Natural biological control of green scale (Hemiptera: Coccidae): a field life-table study

Understanding how the biotic and abiotic factors influence pest-population dynamics is important to implement sound pest management strategies in biological control and integrated pest management (IPM) programmes. Coccus viridis (Green) is an important indirect pest of coffee plants, but very little has been done to understand the factors that contribute most for its biological control in the field. In the present study, we examined the critical life stage and the key factors associated with the mortality of C. viridis in coffee plantations in Brazil by conducting field-based life table studies. Predators, parasitoids, fungi, infested leaf abscission and rainfall were collectively responsible for a total C. viridis mortality of 96.08%. Predation by coccinellids was the key factor governing the mortality of C. viridis. The parasitism of early instars by parasitoids was the second most important factor contributing to C. viridis mortality. Unlike the parasitoids, the fungus Lecanicillium lecanii caused mortality of scales in more advanced life stages. The abscission of infested leaves from the trees, and rainfall also contributed to the mortality of C. viridis. The nymph stage was considered the critical stage for mortality of C. viridis in the field. The results suggest that predators (Coccinellidae) are the most important factors controlling C. viridis, and thus should be the target of conservation measures in coffee plantations infested with this pest.     

Survey of brown soft scale Coccus hesperidum L. parasitoids in southern California citrus

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.     

Seasonal and Scale Size Relationships between Citricola Scale (Homoptera: Coccidae) and Its Parasitoid Complex (Hymenoptera: Chalcidoidea) on San Joaquin Valley Citrus

The phenology of citricola scale, Coccus pseudomagnoliarum (Kuwana), and its associated parasitoid complex were studied on citrus in the San Joaquin Valley of central California over the period April 1995–March 1997. A total of 10,237 parasitoid specimens of 10 species were collected. Two of these species, Marietta mexicana (Howard) and Encyrtus lecaniorum (Mayr), each recovered from individually isolated scales, represent new parasitoid records for citricola scale. A third species, Encarsia citrinus citrinus (Craw), may represent a new parasitoid record, but this requires further confirmation because a single (male) specimen was recovered from individually isolated scales. The three most dominant parasitoid species, Coccophagus lycimnia (Walker), Metaphycus helvolus (Compere), and Metaphycus luteolus (Timberlake), accounted for the majority (>97%) of the specimens recovered. In contrast to the situation on citrus in southern California, where citricola scale is under effective biological control and is very rarely seen, citricola scale on citrus in the San Joaquin Valley is reemerging as a major pest, especially in groves employing integrated pest management with minimal use of broad-spectrum insecticides. Possible reasons uncovered in this study for the lack of effective biological control of citricola scale in the San Joaquin Valley include: (i) reduced presence of Metaphycus spp. because of hyperparasitism by the heteronomous hyperparasitoid C. lycimnia; (ii) absence of alternate hosts for those species of Metaphycus present; and (iii) absence of hosts of suitable size for Metaphycus at critical times of the year. Recommendations for improving the level of biological control in the San Joaquin Valley are discussed.     

Interspecific Interactions among Natural Enemies ofBemisiain an Inundative Biological Control Program

Interspecific interactions among insect natural enemies have seldom been investigated experimentally within the context of biological control. Research in this area is needed due to the often contradictory predictions provided by the many theoretical models, the increasing dependence on biological control, and the concern that biological control agents may adversely affect some nontarget organisms. We describe a study whereby the occurrence and dynamics of interspecific interactions among three natural enemies (two parasitoids:Encarsia formosaandEncarsia pergandiella;and one predatorDelphastus pusillus) of the whitefly,Bemisia argentifolii(previously referred to asBemisia tabacistrain “B”), were evaluated in greenhouse cage experiments. Eight populations consisting of all possible combinations of the three natural enemies and one population of whitefly alone were established to test the following hypotheses: (1) Natural enemy introductions are capable of suppressingB. argentifoliipopulations; (2) all interspecific interactions are detrimental to achieving biological control; (3) the likelihood of achieving biological control decreases as the potential number of interspecific interactions increases; and (4) the species composition of biological control agents is of greater consequence than the number of natural enemy species released. In addition, we tested the hypothesis (5) that the frequency of interspecific interactions increases with a decrease in host or prey availability. Our results demonstrate that all combinations of natural enemies provided significant levels of whitefly suppression. While the intensities of interspecific interactions among natural enemy species were frequently positively and significantly correlated with the densities of parasitized whitefly, interspecific interactions among natural enemies were not detrimental to achieving higher levels of biological control. The composition of species released, rather than the number of species released, was of greater importance to accomplishing biological control. Releases ofD. pusillusin combination with one or both of the parasitoids provided the greatest levels of whitefly suppression. These results suggest that the types of interspecific interactions rather than the numbers of interspecific interactions among natural enemies may be important to the outcome of inundative biological control programs.     

A survey of black scale,Saissetia oleae [Hom.: Coccidae] parasitoids [Hym.: Chalcidoidea] in southern California

A survey of black scaleSaissetia oleae (Olivier) parasitoids present in southern California was conducted between September 1987 and September 1989. From 308 collections of black scale-infested citrus, olive, and oleander twigs from 19 sites in southern California, 1,610 specimens were collected. Nine primary and six secondary parasitoid species were identified. Four primary species were abundant in southern California:Metaphycus bartletti Annecke & Mynhardt,M. helvolus (Compere),Scutellista caerulea (Fonscolombe) (=S. cyanea Motschulsky), andDiversinervus elegans Silvestri. The most common secondary parasitoids wereMarietta mexicana (Howard),Cheiloneurus noxius Compere, andTetrastichus minutus (Howard). In the coastal region of southern California,M. bartletti was the most abundant parasitoid, followed in order byD. elegans, S. Caerulea, andM. helvolus. In the intermediate and interior regions,M. helvolus was most abundant.D. elegans was second most abundant in the intermediate region, but was rare in the interior region.M. bartletti was second in abundance in the interior region and third in the intermediate region.      

Where to sample? Ecological implications of sampling strata in determining abundance and impact of natural enemies of the coffee berry borer,Hypothenemus hampei

Several parasitoids of African origin have been introduced to coffee producing areas of the Americas and Asia as biological control agents of the coffee berry borer (CBB) Hypothenemus hampei (Coleoptera: Curculionidae). These parasitoids have become established in the field but their effect on the CBB has been limited. A two-year field study in Western Kenya has found Prorops nasuta (Hymenoptera: Bethylidae) to be the predominant parasitoid emerging from CBB-infested coffee berries collected on coffee trees or from the ground. P. nasuta comprises more than 75% of the total natural enemies collected. The density of P. nasuta was 90% higher in the berries collected from the ground than from the trees. Its hyperparasitoid, Aphanogmus sp. (Hymenoptera: Ceraphronidae), also emerged from both type of berries. Across the two seasons, the average P. nasuta density per berry was 18–35 times higher than that of Aphanogmus sp. Throughout the two years sampled, significantly higher numbers of P. nasuta and Aphanogmus sp. occurred between February and March, which coincides with the beginning of the rainy season. Higher numbers of live CBB females were recorded in berries collected from the trees. Nevertheless, mortality of adult CBB was considerably higher from January to March and started to decrease from April onwards. The possibly negative effects of cultural control practices in Latin America which include the removal of berries fallen to the ground on biological control of CBB are discussed, and the use of screened collection devices for these berries which would permit the release of parasitoids but prevent escape of the pest is proposed.     

Is one parasitoid enough? A test comparing one with a pair of parasitoid species in the biological control of arrowhead scales

In classic biological control using natural enemies, the question of whether a single species or multiple species should be introduced has been a matter of debate. The introduction of two parasitoids, Aphytis yanonensis and Coccobius fulvus (Hymenoptera: Aphelinidae), to control the arrowhead scale, Unaspis yanonensis (Hemoptera: Diaspididae), which is a serious pest in Japanese citrus orchards, has been one of the most successful biological control projects in Japan. The success of this program may be explained by two alternative hypotheses: (1) the parasitoid species work complementarily, or (2) only one of them plays a major role. To test which hypothesis is applicable to this host-parasitoid system, we conducted caging experiments and observed temporal changes in the proportion of the parasitisms and the densities of arrowhead scales enclosed with one of the following combinations of parasitoids: (1) A. yanonensis and C. fulvus together, (2) A. yanonensis alone, (3) C. fulvus alone, or (4) neither parasitoid. Parasitisms in the cohorts with A. yanonensis and C. fulvus together and C. fulvus alone rapidly increased to approximately 70%; parasitism with A. yanonensis alone also increased slightly, although it remained consistently lower that those with A. yanonensis and C. fulvus together and C. fulvus. At the end of the experiment, parasitisms with A. yanonensis and C. fulvus together and C. fulvus alone were significantly higher than that with A. yanonensis alone. Parasitism by C. fulvus constituted most of (74%) the parasitism in the cohort with A. yanonensis and C. fulvus together. Further, only C. fulvus suppressed the population growth rates of scales significantly. These results suggest that C. fulvus alone successfully suppresses scale populations as efficiently as both species together do.     

Seasonal variations in the encapsulation of eggs of the encyrtid parasitoid Metaphycus stanleyi by the pyriform scale, Protopulvinaria pyriformis

Encapsulation of eggs of the introduced parasitoid Metaphycus stanleyi Compere (Hymenoptera: Encyrtidae) by the pyriform scale, Protopulvinaria pyriformis (Cockerell) (Homoptera: Coccidae) under both greenhouse and field conditions, at Bet Dagan, was found to occur almost all year round (1986–1988). However, encapsulation rates varied considerably during the different seasons and were correlated with the ambient temperatures. The rates of efficient encapsulation (i) in scales infesting Hedera helix and Schefflera arboricola under greenhouse conditions, were lowest during December to May (6–17%) and highest during July to September (78–100%); (ii) in scales infesting avocado in the orchard, were lowest during October to May (0–11%) and highest during June to August (54–57%). Under greenhouse conditions, encapsulation rates did not differ in scales grown on H. helix and on S. arboricola, but were significantly lower in scales grown on avocado. Encapsulation by scales infesting S. arboricola was more frequent at temperatures ranging from 20–28 °C, than from 7–23 °C.The increased resistance by encapsulation of P. pyriformis to successful parasitization by M. stanleyi during the summer, may account for the inability of the parasitoid to prevent the autumn and winter outbreaks of the pest.     

Induced responses of Coffea arabica to attack of Coccus viridis stimulate locomotion of the herbivore

The green scale, Coccus viridis (Green) (Hemiptera: Coccidae), is an insect pest of coffee and several other perennial cultivated plant species. We investigated changes in alkaloid and phenolic contents in coffee plants as a response to herbivory by this insect. Greenhouse‐grown, 11‐month‐old coffee plants were artificially infested with the coccid and compared with control, uninfested plants. Leaf samples were taken at 15, 30, 45, and 60 days after infestation, and high‐performance liquid chromatography was used to identify and quantify alkaloid and phenolic compounds induced by the coccids at each sampling date. Of the compounds investigated, caffeine was the main coffee alkaloid detected in fully developed leaves, and its concentration in infested plants was twice as high as in the control plants. The main coffee phenolics were caffeic and chlorogenic acid, and a significant increase in their concentrations occurred only in plants infested by C. viridis. A positive and significant relationship was found between alkaloid and phenolic concentrations and the infestation level by adults and nymphs of C. viridis. Caffeine and chlorogenic acid applied on coffee leaves stimulated the locomotory activity of the green scale, thus reducing their feeding compared to untreated leaves. This is the first study to show increased levels of coffee alkaloids and phenolics in response to herbivory by scale insects. The elevation of caffeine and chlorogenic acid levels in coffee leaves because of C. viridis infestation seems to affect this generalist insect by stimulating the locomotion of crawlers.     

Assessment of interspecific interactions among parasitoids on the outcome of inoculative biological control of leafminers attacking chrysanthemum

Indigenous natural enemies occur within field grown crops at varying densities dependent upon a variety of other biotic and abiotic parameters. This natural control often does not provide adequate suppression, which results in the application of other pest management solutions including augmentative biological control. When releasing mass-reared natural enemies into a backdrop of existing natural enemy populations, competitive interactions are likely to occur. To assess the influence of these interspecific interactions on the outcome of such biological control practices studies were conducted in a simulated, field cage grown, cut chrysanthemum production system. Competitive interactions of two commercially available parasitoids were studied both in terms of parasitoid-host population dynamics and the impact of interspecific interactions on crop quality at harvest. The parasitoids Diglyphus isaea and Dacnusa sibirica attacking the leafminer Liriomyza langei were used as the model insect system. Both parasitoids are cosmopolitan and are known to occur in many ornamental production areas. Treatment comparisons included single species releases with complimentary releases of both species either simultaneously or with 2-week time lags, as well as a no release control to measure the background effects of natural mortality. Conclusions drawn from results of population-level studies replicated within and among years were that levels of interspecific competition among parasitoid species were undetectable at leafminer densities typical of field-grown ornamental crops (low densities), and thus, the efficacy of one species released into a backdrop of potentially competing parasitoids did not negatively or positively affect the outcome of the augmentative biological control, nor was there a positive outcome; however, crop quality at harvest was influenced.     

Antagonism between two natural enemies improves biological control of a coffee pest: The importance of dominance hierarchies

The relationship between two natural enemies of Coccus viridis (green coffee scale), an important hempiteran coffee pest was determined using a combination of experimental and observational approaches. Adult and larval forms of Azya orbigera, a coccinellid beetle predator were included on leaves of coffee plants with healthy scale populations resulting in lower proportions of scales infected with the second natural enemy, an entomopathogenic fungus (Lecanicillium lecanii). C. viridis populations on leaves where A. orbigera were excluded exhibited twice as much fungal infection by L. lecanii. In addition, field surveys of C. viridis populations on whole coffee plants corroborated experimental findings with eight times less fungal infection for coffee plants where A. orbigera was present than for plants where the predator was absent a month prior to surveys of L. lecanii. Despite a reduction in fungal infection in both the experiment and survey, the presence of the beetle reduced overall biological control of the pest only in the experiment where the receiver of the antagonism (L. lecanii) was more dominant in controlling C. viridis than the instigator of the antagonism (A. orbigera). In the survey, A. orbigera was dominant over L. lecanii, resulting in equal to greater levels of biological control depending on the degree to which A. orbigera was dominant over L. lecanii. Our results indicate that a negative relationship exists between A. orbigera and L. lecanii, but that contrary to expectations, this antagonism may in some cases improve overall biological control of the shared pest target.     

Brood size, sex ratio and egg load of Metaphycus lounsburyi (Hymenoptera: Encyrtidae) when parasitizing adult females of black scale Saissetia oleae (Hemiptera: Coccidae) in the field

Black scale Saissetia oleae (Olivier) (Hemiptera: Coccidae) is a widespread olive pest in California and Europe. Metaphycus lounsburyi (Howard) (Hymenoptera: Encyrtidae) is often one of its main parasitoids. Augmentative releases of M. lounsburyi have been proposed in those areas in which biological control is ineffective. In this paper, we study the relationship between black scale and M. lounsburyi in the field. According to our data, M. lounsburyi parasitizes mainly ovipositing females of black scale. Parasitism rates of ovipositing females reach high levels. In those scales, M. lounsburyi develops as a gregarious parasitoid, with an average of 13 and a maximum of 40 parasitoids developing per scale. The secondary sex ratio is female biased (proportion of males = 0.13) and appears to be brood size dependent. Metaphycus lounsburyi eggs are encyrtiform; however, its egg load is much higher than other Metaphycus that also parasitize black scale. The implications of these results on the behavioral ecology of M. lounsburyi and its use in biological control of black scale are discussed.     

Encapsulation and hemocyte numbers in three lepidopteran stemborers parasitized by Cotesia flavipes-complex endoparasitoids

Determination of the potential and actual host range of a natural enemy is crucial before its importation and release for biological control. We studied some of the factors that are important in determining the physiological host range of insect parasitoids attacking lepidopteran hosts. Our experimental system consisted of novel host-parasitoid associations, with two New World pyralid stalk borers, Diatraea saccharalis and D. grandiosella; one Old World crambid borer, Ostrinia nubilalis as hosts; and three Old World microgastrine braconids, Cotesia chilonis, C. sesamiae, and C. flavipes as parasitoids. Experiments on the chronology of encapsulation of the parasitoid progeny by host hemocytes indicated that lepidopteran stemborers that are taxonomically, behaviorally and ecologically very similar differ in their ability to encapsulate a parasitoid species. D. saccharalis encapsulated C. flavipes sometimes, whereas D. grandiosella consistently encapsulated C. sesamiae and C. flavipes. C. chilonis was not encapsulated by either Diatraea host. If encapsulation occurred it did not start until four days after parasitization and continued during the following days. O. nubilalis was an unsuitable host for all three parasitoid species; parasitoid eggs were killed within 24 hours of parasitization. O. nubilalis had nearly twice as many hemocytes present in the hemolymph compared to the Diatraea species. In many of the host-parasitoid combinations, there was an initial increase of hemocyte number soon after parasitization, which was not due to mechanical damage at oviposition. There was no correlation between total numbers of hemocytes present in the host hemolymph and the observed encapsulation levels. By understanding the encapsulation response we may be able to make better predictions about the host range of a parasitoid species before its release as a biological control agent.     

Parasitism of fruit fliesCeratitis capitata andAnastrepha SPP. [Diptera: Tephritidae] in Guatemala

In a 4-year surveyDoryctobracon crawfordi Viereck andBiosteres longicaudatus Ashmead were the most common parasitoids recovered from bothCeratitis capitata (Wiedemann) andAnastrepha spp. Other braconids recovered from both genera wereD. areolatus Szepligeti,Bracanastrepha anastrephae (Viereck), and a Cynipid. Combined parasitization in both generally by ranged from 0.04 to 7.95% (Av. 1.5%). The numbers were particularly low in economically important fruit crops such as coffee, orange, and peach. Combined parasitoid population was correlated with the combined fruit fly infestation at 5 elevation strata.      

Hymenopteran parasitoids and dipteran predators of the invasive aphid Diuraphis noxia after enemy introductions: Temporal variation and implication for future aphid invasions

Shifts in prevalence and abundance of hymenopteran parasitoids and dipteran predators, Diuraphis noxia, and other aphids were measured in the west-central Great Plains of North America, April–September, in 2001 and 2002, corresponding to over a decade after first detection of D. noxia and first release of D. noxia enemies. Significant temporal shifts in enemy species prevalence and diversity were detected in this study and more broadly during an 11 year time span. At any given time, some species were relatively common. One parasitoid had been predominant throughout (Aphelinus albipodus), two had shifted in dominance (Lysiphlebus testaceipes and Diaeretiella rapae), three parasitoids had been detected infrequently (Aphidius avenaphis, Aphidius matricariae, and Aphelinus asychis), one parasitoid was detected in the 1990s but not during 2001 and 2002 (Aphelinus varipes), two predatory flies occurred at occasional significant levels (Leucopis gaimarii and Eupeodes volucris), and two parasitoids may have been minor members of the fauna (Aphidius ervi and Praon yakimanum). Aphid populations detected were usually very low or not detected, precluding estimation of percent parasitism. The best evidence of suppression was observations of parasitoids in the rare case of D. noxia exceeding economic thresholds, which complemented past studies using high aphid densities. The D. noxia enemies detected were primarily endemic or long-time residents derived from previous introductions. This enemy community may provide flexibility in responding to a future aphid invasion, allowing more strategic use of biological control and other pest management approaches.     

Impacts of biological control and invasive species on a non-target native Hawaiian insect

The potential for classical biological control to cause unintended harm to native species was evaluated in the case of the endemic Hawaiian koa bug, Coleotichus blackburniae White (Hemiptera: Scutelleridae), and parasitoids introduced to Hawaii for control of an agricultural pest, the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae). Parasitism of C. blackburniae eggs, nymphs and adults by biocontrol agents was quantified across a wide range of habitats and compared to other sources of mortality. Egg mortality due to the biocontrol agent Trissolcus basalis Wollaston (Hymenoptera: Scelionidae) was low (maximum 26%) and confined to elevations below 500 m on a single host plant. Predation, mainly by alien spiders and ants, was the greatest source of egg mortality (maximum 87%). Parasitism of adult C. blackburniae by the biocontrol agent Trichopoda pilipes (F.) (Diptera: Tachinidae) was near zero at 21 of 24 sites surveyed. Three sites with high bug density had higher levels of T. pilipes parasitism, reaching maxima of 70% among adult female bugs, 100% among males and 50% among fifth instars. Male-biased parasitism indicated that T. pilipes is adapted to using male aggregation pheromone for finding C. blackburniae hosts. The relative impacts of biocontrol agents and other sources of mortality were compared using life tables. Invasive species, particularly generalist egg predators, had the greatest impacts on C. blackburniae populations. Effects of intentionally introduced parasitoids were relatively minor, although the tachinid T. pilipes showed potential for large impacts at individual sites. In retrospect, non-target attacks by biological control agents on C. blackburniae were predictable, but the environmental range and magnitude of impacts would have been difficult to foresee.     

Notes on natural enemies attackingLepidosaphes species [Homoptera: Diaspididae] associated withCitrus in Costa Rica

Aphytis lepidosaphes Compere (Hymenoptera: Aphelinidae) parasitize two species ofLepidosaphes onCitrus in Costa Rica.Zagloba beaumonti andPentilia discors (Col.: Coccinellidae) also feed on both species.      

Role of Coccophagus sp. in the suppression of the soft green scale Coccus viridis (Green) (Hompoptera: Coccidae) on sapota

The soft green scale Coccus viridis (Green) (Homoptera: Coccidae) has become a major pest of sapota, Manilkara achras (Mill.) Forberg in India. A field study was conducted on the population dynamics of soft green scale Coccus viridis (Green) for 2 years (2004–2006) on sapota at the Indian Institute of Horticultural Research (IIHR) farm, Bangalore, India. The population of green scale declined from 30.72 per leaf in May 2004 to 1.62 per leaf in March 2006. Two coccinellid predators Chilocorus nigrita (Fab.) and Cryptolaemus montrouzieri (Muls.) and one aphelinid parasitoid Coccophagus sp. were recorded on C. viridis. Both the predators played a minor role in the population fluctuation of C. viridis. The parasitoid Coccophagus sp. was the dominant natural enemy observed throughout the study recording a mean of 10.24–94.67% parasitism. A significant positive correlation of the scale population with minimum temperature (r=0.54) and negative relationship with the parasitism by Coccophagus sp. (r=0.81) was recorded. Multiple regression analysis revealed that 75.7% of the variation present in the green scale population could be predicted by abiotic factors and parasitism by Coccophagus sp. Further, step-wise regression procedure employed to arrive at a multiple regression model showed that about 65.60% of the scale population could be predicted by one factor namely, parasitism by Coccophagus sp. These results showed that parasitism by Coccophagus sp. played a major role in regulating the population of the soft green scale infesting sapota.     

Parasitoid complex of black scale <Emphasis Type="Italic">Saissetia oleae</Emphasis> on citrus and olives: parasitoid species composition and seasonal trend

The parasitoid complex of black scale Saissetia oleae (Olivier) (Hemiptera: Coccidae) was studied on citrus and olives to determine their relative abundance, seasonal trend, geographical distribution, and their incidence on black scale populations. Branches and leaves of ten citrus and four olive groves infested with black scale were periodically collected over the period March 2003–December 2005 in eastern Spain, covering an area of 10,000 km². Adult parasitoids were also sampled with a portable engine-powered suction device. Black scale females were attacked by Scutellista caerulea (Fonscolombe) (Hymenoptera: Pteromalidae), which was found beneath 35.4 ± 7.5% and 22.4 ± 3.5% female scale’s body in citrus and olive groves, respectively. However, S. caerulea attacked the scales when most of their eggs had already hatched. The parasitic mite Pyemotes herfsi (Oudemans) (Prostigmata: Pyemotidae) fed on all development stages of S. caerulea. The gregarious female’s endoparasitoid Metaphycus lounsburyi (Howard) (Hymenoptera: Encyrtidae) was common in citrus and olive trees, but the parasitism rates it reached was low. Second and third instars of black scale were mainly parasitized by the solitary endoparasitoid Metaphycus flavus (Howard), and secondarily by Metaphycus helvolus (Compere) which was much less abundant and limited in distribution. Thus, M. helvolus, introduced 30 years ago, has not displaced M. flavus as in other Mediterranean areas. According to their abundance, distribution and incidence, M. flavus and S. caerulea appeared as the main parasitoids of black scale in eastern Spain, whereas M. helvolus and M. lounsburyi, considered the main parasitoids in other citrus and olive areas of the world, had a limited incidence. Recommendations for improving the level of biological control are discussed.     

Measuring parasitoid movement from floral resources in a vineyard

The movement of natural enemies from floral resources is of particular importance in habitat manipulation research, as the distances that they disperse have consequences for the deployment of floral resources to improve insect natural enemy fitness. A number of marking techniques can be used to measure natural enemy movement; however, many of these are labour-intensive and not appropriate for many natural enemy species, the alternative, self-marking techniques, are less common. The aim of this study was to determine whether rubidium chloride (RbCl) could be used to measure the movement of Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) from flowering buckwheat, Fagopyrum esculentum Moench plants in an organic vineyard. D. tasmanica is the most common parasitoid of leafroller larvae, a serious pest of grapevines in Australia and New Zealand. Foliar applications of rubidium chloride were made to a single strip of buckwheat in the centre of each of five vineyard areas. Sticky traps were placed in each area at distances of 0, 4, 10 and 30 m in opposite directions from the buckwheat to collect adult D. tasmanica. D. tasmanica were marked with rubidium after buckwheat plants had been sprayed with RbCl and were trapped up to 30 m from the plants within a seven-day sampling period. This study indicates that RbCl can be used to mark parasitoids to measure their movement from floral resources and may be used to inform decisions on the deployment of appropriate flowering plant species in conservation biological control.