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Robert F Luck - One of the best experts on this subject based on the ideXlab platform.

  • cellular immune response of brown soft scale coccus hesperidum l hemiptera coccidae to eggs of metaphycus luteolus timberlake hymenoptera encyrtidae
    Biological Control, 2009
    Co-Authors: Apostolos Kapranas, Robert F Luck, Brian A Federici, Jeffrey J Johnson
    Abstract:

    Abstract The parasitic wasp, Metaphycus luteolus Timberlake, is an endoparasitoid of various soft scale insects including brown soft scale, Coccus hesperidum L. Development of this parasitoid in scale hosts is hindered by encapsulation. In the present study, using transmission and scanning electron microscopy, we show that hemocytes are responsible for encapsulation, which is mediated by the direct deposition of cells and melanin on the surface of M. luteolus eggs. By 12 h post-oviposition, scale hemocytes, presumably granulocytes, aggregate, spread and directly lyse on the surface of parasitoid eggs. This process continues for at least 1 day and results in the gradual formation of a capsule. Two to three days post-oviposition, a melanized capsule is well formed and signs of chemical deposition are evident by examination of the outer surface of the capsule. These results demonstrate that soft scale insects are fully capable of melanotic encapsulation of foreign material mediated by hemocytes.

  • survey of brown soft scale coccus hesperidum l parasitoids in southern california citrus
    Biological Control, 2007
    Co-Authors: Apostolos Kapranas, Lisa Forster, P Pacheco, Robert F Luck
    Abstract:

    The parasitoid complex of brown soft scale, Coccus hesperidum L., a multivoltine soft scale, was determined in southern California citrus over the period February 2004–March 2006. The survey was conducted by placing brown soft scale-infested yucca leaves in the canopy of citrus trees and subsequently rearing individually isolated parasitized scales in the laboratory. A total of 14 species parasitized brown soft scale in the field, the most abundant ones belonging to the genus Metaphycus Mercet (75%). The most abundant parasitoid species was Metaphycus angustifrons Compere (38% parasitism), and this is a new record of establishment for this species in California. Coccophagus species accounted for only 11% parasitism. There were important spatio-temporal differences across the parasitoid complex survey locations. We also found that the five most abundant encyrtid parasitoid species showed preferences for scales of different sizes. Our results have implications for biological control of citricola scale, Coccus pseudomagnoliarum (Kuwana), an important pest of citrus in the San Joaquin Valley of central California. Notably, this species is nearly absent in southern California. Brown soft scale is considered to be an alternate host for parasitoids of citricola scale, a univoltine soft scale, at times when the latter species is unavailable for parasitism.

  • responses of metaphycussp nr flavus to semiochemicals released from a scale host coccus hesperidum
    Chemoecology, 2004
    Co-Authors: Paolo Lo Bue, Lisa Forster, Stefano Colazza, Jocelyn G. Millar, Robert F Luck
    Abstract:

    Metaphycus sp. nr. flavus (Encyrtidae: Hymenoptera) is a parasitoid species collected from the Mediterranean region which lays its eggs in the immature stages of several economically important soft scale insects (Hemiptera: Coccidae), including brown soft scale, Coccus hesperidum L. (= host insect). Preliminary tests suggested that the parasitoid is most successful in producing offspring when it oviposits in the younger stages of brown soft scale. In Y-olfactometer bioassays measuring wasp choices and residence times, naive parasitoids were significantly more attracted to yucca leaves infested with 26, 27, or 28 d-old scale than to uninfested leaves, whereas leaves with older (29-30 d-old) scale were no more attractive than uninfested leaves. Parasitoids also spent significantly more time in the arm with yucca leaves infested with 26 d-old scale than in the arm with uninfested leaves. These results are consistent with observations of the parasitoid’s reproductive success on scale of different ages, whereby older scale are more likely to encapsulate the developing eggs of M. sp. nr. flavusfemales than are younger scale. Further bioassays determined that yucca leaves that had been infested with 26 d-old scale but from which the scale had been removed were as attractive as infested leaves. In contrast, infested yucca leaves from which scale had been removed and the leaves subsequently washed with distilled water were less attractive than infested leaves. Furthermore, the wash water containing scale residues was attractive to female wasps. In total, these results suggest that Metaphycussp. nr. flavus females utilize volatile, water soluble compounds produced by brown soft scale as cues to locate suitable hosts.

  • metaphycus species near flavus responses to semiochemicals released from a scale host coccus hesperidum
    California Conference on Biological Control IV Berkeley California USA 13-15 July 2004., 2004
    Co-Authors: Lo P Bue, Lisa Forster, Robert F Luck, Stefano Colazza, Jocelyn G. Millar, M S Hoddle
    Abstract:

    Metaphycus sp. nr. flavus (Encyrtidae: Hymenoptera) is a Mediterranean parasitoid species which oviposits in the immature stages of several economically important soft scale insects (Hemiptera: Coccidae), including brown soft scale Coccus hesperidum L. and C. pseudomagnolium (Kuwana). In Y-olfactometer bioassays measuring wasp choices and residency times, naive parasitoids were significantly more attracted to yucca leaves infested with 26, 27, 28, and 29 d-old scale than to uninfested leaves, whereas leaves with 30 d-old scale were no more attractive than uninfested leaves. Parasitoids also spent significantly more time in the arm with yucca leaves infested with 26, 27, 28, and 29 d-old scale than in the arm with uninfested leaves, but they spent substantially more time in the arm with a yucca leaf infested 26 d-old scale than in the arm of any other age class of scale. Further, yucca leaves that had been infested with 26 d-old scale but from which the scales had been removed were as attractive as infested leaves. However, yucca leaves that had been infested with 26 d-old scales but from which the scales had been removed and the leaves washed with distilled water were less attractive than infested leaves. When the wash water containing scale residues was used to impregnate a filter paper disk, the impregnated disk was more attractive than a control disk impregnated with distilled water. In sum, these results suggest that Metaphycus sp. nr. flavus females utilize volatile, water soluble compounds produced by brown soft scale as cues to locate suitable hosts. These results also suggest that 26-28 d-old scales are more attractive than older scales. Significantly, these are the scale ages on which M. sp. nr. flavus develops most successfully and suffers the least mortality from encapsulation. INTRODUCTION Brown soft scale, Coccus hesperidum Linnaeus (Hemiptera: Coccidae), is a cosmopolitan pest of agricultural and ornamental plants (Saakyan-Baranova 1964; Gill and Kosztrab 1997), and of plants in indoor plantscapes (Stauffer and Rose 1997). Dense scale populations feeding on these plants reduce plant vigor, kill twigs, reduce yields, and decrease visual appeal. The scale also produces honeydew on which sooty mould grows, which can further downgrade plant and fruit appearance. C. hesperidum often develops as colonies on a plant’s leaves and twigs because ants tend the scale to obtain honeydew, while protecting the scale from its natural enemies (Ebeling 1959; Gill 1988). In California, C. hesperidum usually occurs at low densities in citrus groves and on outdoor ornamental plants because several biological control agents suppress it in the absence of ants (Bartlett 1978, Bernal et al. 1998). Metaphycus species near flavus (Hymenoptera: Encyrtidae) was imported into California from Kosan, Turkey, in 1996 for release against a closely related scale, citricola scale, Coccus pseudomagnoliarum (Kuwana), which is a periodic pest of citrus in the San Joaquin Valley of California (Bernal et al. 1999). However, citricola scale has an annual life cycle and is difficult to rear in large numbers, so we mass produce M. sp. nr. flavus on brown soft scale (L. D. Forster, P. Pacheco, R. F. Luck, and J. Sinclair, in prep), a natural host for this parasitoid (Guerrieri and Noyes 2000). This strategy works well in providing large numbers of wasps for release but it remains unclear whether M. sp. nr. flavus reared from brown soft scale recognizes and utilizes citricola scale effectively. Thus, we sought: 1) to determine whether M. sp. nr. flavus uses volatile cues associated with C. hesperidum to locate this host and 2), to determine whether these cues are produced directly by the scale, by the plant in response to a scale infestation, or by some combination of the two if volatile cues are involved. MATERIALS AND METHODS Scale and parasitoid cultures A brown soft scale colony was established with scale obtained from a pineapple guava plant, Feijoa sellowiana O. Berg (Myrtaceae), located on the UCR, CA campus. We reared the scales on excised leaves of Yucca sp. (Lilliaceae) maintained hydroponically in the UCR insectary at 27-28°C, 60% R.H., and a 21L: 3D photoperiod (L. D. Forster, P. Pacheco, R. F. Luck, and J. Sinclair, unpubl. data). The excised leaves were obtained from yucca plants maintained on the Ag. Exp. Sta., UCR. We maintained the parasitoid colonies by introducing mated females into plastic tubes (7.5 cm diam. x 50 cm long) containing 1-2 scale-infested yucca leaves, streaked the inside of the tubes with honey, closed them with nylon-vented plastic caps, and maintained them at 25 ± 1°C and 50-70% R.H. under continuous light. Scale size was standardized at ca. 2.0 mm in width. After ca. 14 d, individual scales containing parasitoid pupae were isolated to obtain naive females (= no encounters with healthy scales). Newly

  • sex ratios in field populations of two parasitoids hymenoptera chalcidoidea of coccus hesperidum l homoptera coccidae
    Oecologia, 1998
    Co-Authors: Julio S Bernal, Robert F Luck
    Abstract:

    We tested several assumptions and predictions of host-quality-dependent sex allocation theory (Char- nov et al. 1981) with data obtained for the parasitoid Metaphycus stanleyi Compere on its host, brown soft scale (Coccus hesperidum L.), in a California citrus grove and in the laboratory. Scales ceased growing after pa- rasitization by M. stanleyi. Thus, M. stanleyi may gauge host quality (asize) at oviposition. Host size positively influenced adult parasitoid size, and parasitoid size in turn influenced adult longevity of M. stanleyi. However, parasitoid fitness gains with host size and adult size were similar in males versus females. Sex allocation to indi- vidual hosts by M. stanleyi depended on host size; fe- males consistently emerged from larger hosts than males. Host size was important in a relative sense; the mean host sizes of females versus males, and of solitary versus gregarious parasitoids varied with the available host size distribution. The oAspring sex ratio of M. stanleyi reflected the available host size distribution; the sex ratio of emerging parasitoids varied with the avail- able host size distribution. We did not detect a ''critical host size'' below which males emerged, and above which females emerged; rather, only females emerged from hosts in the upper size range, and a variable ratio of males and females emerged from hosts in the lower size range. We conclude that the sex ratio of field popula- tions of M. stanleyi is driven largely by the available size distribution of C. hesperidum. In addition, we tested predictions resulting from theoretical analyses of sex allocation in autoparasitoids with data obtained on Coccophagus semicircularis (Forster) parasitizing brown soft scale in the field. The sex ratio of C. semicircularis was consistently and strongly female biased (ca. 90% females). Based on available theoretical analyses, we suggest that this sex ratio pattern may have resulted from a very low encounter rate of secondary hosts coupled with a strong time limitation in C. semicircularis females. This explanation was the most plausible given constraints stemming from the detection of secondary hosts, their variable location within primary hosts, and their handling times. Finally, the size of hosts which yielded single versus multiple parasitoids, and the sizes of these parasitoids, were compared. These comparisons suggested that: (1) M. stanleyi females gauge host sizes precisely, and in terms of female oAspring; thus a fitness penalty is not incurred by females which share a host, while males benefit from sharing a host, and; (2) in- stances where multiple C. semicircularis emerged from a single host were probably the result of parasitism by diAerent females, or during diAerent encounters by a single female.

T. Zaviezo - One of the best experts on this subject based on the ideXlab platform.

  • Genetic diversity of armored scales (Hemiptera: Diaspididae) and soft scales (Hemiptera: Coccidae) in Chile
    Scientific Reports, 2017
    Co-Authors: P. Amouroux, P Kreiter, D. Crochard, J.-f. Germain, M. Correa, J. Ampuero, G. Groussier, T. Malausa, T. Zaviezo
    Abstract:

    Scale insects (Sternorrhyncha: Coccoidea) are one of the most invasive and agriculturally damaging insect groups. Their management and the development of new control methods are currently jeopardized by the scarcity of identification data, in particular in regions where no large survey coupling morphological and DNA analyses have been performed. In this study, we sampled 116 populations of armored scales (Hemiptera: Diaspididae) and 112 populations of soft scales (Hemiptera: Coccidae) in Chile, over a latitudinal gradient ranging from 18°S to 41°S, on fruit crops, ornamental plants and trees. We sequenced the COI and 28S genes in each population. In total, 19 Diaspididae species and 11 Coccidae species were identified morphologically. From the 63 COI haplotypes and the 54 28S haplotypes uncovered, and using several DNA data analysis methods (Automatic Barcode Gap Discovery, K2P distance, NJ trees), up to 36 genetic clusters were detected. Morphological and DNA data were congruent, except for three species ( Aspidiotus nerii , Hemiberlesia rapax and Coccus hesperidum ) in which DNA data revealed highly differentiated lineages. More than 50% of the haplotypes obtained had no high-scoring matches with any of the sequences in the GenBank database. This study provides 63 COI and 54 28S barcode sequences for the identification of Coccoidea from Chile.

  • Genetic diversity of armored scales (Hemiptera: Diaspididae) and soft scales (Hemiptera: Coccidae) in Chile
    Scientific Reports, 2017
    Co-Authors: P. Amouroux, P Kreiter, D. Crochard, J.-f. Germain, M. Correa, J. Ampuero, G. Groussier, T. Malausa, T. Zaviezo
    Abstract:

    Scale insects (Sternorrhyncha: Coccoidea) are one of the most invasive and agriculturally damaging insect groups. Their management and the development of new control methods are currently jeopardized by the scarcity of identification data, in particular in regions where no large survey coupling morphological and DNA analyses have been performed. In this study, we sampled 116 populations of armored scales (Hemiptera: Diaspididae) and 112 populations of soft scales (Hemiptera: Coccidae) in Chile, over a latitudinal gradient ranging from 18 degrees S to 41 degrees S, on fruit crops, ornamental plants and trees. We sequenced the COI and 28S genes in each population. In total, 19 Diaspididae species and 11 Coccidae species were identified morphologically. From the 63 COI haplotypes and the 54 28S haplotypes uncovered, and using several DNA data analysis methods (Automatic Barcode Gap Discovery, K2P distance, NJ trees), up to 36 genetic clusters were detected. Morphological and DNA data were congruent, except for three species (Aspidiotus nerii, Hemiberlesia rapax and Coccus hesperidum) in which DNA data revealed highly differentiated lineages. More than 50% of the haplotypes obtained had no high-scoring matches with any of the sequences in the GenBank database. This study provides 63 COI and 54 28S barcode sequences for the identification of Coccoidea from Chile.

Katarzyna Golan - One of the best experts on this subject based on the ideXlab platform.

  • Impact of scale insect infestation on the content of photosynthetic pigments and chlorophyll fluorescence in two host plant species
    Arthropod-Plant Interactions, 2015
    Co-Authors: Katarzyna Golan, Katarzyna Rubinowska, Katarzyna Kmieć, Izabela Kot, Edyta Górska-drabik, Bożena Łagowska, Władysław Michałek
    Abstract:

    The aim of this experiment was to determine plant responses to Coccus hesperidum L. infestation on two host plants. Groups of five lemon and five fern plants were colonised by various numbers of mobile C . hesperidum instar nymphs. After 6 months, all scale insect individuals were counted on each plant. According to the insect density, the plants were divided into a five-degree series. In all density classes of host plants tested, the infestation of scale insects decreased the chlorophyll and carotenoid content as well as the value of three indicators of photosynthetic activity. The strongest decrease in the analysed pigments was observed for the smallest abundance of insects (first-class density) in lemon leaves and in second-class density in fern leaves. The strongest reactions of the chlorophyll fluorescence indicators were observed in density classes III and IV in the fern leaves and density classes IV or V in the lemon leaves. The reactions depended on the specific properties of plants and abundance of insects feeding on them.

  • physiological and biochemical responses of fern nephrolepis biserrata sw schott to coccus hesperidum l infestation
    Acta Biologica Cracoviensia Series Botanica, 2013
    Co-Authors: Katarzyna Golan, Katarzyna Rubinowska, Edyta Gorskadrabik
    Abstract:

    We examined the effects of feeding by the polyphagous insect Coccus hesperidum on its host plant Nephrolepis biserrata under different intensities of infestation. As an effect of scale insect feeding there were significant changes in the values of parameters reflecting the state of cell membranes. N. biserrata plants reacted to the biotic stress by increasing guaiacol peroxidase activity and decreasing catalase activity. Our data show that these processes play key roles in plant tolerance mechanisms, here the fern’s response to insect feeding. The observed complex reaction of N. biserrata testifies to actively proceeding, complex and very often contrasting mechanisms triggered with the aim of neutralizing the effects of biotic stress and enabling normal cell functioning in plants attacked by scale insects.

  • differences in the sugar composition of the honeydew of polyphagous brown soft scale coccus hesperidum hemiptera sternorrhyncha coccoidea feeding on various host plants
    European Journal of Endocrinology, 2011
    Co-Authors: Katarzyna Golan, Agnieszka Najda
    Abstract:

    Plant chemical composition is an important determinant of host plant-insect interactions. For many insects sugars are the main factors determining the acceptability of a plant. This study investigated changes in plant chemical composition and differences in sugar composition of different host plants induced by the feeding of Coccus hesperidum L. (Hemiptera: Sternorrhyncha: Coccoidea). Present in plant extracts and honeydew there were three monosaccharide sugars: glucose, fructose and arabinose, and one disaccharide - sucrose. Arabinose was only found in extracts of Ficus benjamina plants. The sugar content of the honeydew was greater than in the extracts of control plants and lower than that in the extracts of infested plants. The honeydew collected from C. hesperidum feeding on the three plant species differed significantly in sugar content. Extracts of coccid infested plants of the three species used in this study contained more sugar than the un-infested control plants. The results show that honeydew composition of scale insects differ and the differences reflect the chemical composition of the host plants.

Xiaomin Zhang - One of the best experts on this subject based on the ideXlab platform.

  • ultrastructural and cytochemical characterization of brown soft scale coccus hesperidum hemiptera coccidae infected by the lecanicillium lecanii ascomycota hypocreales
    Micron, 2011
    Co-Authors: Yanfeng Zhang, Xiaomin Zhang
    Abstract:

    The ultrastructural and cytochemical characterization of the brown soft scale, Coccus hesperidum L. (Hemiptera: Coccidae) infected by the hyphomycete Lecanicillium lecanii (Zimmermann) Gams & Zare, belonging to the phylum Ascomycota and order Hypocreales, was investigated by light, scanning and transmission electron microscopy. Gold cytochemistry was used to label chitin in the cuticle of the scale insect. The results revealed that the pathogenic fungus, L. lecanii generally infected by penetrating the integument, especially at anus, vulva, spiracles, stigmatic furrow, body margin, and the areas of cuticle with grooves, fissures and rugoses areas. The conidia became attached to the host body surface and germinated into hyphae that established colonies by branching repeatedly. Hyphae penetrated the integument by means of their penetration pegs using mechanical force and extracellular enzymes. During integument penetration, the hyphae extended vertically or parallel along the cuticle. Labeling with the WGA/Ovo-G complex showed disruption of the parallel sheets of chitin and a decrease in the density of the gold particles surrounding the penetrated hyphae. Hyphal invasion also separated the cuticle and epidermis from each other. Once in the haemocoele, blastospores of the fungus infected the haemocytes and internal organs. After some time, the nutritive value of the haemocoele decreased and the insect's internal organs disappeared. The hyphae then produced conidiophores and released them through the cuticle of the scale insect cadaver.

Lisa Forster - One of the best experts on this subject based on the ideXlab platform.

  • survey of brown soft scale coccus hesperidum l parasitoids in southern california citrus
    Biological Control, 2007
    Co-Authors: Apostolos Kapranas, Lisa Forster, P Pacheco, Robert F Luck
    Abstract:

    The parasitoid complex of brown soft scale, Coccus hesperidum L., a multivoltine soft scale, was determined in southern California citrus over the period February 2004–March 2006. The survey was conducted by placing brown soft scale-infested yucca leaves in the canopy of citrus trees and subsequently rearing individually isolated parasitized scales in the laboratory. A total of 14 species parasitized brown soft scale in the field, the most abundant ones belonging to the genus Metaphycus Mercet (75%). The most abundant parasitoid species was Metaphycus angustifrons Compere (38% parasitism), and this is a new record of establishment for this species in California. Coccophagus species accounted for only 11% parasitism. There were important spatio-temporal differences across the parasitoid complex survey locations. We also found that the five most abundant encyrtid parasitoid species showed preferences for scales of different sizes. Our results have implications for biological control of citricola scale, Coccus pseudomagnoliarum (Kuwana), an important pest of citrus in the San Joaquin Valley of central California. Notably, this species is nearly absent in southern California. Brown soft scale is considered to be an alternate host for parasitoids of citricola scale, a univoltine soft scale, at times when the latter species is unavailable for parasitism.

  • responses of metaphycussp nr flavus to semiochemicals released from a scale host coccus hesperidum
    Chemoecology, 2004
    Co-Authors: Paolo Lo Bue, Lisa Forster, Stefano Colazza, Jocelyn G. Millar, Robert F Luck
    Abstract:

    Metaphycus sp. nr. flavus (Encyrtidae: Hymenoptera) is a parasitoid species collected from the Mediterranean region which lays its eggs in the immature stages of several economically important soft scale insects (Hemiptera: Coccidae), including brown soft scale, Coccus hesperidum L. (= host insect). Preliminary tests suggested that the parasitoid is most successful in producing offspring when it oviposits in the younger stages of brown soft scale. In Y-olfactometer bioassays measuring wasp choices and residence times, naive parasitoids were significantly more attracted to yucca leaves infested with 26, 27, or 28 d-old scale than to uninfested leaves, whereas leaves with older (29-30 d-old) scale were no more attractive than uninfested leaves. Parasitoids also spent significantly more time in the arm with yucca leaves infested with 26 d-old scale than in the arm with uninfested leaves. These results are consistent with observations of the parasitoid’s reproductive success on scale of different ages, whereby older scale are more likely to encapsulate the developing eggs of M. sp. nr. flavusfemales than are younger scale. Further bioassays determined that yucca leaves that had been infested with 26 d-old scale but from which the scale had been removed were as attractive as infested leaves. In contrast, infested yucca leaves from which scale had been removed and the leaves subsequently washed with distilled water were less attractive than infested leaves. Furthermore, the wash water containing scale residues was attractive to female wasps. In total, these results suggest that Metaphycussp. nr. flavus females utilize volatile, water soluble compounds produced by brown soft scale as cues to locate suitable hosts.

  • metaphycus species near flavus responses to semiochemicals released from a scale host coccus hesperidum
    California Conference on Biological Control IV Berkeley California USA 13-15 July 2004., 2004
    Co-Authors: Lo P Bue, Lisa Forster, Robert F Luck, Stefano Colazza, Jocelyn G. Millar, M S Hoddle
    Abstract:

    Metaphycus sp. nr. flavus (Encyrtidae: Hymenoptera) is a Mediterranean parasitoid species which oviposits in the immature stages of several economically important soft scale insects (Hemiptera: Coccidae), including brown soft scale Coccus hesperidum L. and C. pseudomagnolium (Kuwana). In Y-olfactometer bioassays measuring wasp choices and residency times, naive parasitoids were significantly more attracted to yucca leaves infested with 26, 27, 28, and 29 d-old scale than to uninfested leaves, whereas leaves with 30 d-old scale were no more attractive than uninfested leaves. Parasitoids also spent significantly more time in the arm with yucca leaves infested with 26, 27, 28, and 29 d-old scale than in the arm with uninfested leaves, but they spent substantially more time in the arm with a yucca leaf infested 26 d-old scale than in the arm of any other age class of scale. Further, yucca leaves that had been infested with 26 d-old scale but from which the scales had been removed were as attractive as infested leaves. However, yucca leaves that had been infested with 26 d-old scales but from which the scales had been removed and the leaves washed with distilled water were less attractive than infested leaves. When the wash water containing scale residues was used to impregnate a filter paper disk, the impregnated disk was more attractive than a control disk impregnated with distilled water. In sum, these results suggest that Metaphycus sp. nr. flavus females utilize volatile, water soluble compounds produced by brown soft scale as cues to locate suitable hosts. These results also suggest that 26-28 d-old scales are more attractive than older scales. Significantly, these are the scale ages on which M. sp. nr. flavus develops most successfully and suffers the least mortality from encapsulation. INTRODUCTION Brown soft scale, Coccus hesperidum Linnaeus (Hemiptera: Coccidae), is a cosmopolitan pest of agricultural and ornamental plants (Saakyan-Baranova 1964; Gill and Kosztrab 1997), and of plants in indoor plantscapes (Stauffer and Rose 1997). Dense scale populations feeding on these plants reduce plant vigor, kill twigs, reduce yields, and decrease visual appeal. The scale also produces honeydew on which sooty mould grows, which can further downgrade plant and fruit appearance. C. hesperidum often develops as colonies on a plant’s leaves and twigs because ants tend the scale to obtain honeydew, while protecting the scale from its natural enemies (Ebeling 1959; Gill 1988). In California, C. hesperidum usually occurs at low densities in citrus groves and on outdoor ornamental plants because several biological control agents suppress it in the absence of ants (Bartlett 1978, Bernal et al. 1998). Metaphycus species near flavus (Hymenoptera: Encyrtidae) was imported into California from Kosan, Turkey, in 1996 for release against a closely related scale, citricola scale, Coccus pseudomagnoliarum (Kuwana), which is a periodic pest of citrus in the San Joaquin Valley of California (Bernal et al. 1999). However, citricola scale has an annual life cycle and is difficult to rear in large numbers, so we mass produce M. sp. nr. flavus on brown soft scale (L. D. Forster, P. Pacheco, R. F. Luck, and J. Sinclair, in prep), a natural host for this parasitoid (Guerrieri and Noyes 2000). This strategy works well in providing large numbers of wasps for release but it remains unclear whether M. sp. nr. flavus reared from brown soft scale recognizes and utilizes citricola scale effectively. Thus, we sought: 1) to determine whether M. sp. nr. flavus uses volatile cues associated with C. hesperidum to locate this host and 2), to determine whether these cues are produced directly by the scale, by the plant in response to a scale infestation, or by some combination of the two if volatile cues are involved. MATERIALS AND METHODS Scale and parasitoid cultures A brown soft scale colony was established with scale obtained from a pineapple guava plant, Feijoa sellowiana O. Berg (Myrtaceae), located on the UCR, CA campus. We reared the scales on excised leaves of Yucca sp. (Lilliaceae) maintained hydroponically in the UCR insectary at 27-28°C, 60% R.H., and a 21L: 3D photoperiod (L. D. Forster, P. Pacheco, R. F. Luck, and J. Sinclair, unpubl. data). The excised leaves were obtained from yucca plants maintained on the Ag. Exp. Sta., UCR. We maintained the parasitoid colonies by introducing mated females into plastic tubes (7.5 cm diam. x 50 cm long) containing 1-2 scale-infested yucca leaves, streaked the inside of the tubes with honey, closed them with nylon-vented plastic caps, and maintained them at 25 ± 1°C and 50-70% R.H. under continuous light. Scale size was standardized at ca. 2.0 mm in width. After ca. 14 d, individual scales containing parasitoid pupae were isolated to obtain naive females (= no encounters with healthy scales). Newly