Antonio Garrido

Effect of Temperature on Life History of Cirrospilus vittatus (Hymenoptera: Eulophidae), an Ectoparasitoid of Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Abstract Cirrospilus vittatus is a generalist parasitoid detected on the invading Phyllocnistis citrella 1 yr after the introduction of this pest into Spain in 1993. In this study, the influence of temperature on parasitoid development, survival, and some selected life history parameters was determined. Development times shortened as the temperature increased from 15 to 30°C, but increased between 30 and 35°C. Larval development times varied the greatest over the range of temperatures, whereas egg development varied the least. The estimated upper and lower development thresholds were 38.2 and 8.2°C, respectively, and the maximal developmental rate (8.75 d−1) occurred at 31.5°C. The thermal constant was 275.1 ± 4.6 degree-days. Cirrospilus vittatus appeared to be a synovigenic species. Mean fecundity at 25°C was 39.17 eggs per female, and the oviposition rate fluctuated around five eggs per day. Superparasitism was quite common (42.8%), but fertility was high (85.6%). Immature C. vittatus survival was 58.1%. From these results, an intrinsic rate of increase of 0.126 females per female per day was estimated. Although under typical Mediterranean climatic conditions, development of C. vittatus could continue throughout the year, its reproductive fitness at 25°C is lower than other leafminer parasitoids attacking P. citrella in Spain. These results could account for the progressive displacement observed in field populations occurring between C. vittatus and the predominant indigenous parasitoids of P. citrella, Cirrospilus sp. near lyncus.

Interspecific competition between two ectoparasitoids of Phyllocnistis citrella (Lepidoptera: Gracillariidae): Cirrospilus brevis and the exotic Quadrastichus sp. (Hymenoptera: Eulophidae)

The eulophid Quadrastichus sp. was released in Spain in 1996 and 1997 to control the recently introduced citrus leafminer, Phyllocnistis citrella Stainton. Although this parasitoid became established, it did not exert any substantial control of P. citrella compared to the native Cirrospilus brevis Zhu, LaSalle and Huang which clearly predominated. To critically evaluate the results of the classical biological control program developed against P. citrella in Spain, we decided to test whether the observed field results concerning the exotic parasitoid Quadrastichus sp. and the indigenous C. brevis could have been forecasted from laboratory assays. An assay focusing on competition between Quadrastichus sp. and C. brevis was executed. The results obtained indicated that Quadrastichus sp. was an intrinsically superior competitor compared to C. brevis, the latter species becoming extinct in the laboratory competition trial. Environmental factors, not present in the conducted laboratory study, probably account for the outcome in the field. Although our laboratory results could be considered misleading, more post-colonization studies are warranted in classical biological control programs and, in any case, pre-introduction studies should still be conducted.

Morphology and Development of Immature Stages of Galeopsomyia fausta (Hymenoptera: Eulophidae: Tetrastichinae)

Abstract Galeopsomyia fausta LaSalle (Hymenoptera: Eulophidae) is a Neotropical eulophid solitary ectoparasitoid of the immature stages of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae). In Central and South America, the activity of this wasp has resulted in good biological control of P. citrella. Characterization of the immature morphology of parasitoids is important for the identification to the species level before adult emergence and for the quantification of the impact of these natural enemies in biological control programs. This article reports our study of the immature stages of G. fausta from a laboratory colony maintained on P. citrella that were examined using scanning electron microscopy (SEM). The wasp has a typical hymenopteriform egg attached to the leaf chamber where P. citrella pupates. The parasitoid has three instars, very similar to each other, holopneustic, hymenopteriform, and 13-segmented. Its cuticle has multiple spines. The cranium is conspicuous and has a mandibulate suctorial mouth. On completion of its larval development an exarate pupa is produced. The distinctive attachment of the egg to the leaf and typical pupal morphology allow the identification of this parasitoid by using a binocular microscope, but identification of the larvae requires SEM.

Effect of Temperature on Development and Survival of Citrostichus phyllocnistoides (Hymenoptera: Eulophidae), a Parasitoid of Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Thermal requirements of Citrostichus phyllocnistoides under laboratory conditions resulted in a lower temperature threshold of 9.8°C, and a thermal constant of 212.0 DD. Development was completed between 15 and 30°C, but was not at 10°C. Therefore, the overwintering of this exotic biocontrol agent would be possible under typical Mediterranean temperatures.

EFFECT OF VARIABLE PHOTOPERIOD ON DEVELOPMENT AND SURVIVAL OF CIRROSPILUS SP. NR. LYNCUS (HYMENOPTERA: EULOPHIDAE), AN ECTOPARASITOID OF PHYLLOCNISTIS CITRELLA (LEPIDOPTERA: GRACILLARIIDAE)

The eulophids Cirrospilus sp. near lyncus and Pnigalio pectinicornis L. are the most abundant parasitoids of the citrus leafminer, Phyllocnistis citrella Stainton, in Spain (Urbaneja et al. 2000). These were opportunistically recruited onto this pest after its introduction in 1993. C. sp. near lyncus is a late larval solitary idiobiont ectoparasitoid which can also behave as a hyperparasitoid. Its impact on P. citrella relies on both parasitism and host feeding (Urbaneja et al. 1998a). C. sp. near lyncus populations in citrus orchards increase from mid-July until the end of October, but remain almost undetectable during the rest of the year (Urbaneja et al. 1999). A previous study demonstrated that C. sp. near lyncus was very well adapted to temperatures prevailing on the western part of the Mediterranean Basin. That is the range between 7.1 ° C, mean of minimum temperatures of the coldest month (January), and 29.0 ° C, mean of maximum temperatures of the hottest one (August) (Urbaneja et al. 1999). To further study the influence of environmental conditions on the biology of this wasp, the effects of photoperiod on development and survival were investigated. Environmental chambers were used to check the effects of three different photoperiods: 16:8, 12:12 and 8:16 (L:D). Temperature fluctuated from 10 ° C to 30 ° C in eight 3h-steps of 5 ° C (mean temperature 20 ° C). Highest temperature always coincided with the mid-point of the photophase. This sequence mimics the regime of field temperatures both in spring and autumn. Therefore results obtained under both 16:8 and 8:16 (L:D) photoperiods are presumed to reflect field conditions at those seasons. Insects were reared at the Institut Valencià d’Investigacions Agràries as described by Urbaneja et al. (1998b). Eggs of C. sp. near lyncus were obtained by offering detached citrus leaves containing P. citrella third instar larvae (LIII) to isolated mated females (12 LIII per female). Exposure took place in Petri dishes (140 mm diameter) where leaves were placed on a layer of agar (2% weight) under a temperature of 25 ± 1 ° C during 4 hours. After exposure, leaves were checked under a stereoscopic binocular microscope and those containing parasitized hosts (recognized by the presence of C. sp. near lyncus eggs on them) were randomly transferred to the corresponding experimental photoperiod on a layer of