Wind dispersal and settling of first-instar crawlers of the cochineal insect Dactylopius austrinus (Homoptera: Coccoidea: Dactylopiidae)

Abstract. 1. The efficiency of D.austrinus as a biological control agent depends on successful colonization of the cactus weed Opuntia aurantiaca .
2. Unlike other coccoid insects, the female crawlers (first-instar larvae) of cochineal insects develop long wax fiaments on the dorsal surface of the body that reduce their terminal velocity in air and enhance wind dispersal.
3. Dactylopiid males are dispersed as winged adults and male crawlers of D.austrinus have fewer and shorter filaments than the females and they are blown a shorter distance in a wind tunnel.
4. Vertical and horizontal wind dispersal of D.austrinus from O.aurantiaca in the field is usually very limited, but was greatly improved when crawlers were launched from an elevated 'tower'.
5. Preparatory to dispersal, female crawlers climb to the top of the host plant and 'take-off' from there. This behaviour is most marked in crawlers 2–3 days old at which stage the wax filaments are best developed: the behaviour is never manifest following artificial 'dispersal'.
6. Final settling on cladodes of the host plant is a function of the age of the female crawlers and of the condition of the cladodes.
7. When given a choice, approximately equal numbers of crawlers settled on cladodes that had received high and low fertilizer treatments. More crawlers settled on cladodes that had been kept in the shade than on those kept in the sun, and on basal rather than terminal cladodes.
8. The highest percentage of crawlers settled on cladodes that were 20% dehydrated. Settling success was much lower on more desiccated cladodes.     

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.     

Host selection behaviour and specificity of the solitary parasitoid of mealybugs Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera,Encyrtidae)

The host selection behaviour of Anagyrus sp. nr. pseudococci was compared in no-choice tests among five mealybug species of different geographical and phylogenetic origin, including the Mediterranean native host, Planococcus ficus and four exotic mealybug species, one of the same genus, Pl. citri, two Pseudococcus species, Ps. calceolariae and Ps. viburni and a more distant one, Phenacoccus peruvianus. All five studied mealybug species were recognised by the parasitoid as potential hosts and parasitised, but the behavioural pattern of host recognition, host handling and the level of host acceptance of Anagyrus sp. nr. pseudococci significantly varied among the five studied species, indicating a clear preference for the two Planococcus species, Pl. ficus in particular. The results suggest that A. sp. nr. pseudococci has a broader host range and a more generalist behaviour in comparison with other Anagyrus species. Practical implications of the findings are discussed.     

Host specificity testing and suitability of a European biotype of the braconid parasitoid Microctonus aethiopoides as a biological control agent against Sitona lepidus (Coleoptera: Curculionidae) in New Zealand

The European biotype of the parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae) is being considered for release against Sitona lepidus Gyllenhal (Coleoptera: Curculionidae) in New Zealand. Host specificity was evaluated in the laboratory using both endemic and introduced weed biological control curculionid species, with 12 no-choice and three choice experiments carried out comparing the S. lepidus and test weevils. Two further no-choice tests used the Moroccan M. aethiopoides biotype to compare attack rate between European and Moroccan M. aethiopoides, the latter released in 1982 to control the lucerne pest S. discoideus. Across all experiments, total parasitism of S. lepidus was 69% compared with 15% for the test weevils. European M. aethiopoides was able to develop in the native weevils Irenimus aequalis, Nicaeana cervina, Catoptes cuspidatus, Protolobus porculus and Steriphus variabilis with parasitism rates of 13, 28, 2, 7 and 8%, respectively. These levels were significantly less than those in the corresponding S. lepidus control. Total parasitism of I. aequalis and C. cuspidatus increased significantly in the presence of S. lepidus than recorded under no-choice conditions. The presence of European M. aethiopoides caused minor, if any, test weevil mortality prior to the onset of prepupal emergence and there was no significant reproductive suppression in parasitoid-exposed test weevils. Parasitism of the introduced weed control agent R. conicus by European M. aethiopoides was significantly lower (1.1%) compared to the Moroccan biotype (47.5%). Based on these and other experiments, should the European M. aethiopoides be released as a biological control agent of S. lepidus, its ecological impacts are likely to be less severe than those already exhibited by the Moroccan M. aethiopoides.     

Distribution and Abundance of Mymarid Parasitoids (Hymenoptera: Mymaridae) of Sophonia rufofascia Kuoh and Kuoh (Homoptera: Cicadellidae) in Hawaii

The abundance of mymarid parasitoids attacking the two-spotted leafhopper (Sophonia rufofascia [Kuoh and Kuoh]), a polyphagous pest recently adventive to Hawaii, was monitored using yellow sticky cards deployed in several areas on the islands of Kauai and Hawaii. The yellow cards captured Chaetomymar sp. nr bagicha Narayanan, Subba Rao, & Kaur and Schizophragma bicolor (Dozier), both adventive species, and Polynema sp. Haliday, which is endemic to Hawaii (Hymenoptera: Mymaridae). The former two species were most abundant at all sites. On Kauai, there was a negative correlation between the captures of C. sp. nr bagicha and those of Polynema sp. Throughout the season, the increase in parasitoid numbers generally followed the increase in leafhopper numbers. C. sp. nr. bagicha and S. bicolor showed distinct habitat preferences. Removal of Myrica faya Aiton, an invasive weed that is a highly preferred two-spotted leafhopper host, decreased the overall numbers of captured parasitoids, but led to a twofold increase in the ratio of trapped parasitoids/hosts in weed-free areas.     

Links between host-plant type and site of feeding as revealed by the evolution of Palaearctic Eriococcidae (Sternorrhyncha: Coccoidea)

This work is an assessment of the biogeographical, taxonomic, biological and phylogenetic knowledge of the poorly defined family Eriococcidae. The study of its geographical diversity shows the richness of the Palearctic fauna on which the present analysis focuses. The numerous systems dealing with the taxonomy of Eriococcidae are detailed, and the specific taxonomical status of the genus Eriococcus, which contains 155 out of the 175 known Palearctic species is reevaluated. The phylogeny of the palaearctic members of the scale insect family Eriococcidae is reconstructed, using 9 genera and 52 species. Three more scale insect species belonging to 3 families were used as outgroups. The cladistic analysis of 130 morphological characters of the adults resulted in 10 most parsimonious trees, placing Eriococcus buxi as the sister-group of all other sampled Eriococcidae. The genera Acanthococcus, Rhizococcus, Greenisca and Anophococcus appear as para- or polyphyletic, but the weakness of most of the clades does not allow to denounce strictly the monophyly of these genera. However, some clades are supported with high confidence, like (Kaweckia + Neokaweckia), (Anophococcus parvispinus(Anophococcus inermis+Greenisca placida) and (Gossyparia spuria+Acanthococcus aceris). Concerning host-plant relationships, the phylogeny supports an evolutionary scenario whereby the ancestor of the family Eriococcidae fed originally on woody plants, and more typically on leaves. The switch observed from Poaceae to other herbaceous plants is correlated to the switch from leaves as preferred site of nutrition to branches and stems. The supported scenario shows another switch, back from other herbs to Poaceae, associated to the choice of leaves as nutrition site.     

Interactions between the Parasitoid Rhopus nigroclavatus (Ashmead) (Hymenoptera: Encyrtidae) and its Mealybug Hosts Tridiscus sporoboli (Cockerell) and Trionymus sp. (Homoptera: Pseudococcidae)

This research investigated age-class-specific parasitism rates of the buffalograss mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. by Rhopus nigroclavatus (Ashmead) (Hymenoptera; Encyrtidae), size class preference of this parasitoid, and mealybug–parasitoid interactions through choice and no-choice studies. In the no-choice studies, the mean rates of parasitism by R. nigroclavatus were 45, 20, 0, and 0%, respectively, for mealybugs adult female, third and fourth instars, first and second instars, and eggs. Choice studies indicated that rate of parasitism increased with host size. The mean rates of parasitism on mealybugs in the choice studies were 100% for adult females, 24% for third and fourth instars, 0% for first and second instars, and 0% for eggs. A second set of choice studies investigating mealybug/parasitoid behavior revealed that R. nigroclavatus oviposits in all post-egg mealybug age classes, but first and second instars were less often parasitized than older mealybugs.     

Selecting the right parasitoid for the environment in classical biological control programmes: the case of Diadegma semiclausum (Hymenoptera: Ichneumonidae) and Plutella xylostella (Lepidoptera: Plutellidae) in the Kofele highland of Ethiopia

The careful selection of parasitoids with a track record of success in similar environmental conditions may increase the likelihood of effective biocontrol. Diamondback moth (DBM) population and level of parasitism were assessed for three years prior to the release of Diadegma semiclausum (Hellén) in June 2008. Thereafter, the DBM population and severity of crop damage and the occurrence of D. semiclausum and indigenous DBM parasitoids were monitored by monthly surveys during the main production season of June to December for three years. Before release, DBM numbers fluctuated between 4.2 and 11.2 per plant and parasitism ranged between 6.5 and 24.7%. DBM density declined to 2.8, 0.9 and 0.7 per plant whilst parasitism levels increased successively to 21, 39 and 38% in 2008, 2009 and 2010, respectively. A significant shift in parasitoid guild was observed after D. semiclausum release: it comprised 18.6, 80.3 and 88.6% of total parasitism in the first, second and third year, respectively. The decline of DBM density following the release of the introduced parasitoid and its establishment will ensure production of Brassica spp. without pesticide use against DBM in the affected area.     

Biological parameters and thermal requirements of the parasitoid Praon volucre (Hymenoptera: Braconidae) with Macrosiphum euphorbiae (Hemiptera: Aphididae) as host

The effect of temperature on the biology of Praon volucre (Haliday, 1833) (Hymenoptera: Braconidae) in Macrosiphum euphorbiae (Thomas, 1878) (Hemiptera: Aphididae) hosts was studied and the thermal requirements of the parasitoid were determined. Experiments were carried out at 16, 19, 22, 25, and 28 ± 1°C with 70 ± 10% relative humidity and 12 h photophase. The developmental time of P. volucre males and females decreased between 16 and 23°C. The highest percentages of aphid parasitism and adult parasitoid emergence were observed at 16, 19, and 22°C. The sex ratio (expressed as % females) decreased between 16 and 23°C. Male and female longevity was high between 19 and 22°C and decreased strongly at 25°C. The lower temperature threshold for P. volucre was 5.17°C and the thermal constant was 243 degrees-days.     

Biological control of the mediterranean black scale,Saissetia oleae (Hom.: Coccidae) in Israel

During the years 1975–1982, the “Israel Cohen” Inst. for Biological Control conducted a biological control project, against the black scale,Saissetia oleae (Olivier) (Homoptera: Coccidae). Seventeen species of natural enemies were introduced into Israel during that period, and their action reduced the populations of the pest to an acceptable level. The major parasitoid responsible for that transition wasMetaphycus bartletti Annecke &; Mynhardt (Hymenoptera: Encyrtidae). This article describes the project and introduces some notes on the biology of the introduced parasitoids.     

Parasitoid biodiversity conservation for sustainable management of the African rice gall midge,Orseolia oryzivora (Diptera: Cecidomyiidae) in lowland rice

Platygaster diplosisae and Aprostocetus procerae attack both the African rice gall midge (AfRGM), Orseolia oryzivora, and Orseolia bonzii, a closely related gall midge that feeds on Paspalum scrobiculatum. Recent research has shown that managing this weed at the edge of rice fields offers African farmers, low-cost non-chemical control of AfRGM.     

Influence of flowering cover crops on Anagrus parasitoids (Hymenoptera: Mymaridae) and Erythroneura leafhoppers (Homoptera: Cicadellidae) in New York vineyards

Abstract 1 We tested the hypothesis that providing nectar‐producing cover crops will enhance the biological control of grape leafhoppers (Erythroneura spp.) by Anagrus wasps in commercial vineyards in New York, U.S.A. 2 We established three cover crops between vine rows in a commercial vineyard: buckwheat (Fagopyrum esculentum (Moench)), clover (Trifolium repens L.) and mowed sod (Dactylis glomerata L.). 3 There was no effect of cover crop on adult Anagrus in 1996, whereas in 1997 adults were more abundant within edge vines with buckwheat compared to vines with clover or sod; adults were more abundant at the vineyard edge, especially early in the season. 4 Parasitism of ‘sentinel’ leafhopper eggs was higher on vines with buckwheat compared to parasitism on vines with clover or sod in 1996; a similar, non‐significant trend, was observed in 1997. 5 Neither the abundance nor the distribution of leafhoppers was influenced by cover crops, although in 1997 there was a trend toward greater numbers of nymphs on edge vines with buckwheat. 6 In a cage experiment, parasitism by Anagrus of leafhopper eggs on grapes was greater when adults had access to flowering buckwheat rather than buckwheat without flowers. 7 In a laboratory study, longevity of female Anagrus was increased when provided with honey or sugar water compared to water only or nothing. 8 Our results suggest that parasitism of grape leafhoppers by Anagrus may be enhanced by providing floral resources within vineyards in New York, although it is unclear whether this will produce meaningful reductions in pest abundance.     

Disruptive Sublethal Effects of Insecticides on Biological Control: Altered Foraging Ability and Life Span of a Parasitoid after Feeding on Extrafloral Nectar of Cotton Treated with Systemic Insecticides

Predictions in integrated pest management on the compatibility of an insecticide with biological control often are based on incomplete screening tests. While measuring levels of mortality from direct insecticide exposure is a very common screening method, possible sublethal effects as a result of either direct or indirect insecticide exposure remain relatively unknown. The impact of sublethal effects on the success of biological control can be as deleterious as mortality. Here, we report the reduced host foraging ability and longevity of the parasitoid Microplitis croceipes Cresson (Hymenoptera: Braconidae) after feeding on extrafloral nectar from cotton (Gossypium hirsutum L., Malvaceae) plants that were treated with systemic insecticides. The insecticides used in this study are regularly applied in cotton-growing areas in the United States. For all tested insecticides, longevity of M. croceipes females that fed on nectar from cotton was affected for at least 10 days after plants were treated with insecticides. Moreover, the parasitoid's host foraging ability was severely affected for periods ranging from 2 days (imidacloprid) to 18 days (aldicarb) after insecticide application. The consequences of these sublethal effects on the success of biological control are discussed.     

Effect of temperature on the life history and demographic parameters of Spalgis epius (Lepidoptera: Lycaenidae), a candidate biological control agent of mealybugs (Hemiptera: Pseudococcidae)

Many species of mealybugs (Hemiptera: Pseudococcidae) are serious pests of economically important crops worldwide. We evaluated the influence of constant temperatures: 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 and 34°C on the life history and demographic parameters of Spalgis epius (Lepidoptera: Lycaenidae), a candidate biological control agent of various species of mealybugs. No eggs completed their development at 14 and 34°C. Egg-to-adult developmental time significantly decreased from 89.9 days at 16°C to 20.4 days at 32°C. The estimated lower temperature threshold of 10.2°C and 416.6 degree-days were required to complete egg-to-adult development. The mortality of immature stages was maximum at 16 and 32°C and minimum at 28°C. The highest lifetime fecundity was recorded at 28°C and it significantly decreased at 32°C. The longevity of adults was about three times more at 16°C than at 30 and 32°C. The net reproductive rate (R ₀) significantly increased with increased temperatures up to 28°C and significantly decreased at 32°C. The mean generation time (T) significantly decreased with increased temperature up to 30°C, but it significantly increased at 32°C. The intrinsic rate of population increase (r _m ) was highest at 30°C. The finite rate of increase (λ) was significantly greater at 30°C than at other temperatures. These data suggest that S. epius can develop, reproduce and survive in a wide range of temperatures and thus could be regarded a potential biological control agent of mealybugs.     

Evaluation of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) as a mortality factor of Ceratitis capitata (Diptera: Tephritidae) infesting Citrus species under laboratory and field-cage conditions

Ceratitis capitata (or medfly) is one of the major pests currently affecting fruit crops in northwestern Argentinian Citrus-producing areas. Medfly populations are sustained in large exotic fruits, such as Citrus paradisi, Citrus aurantium and Citrus sinensis, which are known to hinder the activity of almost all native parasitoid species. Therefore, a feasible approach to controlling medfly involves the use of exotic parasitoids such as Diachasmimorpha longicaudata. In this study, the prediction that parasitoid females would be proficient at finding medfly larvae infesting the Citrus species mentioned earlier was tested. Particularly, the variation in fruit species preference by parasitoid females, the efficacy of the parasitoid to kill medfly and the effect of host density on parasitoid performance were determined. Parasitoids were allowed to forage for 8 h on grapefruits and oranges artificially infested with medfly larvae under controlled (laboratory) and uncontrolled (field cage) environmental conditions. Fruit choice and no-choice tests were performed. Results were assessed by comparing the number of female visits to and ovipositor insertions into the fruit, and parasitoid emergence, parasitism and additional host mortality percentages. Parasitoid preference for visiting larger fruits (sour orange and grapefruit) may be related to the increased fruit surface area. Ovipositional activity on fruit was influenced by the variation of the larval host density per unit of fruit surface. The higher parasitism rates recorded from sweet orange would be mainly a result of both increased host density and fruit physical features. Nevertheless, D. longicaudata showed the capacity to parasitise hosts in all Citrus species tested.     

Parasitism of the Wheat Stem Sawfly (Hymenoptera: Cephidae) in Montana

The wheat stem sawfly,Cephus cinctusNorton (Hymenoptera: Cephidae) was first found in wild grasses and soon became an economically important pest of wheat after cultivation began in the northern Great Plains. Of the species of parasitoids that attackC. cinctusin wild grasses, onlyBracon cephi(Gahan) andB. lissogasterMuesebeck (Hymenoptera: Braconidae) have been found in wheat. Levels of parasitism vary between wheat-producing regions in Montana. Parasitism levels were increased by releasing individuals from a region with high levels of parasitism into a region where parasitism levels were low. This suggests that there has been unequal rates of parasitoid adaptation from wild grasses to wheat in different regions of Montana.     

Population dynamics of Plutella xylostella (Lep., Yponomeutidae) and its parasitoids in the region of Brasilia

Abstract: The diamond back moth Plutella xylostella (L.) is the most serious pest of Brassicaceae in the world. It is resistant to many insecticides which has led to a search for alternative techniques of control, principally biocontrol-based pest management. The impact of P. xylostella and its parasitoids was analysed in a 6-month study of cabbage crops in the Brasilia region of Brazil, from June to November 1998. The population of the pest and its guild of parasitoids were quantified on two experimental plots at the Embrapa-Hortaliças research station by weekly samplings. In the first cropping (June to early September), populations of P. xylostella followed a logistic growth curve leading to the destruction of the crops. In the second cropping, rains prevented the development of P. xylostella . Seven species of parasitoids were observed, Diadegma leontiniae (Brethes) and Apanteles piceotrichosus (Blanchard) being dominant. Cotesia plutellae (Kurdjumov) and Actia sp., previously more abundant, became very minor parasitoids. Significant differences were observed in specific parasitism rates between the plots. The combined parasitism rates were identical on both plots (around 23%) and were insufficient to regulate the populations of P. xylostella . Six species of hyperparasites were reared from Diadegma leontiniae and Apanteles piceotrichosus , showing a high diversity of natural enemies in this region of recent colonization by P. xylostella .     

Potential of the parasitoid Heterospilus prosopidis (Hymenoptera: Braconidae) as a vector of plant-pathogenic Colletotrichum spp.

A braconid parasitoid Heterospilus prosopidis was contaminated with either Colletotrichum coffeanum or C. gloeosporioides, causal agents of coffee berry disease and mango anthracnose respectively. Adult parasitoids could collect wetted and unwetted spores of both pathogens on their bodies. Viable spores were recovered in washings from these insects 10 days after infestation. Wetted spores of both species of pathogen had lower viability on the parasitoid's body than unwetted spores, probably because of the loss of the mucilage coating which protects against desiccation. The results suggest that the use of a related parasitoid, H. coffeicola, in biological control against the coffee berry borer, Hypothenemus hampei could pose a phytosanitary risk.     

Biological control of the wetlands weed purple loosestrife (Lythrum salicaria) in the Pacific northwestern United States

Purple loosestrife (Lythrum salicaria) is an Eurasian perennial hydrophyte that has become naturalized in wetlands and in and along waterways throughout temperate North America. The ecological integrity of such areas is threatened by rapidly forming monotypic infestations that displace valued flora and diminish critical fish and wildlife habitat. The inability of physical, cultural, and chemical methods to provide adequate control of the weed has led to the development of an insect-based biological control program. The first field releases of the bud and leaf feeding beetles, Galerucella calmariensis and G. pusilla, and a root-mining weevil, Hylobius transversovittatus, were made in the United States and Canada in 1992. A total of 4740 Galerucella spp. adults were released in central Washington during 1992 and 1993 at eight sites and 471 H. transversovittatus egg inoculations were made in 1993 at three locations. Establishment of both Galerucella spp. was confirmed and Hylobius colonization was achieved.     

Potential non-target impact of Microctonus aethiopoides Loan (Hymenoptera: Braconidae) on Cleopus japonicus Wingelmüller (Coleoptera: Curculionidae), a biocontrol agent for putative release to control the butterfly bush Buddleja davidii Franchet in New Zealand

Abstract  Cleopus japonicus Wingelmüller (Coleoptera: Curculionidae) is being considered for release to control buddleia Buddleja davidii in New Zealand. As part of the pre-release testing, Moroccan and Irish biotypes of the solitary endoparasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae) were evaluated for potential non-target impacts on adult C. japonicus should release occur. Laboratory experiments evaluated both the behavioural and physiological suitability of C. japonicus to both biotypes of the parasitoid. Parasitoid behavioural attraction was assessed using the pathenogenic bacterium Serratia marcescens (Enterobactereaceae), as an indicator of ovipositor penetration. Physiological suitability was assessed by comparing parasitism of C. japonicus with the natural hosts of the respective parasitoid biotypes. The parasitoid-bacteria study showed that C. japonicus was behaviourally acceptable to both Moroccan and Irish M. aethiopoides , with the two experiments producing 34% and 8% mortality, respectively. Cleopus japonicus did not support development of either Moroccan or Irish M. aethiopoides biotypes. None of the weevils dissected at the end of the experiment contained immature parasitoids. Comparison between unexposed and parasitoid-exposed C. japonicus found no difference in premature mortality during the experiment nor in the number of fully reproductive females at its conclusion. The results of this study predict that should C. japonicus be released, the potential impact of M. aethiopoides on field populations will be negligible.