Dec 6, 1986 - :ics of house fly resistance to car- ... growth and economic yield were significa nt ly lower among ...... additional tiefuiiatinr : ft,htt«topping Ma V.
e
Effects of Simulated Tobacco Hornwor m (Lepidoptera : Sphingidae) Defoliation o n Growth Dynamics and Physiology of Tobacco a s Evidence of Plant Tolerance to Leaf Consumption '
' gents : a review . Trans . R . Ento 27 : 115-140 . . Predator insecticide relation Mem . Ser . 7 . Glasser . 1952 . Selection fo r a beneficial insect parasite . SciBiochemical genetics of insecti-
DOUGLAS NI . KOLODNY-HIRSCH, : JAMES A . SAUNDERS, ' AND FLOYD P . HARRISO N
. el . Rev . Entomol . 21 : 179-197
cans of avoiding or amelioratin g icicles, pp . 244-249 . In Proceednal Congress on Plant Protection,,, ;
3~cpartment of Entomology Universityof
Environ Enimoc,t 15 : 1137-1144 (19th5' ' Simulated tobacco hornwerm, Maw/two sexta (L-), defoliation was conducte d by hand at four growth stages of tobacco, Nicottana tabacum (I_ ) . to investigate potentia l compensatory nn)(b :biisms for buffering ',Mar losses . Plants defoliated at Man! establishmen t and posttopping growth stages employed several compensator\ processes including a! l~• riods of increased efficiency in assimilating dry matter, necasionaliy correlated with increase s in chlorophyll, soluble proteins, and ribulose 1 .5-hisphosphate :arboxy!ase nxvgenase cm, tent ; b ., partitioning of assimilates to leaf tissue at expense of support structures ; c) increase d leaf area per unit of total plant dry weight, ;i ; delayed l>!ant sc•nr>cence . At ,maturity, despa e these compensatory mechanisms, growth and economic yield were significa n t ly lower among plants defoliated before the topping growth stage . Our results suggest that reduction i n growth and yield was related to summation of reduced leaf area and lower net assimilatio n rate among remaining foliage . Plants defoliated at the posttopping stage, however, showe d no significant yield loss or impairment of growth . This study pr ovides additional evidenc e that plants have evolved physiological mechanisms for minimizing adverse effects of defoli ation by leaf-chewing insects . ABSTRACT
Changes in resistance to DD T • :r{i~it'orns Rol>w . (H ymenb]> (' a Zool . 35 : 629-4 i33 '4 . Russell & N . E . Savin . 1980 . .:dc to probit of logit analysis . U .S . ithwest For . Range Exp . Stn . Gen . S. . Hoy . 1981 . Genetic improve alus occidentalis : selection wit h
noate, and carbaryl and geneti c . 74 : al resistance . J . Econ . Entomol
304-307 .
Shrivastava & J . E . Casida . 1968 . :ics of house fly resistance to car chemicals. J . Econ . Entomol . 61 : Mass rearing techniques, pp . 213 T . Semeria & T . R . New [eds .); oidae. Junk, The Hague . )a Hon
6 November 19S5 ; acccp
Maryland,
College ?':+rr . Naryland 2074 =
orniew, J . It . Berge & A . Cuanv . d auxillancs r .'sist :uits mix per dons les programmes de lutt e fiction 65 : 1-7 . Canard . 1984 . Feeding habits , unard, Y . Semeria & T . It . New hrysopidae . Junk, The Hague . l . Biologica 1- . Murphy . 1984 p p . 220-225 . In NI . Canard, Y . . •w [eds .], Biology of ( .1 rysepidac
Plapp, Jr. 1982 . Biochemical :tee to aryl carbamate insecticide s mite, Afetasefulus occidentalis .
wer,' tern
KEY WORDS
Manduca sexta, simulated defoliation, tobacco, yield los s
INSECT DAMAGE to the tobacco plant has been wel l documented (Lawson & Rabb 1964, Mistric & Pittard 197 .3, Johnson 1975, 1979, Cheng 1977, Colodny-Hirsch & Harrison 1980, 1982, 1986) . How ever, with few exceptions (Kolodny-Hirsch & Harrison 1982), little recognition has been given t o the ability of tobacco to compensate for insect in jury . In light of previous studies, perhaps ther e exists a " tissue reduction level " (McNaughton 1979 ) tobacco that is equaled or exceeded by compensatory growth, resulting in no net loss of yield . Kolodnv-Hirsch & Harrison (1986) recently re ported the results of a study that quantified th e relationship between tobacco hornworm (THW) , Alanduca sexta (L .), and tomato hornworm, \ .f quinquemaculata (Haworth) . and leaf yield o f Maryland tobacco at several growth stages . Th e results of that experiment provided a rationale fo r inv estigating compensatory growth and foliar yiel d
Tins article reports the results of research only . Mention of a
I'o 'prietary
product does not constitute an endorsement or a rec ern mendation for its use by USDA . 'Current address Maryland Dep . of Agric . . Gypsy Moth In 0 .grated Pest Management, 50 Harry S. Truman Pkwy ., Annap„hr . \ID 2 1401 . ' Tissue Culture and Molecular Binloaay Ag ri ; Pies. Center, belts tIe' \tD 20705. Lab USDA . Behr: iUt
of tobacco following THW defoliation The objectives of our study reported here were to examin e the following : 1) if tobacco, :,'icotiana tabacu m (L .) ` Maryland 872 ' , is capable of compensatin g for moderate defoliation equivalent to that cause d by one THW per plant : 2) if tolerance to defoliation increases with plant maturity at the time o f leaf removal ; 3 if the major compensatory processes involved included a) enhancement of ne t photosynthesis, accompanied by either increase d chlorophyll, soluble proteins, or ribulose 1 .5-bisphosphate carboxylase oxygenase (RuBPase) activity or b) diversion of dry matter favoring leaf biomass .
Materials and Method s Experiment Design and Method of Defoliation . N . tabacum ' Maryland 872 ' was transplante d on 26 May 1982 and treated with acephate an d fenamiphos in the transplant solution at the recommended rate . Weeds were controlled by per iodic mechanical cultivations . A single applicatio n of aidicarb 15 granular was made after 8 weeks a t the rate of 1 .68 kg (AI)/ha for aphid control . Flowers and suckers were removed by hand a t anthesis . Topp :ng was done- by breaking stalks lf)
1138
ENVIRONMENTAL ENTOMOLOG Y
Vol . 15, no . li
~~~~ 986 ,,,,e: -~
KOLOD N
nodes below the main flower terminal followed by sired at 645 and 663 nm in a spectrophotometer -' o' A 40 an application of maleic hydrazide at the recom- (Bausch and Lomb) . Concentrations of total chlumended rate Plants were topped completely after rophyll were calculated by the formula of Arno n 10 weeks and harvested at maturity after 13 weeks . (1949) . 6° The experimental design was a randomized 2) Soluble .Proteins: :From each leaf sample) complete .block-with -four treatments (defoliation g fresh weight was excised and homogenized in a 40 l date) and three replications . Plots consisted of eigh t tnurtar and pestle using 5 ml of 0 .1 JI Tris-11( : l rnw'S 5 .5 in long containing 10 plants each . Ross' s buffer (pll 7 .9) containing 1(1 m :\1 NlgC1 2 , 5 nul l 20 v V.ere spaced 0 .89 m apart . Plots Were separate d sodium ascorbate, 5 mM dithiothreitol (D"I'T), an d 10 tr E . +. . by single buffer rows and two buffer plants withi n 0 .25 mM Na_EDTA . The mortar and pestle wer e 6 38 54 the row . Defoliation was started on 30, 38, 49, an d rinsed with 2 ml of grinding solution and the suu 2c E 30 (i8 clays posttranspiarnt when the plants were in th e pernatants were combined for a total volume d 7 8-leaf (plant establishment) . 14-leaf (vegetative) , ml . Samples were centrifuged for 10 min ;i : 2d l,utttutitig, and p Sttopping gloWth stages . respec- 10,000 x g and the supernatant seas chilied in al l T tively . All results were subjected to analysis of vari- ice bath for subsequent protein and I(ulil'ase as • ance for a randomized complete block design Be - says . Protein determinations were made on 50-a l 10 10 4 fore each defoliation date, selected plants adjacen t aliquots of the leaf homogenates by the Coomassi e to experimental plots were infested with late third - blue dye-binding method of Bradford ( 1576) . Pro14 30 38 or early fourth-iustar "I"H\\" at one larva per plan t tein content was expressed as mg protein•gra m 22 Dais Pust-Defo and covered with fiberglass screen cages . As feed- fresh weight (gfw)-' of leaf . ing progressed, drawings were made showing th e 3) RuBPase: 10 A rno] of sodium bicarbonat e 1 . Net assimilation rate 1 number of damaged leaves per plant and the ex - containing 5 iCi of NaH"CO 2 in 50 al of protei n control (0) tobacco plants at f o n tent and site of injured leaves . Based on these ob- supernatant, and 50 al of 0 .2 mM RuBP were inplant establishment . (B) vegetati v servations, composite drawings were compiled tha t cubated in a reciprocating water bate- at 30°C for (D ~ „posttoppinb . Significant diffe r indicated by " . subjectively illustrated average defoliation by on e 20 min . with 250 µl of 0 .1 M Tris-HCI (pH 7 .9) , THW per plant . These drawings served as guides containing 10 mM MgC1 2 , 250 mM N a 2 EDTA, an d for defoliating test plants by hand . Plants were 5 mM DTT . The reaction was stopped with 10 a l defoliated over a 5-day period by removing 180 , of 6 N HC1 . A 100-al aliquot was taken and drie d determined using an area m e 345, 345, and 420 cm' of leaf (=1,290 cm') on day s in a 20-m1 scintillation vial under a vented hoo d plant parts were put in pape r 1 . 2, 3, and 5, respectively . Plants were defoliated to drive off unreacted "CO : . The sample was re 80°C for 48 h for dry weight d in this manner as this closely simulated the exten t suspended in 1 ml of distilled water and mixed The dry weight and leaf t and node of TH'SV feeding. All excised leaf tissu e with 10 ml of scintillation cocktail composed of were used to calculate the n < was dried at 80°C for 2 days and weighed . At th e 500 ml of Triton X-100, 1 liter of toluene, 0 . 5 (NAR), the specific leaf w•ei g ' 8-leaf, 14-leaf, buttoning, and posttopping stages , (set/vol) 2,5-diphenyloxazole (PPO) . and 0 .02 leaf area ratio (LAR), as o u 3 .3, 3 .9, 3 .0, and 3 .0 g of dry-weight leaf wer e (wt 'vu1) 1 .4-bis[2-(5-phenyloxazoi%l)]-benzen e (1967) . NAR is defined as tin removed, respectively . Treatments were equiva- (POPOP) . The amount of "CO, incorporated int o material per leaf area per uni t lent to 50, 20, 7, and 5 c7 removal of the total lea f nonvolatile photosynthetic assimilates by the carered a good index of net phot area, respectively . boxylase enzyme was quantified using a liquid scin the ratio of leaf dry weight pe r On day 5 of each defoliation period, one nod e tillation counter (Packard model 2 .125 Tricarb) . Af is the ratio of leaf area per u r was tagged from the upper, middle, and lowe r ter correcting for quenching, data were expresse d The harvest index, representi n third of the plant canopy for future biochemica l as dpm . nmol-' -min-' • g protein -' • gf w- ' laminae and stem relative to t analysis . The upper two nodes were selected fo r and the economic yield, whi c Growth Analysis . Immediately before the firs t leaves showing 25–50% excision . The lowest nod e defoliation treatment, three uniform undamage d laminae and stem, were also c was selected for an undamaged leaf . Identica l plants were harvested to serve as " t, " plants for nodes were concurrently tagged on control plants . the growth analysis described below . Total dr y Result s Partially excised leaves were tagged and later asweights and total leaf areas were determined fo r sayed because we expected changes in photosynEstablishment Stage . In th e these " t, " plants . Thereafter, plants were harvestthetic chemistry to have been more prevalent i n ed on 1 July, 13 July, 2 August, and 22 August ; 1 0 following defoliation . NAR w a those leaves . July, 17 July, and 22 .August ; 20 July . 26 July, an d and treated plants, but by 1 8 Biochemical Analysis . From each tagged leaf , 22 August ; and 9 August and 22 August, for th e tion, NAR in treated plants W a ca . 5 cm' of laminae was excised, placed in a plasplant establishment, vegetative, buttoning, an d in controls (Fig . 1A) and, as a tic bag (Ziploc), labeled, and transported to th e posttopping stages, respectively . At each harves t stem biomass was much lower ( laboratory in a cold styrofoam chest . Leaf disk s date, one plant within each replicate swas cut a t Also, aiming treated plants, sig n were analyzed for chlorophyll, soluble proteins, an d the stalk, placed in a large plastic bag containin g total r'`ntemni S', P,t)o-Si5 was s i RuBPase activity according to the following pro- chilled water, and transferred to the iai_,uratury . A Rulil'ase enzyme from the low ' cedures . soil core (35 .5 cm diameter by 35 .5 en ; deep' conversus 16 dpm •umnol-'•min-' • g 1) Chlorophyll : A leaf disk (1 cm) was removed , taining roots % vas removed . placed in a large stee l 0.05) . However . 20 days latc h weighed, and ground in cold 80'vol vol) ace - funnel, and rinsed over a C2-mesh screen sie g e t o was 1 . ::-fold higher than that o f tone (2 ml) in a mortar and pestle The mortar wa s extract roots . (Fig . 1 :A) . rinsed with an additional 2 ml for a total of 4 ni l By maturity, the harvest i In the laboratory, plants were washed free o f acetone homogenate . After centrifugation for 3 mi n soil and separated into leaf (laminae), stem (petitreated plants allocated a great e at 800 x g , the absorbance of the extract was mea - oles and midribs) . stalk, and roots . Leaf area was assimilates to leaves than cont r
Vol. 15, no . 6 . u ., i . ,,uiet 1 ntcentrattons of total chlo I by the formula of Arno n = rom each leaf sample, 0 . 5 .sed and homogenized in a g 5 ml of 0 .1 M Tris-HC I ling 10 mM MgCl 2 , 5 m M 1 dithiotllrcitol (DTT), an d he mortar and pestle wer e aiding solution and the suned for a total volume of 7 ntrifuged for 10 min a t rernatant was chilled in a n l 1)10te111 :ul ;i Ituli l ' ascence . There is a substantial literature suggesting tha t following defoliation there are many physiologica l and growth responses that may confer to the plant
huLU t December 1986 ter« ~. .;t ., a degree of tileralltt' to i Donald 1956, Lucas & Asau , Harris 1974, Dyer & Bokh a 1979, Caldwell et al . 1981) . severe defoliation rarely oc c the present stocis, and (ithe ( that tr, :utc. i . it , insects that bake Li ) chemical barrit'rts) cc lilt :o . . processes that lid in Mill i
1
Frtnidt'd t i nt' • IliCal assistance . .;1SO, t . t•. are 11 , pater Science Center, College 1 funds for corn! . .rr tic, i' S l y tc \\ :iliam K Al :e n that provided a basis for this w debted-.to Thelma Golden, Kart S . Harrison for their assistanc e dissertation submitted by D .iS I faculty of the Univ . of ?slarvla m of the req uirements for the Pt : entinc Article No . A-4226, Con t Maryland Agric . Exp . Stn . Reference s .Amon . D . I . 1(11 0 . t . iin : Polsphenoi ixi-,likes in ilcr e 24 : 1-15 .
Avundzian . E . S . & C . G . Gab , physiological nature of acti n Tr . Bet Ir,et =\s . ; :! \ .ci s Borth . P . W . & F . 1' . Ilarri .rn i distribution, I ; ee righ worm (Lepidi,pler a ulations in t(,t :tller :, .c.Lerc'i a Univ . of \iarvland . Cnliec c Bradford, \I . \I . 1976 . :\ ra t for the quantization of nritert iglu utilizing the principl e Anal . Bioclerr : 72 . 2-1s-2 :5 4 Caldwell, .i ' . )1 . . J . H . Itichar,: Nowak & It . S . Dzurt•c . I t bivory : pia toes nthetic Cap] cation in ticti semiarid :? , Oecolocia Berlin' 5 e i 1-1-2 Cheng, H . 11 . 1977 . Flue-cu r by the ballot(' hnrn•.c,•nn . lata (Lepidnptera S1(11in,etil : levels in Orlturit• ( :, :1 : End , Davidson, J . L . & C . )1 . Dona l of sicards of suhtc'rrancall c l ere•nt•e ta leaf area :\ux ; Detiing, J . K . . )1 .1 . 1) .t•r & I ) photosynthesis • at rr .ni r Bo uiiI ta ; : _ Ot'e'nloula herl!n' 4 :27- 1 Mier . '\i . 1 . & 1 . 1 . . Bokhar i nt(rractionc . Stii, :ic•s ni th e grazing eltl bled' grainy goes: Ericsson, A ., J . Hellkvist, K . I I Larsson, E . Mattson-Djo s Consumption and pins-cross
saVol . .15, no . 6 IL, s l lggos
.. .
tar yield aiming tottion appeared to b e if area and lower efatter among remain :on (1986) recentl y ,' Cattle more tttlt'ran t ti;l rssn t• plant devolesented here are onl y Conclusion . Both thei r show that no signifi = -Itod from defoliatio n ill slake I l„ss, s''t . II I tisistcut m o od in sit l d melds occurring bold liuttonint; nnt dinar bill nt .i\ b e It'lcl leti, dtlll ~ hit s ul IlrnI ('I repit,•atr„ n i• („h .tlion r,•_i :`i,• s .i t I ., .Irs• ' did "I [eat tissuo earlier renitude . These data d o ode earlier by Lawso n the equivalency be )f leaf yield at harvest . ion is complex (Har e Its id lincants i. 'inert , lative to leaf area ar e e a variety of functions production, includin g iesis, storage, and tran functions are modifie d ge . Therefore, defoliabe rather distant fro m yu :ts leading to growt h delays the onset of se - 4 ice in response to lea f a wide Tango of plant s et al . 196,5 . Gifford & ed bs inhibition of prome degradation . redue- . ifusion, reduced starc h f photosynthetic mate nn of mature leaves . I n rt senescence was doc u following defoliation at ' act . the cultural practice- a flower stalk' is known = and protein synthesi s 1956), presumabl y 'e of root-derived cyto . S' . In the present study, . i\ytr :g topping ma y have_ tion by the remaining _ lone and . thus, delayed ,
rat fart si : .sting t hat ; arc many ~p~hiysiological j Wray confer to the plant
December 1986
Kot .onNV-HiHSCH ET Al ..' PI .ANT
Tonsil
4
\'rF Tr)
r s r- C'rr\•ki '
l .,o,c , 1, ti,lstA tIas tdsul l ill gross Hi pl ot',', .,s Iii l„•t'd Ie•-,• ;Il lllg irlot•st s Bull . 32 .53 - -54 3 )oihdd 1958 . Locos d As :uia 1 :05 . Osburnt• 1973 . Evans . L . T . led .) . 1978 . Crop phvsluings Snow cas e Harris 1974, Dyer d lfokltari 197(1, McNaughto n histories . Cambridge t'Ilis' . I .ondon . 1979 . Caldwell et al . 1981 ) . Although tolerance t o Gifford . It . M . & C . Marshall . 1973 . Photosynthesi s Cr,' defoliation rarely occurs, results explored i n and assimilate distribution in Lolium mul(ijloru m the present study, and others, collectively sugges t Lam . following differential tiller defoliation . Aust . J . that many plants respond to those leaf-chewin g Bin] Sci 26 517 11,2 1 1 I,, .I .s,• insects that 11 .isr In i ,l,lnt s dolonsiv'' Il, km . ( . . I973 . c :ul,,n,'snii inmeal ttarltttts ; with :iii allay of compensatory only of the tobacco plain I . Inferences from a situ processes that aid in buffering potential losses . ulation . Aust . J . Biol . Sci . 26 : 1057-1071 . — =Aare, J . Z. 1980 .- -impact of defoliationTh the Cit i nrado ildtale hnetlry nti n , 'talr , yi!•I,t's Ebb . Aeknowledgment n, I Harris . I' . I'17 1 . 1,1, 6\1,1,16,111611 14 ji. ,,l \ \(r ,•spn•ss i ii : Note n,• ct .,litUde lu ( . ( . M i ke,-, ss h o Mt:m ws tolluss I I Il, .rrI darn,,Cr :\gr,rl'a','ssslen, . I=I .,c tded the e-spt•rimcntal station facilities and tech 1 219-22 5 al assistance . Also . sit• arr Most grateful to (ht• C6111 .Iolm .on . A . \\ . I c 175 . \,I!Intl, n ill IIii' c,", ., i ti, n•nce (',•nt,•r, ( :allege I'atk . \td ,fur prmidio t I• . , s hoof Mit,aenl nilestall„n Ies .F I I ~,~! rolnlruter usage . spe, ial thanks are est,•nd,' d ,n l „~ , .ti .11s ' u 1 Il f \t, II• . I, I th :n p! lilt Ili.u . .n,u 1 '1 7 9 . I i .l, .l,oi CI,l . .iii, o . .I .. :I ., bad', I,, : Illls \ .)t h . I ,11 .111\ . \\,' ,(rc I! 1 ` , at dllt,'l, III 'Lult zo .s s I hrinl .l (bilden . I .nrtl Il .nnnn . and ' I' assislai .,,• Ibi s Is .1 pi,rtidl , K ,1 ,tea-1lirth . U . M . \ i . I' . Damson . Pilaf . I , 's i \l F 11 „ Co, gia,iu .,t, ' liar loss assessments and economic decision-makin g is „t the lads . of Maryland in partial fulfillmen t for the tobacco budworm on Alarvlaod tr,l,,,,, ., , of the requirements for the Ph .D . degree . This is Sol Econ . Etiton,oi . 73 . 4, 5-4n,5 oho!), Article No . A-422:5, Contribution No 721S of th e 19112 . Comparative damage and teal area consump' .1 .~r'.i,l :tcf Agric . Esp . Stn . tion of the tobacco budworm and the corn earworm on Maryland tobacco ? Econ . Entomol . 75 : 16S-i72 . 1986 . Yield loss r, 11 , .. . allU . ,Inat, N References Cite d hornworms ;Lepidoptera . Sphingidae' at severa l A1-nom U . I . 1949 . Copper enzymes in chioropiasts . growth stages of Maryland tobacco . J . Econ . EntoPeiyphenolexicases in Bete vu :garia P liant Physiol . mol . 79 . 731-735 . 24 . 1-15 . Lawson, F . R . & R . L . Rabb . 1964 . Factors control Avundzian, E . S . & C . G . Cabrielian . 1956. On th e ling hornworm damage to tobacco and methods of physiological nature of aging on leaves of annuals . predicting outbreaks Tob . Sci . S . 1-15-149 . T :- Rot lost Akad \auk Arm . SSE 10 : 139-157 . Lucas . D . & R . D . Asana . 1968 . Effect of defoliatio n Borth . P . W . & F . P . Harrison . 1980 . Within-fiel d on the growth and yield of wheat . Physiol . Plant . 21 . . . :striouunn patterns of tobacco and tomato horn 1217-1223 . .,Lepidoptera Sphingidaei cog and larval popMarrs, D . IL 1964 . Growth rates in relation to assim:I,,bons in southern Slarviand tobacco . N1 .S . thesis , ilate supply and demand . I . Leaves and roots as limI.nits of Mass land . College Park . iting regions. J . Exp . Rot . 15 : 574-5S3 . Bradford . M . M . 1976 . A rapid and sensitive metho d Mc\aughton . S . J . 1979 . Grazing as an optimizatio :: • gi :antitation of microgram quantities of pro process : grass-Ungulate re•iationships in the Sere :ic this principle of protein-dye binding geti . Aril . Nat . 113 : 691-703 . oi .iicn, 7 -72 : Meidner . H . 1970 . Effect-of :soli/darnphotopentah c \I . . J . Ii . Richards. U . :1 . Johnson . Ii . S . and debudding in pcnnsylcurucr:tn an d \o ..ak & It . S . Uzurec . 1981 . Coping with her partial defoliation -1 host'ulus eafgaris on rates o f !, :' : .r.nsyntactic capacity and resource . allonet photosynthesis and stomata] conductances . 1 Es p n two semiarid Agropyron bunchgrasses . Bot . 21 : 164-169 . Berlin ' 50 : 1 .1 —224 . Mistric . W . J . & W . W . Pittard . 1973 . Darnas e t o II .- . It . H . 1977 . Flue-cured tobacco losses caused flue-cured tobacco ;is bi :dw,irm and con ; soak) hornworm . Jlcnduca quinquemacu earworm alone and at :arinus infestation rh•nsitie s Lelntiontera Sphingidae' . at various infestatio n Loot : Entomol no. -_--2 5 mono Can . Entomol . 109 : 1091-1095 . \eales . T . F . & L . U . lucid! . 19617 . The control , o tss i,s .nn . J . L . & C . M . Donald . 1958 . The growt h leaf photosynthesis rat ;• i,y the Iesr-I of assimilat e ss .trds of subterranean clover with particular ref concentration in Hat leaf a reyu•ss of the hypothesis . , re :ice t ti leaf area . Aust . J . Agric . Res . 9 : 53-7 22 . Pot Pie•. 3-4 .107-12 5 D, dins: - I . K . . Vii . 1 . Dser & D . T . Winn . 1979 . Net Oshurnt• . D . 19 7 3 . Alu :ual regulation of Cresol an d Iidsis . riot ,ec ii in, and rostrosvta o f doseiop :nc•nt . .i r' .0 ., :,d Inscsts . p .31-41 Is 1 1 .on : ercci .'u following simulated grazing . , F . \'anEm,lrri Hal p! .,m re, .aionsl .i ., s ,'.a .Burin : 41 . 127-13 4 Ies . Nest Yor k Uses, \I . I . & C . G . 13okhari . 1976 . Plant-anima l Peterson . R . B . & I . 7elitrh . 1'012 . Relationship he. ;iota st :idles the effects of grasshoppe r tisr, ., t„'t ( .O et,cl tlry ssc•i_!I t ;,i, . gr,tma Crass Ecology 57762_77 2 ._ tnulatinn in field-guns!, t,ii)acc', . Plant l'hysiol . -U . I --,m . A . . J Ilellks ist, K . Hillerdal-Ilagstromer . S . 677-6'55 . l .a r . .on . E . Mattson-1)jo- & 11 . la-nos. . 19110 . Radford . P . J . 1967 . ( :oat tl, analysis forr.tulae . thei r . . s is ittuptlihi arid pine- r in th hypotheses effects uses and abuser Cry . s 7 171-17 5
114 4
~E's'vino'AIF\T\L
Vol . 15, la ,
ENTOMOLOG Y
Ryle, C . C . & C . E . Powell . 1975 . Defoliation an d regrO‘N't1l in flit) !h i
pp . 481-499 . In J . P . Cooper [ed .], Photocvnthr . . : n,1 rnxLu tiyit . ~hffr :r ,•~ ns ~~,r~ ~ nt . uge L-tuv ., London . Thorne, J . 11 . & H . It . Koller . 1974 . Influence o f Wareing, P . M . Khalifa & K . J . Treharne . 1968 . assimilate demand On photosynthesis, diffusive resisRate-limiting processes in photosynthesis at saturat tances, transiocation, and carbohydrate levels of soy- - -- ing light intensities. Nature (London) 220'453-45 7 bean leaves . Plant Physic)] . 54 : 201-207 . Wnrrlhn ,se, II . w . 1 0 67 . The a ... F .,
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rant etaivsis ssa, and those that did i s ulation load for 91 . important variable t : KEY a'OP..DS
APHID . INFESTATIONS
on sha
problems in many urban arc
of aphids on the growth an , tree species include decrease d early leaf senescence and a i leaf size in the .'ear follow i 1971a,b) . These effects eer u tree mortality and often g o deleterious consequence of s ence in urban areas comes f production . Honeydew is h i heres to sidewalks, cars, et c trees . Sooty molds te .g ., Cc ; often grow on honeyde w both sidewalks and trees bt sticky and create a nuisanc e European white birch, B e probably the most commo n tree in western North A ;u e California, B . he ndula is n parks and gardens and is n o because of its pendulous ha aphids, Euceruphis het ula c calliptera (Hartit{), and B Borner, occasionally des clo p and produce copious arnu c birch trees . Homeowners a aphids frequently use prcvc n A previous stud y ed that this practice is ofte n ski et al . 1976) . Aphids Wer t trees that ssere s prayed ; :r s the highly a_e_reoatcd nat u tic us . 'Current address: Dep. of Entorn NY 14853.
