Evaluation of damage to satsuma mandarin (Citrus unshiu) by the leaffooted bug, Leptoglossus zonatus (Hemiptera: Coreidae)

Transcription

1 J. Appl. Entomol. Evlution of dmge to stsum mndrin (Citrus unshiu) by the leffooted bug, Leptoglossus zontus (Hemipter: Coreide) Y. F. Xio 1,2 & H. Y. Fdmiro 1 1 Deprtment of Entomology nd Plnt Pthology, Auburn University, Auburn, AL, USA 2 Deprtment of Entomology nd Nemtology, MREC, University of Florid, Ginesville, FL, USA Keywords dmge estimtion, feeding, Leptoglossus zontus, stsum mndrin Correspondence Dr. Henry Fdmiro (corresponding uthor), Deprtment of Entomology & Plnt Pthology, 31 Funchess Hll, Auburn University, Auburn, AL 36849, USA. E-mil: fdmhy@uburn.edu Received: August 5, 29; ccepted: December 8, 29. doi:.1111/j x Abstrct The leffooted bug, Leptoglossus zontus (Dlls) (Hemipter: Coreide) is key direct pest of stsum mndrin (Citrus unshiu Mrcovitch) in much of the Gulf Cost region of the United Sttes. The injury nd mount of dmge to stsum fruit cused by L. zontus dults nd nymphs t vrious insect densities ( 3 individuls per fruit) nd feeding durtions ( 14 dys fter infesttion) were ssessed in lortory nd field experiments. The prmeters evluted included fruit dmge symptoms, fruit colour, premture fruit ortion (PFA), fruit weight loss (FWL), percentge of dmged sections (PDS), nd soluble solids content (SSC) of the fruits. Feeding by L. zontus on stsum produced typicl dmge symptoms including the presence of green spots nd drk spots on the outer rind nd the collpsing nd drying out of the juice vesicles in the inner rind. Insect density nd feeding durtion hd significnt effects on most dmge prmeters. Fruit weight loss nd PDS incresed with insect density nd feeding durtion. Soluble solids content decresed with both fctors, nd ws lso negtively correlted to PDS. Premture fruit ripening (yellowing) ws recorded t densities of 1 or more insects per fruit. Premture fruit ortion ws significntly higher in fruits infested by L. zontus thn in uninfested fruits, but insect density my not fully explin the PFA dt. Leptoglossus zontus femle nd mle produced similr mounts of dmge, which were slightly more thn the dmge produced by the nymphs. In generl, the results were firly consistent between lortory nd field experiments, lthough some minor differences were recorded. The dt suggest n economic injury level of 1 2 L. zontus per stsum fruit. The results re discussed in reltion to the ecology nd mngement of L. zontus on stsum. Introduction Stsum mndrin, Citrus unshiu Mrcovitch, hs been grown for over century in the Gulf Cost region of the United Sttes (English nd Turnipseed 194). However, the lst decde hs recorded mjor increse in the production of this crop in southern Alm, fuelled by improved production nd tree protection methods nd strong industry nd stte support (Cmpbell et l. 24). Studies hve identified severl pest species cple of limiting the expnsion of stsum mndrin production in the region (Henne et l. 23; Fdmiro et l. 27, 28). In prticulr, two species of leffooted bugs (Hemipter: Coreide), Leptoglossus zontus (Dlls) nd L. phyllopus (L.), were identified s key direct pests of stsum with the potentil for mjor economic losses (Henne et l. 23; Fdmiro et l. 28). In southern Alm, the predominnt Leptoglossus spp. on stsum is L. zontus (Dlls), 694 J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH

2 Y. F. Xio nd H. Y. Fdmiro Dmge to stsum by L. zontus wheres L. phyllopus (L.) is considered minor pest (Fdmiro et l. 28). Recent surveys showed tht L. zontus is widely distributed nd perennil pest of stsum in Alm, which ws recorded t high popultion densities in most of the surveyed orchrds (Fdmiro et l. 28). Like mny other Leptoglossus species, L. zontus hs recently risen in sttus s pest of wide rnge of crops in the southern U.S., including cotton, tomto, eggplnt, sorghum, wtermelons, corn, peches, citrus, nd pecns (Albrigo nd Bullock 1977; Mtrngolo nd Wquil 1994; Johnson nd Allin 1998; Schefer nd Pnizzi 2; Buss et l. 25). In southern Alm, L. zontus dults typiclly move from crop fields (e.g., cotton, tomtoes, wtermelons, etc.) into djcent or nerby stsum orchrds in the fll when the fruits strt to ripen (Y. F. Xio nd H. Y. Fdmiro, personl observtion). A recent study by our group suggests tht stsum fruit is suitle host for L. zontus, which cn mintin modest to high popultions of the pest, but tomto is preferred over stsum (Xio nd Fdmiro, 29). Feeding on citrus fruit by leffooted bugs nymphs nd dults cn result in reduction in qulity nd quntity of fruits, including premture colour brek, fruit drop, nd unmrketle fruit (Griffiths nd Thompson 1957; Albrigo nd Bullock 1977; Henne et l. 23). The insects cn lso trnsmit yest disese pthogen, Nemtocer coryli Peglion, to fruit, which cuses dryness in the ffected wedges of the fruit nd produces bd fruit flvour (Henne et l. 23). However, severl of the bckground informtion nd dt necessry for effective mngement of L. zontus on stsum re missing, including the sence of systemtic ssessment of injury nd economic thresholds for L. zontus on stsum. The objectives of this study were to (i) chrcterize interior nd exterior dmge symptoms on stsum fruit cused by L. zontus; (ii) determine reltionship between insect density, feeding durtion nd fruit dmge; nd (iii) propose n economic injury level for L. zontus on stsum bsed on the dt from the ove lortory nd field studies. It is hoped tht the results will support the development of n effective integrted pest mngement progrm for mnging L. zontus on stsum mndrin. Mterils nd Methods Rering of Leptoglossus zontus Adults of L. zontus collected from stsum orchrds in southern Alm in the fll of 27 were used to strt lortory colonies. Adults were rered in wooden sleeve cges (6 4 3 cm; 5 pirs per cge) with screened wlls, nd provided lim ben seedlings (3 potted plnts per cge), fresh mture stsum fruits (3 per cge), fresh tomtoes (3 per cge) nd wter. The cges were checked dily to collect freshly lid eggs nd to replce diet, s necessry. Lim ben seedlings were replced monthly, wheres stsum nd tomto fruits were replced biweekly nd weekly, respectively. Stsum fruits used were hrvested from the field nd stored in the refrigertor until use, while tomto fruits were purchsed loclly. The rering conditions were 25 2 C, 5 % RH, nd photoperiod of 14 : (L : D) h. Lortory tests Dmge to stsum fruit by L. zontus ws evluted under lortory conditions (25 2 C, 5 % RH, nd 14 : (L : D) h during fll 28. Fresh, mture stsum fruits were weighed nd plced individully into glss jrs (18 cm long 7.5 cm dimeter, 1 fruit per jr). Newly-emerged L. zontus femles (2 5 dys old) were introduced into ech jr t one of four densities: (control), 1, 2, or 3 per fruit. The jr ws covered with screening nets. The set up consisted of totl of 48 jrs distributed into four groups of 12 jrs for ech insect density. Ech fruit ws weighed t 1 (12 replictions), 3 (12 replictions), 7 (9 replictions), (6 replictions), nd 14 (3 replictions) dys fter infesttion. At 3, 7,, nd 14 dys fter infesttion, three fruits were selected from ech group nd dissected to determine interior dmge. Fruit weight loss (FWL) ws clculted by compring weight before nd fter infesttion. The percentge of dmged sections (PDS) ws clculted for ech fruit by dividing the number of dmged sections by the totl number of sections (usully sections). The soluble solids content (SSC) of the fruit ws then mesured with refrctometer (Westover Scientific model RHB-32ATC; Settle, WA, USA). Similr experiments were performed with L. zontus mle nd lte (4th 5th) instrs. Erly instrs (2nd 3rd) were not tested bsed on preliminry experiment which showed tht they produce very little mesurle dmge to stsum. Field tests Field experiments were performed in two stsum orchrds locted in Bldwin county, southern Alm during 27 (preliminry tril) nd 28: Gulf Cost Reserch nd Extension Center (GCREC) J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH 695

3 Dmge to stsum by L. zontus Y. F. Xio nd H. Y. Fdmiro orchrd nd Coker orchrd. Both orchrds were comprised minly of stsum mndrin (Owri vriety) nd were not conventionlly spryed during the trils. For the 27 tril, three premture stsum fruits on tree brnch were rndomly selected nd covered with cge (35 15 cm dimeter) mde from white colour screening net. Leptoglossus zontus femles were plced into the cges t n pproximte density of (control),.3,.7, 1.4, or 2 individuls per fruit for period of 14 dys. Ech insect density tretment ws replicted four times (4 cges) per orchrd. On dy 15, the fruits were hrvested (by hnd) nd crefully trnsported (in plstic bg kept in ice) to the lortory where they were weighed nd inspected for externl nd interior dmge. A similr technique ws used for the 28 tril but with some modifictions. Two premture fruits were cged (insted of 3 in 27) nd L. zontus were plced in the cges t density of,.5, 1, 2 or 3 individuls per fruit. Also both femle nd mle were tested seprtely in 28. Ech insect density tretment ws lso replicted four times (4 cges) per orchrd. In both yers, fruits were ssessed for dmge by collecting the following dt: fruit colour, premture fruit ortion (PFA), fresh fruit weight (FFW), PDS, nd SSC. Sttisticl nlysis For the lortory test, FWL ws clculted s the difference in fruit weight before nd fter infesttion. Fruit weight loss dt were converted to percentges nd used in the sttisticl nlyses. Dt on dmge fruit sections (PDS) nd SSC were lso expressed s percentges. All dt were first normlized by using the rcsine squre-root trnsformtion (Öx +.5). Lortory dt (FWL, PDS, nd SSC) were first nlyzed with two-wy nlysis of vrince (nov) with insect density nd feeding durtion (dys fter infesttion) s the min fctors. Dt collected on dy 14 fter infesttion were further nlyzed with one-wy nov to test for effect of insect density on FWL, PDS nd SSC. Field dt (PFA, FFW, PDS, nd SSC) collected from ech orchrd on dy 15 fter infesttion were nlyzed with one-wy nov using insect density s the independent vrile. In ll tests, dt for the different stges (femle, mle or nymphs) were nlyzed seprtely. Significnt differences between mens were estlished by using Tukey-Krmer honestly significnt difference (HSD) comprison test (P <.5, jmp version 7.1, SAS Institute Inc. 27). Results Description of fruit dmge Leptoglossus zontus pierced stsum fruit skin with its mouthprts nd sucked fluids directly from the underlying vesicles. A green islnd on outer rind (fig. 1) nd necrosis on inner rind (fig. 1b) often ppered on injured stsum fruits. Drk spots were lso observed on some injured fruits. Feeding my lso result in interior fruit dmge including collpsing nd drying out of the juice vesicles (fig. 1c). Premture ripening (yellowing) of infested fruit ws lso observed in the field tests. There ws no difference in the ppernce of dmge cused by ll life stges of L. zontus. Lortory tests For L. zontus femle, two-wy nov reveled significnt effects of insect density nd feeding durtion (dys fter infesttion) on ll three prmeters evluted: FWL, PDS, nd SSC, s well s significnt density durtion interction on PDS nd SSC (tle 1). Insect density nd feeding durtion ech exerted significnt positive effect on FWL (fig. 2) nd PDS (fig. 3), but negtive effect on SSC (fig. 3). In other words, FWL nd PDS incresed with incresing insect density nd feeding durtion, while SSC decresed with both fctors. Similr results were obtined for L. zontus mle nd nymphs. The sttistics for both sexes nd the nymphs re shown in tle 1. For brevity, dt obtined on dy 14 of infesttion (feeding durtion of 14 dys) were nlyzed by one-wy nov nd presented in tle 2. In generl, FWL nd PDS incresed with incresing insect density nd feeding durtion, while SSC decresed with both fctors. For instnce, FWL incresed from 19.6% to 24.3% nd PDS from 3% to 71%, wheres SSC decresed from 8.4% to 6.3% t densities of one femle/fruit nd three femles/fruit, respectively (tle 2). The dt lso indicted tht slightly higher fruit dmge (FWL nd PDS) were cused by L. zontus femles or mles thn by the nymphs (fig. 3), lthough no sttisticl comprisons were mde since the dt for the different stges were not collected t the sme time. Field tests Feeding by L. zontus femle or mle cused notle dmge to stsum fruits s determined by fruit colour, PFA, FFW, PDS, nd SSC. In the 27 tril, only femle were evluted t both orchrds. 696 J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH

4 Y. F. Xio nd H. Y. Fdmiro Dmge to stsum by L. zontus () 1 2 (b) b1 b2 (c) c1 c2 Fig. 1 Dmge symptoms on stsum fruits infested by Leptoglossus zontus. () (externl dmge): control fruit showing no dmge (1), green islnds on outer rind of infested fruit (2); (b) (necrosis): control fruit showing no necrosis (b1), necrosis on inner rind of infested fruit (b2); (c) (internl dmge): control fruit showing no internl dmge (c1), infested fruit showing dried-out juice scs (c2). Anlysis of the dt collected t Coker orchrd showed tht femle density hd significnt positive effect on PFA (F = 23.3; d.f. = 4, 55; ) nd PDS (F = 118.2; d.f. = 4, 55; ), but negtive effect on FFW (F = 19.6; d.f. = 4, 55; P <.1) nd SSC (F = 21.8; d.f. = 4, 55; ). Similr results were obtined t GCREC orchrd: insect density hd significnt positive effect on PFA (F = 33.4; d.f. = 4, 55; ) nd PDS (F = 96.4; d.f. = 4, 55; P =.1) nd negtive effect on FFW (F = 3.33; d.f. = 4, 55; P =.1) nd SSC (F = 96.3; d.f. = 4, 55; P =.1). Premture fruit yellowing ws recorded t densities of.7 or more insects per fruit. In 28, both femle nd mle were evluted t the two orchrds nd the results were generlly similr to those obtined in J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH 697

5 Dmge to stsum by L. zontus Y. F. Xio nd H. Y. Fdmiro 3 () Femles (control) 1 per fruit 2 per fruit 3 per fruit bc c bc c 5 3 (b) Mles Men ( SE) FWL ( ) (control) 1 per fruit 2 per fruit 3 per fruit b c bc c (c) Nymphs (control) 1 per fruit 2 per fruit 3 per fruit 7 b b Dys fter insect infesttion Fig. 2 Effects of insect density nd feeding durtion on percentge fruit weight loss (% FWL) of stsum fruits infested by Leptoglossus zontus in lortory tests. () Femles, (b) Mles, (c) Nymphs. Figure shows men (SE) number of FWL (%) over different feeding periods. 27. At both orchrds, femle density hd significnt positive effect on PFA nd PDS, but negtive effect SSC (tle 3, fig. 4). Similr results were recorded lso for mle: incresing mle density resulted in incresed PFA nd PDS nd reduced SSC (tle 4). An effect of insect density on fruit colour ws lso recorded t both loctions nd for both sexes. Premture fruit yellowing ws recorded t densities of 1 or more insects per fruit, wheres fruits cged with 1 insects per fruit were still minly green 14 dys fter infesttion. However, no significnt effect of insect density on FFW ws recorded in 28 (tles 3 nd 4). In generl, no significnt differences were recorded between the densities of (control) nd.5 insect per fruit for most dmge prmeters. 698 J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH

6 Y. F. Xio nd H. Y. Fdmiro Dmge to stsum by L. zontus () PDS 3 dys 7 dys dys 14 dys Men ( SE) PDS ( ) dys 14 dys Feeding durtion (dys) Femles Mles Nymphs (b) SSC 3 dys 7 dys dys 14 dys Men ( SE) SSC ( ) dys 14 dys Feeding durtion (dys) Femles Mles Nymphs Density/fruit Fig. 3 Effects of insect density nd feeding durtion on () percentge dmged sections (PDS) nd (b) soluble solids content (SSC) of stsum fruits infested by Leptoglossus zontus in lortory tests. Tle 1 Two-wy ANOVA testing for effects of insect density, feeding durtion, nd interctions of both fctors on fruit weight loss (FWL), percent dmged sections (PDS), nd soluble solids content (SSC) of stsum fruits infested by Leptoglossus zontus in lortory tests Femle Mle Nymphs Effect d.f. F P F P F P FWL Density Durtion Density durtion PDS Density Durtion Density durtion SSC Density Durtion Density durtion FWL, fruit weight loss; PDS, percent dmged section; SSC, soluble solids content. Four levels of insect density (, 1, 2 or 3 per fruit) were evluted t feeding durtions of 1, 3, 7,, nd 14 dys fter infesttion for FWL nd t 3, 7, nd 14 dys fter infesttion for PDS nd SSC. Discussion The symptoms of L. zontus feeding dmge on stsum fruit recorded in this study hve been previously reported on stsum or other citrus species (Ebeling 195; Griffiths nd Thompson 1957; Albrigo nd Bullock 1977; Kubo nd Filho 1992; Henne et l. 23; Buss et l. 25). Henne et l. J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH 699

7 Dmge to stsum by L. zontus Y. F. Xio nd H. Y. Fdmiro Tle 2 Effect of insect density on fruit weight loss (FWL), percent dmged section (PDS), nd soluble solids content (SSC) of stsum fruits infested by Leptoglossus zontus for 14 dys in lortory tests Men (SE) per fruit Stge Density (no. per fruit) FWL (%) PDS (%) SSC (%) Femle c c bc c b b F = P =.15 F = P =.1 F = 2.86 P =.4 Mle c c bc bc b b F = 9.4 P =.5 F = 31.4 P =.1 F = 4.8 P =.32 Nymphs b c bc b b F = 5.71 P =.21 F = P =.1 F = P =.2 FWL, fruit weight loss; PDS, percent dmged section; SSC, soluble solids content. Men (SE) within the sme column for ech stge followed by different letters re significntly different (P <.5, Tukey-Krmer HSD test; d.f. = 3, 8). Tle 3 Evlution of dmge to stsum fruit infested by Leptoglossus zontus femle in two south Alm stsum orchrds in 28 Men (SE) per fruit Loction Density (no. per fruit) Fruit colour PFA (%) FFW (g) PDS (%) SSC (%) Coker G b d G b d Y c Y b 6..4 b 3 Y bc F = 28. F = 2.14 P =.9 F = F = GCREC G c d G bc cd Y c b 2 Y b c 3 Y c F = 11.8 F =.512 P =.691 F = F = GGREC, Gulf Cost Reserch nd Extension Center, Firhope, AL; G, green colour; Y, yellow colour; PFA, premture fruit ortion; FFW, fresh fruit weight; PDS, dmged fruit sections; SSC, soluble solids content. Men (SE) within the sme column for ech loction followed by different letters re significntly different (P <.5, Tukey-Krmer HSD test; d.f. = 4, 35). (23) reported externl dmge to the rind of stsum fruit infested by L. zontus, in the form of green spots tht remin for time fter the rind hs turned ornge. Leptoglossus spp. hve lso been reported to cuse similr dmge to other crops (Hll nd Teetes 1982; Wheeler nd Miller 199; Grimm 7 J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH

8 Y. F. Xio nd H. Y. Fdmiro Dmge to stsum by L. zontus Tle 4 Evlution of dmge to stsum fruit infested by Leptoglossus zontus mle in two south Alm stsum orchrds in 28 Men (SE) per fruit Loction Density (no. per fruit) Fruit colour PFA (%) FFW (g) PDS (%) SSC (%) Coker G c d G c d Y bc c b 2 Y b b b 3 Y b F = 12.4 F = 2.36 P =.7 F = F = GCREC G c c G c c Y b c b 2 Y b b 3 Y c F = 21.6 F = 2.34 P =.9 F = F = GGREC, Gulf Cost Reserch nd Extension Center, Firhope, AL; G, green colour; Y, yellow colour; PFA, premture fruit ortion; FFW, fresh fruit weight; dmged fruit sections; SSC, soluble solids content. Men (SE) within the sme column for ech loction followed by different letters re significntly different (P <.5, Tukey-Krmer HSD test; d.f. = 4, 35). () Men ( SE) SSC ( ) (b) Men ( SE) SSC ( ) SSC SSC Density/fruit PDS PDS Fig. 4 Negtive correltion between soluble solids content (SSC) nd percentge dmged sections (PDS) of stsum fruits infested by Leptoglossus zontus femle t different densities. () Dt from the lortory test, (b) Dt from the field tril in Coker orchrd in Men ( SE) PDS ( ) Men ( SE) PDS ( ) 1999). The premture ortion of L. zontus-infested fruit recorded in our field tests hs lso been documented in other citrus species (Griffiths nd Thompson 1957; Albrigo nd Bullock 1977), s well s in other crops (Ebeling 195; Wisemn nd McMillin 1971; DeBrr nd Kormnik 1975; Bolkn et l. 1984; Grimm 1999). DeBrr nd Kormnik (1975) reported tht L. corculus (Sy) nymphs fed on the cytoplsm of cells of the nucellr tissue of pine conelets resulting in totl conelet ortion fter 4 dys of feeding. Albrigo nd Bullock (1977) suggested tht citrus fruit drop from leffooted bug feeding my be due to secondry infections by microorgnisms. However, this hypothesis ws not tested in the present study. In ddition to direct feeding injury, L. zontus nd other relted species hve lso been reported to trnsmit the yest, Nemtospor coryli, which cuses further fruit dmge including drying rot (Clrke nd Wilde 197; Henne et l. 23). Henne et l. (23) ttributed the collpsing nd drying out of the juice scs inside the rind of stsum fruit infested by L. zontus to this yest. Although, we did not ttempt to isolte this pthogen nd other microorgnisms, it is possible tht some of the symptoms of internl fruit dmge observed in this study were due to yest or similr pthogens. J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH 71

9 Dmge to stsum by L. zontus Y. F. Xio nd H. Y. Fdmiro As expected, our results showed mjor effects of L. zontus density nd feeding durtion on most fruit dmge prmeters. In generl, higher insect density nd longer feeding durtion resulted in incresed FWL nd PDS, but lower SSC. The results were firly consistent between lortory nd field experiments lthough minor differences were recorded. This is the first systemtic evlution of dmge by L. zontus or relted species to stsum or other citrus species. Similr results hve been reported for some non-citrus crops dmged by Leptoglossus spp. (Hll nd Teetes 1982; Grimm 1999). Hll nd Teetes (1982) ttributed the significnt reduction in the yield of sorghum infested by L. phyllopus to direct seed feeding. Similrly, physic nut dmged by L. zontus lso showed significnt reduction in fruit weight nd slight reduction in oil contents (Grimm 1999). We were not surprised to find negtive correltion between the PDS nd SSC of stsum fruit infested by L. zontus. The SSC is commonly used s mesure of fruit juice qulity (Widodo et l. 1996). Our dt showed tht significnt decline in SSC ws not lwys recorded t densities lower thn 2 individuls per fruit, suggesting tht this prmeter my not be very good mesure of L. zontus feeding dmge on stsum. Also, SSC declined fster in the field trils thn in the lortory tests. For instnce, the decrese in SSC ws significnt t the density of 1 2 individuls per fruit in the field trils but significnt decrese in SSC ws not recorded in the lortory tests below the density of 3 individuls per fruit. These differences my be relted to the hotter nd unstle field conditions. In generl, L. zontus femle nd mle produced similr mounts of dmge, which were slightly more thn the dmge produced by the nymphs. Grimm (1999) reported similr finding on physic nut: L. zontus dults of both sexes produced more dmge thn the nymphs. One of the objectives of this study ws to extrpolte the fruit dmge dt to possibly propose n economic threshold for L. zontus on stsum. Leptoglossus zontus feeding ffected fruit weight, yield, nd qulity, but the dt showed tht not ll feeding resulted in significnt mesurle dmge. For exmple, compred to uninfested (control) fruits, significnt FWL ws not recorded below the density of 1 individul per fruit or t feeding durtions of < dys. Hll nd Teetes (1982) reported similr result on sorghum nd concluded tht two dults of L. phyllopus were generlly not enough to cuse significnt reduction in the yield of green sorghum. Dt from the lortory tests showed tht FWL nd PDS vlues of uninfested control fruits were not significntly different from vlues for fruits infested by L. zontus t density of one individul per fruit, but significntly different from vlues for fruits infested t density of two or more individuls per fruit. In contrst, PDS nd PFA were significntly greter t the density of one individul per fruit compred to the control. We lso observed premture ripening of infested fruit t densities of 1 or more individuls per fruit. Similr results on PFA were reported for pistchio fruits infested by L. clypelis L., which resulted in n increse in PFA from 3.8% in the control to 32.9% in fruit clusters fed upon for 48 h by single L. clypelis (Bolkn et l. 1984). However, Grimm (1999) cutioned ginst relince on PFA to dignose economic dmge by bugs, since fruit ortion my be cused by other fctors which re unrelted to insect feeding. For instnce, Umñ nd Crbllo (1995) reported tht only 33 49% of orted mcdmi nuts showed symptoms of bug feeding dmge. Thus, our dt on PFA my not be used s relile indictor of economic dmge by L. zontus. In generl, our field results corroborted our lortory dt. The minor differences between our lortory nd field results my be relted to differences in environmentl conditions, s well s the impct of other field fctors. Altogether, our dt suggest n economic injury level (lowest insect density tht will result in economic dmge) of 1 2 L. zontus per stsum fruit. Although dt collected from studies in which insects were confined on fruit my not necessrily provide n ccurte estimtion of fruit dmge in the field becuse insects re not confined in nture, we consider our dt on L. zontus relile given our field observtion tht dults nd nymphs cn sty continuously on host tree or fruit for severl hours to dys. At present, it is difficult to ccurtely propose n economic or ction threshold (insect density tht will trigger control mesures to prevent the density from reching economic injury level) for L. zontus on stsum, due to severl fctors including lck of effective monitoring nd smpling techniques nd the inility to ccurtely predict its movement from djcent crop fields into stsum orchrds. Knowledge of these fctors nd the economics of mnging L. zontus will id the development of prcticl economic threshold for the pest on stsum mndrin. Acknowledgements We thnk Mr. Monte Nesbitt for helping with field collection of leffooted bugs used in strting our 72 J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH

10 Y. F. Xio nd H. Y. Fdmiro Dmge to stsum by L. zontus lortory colonies. Funding for this study ws provided by the Alm Agriculturl Experiment Sttion nd Auburn University Horticulture Line Item grnts progrm. References Albrigo LG, Bullock RC, Injury to citrus fruit by leffooted nd citrus plnt bugs. Proc. Fl. St. Hort. Soc. 9, Bolkn HA, Ogw JM, Rice RE, Bostock RM, Crne JC, Lef-footed bug (Hemipter: Coreide) nd epicrp lesion of pistchio fruits. J. Econ. Entomol. 77, Buss L, Hlbert S, Johnson S, 25. Leptoglossus zontus new lef-footed bug in Florid (Hemipter: Coreide). FDACS-DPI Pest Alerts. enpp/ento/l.zontus.html (ccessed on 28 October 27). Cmpbell BL, Nelson RG, Ebel RC, Dozier WA, Adrin JL, Hockem BR, 24. Fruit qulity chrcteristics tht ffect consumer preferences for stsum mndrins. HortScience 39, Clrke RG, Wilde GE, 197. Assocition of the green stink bug nd the yest spot disese orgnism of soybens. II. Frequency of trnsmission to soybens, trnsmission from insect to insect, isoltion from field popultion. J. Econ. Entomol. 63, DeBrr GL, Kormnik PP, Antomicl bsis for conelet ortion on Pinus echint following feeding by Leptoglossus corculus (Hemipter: Coreide). Cn. Entomol. 7, Ebeling W, 195. Subtropicl entomology (fruit pests). Lithotype Process Co., Sn Frncisco, CA. English LL, Turnipseed GF, 194. Control of the mjor pests of stsum ornge in south Alm. Al. Agric. Exp. St. Bull., Auburn, AL Fdmiro HY, Nesbitt M, Wll C, 27. Crop profile for stsum mndrin in Alm. nr/ipm/crop_profiles/_stsum_citrus.pdf (ccessed on 28 October 27). Fdmiro HY, Xio YF, Hrgroder T, Nesbitt M, Umeh V, Childers C, 28. Sesonl occurrence of key rthropod pests nd ssocited nturl enemies in Alm stsum citrus. Environ. Entomol. 37, Griffiths JT, Thompson WL, Insects nd mites found on Florid citrus. Fl. Agric. Exp. St. Bull., Ginesville, Fl. 591, Grimm C, Evlution of dmge to physic nut, Jtroph curcs, by true bugs. Entomol. Exp. Appl. 92, Hll DG, Teetes GL, Dmge to grin sorghum by southern green stink bug, conchuel nd lef-footed bug. J. Econ. Entomol. 75, Henne DC, Johnson SJ, Bourgeois WJ, 23. Pest sttus of lef-footed bugs (Hemipter: Coreide) on citrus in Louisin. Proc. Ann. Meet. Fl. St. Hort. Soc. 116, Johnson SR, Allin LK, Observtions on insect use of Chinese tllow (Spium sebiferum (L.) Roxb.) in Louisin nd Texs. Cstne 63, Kubo RK, Filho AB, Ocorrenci e dnos provocdos por Leptoglossus zontus (Dlls) (Hemipter: Coreide) em citros. Ann. Soc. Entomol. Brsil. 21, Mtrngolo WJR, Wquil JM, Biology of Leptoglossus zontus (Dlls) (Hemipter: Coreide) fed on mize nd sorghum (English strct). Ann. Soc. Entomol. Brsil. 23, SAS Institute, 27. JMP sttistics nd grphics guide, version SAS Institute, Cry, NC. Schefer CW, Pnizzi AR, 2. Heteropter of economic importnce. CRC Press, Boc Rton, FL. Umñ ME, Crbllo V, Biologí de Antiteuchus tripterus L. (Hemipter: Penttomide) y su prsitoide Trissolcus rdix (Johnson) (Hymenopter: Scelionide) en mcdmi. Mnejo Integrdo Plgs (Cost Ric) in English strct 38, Wheeler AG, Miller GL, 199. Leptoglossus fulvicornis (Hemipter: Coreide), specilist on mgnoli fruits: sesonl history, hits, nd descriptions of immture stges. Ann. Entomol. Soc. Am. 83, Widodo SE, Shirishi M, Shirishi S, On the interprettion of Brix vlue for the juice of cid citrus. J. Sci. Food Agri. 71, Wisemn BR, McMillin WW, Dmge to sorghum in south Georgi by Hemipter. J. G. Entomol. Soc. 6, Xio YF, Fdmiro HY, 29. Host preference nd development of Leptoglossus zontus on stsum mndrin. J. Econ. Entomol 5, J. Appl. Entomol. 134 (2) ª 2 Blckwell Verlg, GmbH 73