd Deis flvpit (Stl) use extensive dmge t Brhiri deumbens Stpf. pstures in entrl Brzil. The dry sesn in this r f Brzil usully extends frm April t September. During this time preipittin verges but 50 mm/mnth. Dipuse spittiebug eggs whih re in the sil nd litter usully begin t hth ner the end f September s rin shwers beme mre frequent Hwever, during the dry sesn sever1 envirn- Aepeted fr publitin n Februry 17, 1986. 2 nsultr f IIA/EMBRAPA-entr Ninl de Pesquis de Gd de rte (NPG), ix Pstl 154, EP 79100 mp Grnde, MS, Brzil. mentl fts my influene egg survivl nd subsequent hthing. It hs been stted tht imprted frges suh s B. deumbens n better withstnd dult spittlebug dmge when mintined t mderte height (15 m- 30m) s mpred t lw height (< 15 m) (Mrtin 1983, Rmir et i. 1984). 1-lwever, little is knwn but the influene f hbitt ftrs fund in pstures mintined t different plnt heights n spittlebug egg survivl nd hthing. Suh infrmtin shuld be mst benefiil in plnning spittlebut ntrl strtegies. Thus, this study mpres egg survivl nd hthing in B. deuin bens pstures where differenes ur in grss height, plnt ver, munt f litter, ptentil invertebrte predtrs, nd grzing intensity. Pesq. grpe. brs., Brsili, 21(12):1237-1243, dez. 1986.
1238 G.B. HEWIfl MATERIAL AND METHODS Tw study sites were seleted; ne site ws lted ner mp Grnde, MS nd ne ner Durds, MS, Brzil. Eh site ntined tw pstures (B. deumbens), ne with high grss (> 30 m) nd ne with lw grss (< 20 m). Envirnmenti mesurements nd smpling ws rried ut frm My t September t bth sites. Eggs nd dults í Zuli entrerin were used in the study. Experiment 1 -mp Grnde, MS The grss in ne ptsture verged > 30 m in height in My (high grss psture) nd < 20 m in the ther psture (lw grss psture). The pstures were seprted by n unimprved rd. Eh psture ntined six heifers during the time f the study. Sine the pstures were different sizes the stking rte ws 1.05 AUM's in the liigh grss psture nd 1.75 AUM's in Use lw grss psture. A wden stke 12 m in dimeter nd 60 m lng ws prtiily buried ner the enter ( eh psture but extended 16 m bve the grund. The stkes were used s permnent referene pirfis fr mesuring envirnmentl ftrs nd fr iting spittlebug eggs tht were pied in the pstures. A rpe ws tthed t the stke nd mesurements were mde in irle equl distnes ut frm the stke. Fr exmple, twelve mesurements f grss height, plnt vei, nd the munt í litter in 50 m 2 re were mde in My nd September in bth pstures. Eh mesurement f grss height ws n veige t three heights nd pint ver (%) ws estimted. Spittlebug eggs were pled in the pstures in My nd revered in Septejnber. Three methds f pling eggs in the pstures re desribed s filws: (1) (emles were liwed t ly eggs in sil-fihled plsti ups in the lbrtry. The sil re ntining the eggs ws then refuliy remved frm the up nd pled in hle (g the eggs were t grund levei) t mrked ltins in eh psture; (2) lnwn number í eggs were pled in smll (8 mx x 4 m) nyln sks nd these in turn were pled in the pstures; (3) femles were ged in eh psture nd ilwed t vipsit diretiy int the psture sil r litter. A ttl í 24 sil smpies ntining eggs lid in the lbrtry were pled in eh psture. Litter ws pled ver 12 smples t depth í 0.5 m. The ther 12smpIes were pled in the grund nd left expsed. The men number f eggs per sil smple ws determined by unting the eggs in 12 ntrl ups fliwing vipsitin. The nyln sks eh ntined 20 dipuse eggs. Sixteen sks were pled in eh psture; eight were lsed t prtet the eggs (rm predtrs nd eight were kept pen t ne end by extending tw smll stiks thrugh Use pening. Fur f the pen sks were vered with litter nd fur were vered with sil t depth f 0.5 m. The sme ws true fr the eight lsed sks. Twenty femies were pled in eh ge nd llwed t ly eggs fr perid f three dys fter whih time the ges were remved. In eh psture fur ges were pied ver mil nd fur ver litter. The men number f eggs depsited in eh psture in sil nd litter ws determined by unting Use eggs lid in eight dditinl ntrl ges fllwing vipsitin. Ltins í li eggs pled r lid in the pstures were mrked by smlt stke 50 Use ext sil smple uld be revered in September. The perent hth ws determined frm li eggs revered iri September exept fr Use eggs revered frm the smll pen sks. Eggs were pled n mistened fulter ppei in petri dishes nd the hth rerded dily. Mnthly preipittin ws Terded during tlie dry sesn. Twenty-first genertin nymphl unts (0.0625 m 2 ) were mde ne time in eh psture n Otber 11. Sweep net smples í miseilneus insets were lleted frm eh pstureseven times frm July 19 t Nvember 1. Vive smples were btined n eh dte. A smple nsisted f 15 (180 0) sweeps with 45 m dimeter sweep net. Experiment 2 - Durds, MS The vegettin in bth pstures t this site ws equl in terms f grss height, plnt ver, nd munt í litter present when the nturl spittlebug ppuitin í the pstures were vipsiting in Mrh nd Aprii. Befre this experiment ws initited Use grss in ne psture (lw grss psture) ws trmpled nd grzed t the extent tht very little upright vegettin ws present. The men height f the grss in the ther psture (high grss psture) ws > 50 m. The grss height nd plnt ver (%) were mesured t tweive ltins in eh psture in My nd August. Frty-first genertin nymphl unts (0.0625 m 2 ) were mde weekly beginning in Nvember in eh psture. N ttle were in either psture during the test. Ten ges in eh psture were eh infested with ten (emles in My nd eggs were lid diretiy int the sil. After three dys the ges were remved nd their ltins mrked with smil stkes. Ten dditinl ges were ls infested nd fiei three dys the eggs were unted t give men number í eggs per ge. in August the eggs remining beneth Use ther 20 ges were revered nd the perent survivl determined. Experiment 1 RESULTS The men number f eggs revered frm bth pstures filwing vipsitin nd t the end f the dry sesn is shwn in Tble 1. The perentge f eggs hthing in li tretments is shwn iii Tble 2. Sil ntining eggs tht were pled in psture! - - Signifintly (P < 0.05) mre eggs were revered Pesq. grpe. brs., Brsíli, 21(12):1237.1243, dez. 1986.
ENVIRONMENTAL FATORS AFFETING SPITFLEBUG EGG 1239 fliwing vipsitin thn thse revered frm the field fur mnths lter. Egg redutin ws 90% r greter in bth pstures in bth the litter nd sil tretments using this methd f egg plement. Of the eggs remining in the grund in bth pstures fr the fur-mnth perid signifintly (P < 0.05) mre eggs whih were vered with litter were revered IR the lw grss psture thn itt ther tretments. E995 Iãid diretly int pstures -In the high grss psture mre eggs were revered fliwing vipsitin thn fter fur mnths but the differenes were nt signifint (P > 0.05). In the Iw grss psture signifintly (P < 0.05) mre eggs were revered fliwing vipsitin in the litter tretment thn in the ther tretments. Als, signifintly (P < 0.05) mre eggs were revered frer fur mnths in the lirter thn thse lid in the su. The egg redutin verged 58% fter fur mnths in bth pstures using this methd f egg plement. The egg redutin fter fur mnths in bth pstures ws greter i the tretments where eggs were lid diretly int the su thn thse IM int litter ver su. SnnII sks f eggs pled in pstures - The verli egg redutin using this methd verged 73%. Five pen sks uld nt be fund fter fur mnths s survivl in sl' r!itter r between pstures uld nt be determined. In the higli grss psture the npy height in My verged 34 m nd in September 23 m. The plnt ver ws 65% in My nd 61% itt September. The litter deresed frm n verge f 64 g per qudrt in My t 55 g in September. I the lw grss psture the npy height i My verged 16 m nd 9 m in September. The plnt ver deresed frm 57% in My t 43% in September. The verge munt f litter ws 12 g per qudrt IR My nd 15 g i September. Preipittin (mm) befre nd during the test ws s fliws: April (69.2), My (56.7) June (11.7), July (80.4), August (21.7), nd September (33.0). Thrughut the dry sesn mderte t hevy rin shwer (> 20 mm) urred every 3-4 weeks. During the!st week in September sme preipittin (6.0 mm) resu!ted in prtil egg hth but the mjrity f eggs begn t hth fllwing 43.1 mm f preipittin during the perid f Otber 8-11. At this time nymphl density i the high grss psture ws 14/m t nd 81m 2 in the lwgrss psture. lietins f generl insets frm the mp Grnde pstures whih my inlude ptentil predtrs f spittlebugs re shwn in Tble 3. Mny mre spiders (Arneid) were lleted itt the tl1 grss psture thn in the lw grss psture. It is pssible tht sme fthe spiders nd mntids might prey n either spittlebug nymphs r dults. The shrt grss psture prvided fvrble hbitt fr grsshppers (Aridide) nd their presene is signifint sine they lng with spittlebugs mpete with livestk fr the vilble frge. Experiment 2 There were n signifint differenes (P > 0.05) in the men number f eggs revered fliwing vipsitin (2.9 ± S.E f 1.01) nd thse revered lter in the high grss psture (3.3 ± 1.37) nd the lw grss psture (0.3 ± 0.21). First genertin nymphl density n Nv. 1 i the high grss psture ws 551m 1 nd 161mt in the!w grss psture. l My, npy height in the high grss psture verged 52m, nd ner the end f August 28m. The plnt ver ws 58% in My nd 63% in August. The grss height in My in the lw grss psture verged 58 m (befre grzing) nd 12 m in August. The plnt ver deresed frm 62% in My t 10% in August s result f hevy grzing nd trmpling prir t the strt f the study. O ISUSSI ON Bsed n the results f these tw experiments it is pprent tht usully there is lrge redutin in spittlebug egg numbers frm the time fvipsitin in Mrh r April t the time f hthing in September nd/r Otber. The ne exeptin in this study urred i the ungrzed psture t Durds, where grss height nd plnt ver remined high during the dry sesn. At this site 33 eggs were revered in August frm the higli grss psture mpred t 3 in t}ie '0w grss psture. A ttl f 29 eggs were revered fliwing vipsitin in My, inditing n egg redutin in the high grss psture. Pesq. grpe. brs., Brsíli, 21(12):1237-1243, dez. 1986.
1240 G.B. HEWIrI' ( 4, 0 0 (, w _ml OON.w r E m r.no +1+1+1+1 +1+1 (0(0(0(0 (OOfl eiqu0 p (00, ')'NO N(NO 0 O Z O -. 5 0 > 5,O O ) O) - >. -. O=0 t.e2 E O= Eg (0 0 (0 à ) 000_ 000L E t -.0 00 > O O ±.-ç4ç4. j B-.rti 4, O" O'flOO tno0 Nr fln çujj.-,-,_,-.- +1+1+1+1+1 i+i +1+1+1+1 (0fl.0.O wix,o q N uw ( (,, 4, ' ( '(4 E.5.E.EE.E (0 '....... E s!e!ee!22 O 2,4fl' & _t g's E-. Ç Pesq. grpe. bts., Brsíli, 21(12):1237-1243, dez. 1986.
ENVIRONMENTAL FATORS AFFETING SPIflLEBUG EGG 1241 TABLE 2. The perentge f eggs hthing f ter remining in the pstures during the dry sesn, mp Grnde, MS, Brzil, 1985. Hth/ Hth/ Hth/ Hth/ Hth Type f egg plement Tretmnt litter r pstu re plement piement n bth pstures/ SOU Iluer SOU pienient A. Eggs lid in lbrtry High psture: & pled in pstures Eggs in litter 77 84 Eggs in sil 91 Lwpsture: 69 73 71 Eggs in litter 66 60 Eggs in sil 36 B. Srnll lsed sks ntining Hiqh psture: knwn number f eggs pled Eggs Lii lunr 74 65 in pstures Eggs in sil 56 Lw psture: 72 58 65 Eggs in litter 69 65 Eggs in su. Adults ged 'ri pstures nd High psture: eggs lid diretly int field Eggs in litter 38 55 Eggs in sil 100 49 I_w psture: - 52 Eggs in litter 51 51 Eggs in su - Ali tretments mbined High grss - 74%, su 66% Lw grss - 59%, Iitter '66% Ffrst genertin nymphl unts n Nv. 1 ls shwed tht mre nymphs were present in the higli grss psture (551m 2 ) thn in the '0W grss psture (16/m 2 ) t the Durds site. Sine bth pstures were nerly equl in terms f vegettive hrteristis when the eggs were being lid by the nturl spittlebug ppultin, then first genertin nymphl unts shuld be gd inditr f egg survivl between the tw pstures. Thus, egg redutin wuld be 71% bsed n nymphl unts. Ab in the mp Grnde pstures mre nymphs were unted in the high grss psture (141m 2 ) thn in the lw grss psture (81m 2 ). Hwever, these pstures were nt equl in terms f vegettive hrteristis when the dutts were lying dipuse eggs, nd s mre eggs uld hve been Iid in the high grss psture. Therefre, these nymphl unts d nt neessrily revel egg survivl between higli nd lw grss pstures but my indite preferene fr vipsiting in high grss pstures. Lwer nymphl unts in the lw grss psture my ls be due t greter grzing pressure. Thus, it ppers tht grzing nd the trmpling effet f livestk during the time the eggs re in the grund is unfvrble t egg survivl. Als t the mp Grnde site mre eggs tht were lid iii litter r were vered with Iitter were revered in September thn eggs tht were lid in su. Pstures with well-defined litrer lyer nd minimum grzing pressure shuld be mst fvrble fr egg survivl. At the mp Grnde lie when li the tretments were mbined the perentge f eggs hthing Ws the sme (66%) fr thse revered frm the sil nd thse revered frm the litter. Hwever, the hth ws higlier in the tl1 grss psture (74%) thn in the lw grss psture (59%) (Tble 2). If spittlebug ntri is mjr nsidertin then shrt grss pstures with firiy hevy grzing pressure shuld derese egg survivl nd thereby Pesq. grpe. brs., Brsili, 21(12):1237-1243, dez. 1986.
1242 G.B. 1-TE win redue the verlt spittlebug ppultin. Hwever, in entrl Brzil mst pstures re grzed s tht frge height is mintined between 15m -20 m. This height seems t prvide mximum frge prdutin nd qulity resulting in ptimum beef gins. Therefre, the disdvntges f mintining grss > 30 m pper t utweigh the dvntges. Likewise, grss height mintined belw 10 m will nt prvide the best utiliztin f the frge resure. Wiegert (1964) pinted ut tht the vilbility f fd fr spittlebugs is relted t the rte f plnt prdutin nd nt neessrily t the stnding rp. This uld explin why tl1 grss (nt high prdutin frge) reeives less feeding dmge thn shrter fster grwing frge (Mrtin 1983, Rmir et i. 1984). TABLE 3. Sme invertebrtes lleted frm 'LOW" nd "111G11' gxss pstures frm July t Nvember. mp Grnde, MS, Brzil, 1985. Dte iietel Number f invertebrtes lieted Fmily r rder Aridide Arneid hryspide Mntide Ttis Lw grss psture 19107 32 18 50 02108 15 15 2 16/08 16 9 25 10/09 35 3 38 02110 36 7 43 10110 30 3 33 01111 35 3 38 Ttis 199 58 2 259 F4igh grss psture 19/07 4 23 1 28 02108 10 48 2 2 62 16108 1 34 3 38 10109 8 11 19 02/10 16 14 1 31 10110 13 38 1 52 01111 6 5 11 Ttis 68 173 3 7 241 A mjr prt f this study ws n ttempt t determhie the number f spittlebug eggs surviving the dry sesn nd the degree f hth. In nther study (unpublisl-ied) the uthr determined tht there ws 66% redutin in egg numbers during the riny sesn in entrl Brzil. Iii the present study three methds were used t pie eggs in pstures nd evlute egg survivi. The verge perent egg redutin per methd ws s fllws: smii sks ntining knwn number f eggs (73%), egg lid diretiy int the psture by ged femles (58%), nd eggs Iid in ups in the lbrtry nd pled in the psture (94%). The methd using smii sks f eggs ws thught t be the mst relibie sine knwn numbers f eggs were pied iii the pstures. This methd is used t estimte egg survivl til hthing begn, s fllws: Disregrding the ltin f the sks in pstures (under litter r sil), ttl f 16 lsed sks nd 16 pen sks were pled in pstures t the mp Grnde site. Eh sk ntined 20 dipuse eggs. After fur mnths nly 15 lsed sks uid be fund nd thus the ttl eggs revered shuld hve been 300. Hwever, 65 eggs were missing frm the ised sks, r 4.3 eggs per sk. Oniy 11 pen sks were fund whih riginily Pesq. grpe. brs., Brsíli, 21(12):1237-1243, dez. 1986.
ENVIRONMENTAL FATORS AFFETING SPITFLEBUG EGG 1243 ntined 220 eggs. Using rretin ftr f 4.3 eggs missing per sk 173 eggs (4.3 xli.47; 220-47.173) shuld hve been fud in the pen sks, ssuming tht n predtin urred. Atully, ttl f 46 eggs were fund in the pen sks, tini 73% egg mrtlity uld be sribed tó predtrs, svengers, et. This is in dse greement with the 71% egg mrtlity determined fr the '0w grss psture t Durds bsed n nymphl unts between the tw pstures. Of the 235 eggs (300-65) revered frm the lsed sks, 81 (34%) were desited. Of the remining 154 pled t hth, 54 (35%) filed t hth nd were lbeled nnvible. With this infrmtin it is pssible t estimte egg survivl. Assumetht 235 eggs re in psture t the beginning f the dry sesn. After fur mnths, 73% f the eggs re lst t predtrs nd svengers, 53 re left t hth. Hwever, 69% f the 63 eggs will nt hth (34% desited + 35% nnvibte). Thus nly 20 f the riginl 235 eggs r 8.5% survived the dry sesn. li wuld be pssible t estirnte first genertin nymphl densities if egg densities re knwn, ONLUSIONS Generily there is lrge redutin in dipuse egg numbers between the time f vipsitin nd the time f hth. T}ie survivl rte ws estimted t 8.5%. Spittlebug eggs seem t hve higher survivl rte nd hthing suess in pstures with the fliwing hrteristis: (1) grss height >-30 m; (2) bundnt litter; (3) plnt ver> 50%; (4) miniml r n grzing. First genertin nymphl unts t the strt f the riny sesn ls shwed tht nymphl density ws higher in pstures with the bve hrteristis. This indites tht high grzing pressure resulting in iw npy ver will be unfvrble fr spittlebug egg survivl. Hwever, pstures with grss height f 15 m - 20 m pper t prdue high qulity frge neessry fr ptimum beef prdutin. Therefre, li my nt be enmilly dvntgeus t mintin grss plnt belw 15 m while t the srne time plnts ver 30 m high inrese spittlebug egg survivl. AKNOWLEDGEMENT This wrk ws nduted while n ssignment with Inter-Amerin Institute fr pertin n Agriulture, Orgniztin f the Amerin Sttes, Sn Jsé, st Ri, nd Empres Brsileir de Pesquis Agrpeuúi nnpg, prjet number 800.84.06211. The uthr thnks Esther Guimrâes rds fr liwing this study t be rried ut in pstures under her supervisin, nd Léli Inês Zmpieri Ver, Mrlene. Mnteir, nd Irineu viine fr lbrtry nd field ssistne. REFERENES MARTIN, P.B. lnset hbitt mngement in psture systems. Envirnm. Mnge, 7:59-64, 1983. RAMIRO, ZÀ.; MIRANDA, ia. de; BAT1STA FILHO, A. Observções sbre flutuçâ de igrrinhs (Hmpter: erpide) em pstgem frmd m Brhiri deumbens mntid em diferentes níveis de desenvlviment vegettiv. An. S. Entrn!. Brsil, 13:357-70, 1984. WIEGERT, R.G. Ppultin energetis f medw spittlebugs (Philenu: spumrius L.) s ffeted by migrtin nd hbitt. El. Mngn, 34:217-41, 1964. Pesq. grpe. brs., Brsíli, 21(12):1237-1243, dez. 1986.