No differences could be observed neither in development times nor on survival of C. sp. near lyncus exposed to three different photoperiods: 16:8; 12:12 and 8:16 (L.D). Therefore, conservation tactics aimed at favoring the winter permanence of this species in citrus orchards could increase the impact of this opportunistic parasitoid on its host P. citrella

Garrido, Antonio

Jaques, Josep A.

Llácer, Elena

Urbaneja, Alberto

ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries

 Scientific   Notes 305 EFFECT OF VARIABLE PHOTOPERIOD ON DEVELOPMENTAND SURVIVAL OF  CIRROSPILUS  SP. NR.  LYNCUS (HYMENOPTERA: EULOPHIDAE), AN ECTOPARASITOIDOF  PHYLLOCNISTIS   CITRELLA  (LEPIDOPTERA: GRACILLARIIDAE) A LBERTO  U RBANEJA 1 , E LENA  L LÁCER , A NTONIO  G ARRIDO   AND  J OSEP -A NTON  J ACAS 2 Departament de Protecció Vegetal i Biotecnologia; Institut Valencià d’Investigacions Agràries, IVIACtra. de Montcada a Nàquera km. 5; E-46113-Montcada, Spain 1 Present address: R & D Department. Koppert Biological Systems. Finca Labradorcico del Medio s/nApartado de Correos 286. 30880 Águilas, Spain 2 Present address: Departament de Ciències Experimentals; Universitat Jaume I; Campus de Riu SecE-12071-Castelló de la Plana, Spain The eulophids  Cirrospilus  sp. near  lyncus  and Pnigalio pectinicornis  L. are the most abundantparasitoids of the citrus leafminer,  Phyllocnistiscitrella  Stainton, in Spain (Urbaneja et al. 2000).These were opportunistically recruited onto thispest after its introduction in 1993.  C.  sp. near  lyn-cus  is a late larval solitary idiobiont ectoparasi-toid which can also behave as a hyperparasitoid.Its impact on  P. citrella  relies on both parasitismand host feeding (Urbaneja et al. 1998a).  C.  sp.near  lyncus  populations in citrus orchards in-crease from mid-July until the end of October, butremain almost undetectable during the rest of theyear (Urbaneja et al. 1999). A previous studydemonstrated that  C.  sp. near  lyncus  was verywell adapted to temperatures prevailing on thewestern part of the Mediterranean Basin. That isthe range between 7.1 ° C, mean of minimum tem-peratures of the coldest month (January), and29.0 ° C, mean of maximum temperatures of thehottest one (August) (Urbaneja et al. 1999). Tofurther study the influence of environmental con-ditions on the biology of this wasp, the effects ofphotoperiod on development and survival wereinvestigated.Environmental chambers were used to checkthe effects of three different photoperiods: 16:8,12:12 and 8:16 (L:D). Temperature fluctuatedfrom 10 ° C to 30 ° C in eight 3h-steps of 5 ° C (meantemperature 20 ° C). Highest temperature alwayscoincided with the mid-point of the photophase.This sequence mimics the regime of field temper-atures both in spring and autumn. Therefore re-sults obtained under both 16:8 and 8:16 (L:D)photoperiods are presumed to reflect field condi-tions at those seasons. Insects were reared at theInstitut Valencià d’Investigacions Agràries as de-scribed by Urbaneja et al. (1998b). Eggs of  C.  sp.near  lyncus  were obtained by offering detachedcitrus leaves containing  P. citrella  third instar lar-vae (LIII) to isolated mated females (12 LIII perfemale). Exposure took place in Petri dishes (140mm diameter) where leaves were placed on a layerof agar (2% weight) under a temperature of 25  ± 1 ° C during 4 hours. After exposure, leaves werechecked under a stereoscopic binocular micro-scope and those containing parasitized hosts (rec-ognized by the presence of  C.  sp. near  lyncus  eggson them) were randomly transferred to the corre-sponding experimental photoperiod on a layer of T ABLE  1. M EAN   DEVELOPMENT   TIMES  ( DAYS )  OF   MALE   AND   FEMALE   C .   SP .  NEAR   LYNCUS   UNDER   THREE   DIFFERENTPHOTOPERIODS  ( MEAN   ±  SE).16:8 (L:D) 12:12 (L:D) 8:16 (L:D)Egg 2.16  ±  0.18 2.28  ±  0.22 2.26  ±  0.15Male Larva 5.39  ±  0.32 5.72  ±  0.28 5.74  ±  0.21Pupa 8.84  ±  0.31 8.47  ±  0.41 8.50  ±  0.24Total 16.39  ±  0.33 16.47  ±  0.24 16.50  ±  0.19(n = 14) (n = 16) (n = 17)Egg 2.25  ±  0.22 2.11  ±  0.12 2.67  ±  0.25Female Larva 5.71  ±  0.38 6.07  ±  0.22 5.88  ±  0.30Pupa 9.14  ±  0.28 9.09  ±  0.25 9.29  ±  0.35Total 17.11  ±  0.39 17.27  ±  0.36 17.83  ±  0.28(n = 19) (n = 22) (n = 12) 306 Florida Entomologist  84(2) June 2001 agar (2% weight) in a Petri dish (55 mm diameter).Sixty replicates (= leaves) were used for each pho-toperiod. Leaves decaying during the study periodwere excluded from the analyses. Parasitoid de-velopment was checked daily until adult emer-gence. Development times and stage-specificmortality were recorded and eventually emergingadults were sexed. These results were subjected toa two-way analysis of variance (STSC 1987).Development times for the three experimentalphotoperiods are presented in Table 1. There wereno differences among photoperiods (F = 2.951; df =2, 98; P = 0.0572). Although there were differencesbetween sexes (F = 48.059; df = 1, 98; P < 0.0001),no interaction between sex and photoperiod fac-tors occurred (F = 1.820; df = 2, 98; P = 0.1677).Furthermore, there was good agreement betweendevelopment times obtained in the present studyand that reported previously (Urbaneja et al.1999) under a constant temperature of 20 ° C and aphotoperiod of 16:8 (L:D): 17.20  ±  0.30 d. Survivalof the different stages are shown in Table 2. Lar-vae were the most sensitive stage, whereas botheggs and pupae were more resistant. Similar re-sults had already been found under different con-stant temperatures (Urbaneja et al. 1999).However, no effect of photoperiod on survival wasfound. Agreement between results obtained inthis study and those obtained under a constanttemperature regime (Urbaneja et al. 1999) indi-cates usefulness of the latter for prediction of fieldperformance based on a thermal constant.Photoperiod is one of the signals insects use toperceive environmental changes and adjust theirlife cycle accordingly (Tauber et al. 1986). Abramset al. (1996) indicated shorter development timesshould be expected in insects developing late inthe season relative to either an upcoming winteror an approaching optimal date for adult emer-gence. Although  C.  sp. near  lyncus  is presumed tobe native to a temperate area, such as the Medi-terranean Basin (Schauff et al. 1998), where pho-toperiod changes considerably along the year, noeffects of this factor alone could be detected. How-ever, influence of the combined effect of photope-riod and with temperature cannot be excluded.Based on these results and on those previouslypresented by Urbaneja et al. (1999),  C.  sp. near lyncus  should be able to breed continuously undertypical Mediterranean conditions. The absence ofthis wasp in citrus orchards from autumn untilearly summer may be related to the extraordi-nary scarcity of  P. citrella  during winter months.We hypothesize that  C.  sp. near  lyncus  is forced toabandon citrus orchards and does not return until P. citrella  populations have already peaked up.For this reason, conservation tactics aimed at fa-voring the permanence of  C.  sp. near  lyncus  couldincrease the impact of parasitism early in the sea-son.  C.  sp. near  lyncus  was first noticed in Spainas a parasitoid of  P. citrella , and its original hostrange remains unknown. Therefore, as a first stepto implement conservation strategies, its hostrange should be determined.S UMMARY No differences could be observed neither in de-velopment times nor on survival of  C.  sp. near  lyn-cus  exposed to three different photoperiods: 16:8;12:12 and 8:16 (L:D).Therefore, conservation tac-tics aimed at favoring the winter permanence ofthis species in citrus orchards could increase theimpact of this opportunistic parasitoid on its host P. citrella .We thank J. E. Peña (TREC-University of Flor-ida) and C. Rodríguez-Saona (USDA-ARS Phoe-nix, USA) for their comments on an early draft ofthis note, and R. Hinarejos, A. Muñoz and J.Torres for technical assistance. A.U. and E.L.were recipients of a predoctoral grant from IVIA.R EFERENCES  C ITED A BRAMS , P. A., O. L EIMAR , S. NYLIN, AND C. WIKLUND.1996. The effect of flexible growth rates on optimalsizes and development times in a seasonal environ-ment. American Nat. 147: 381-395.SCHAUFF, M. E., J. LASALLE, AND G. A. WIJESEKARA.1998. The genera of Chalcid parasitoids (Hy-menoptera: Chalcidoidea) of citrus leafminer Phyl-locnistis citrella (Lepidoptera: Gracillariidae). J.Nat. Hist 32: 1001-1056.STSC. 1987. Statgraphics user’s guide, version 5.0.Graphic software system STSC, Rockville, MD.TAUBER, M. J., C. A. TAUBER, AND S. MASAKI. 1986. Sea-sonal adaptations of insects. Oxford UniversityPress. 441 pp.URBANEJA, A., E. LLÁCER, J. JACAS, AND A. GARRIDO.1998a. Ciclo biológico de Cirrospilus sp. próximo alyncus, parasitoide autóctono del minador de las ho-jas de los cítricos. Bol. San. Veg. Plagas 24: 704-714.TABLE 2. STAGE SPECIFIC SURVIVAL (%) OF C. SP. NEAR LYNCUS UNDER THREE DIFFERENT PHOTOPERIODS. INITIALNUMBER OF REPLICATES WAS 60, BUT CALCULATIONS ARE BASED ON THE NUMBER OF NON-DECAYING LEAVES(=REPLICATES) AT THE END OF EACH PERIOD.Photoperiod Egg-larva Larva-pupa Pupa-adult Total16:8 (L:D) 93.3 85.7 91.7 73.312:12 (L:D) 93.0 97.5 97.4 88.48:16 (L:D) 92.5 89.2 87.9 72.5Scientific Notes 307URBANEJA, A., E. LLÁCER, R. HINAREJOS, J. JACAS, ANDA. GARRIDO. 1998b. Sistema de cría del minador delas hojas de los cítricos, Phyllocnistis citrella Stain-ton, y sus parasitoides Cirrospilus sp. próximo a lyn-cus y Quadrastichus sp. Bol San. Veg. Plagas 24:787-796.URBANEJA, A., E. LLÁCER, A. GARRIDO, AND J. JACAS.1999. Effect of temperature on development and sur-vival of Cirrospilus sp. near lyncus (Hymenoptera:Eulophidae), a parasitoid of Phyllocnistis citrella(Lepidoptera: Gracillariidae). Environ. Entomol. 28:339-344.URBANEJA, A., E. LLÁCER, Ó. TOMÁS, A. GARRIDO, ANDJ. JACAS. 2000. Indigenous natural enemies associ-ated with Phyllocnistis citrella (Lepidoptera: Gracil-lariidae) in Eastern Spain. Biol. Control 18: 199-207.

Effect of variable photoperiod on development and survival of Cirrospilus sp. nr. Lyncus (Hymenoptera: Eulophidae), an ectoparasitoid of phyllocnistis citrella (Lepidoptera: Gracillariidae)

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Effect of variable photoperiod on development and survival of Cirrospilus sp. nr. Lyncus (Hymenoptera: Eulophidae), an ectoparasitoid of phyllocnistis citrella (Lepidoptera: Gracillariidae)

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