Purification and characterization of esterase 1F, the albumin esterase of the house mouse (Mus musculus)

Esterase 1F was isolated from mouse serum and purified by ion-exchange chromatography, isoelectrofocusing, and molecular sieve chromatography. It is considered to be a glycoprotein with an apparent molecular weight of 75 000. The equivalent weight (approximately equal to 77 000 X g/mol) was estimated by titration of the catalytic site with diethyl p-nitrophenyl phosphate. The Michaelis constant Km and the catalytic constant kcat of the enzyme for 4-nitrophenyl hexanoate were determined. Esterase 1F is characterized by its ability to split a wide spectrum of substrates and its relatively low turnover rates towards the substrates tested. It belongs to the isozyme system of carboxylesterase (EC 3.1.1.1) coded for by chromosome 8. Esterase 1F was compared with three other genetically related isozymes, esterase 2, esterase 7 and esterase 9, with respect to some physical and catalytic properties.     

Effects of selected insecticides on Diadegma semiclausum（Hymenoptera： Ichneumonidae） and Oomyzus sokolowskii （Hymenoptera： Eulophidae）, parasitoids of Plutella xylostella （Lepidoptera： Plutellidae）

Abstract Field doses of six selected insecticides were tested against the immature (pupae) and mature (adult) stages of Diadegma semiclausum (Hellén) and Oomyzus sokolowskii (Kurdjumov), parasitoids of the diamondback moth, Plutella xylostella (L.). Effects of contact toxicity (direct spraying) of the six insecticides on emergence of parasitoids were found negligible on both species except permethrin which caused 37.5% mortality. All adults of both parasitoid species died 24 hours after exposure to chlorfenapyr, emamectin benzoate and permethrin. In contrast, the three insect growth regulators (IGRs), chlorfluazuron, flufenoxuron and teflubenzuron, were found harmless to both species, and adult mortality of both parasitoid species was 0–16.7%. However, parasitism by the females of both parasitoid species was severely impaired when the females were offered the three IGR diluted solutions for 24 hours. Effects of oral toxicities of the IGRs on longevity of both parasitoids after 12 hours exposure were found to be significantly different between males and females. Compatibility of tested insecticides with D. semiclausum and O. sokolowskii and integration of compatible insecticides with these parasitoids in integrated pest management programs of crucifers are discussed.     

Development of Encarsia bimaculata (Heraty and Polaszek) (Hymenoptera: Aphelinidae) in Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) nymphs

Encarsia bimaculata was recently described from India as a potentially useful parasitoid of Bemisia tabaci. Its developmental biology was studied in the laboratory at 25–30 °C and 70–75% RH. Results showed that E. bimaculata is a solitary, arrhenotokous, heteronomous, autoparasitoid. Mated females laid eggs internally in B. tabaci nymphs that developed as primary parasitoids. Males developed as hyperparasitoids, either in females of their own species or in other primary aphelinid parasitoids. Superparasitism was common under cage conditions. Both sexes have an egg, three larval instars, prepupal, and pupal stages. Development from egg to adult took 12.70 ± 2.10 days for females and 14.48 ± 2.60 days for males. Individual B. tabaci nymphs were examined for E. bimaculata parasitization using three isozymes: esterase, malate dehydrogenase, and xanthine dehydrogenase. All three isozymes showed differential banding patterns that identified E. bimaculata parasitized or unparasitized B. tabaci nymphs.     

Polymorphism and antigenic specificity of monocytic acid esterase (EC 3.1.1.6)

With the aim to provide a biochemical or immunological marker for human blood monocytes, their differentiational derivatives, and neoplastic variants the polymorphism of acid α-naphthyl acetate esterase was investigated. Using an isoelectric focusing technique it could be shown that the five enzyme variants of normal human blood monocytes, which do not occur in other human blood cell types, were regularly detectable in human peritoneal and alveolar macrophages. Antisera, raised against isoenzymes of monocytic acid esterase in rabbits, reacted in all cases with every five isoenzymes of blood monocytes; no cross-reactivity was observed with the isoenzymes of acid esterase obtained from purified human granulocytes, peripheral lymphocytes, B lymphocytes, and thymocytes as shown by immunoprecipitation. The results indicate that monocytic acid esterase and its variants could be regarded as a biochemical as well as immunological marker for this cell line.     

Side effects of insecticides on aphidius rhopalosiphi (Hym.: Aphidiidae) In laboratory

The toxicity of bifenthrin, cyfluthrin, λ-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fluvalinate, phosalon and pirimicarb have been assessed in laboratory on the parasitic hymenoptera Aphidius rhopalosiphi. A strong toxic effect was found with every tested product when adult parasitoids were exposed to freshly applied residues on both glass plates and maize leaves for 24 hours. Only two products, fluvalinate and esfenvalerate, did not kill all the insects. No differences were observed between mortalities on glass plates and leaves. Applied on aphids mummies, cyfluthrin and deltamethrin slightly reduced the emergence of young parasitoids, but not their reproductive performance. The other tested products had no effects on adult emergence. On basis of these results, the insecticides are of comparable toxicity to A. rhopalosiphi in laboratory.     

Effects of selected insecticides on adults of two parasitoid species of Liriomyza trifolii: Ganaspidium nigrimanus (Figitidae) and Neochrysocharis formosa (Eulophidae)

Abstract Liriomyza trifolii is an important pest of vegetables and ornamental crops around the world. This pest is attacked by many parasitoid species. The principal management tactic used against L. trifolii is insecticide application. Insecticides vary in their effects on parasitoid species and insecticides that have less harmful effects should be preferred for the control of this pest. In this study, novaluron, abamectin, λ‐cyhalothrin and spinetoram were investigated for their lethal effects on adults of Neochrysocharis formosa and Ganaspidium nigrimanus, two important parasitoids of L. trifolii. Three different bioassays were used on adult parasitoids: direct insecticide application, insecticide intake and insecticide residue. Adult parasitoid response to novaluron exhibited the least lethal effects among the bioassays and insecticides tested. Abamectin had significant mortality to both parasitoid species in the direct application and insecticide intake bioassays and mortality were high for G. nigrimanus in the residue bioassay. Spinetoram was the most harmful insecticide to the adult parasitoids in all three bioassays. λ‐cyhalothrin effects varied between the two parasitoids. In the direct application, it was harmful to G. nigrimanus and had no effect on N. formosa. In the insecticide intake bioassay λ‐cyhalothrin had no effect in survival of either species, and in the residue bioassay it reduced parasitoid survival of both species. Potential tolerance of N. formosa to λ‐cyhalothrin is discussed.     

A Retrospective Analysis of the Establishment and Dispersal of the Introduced Australian Parasitoids Xanthopimpla rhopaloceros (Krieger) (Hymenoptera: Ichneumonidae) and Trigonospila brevifacies (Hardy) (Diptera: Tachinidae) within New Zealand

Two Australian parasitoids, Xanthopimpla rhopaloceros (Krieger) and Trigonospila brevifacies (Hardy), were introduced to New Zealand to control the light-brown apple moth (Epiphyas postvittana Walker). Dispersal by the parasitoids has since occurred naturally and with the aid of releases in fruit-growing areas. The present geographical range of the parasitoids includes all the North Island and some offshore islands to latitude 41 20 S. X. rhopaloceros is also present to latitude 41 48 S in the South Island. Comparisons of these distributions with those in Australia indicate that climatic conditions may have played a major role in the areas of establishment of both species in New Zealand. The mean winter temperature may be a limiting factor in the dispersal of T. brevifacies and X. rhopaloceros in New Zealand. Other factors that have probably aided the successful dispersal of the parasitoids include the wide distribution of host Tortricidae and the occurrence of tortricid host plants. The areas of New Zealand that appear suitable for further colonization by T. brevifacies include northern areas of the South Island, and both parasitoids could disperse further into suitable climate areas of the east and west coasts of the central South Island. The rate of dispersal for X. rhopaloceros was estimated at 13-24 km/year, and for T. brevifacies at 8-15 km/year.     

Development of the parasitoid,Cotesia rubecula (Hymenoptera: Braconidae) in Pieris rapae and Pieris brassicae (Lepidoptera: Pieridae): evidence for host regulation

Several recent models examining the developmental strategies of parasitoids attacking hosts which continue feeding and growing after parasitism (=koinobiont parasitoids) assume that host quality is a non-linear function of host size at oviposition. We tested this assumption by comparing the growth and development of males of the solitary koinobiont endoparasitoid, Cotesia rubecula, in first (L1) to third (L3) larval instars of its preferred host, Pieris rapae and in a less preferred host, Pieris brassicae. Beginning 3 days after parasitism, hosts were dissected daily, and both host and parasitoid dry mass was determined. Using data on parasitoid dry mass, we measured the mean relative growth rate of C. rubecula, and compared the trajectories of larval growth of the parasitoid during the larval and pupal stages using non-linear equations. Parasitoids generally survived better, completed development faster, and grew larger in earlier than in later instars of both host species, and adult wasps emerging from P. rapae were significantly larger than wasps emerging from all corresponding instars of P. brassicae. During their early larval stages, parasitoids grew most slowly in L1 P. rapae, whereas in all other host classes of both host species growth to pupation proceeded fairly uniformly. The growth of both host species was markedly reduced after parasitism compared with controls, with the development of P. brassicae arrested at an earlier stage, and at a smaller body mass, than P. rapae. Our results suggest that C. rubecula regulates certain biochemical processes more effectively in P. rapae than in P. brassicae, in accordance with its own nutritional and physiological requirements. Furthermore, we propose that, for parasitoids such as C. rubecula, which do not consume all host tissues prior to pupation, that parasitoid size and host quality may vary independently of host size at oviposition and at larval parasitoid egression.     

Ecological and morphological characteristics of endoparasitoids on Elcysma westwoodii (Vollenhoven) (Lepidoptera: Zygaenidae)

Six species of insect endoparasitoids were identified from Elcysma westwoodii, which is the most damaging lepidopteran pest of Prunus yedoensis. From Hymenoptera, two species were identified: a species in Braconidae and Charops striatus in Ichneumonidae. From Diptera, there were four species in Tachinidae: Compsilura concinnata, Exorista sp., Pales sp. and Tachinidae spp. The parasitic ratio was 4.86% (45 of 926 larvae). The hymenopterans were parasitic on 31 individuals of E. westwoodii (68.9%) and the dipterans were parasitic on 14 individuals (31.1%). It was found that parasitoids from the larvae of E. westwoodii were all either endoparasitoids or larval parasitoids. However, Exorista sp. of Tachinidae was found to be either a larval parasitoid or larval-pupal parasitoid. Additionally, all the identified parasitoids were solitary parasitoids, as only one parasite occurred in a larva of E. westwoodii. Because the larva of E. westwoodii eats and molts after it is parasitized, all the parasitoids were identified as koinobionts. There were no big differences in morphological characteristics and life histories between C. striatus and C. concinnata. However, for Exorista sp. and Pales sp., males took 3–5 days longer to emerge from their pupae and had remarkably longer body lengths than females.     

Increasing vineyard floral resources may not enhance localised biological control of the leafroller Epiphyas postvittana (Lepidoptera: Tortricidae) by Dolichogenidea spp. (Hymenoptera: Braconidae) parasitoids

In agroecosystems, the efficacy of biological control exerted by many parasitoids is predicted to be enhanced where the availability of floral resources is increased. Such resources may attract parasitoids and enhance their longevity and fecundity. In Hawke's Bay, New Zealand, this prediction was tested by adding varying quantities of potted flowering alyssum (Lobularia maritima) (Brassicaceae) to plots containing apple plants (Malus domestica) inoculated with larvae of the leafroller, Epiphyas postvittana (Lepidoptera: Tortricidae). In two replicated trials, over 90% of the parasitoids from recovered larvae were Dolichogenidea spp. (Hymenoptera: Braconidae). In both trials increasing the percentage of alyssum did not result in a corresponding increase in the leafroller parasitism rate. Instead, the primary influence on parasitism rates was due to Dolichogenidea spp. dispersing from a nearby orchard. A significant negative correlation was observed in leafroller parasitism as a function of distance from this orchard. A vineyard to the north of the study site also influenced parasitism rates. Our results suggest the orchard was a regional source population for this parasitoid, and the abundance of local resources such as alyssum did not influence parasitoid foraging. At the level of our entire study block, our effective area of resource provision was 0.1%. A level of resource provision higher than that used in this study may be necessary to test for a positive influence on local parasitism rates. From our results, it appears that for parasitoids with relatively high dispersal rates, the availability of local resources may not be as important as a regional source population.     

Isolation and characterization of sialate 9(4)-O-acetylesterase from influenza C virus

An esterase was isolated from influenza C virus with a specific activity from 1.7-5 U/mg protein, and its substrate specificity was tested with various naturally occurring O-acylated sialic acids, synthetic carbohydrate acetates, and other esters. The enzyme hydrolyses only acetic acid esters at significant rates. The non-natural substrates 4-methyl-umbelliferyl acetate, 4-nitrophenyl acetate, and alpha-naphthyl acetate are cleaved at highest hydrolysis rates, followed by the natural substrate N-acetyl-9-O-acetylneuraminic acid. The esterase also acts on N-glycoloyl-9-O-acetylneuraminic acid and, much slower, on N-acetyl-4-O-acetylneuraminic acid; N-acetyl-7-O-acetylneuraminic acid is not hydrolysed. 2-Deoxy-2,3-didehydro-N-acetyl-9-O-acetylneuraminic acid is also a substrate for this enzyme, however, 6-O-acetylated N-acetylmannosamine and glucose are not. Esterification of the carboxyl function of sialic acids strongly reduces or prevents esterase action on O-acetyl groups. The carboxyl ester is not hydrolysed. The relative cleavage rates also depend on the type of the non-sialic acid part of the molecule. N-Acetyl-9-O-acetylneuraminic acid as component of sialyllactose and rat serum glycoprotein shows hydrolysis rates close to the free form of this sugar, while acetyl ester groups of bovine submandibular gland mucin and rat erythrocytes are hydrolysed at slower rates. Gangliosides and 4-O-acetylated glycoproteins are no substrates for the purified enzyme. A slow hydrolysis is observed by incubation of 9-O-acetylated GD1a with intact influenza C viruses. As other natural acetyl esters (acetyl-CoA and acetylthiocholine iodide) are not hydrolysed, the enzyme can be classified as sialate 9(4)-O-acetylesterase (EC 3.1.1.53).     

Susceptibility of house flies (Diptera: Muscidae) and five pupal parasitoids (Hymenoptera: Pteromalidae) to abamectin and seven commercial insecticides.

Assays of five commercial insecticides applied as residual sprays at label rates to plywood indicated the most toxic insecticide overall for pteromalid parasitoids of house flies, Musca domestica L., was Atroban (permethrin), followed by Ciodrin (crotoxyphos), Rabon (tetrachlorvinphos), Ectrin (fenvalerate), and Cygon (dimethoate). Insecticide-susceptible house flies were susceptible to all five insecticides (mortality, 62-100%). Flies that were recently colonized from populations on dairy farms in New York were susceptible only to Rabon. Urolepis rufipes (Ashmead) was the most susceptible parasitoid species overall to these insecticides, followed by Muscidifurax raptor Girault & Sanders, Nasonia vitripennis Walker, Pachycrepoideus vindemmiae (Rondani), and Spalangia cameroni Perkins. Compared with susceptible flies, newly colonized flies showed moderate resistance to avermectin B1a (abamectin). Abamectin was more toxic to all of the parasitoids except N. vitripennis and S. cameroni than to newly colonized house flies when exposed for 90 min to plywood boards treated with 0.001-0.1% abamectin. Space sprays with Vapona (dichlorvos) killed all of the parasitoids and susceptible flies and 64% of the newly colonized flies when insects were placed directly in the path of the spray; mortality was substantially lower among flies and parasitoids protected under 5 cm of wheat straw. Space sprays with Pyrenone (pyrethrins) killed greater than 86% of all insects exposed to the spray path except for the newly colonized flies (1% mortality); mortality of insects protected under straw was low (less than 12%) except for S. cameroni (76%). Because responses of the five parasitoids to the different insecticides varied considerably, general conclusions about parasitoid susceptibility to active ingredients, insecticide class, or method of application were not possible.     

The esterase from the thermophilic eubacterium Bacillus acidocaldarius: structural-functional relationship and comparison with the esterase from the hyperthermophilic archaeon Archaeoglobus fulgidus

The esterase from the thermophilic eubacterium Bacillus acidocaldarius is a thermophilic and thermostable monomeric protein with a molecular mass of 34 KDa. The enzyme, characterized as a "B-type" carboxylesterase, displays the maximal activity at 65 degrees C. Interestingly, it is also quite active at room temperature, an unusual feature for an enzyme isolated from a thermophilic microorganism. We investigated the effect of temperature on the structural properties of the enzyme, and compared its structural features with those of the esterase from the hyperthermophilic archaeon Archaeoglobus fulgidus. In particular, the secondary structure and the thermal stability of the esterase were studied by FT-IR spectroscopy, while information on the conformational dynamics of the enzyme were obtained by frequency-domain fluorometry and anisotropy decays. Our data pointed out that the Bacillus acidocaldarius enzyme possesses a secondary structure rich in alpha-helices as described for the esterase isolated from Archaeoglobus fulgidus. Moreover, infrared spectra indicated a higher accessibility of the solvent ((2)H(2)O) to Bacillus acidocaldarius esterase than to Archaeoglobus fulgidus enzyme suggesting, in turn, a less compact structure of the former enzyme. The fluorescence studies showed that the intrinsic tryptophanyl fluorescence of the Bacillus acidocaldarius protein was well represented by the three-exponential model, and that the temperature affected the protein conformational dynamics. The data suggested an increase in the protein flexibility on increasing the temperature. Moreover, comparison of Bacillus acidocaldarius esterase with the Archaeoglobus fugidus enzyme fluorescence data indicated a higher flexibility of the former enzyme at all temperatures tested, supporting the infrared data and giving a possible explanation of its unusual relative high activity at low temperatures. Proteins 2000;40:473-481.     

Potential for classical biological control of the potato bug Closterotomus norwegicus (Hemiptera: Miridae): description, parasitism and host specificity of Peristenus closterotomae sp. n. (Hymenoptera: Braconidae)

The potato bug, Closterotomus norwegicus (Gmelin) (Hemiptera: Miridae) is an introduced pest of lucerne, white clover and lotus seed crops in New Zealand and a key pest of pistachios in California, USA. Efforts were made to identify potential biological control agents of C. norwegicus in Europe. A total of eight parasitoids, including six primary parasitoids from the genus Peristenus (Hymenoptera: Braconidae) and two hyperparasitoids from the genus Mesochorus (Hymenoptera: Ichneumonidae), were reared from C. norwegicus nymphs collected in various habitats in northern Germany. With a proportion of more than 85% of all C. norwegicus parasitoids, Peristenus closterotomae (Hymenoptera: Braconidae), a new species, was the most dominant parasitoid, whereas other parasitoid species only occurred sporadically. Peristenus closterotomae did not fit in the keys to any described species and is described as new to science. Parasitism caused by P. closterotomae was on average 24% (maximum 77%). To assess the host specificity of parasitoids associated with C. norwegicus, the parasitoid complexes of various Miridae occurring simultaneously with C. norwegicus were studied. Peristenus closterotomae was frequently reared from Calocoris affinis (Herrich-Schaeffer), and a few specimens were reared from Calocoris roseomaculatus (De Geer) and the meadow plant bug, Leptopterna dolobrata (Linnaeus) (all Hemiptera: Miridae). The remaining primary parasitoids associated with C. norwegicus were found to be dominant in hosts other than C. norwegicus. Whether nymphal parasitoids may potentially be used in a classical biological control initiative against the potato bug in countries where it is introduced and considered to be a pest is discussed.     

Cloning and identification of a new group esterase (Est5S) from noncultured rumen bacterium

The gene encoding an esterase enzyme was cloned from a metagenomic library of cow rumen bacteria. The esterase gene (est5S) was 1,026 bp in length, encoding a protein of 366 amino acid residues with a calculated molecular mass of 40,168 Da. The molecular mass of the enzyme was estimated to be 40,000 Da. The Est5S protein contains the Gly-X-Ser-X-Gly motif found in most bacterial and eukaryotic serine hydrolases. However, the Asp or Glu necessary for the catalytic triad [Ser-Asp-(Glu)-His] was not present, indicating Est5S represents a novel member of the GHSQG family of esterolytic enzymes. BlastP in the NCBI database analysis of Est5S revealed homology to hypothetical proteins and it had no homology to previous known lipases and esterases. Est5S was optimally active at pH 7.0 and 40 degrees C. Among the p-nitrophenyl acylesters tested, high enzymatic activities were observed on the short-chain p-nitrophenyl acylesters, such as p-nitrophenyl acetate, etc. The conserved serine residue (Ser190) was shown to be important for Est5S activity. The primers that amplified the est5S gene did not show any relative band with 49 species of culturable rumen bacteria. This implies that a new group esterase gene, est5S, may have come from a noncultured cow rumen bacterium.     

Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species (Diptera: Tephritidae) and their parasitoids (Hymenoptera: Braconidae)

The feeding toxicity of the natural insecticide spinosad in Provesta protein bait was evaluated for three economically important fruit fly species, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the melon fly, Bactrocera cucurbitae Coquillett; and the oriental fruit fly, Bactrocera dorsalis Hendel. Both females and males were evaluated. Spinosad was remarkably similar in toxicity to all three fruit fly species. Male C. capitata (24 h LC50 values and 95% fiducial limits = 2.8 [2.60-3.0] mg/liter spinosad) were significantly, although only slightly more susceptible to spinosadthan females (4.2 [3.8-4.6] mg/liter). Male (5.5 [4.7-6.6] mg/liter) andfemale (4.3 [3.7-4.9] mg/liter) B. cucurbitae were equally susceptible to spinosad. Female (3.3 [3.1-3.6] mg/liter) and male (3.1 [2.9-3.3] mg/liter) B. dorsalis also were equally susceptible to spinosad. Provesta bait containing spinosad also was evaluated against two parasitoids of tephritid fruit flies, Fopius arisanus (Sonan) and Pysttalia fletcheri (Silvestri). These parasitoids did not feed on the bait, so a contact toxicity test was conducted. Significant amounts of mortality were found only after exposure of parasitoids to spinosad-coated glass vials with concentrations > or =500 mg/liter spinosad. Parasitoids were less susceptible than fruit flies to such a degree that use of spinosad in bait spray should be compatible with these parasitoid species. Because the fruit flies tested in this study were so susceptible to spinosad, this product seems to be promising as a bait spray additive and a replacement for malathion for control of these species.     

Lipase of Mucor pusillus

Lipase of Mucor pusillus NRRL 2543 was recovered with ammonium sulfate precipitation, gel filtration on Sephadex G-75, and anion-exchange chromatography on diethylaminoethyl-Sephadex A-50. Maximal glycerol ester hydrolase (lipase) activity was observed at pH 5.0 to 5.5 and 50 C when trioctanoin and olive oil were used as substrates. The enzyme also showed esterase activity; it hydrolyzed, with the exception of methyl butyrate, all methyl esters tested. A minimum chain length of six carbons appeared to be a requirement for esterase activity, which was maximal at about pH 5.5 with methyl dodecanoate (C(12)) as the substrate. Neither the glycerol ester hydrolase (lipase) nor the esterase activity of the enzyme appeared to be affected by thiol group inhibitors, chelating agents, and reducing compounds. On the other hand, hydrolysis of triolein and methyl dodecanoate was arrested to the same extent in the presence of diisopropyl fluorophosphate, which suggested the involvement of serine in the active center of the enzyme. The enzyme remained stable during a 30-day storage at - 10 C.     

Cardinium in Plagiomerus diaspidis (Hymenoptera: Encyrtidae)

The bacterial symbiont Cardinium (Bacteroidetes) was previously implicated in the thelytokous reproduction of the parasitoid Plagiomerus diaspidis Crawford (Hymenoptera: Encyrtidae). Horizontal transmission of the symbiont among the cactus scale Diaspis echinocacti Bouché (Homoptera: Diaspididae) and its hymenopteran parasitoids has been suggested. In this study, the bacteria associated with D. echinocacti, its parasitoids P. diaspidis and Aphytis sp. (Hymenoptera: Aphelinidae), and the hyperparasitoid Marietta leopardina Motschulsky (Hymenoptera: Aphelinidae) were characterized using molecular fingerprinting techniques, and the localization of Cardinium in P. diaspidis was studied using fluorescence in situ hybridizations (FISH). Cardinium was the only bacterium found in P. diaspidis, but it could not be detected in any of the other insects tested. The symbiont was specifically located in the reproductive tissues of its P. diaspidis host.     

Juvenile and sublethal effects of selected pesticides on the leafminer parasitoids Hemiptarsenus varicornis and Diglyphus isaea (Hymenoptera: Eulophidae) from Australia

The pest leafminers Liriomyza huidobrensis (Blanchard), Liriomyza sativae (Blanchard), and Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) have spread into South East Asia and Oceania, and they are likely to reach Australia in the near future. Two translaminar pesticides, cyromazine and abamectin, currently provide effective chemical control of these pests, but because parasitoids can play an important role in controlling and preventing leafminer outbreaks, understanding the impact of pesticides on leafminer parasitoids is vital. Here, we tested larval and pupal mortality and sublethal effects of abamectin, cyromazine, and the widely used fungicide mancozeb on two common Australian leafminer parasitoids, Hemiptarsenus varicornis (Girault) and Diglyphus isaea (Walker). Abamectin caused significant mortality to larvae and pupae of both parasitoid species but cyromazine and mancozeb did not. Progeny production and longevity of H. varicornis were not affected by adult exposure to cyromazine and mancozeb, nor did direct pupal exposure decrease number of progeny produced by either parasitoid. Mortality of H. varicornis females emerging from leaves treated with abamectin was high for up to 72 h after eclosion but those surviving beyond 72 h did not differ from control females in the number of progeny produced. Mancozeb did not influence leaf residence time or parasitism by H. varicornis females. Cyromazine and the fungicide mancozeb were concluded to be compatible with the parasitoids tested and suitable for integrated pest management of leafminers should outbreaks of pest species occur in Australia. Abamectin should be used with caution because it caused significant mortality in both parasitoids tested here.