The occurrence of leafminers and their parasitoids on vegetables and weeds in Hangzhou area, Southeast China

Leafminers are the mostimportant insect pests of vegetables inHangzhou area, Zhejiang province, SoutheastChina as well as in the rest of China, but havenever been investigated for speciescomposition, relative abundance and theirassociated parasitoids. A survey was conductedin four localities of Hangzhou area during 1998–2000to determine the distribution ofleafminers and their parasitoids on vegetablecrops and weeds in the field. Over 20,000leafminers were collected and reared. Theleafminer species found were Liriomyzasativae, L. chinensis and Chromatomyia horticola, with C.horticola and L. sativae the mostabundant in spring and autumn, respectively.About 11,000 parasitoid adults were reared fromthe leafminers collected. In total 14hymenopteran species of four families (onebraconid, 10 eulophids, one megaspilid and onepteromalid) were found. Eleven species werereared from C. horticola, nine from L. sativae and seven from L. chinensis.Opius caricivorae and Chrysocharispentheus were the dominant species. Sevenspecies were recorded from L. chinensisfor the first time. Eleven parasitoid specieswere reared from leafminers on two weeds (Veronica undulata and Sonchusoleraceus). Parasitoids caused 48.5–68.8%parasitism on leafminers on crops and 83.7%parasitism on leafminers on weeds in the latergrowing season of vegetable crops. The resultssuggest that leafminer populations areregulated to a certain extent by their naturalenemies in the field.     

Light brown apple moth in California: a diversity of host plants and indigenous parasitoids

The light brown apple moth, Epiphyas postvittana (Walker), an Australia native tortricid, was found in California in 2006. A field survey of host plants used by E. postvittana was conducted in an urban region of the San Francisco Bay Area. An inspection of 152 plant species (66 families), within a 23-ha residential community, found E. postvittana on 75 species (36 families). Most (69 species) host plants were not Australian natives, but had a wide geographic origin; 34 species were new host records for E. postvittana. Heavily infested species were the ornamental shrubs Myrtus communis L., Pittosporum tobira (Thunb.) W.T. Aiton, Euonymus japonicus Thunb., and Sollya heterophylla Lindl. To survey for parasitoids, four urban locations were sampled, with E. postvittana collected from five commonly infested plants [M. communis, P. tobira, E. japonicus, Rosmarinus officinalis L., and Genista monspessulana (L.) L.A.S. Johnson]. Twelve primary parasitoid species and two hyperparasitoids were reared; the most common were the egg parasitoid Trichogramma fasciatum (Perkins), the larval parasitoids Meteorus ictericus Nees, and Enytus eureka (Ashmead), and the pupal parasitoid Pediobius ni Peck. Meteorus ictericus accounted for >80% of the larval parasitoids, and was recovered from larvae collected on 39 plant species. Across all samples, mean parasitism was 84.4% for eggs, 43.6% for larvae, and 57.5% for pupae. The results are discussed with respect to the potential for resident parasitoid species to suppress E. postvittana populations.     

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.     

Evaluation of the community of native eulophid parasitoids on Cameraria ohridella Deschka and Dimic in urban areas

The parasitoid complex associated with the exotic leafminer Cameraria ohridella Deschka and Dimic (Lepidoptera: Gracillariidae), which attacks horse chestnut (Aesculus hippocastanum L.), was studied in the urban environment of Turin (northern Italy). The studies were carried out over 5 yr after the first detection of the pest in our region in 1999. To evaluate parasitism, 438,029 leaf mines were examined over the 5-yr period, of which 29,033 were found to be parasitized (6.6%). Also, ornamental broadleaf trees attacked by other native gracillariid leafminers and located in the proximity of the target horse chestnut trees were sampled. A total of 11 parasitoid species (Hymenoptera: Eulophidae) were recorded on C. ohridella, and the most common species were Minotetrastichus frontalis (Nees), Closterocerus trifasciatus Westwood, and Pnigalio agraules (Walker). The first species accounted for >77.5% of all parasitoids collected. Cirrospilus talitzkii Boucek was found for the first time in 2005. The high population level of the pest and the low parasitism rate show that the parasitoid complex is currently inadequate to contain C. ohridella populations effectively. The most frequent parasitoids of the moth were also found on the most common broadleaf trees in the studied area, showing how native leafminer parasitoid species are able to switch to other hosts. These results show that both native and broadleaf plants species may potentially provide an important reservoir of parasitic wasps to help protect a simple biotope, such as the urban environment, from pests.     

Quantitative food webs of lepidopteran leafminers and their parasitoids in a Japanese deciduous forest

Quantitative food webs were constructed to explore the community structure of leaf-mining moths in the family Gracillariidae and their parasitoid wasps in a deciduous forest in Hokkaido, Japan. A whole food web was constructed from data collected from June to October 2001. In the web, 16 leafminer species on seven tree species were attacked by 58 species of hymenopteran parasitoid; 376 links between leafminers and parasitoids were observed. Leafminers were specialist herbivores, but most parasitoids were generalists. Five webs were constructed for the seasonal prevalence of leafminers over the one-year period to reveal the temporal dynamics in community structure. Among the seasonal webs, the first web in June was distinctive because two tree species, Japanese umbrella tree Magnolia obovata and Japanese magnolia M. kobus, supported the community. Second to fourth webs from July to September were dominated by the leafminer species on Japanese oak Quercus crispula, and the fifth web was marked by that on Carpinus cordata. The extent of potential apparent competition among leafminers was evaluated using quantitative parasitoid overlap diagrams. These diagrams suggested that abundant host species are likely to have large indirect effects on less abundant species. Moreover, the potential for apparent competition between leafminer species inhabiting different host tree species can occur, although leafminers sharing the same tree species are prone to interact via shared parasitoids. In this system, particular leafminer species, acting as potential sources of apparent competition, can affect other species as sinks, and control whole-community dynamics. Directed apparent competition may potentially occur around oak trees.     

甘肃白银地区潜叶蝇及其寄生蜂的组成和发生调查

【目的】明确严重危害甘肃省白银地区作物的潜叶蝇及天敌寄生蜂的多样性和种群组成。【方法】采用五点取样法田间调查潜叶蝇危害的蔬菜、花卉、杂草并采样,室内对潜叶蝇及其寄生蜂进行形态鉴定和分子鉴定。【结果】在2016-2020年在甘肃白银地区采集的样本中发现6种常见潜叶蝇,包括本地种豌豆彩潜蝇Chromatomyia horticola和葱斑潜蝇Liriomyza chinensis,入侵种南美斑潜蝇L. huidobrensis、三叶草斑潜蝇L. trifolii、番茄斑潜蝇L. bryoniae和美洲斑潜蝇L. sativae。其中,豌豆彩潜蝇为优势种,可危害多科寄主植物;葱斑潜蝇仅在大葱上发现危害;南美斑潜蝇在温室内的蔬菜上发生严重;三叶草斑潜蝇首次在白银市发现;番茄斑潜蝇与美洲斑潜蝇的危害相对较轻。此外,调查的潜叶蝇寄生蜂包括3科12属24种,优势种包括豌豆潜蝇姬小蜂Diglyphus isaea、芙新姬小蜂Neochrysocharis formosa、万氏潜蝇姬小蜂D. wani和西伯利亚离颚茧蜂Dacnusa sibirica。【结论】一方面白银市应加强监测和预警入侵性潜叶蝇的发生,另一方面白银市潜叶蝇的天敌寄生蜂种类丰富,对田间主要危害的潜叶蝇可能发挥着重要的自然防控作用,建议保护利用本地寄生蜂天敌。     

A survey of hymenopteran parasitoids of forest macrolepidoptera in the central Appalachians

In 1995 and 1996, we conducted a study of the hymenopteran parasitoids of macrolepidopteran larvae in the George Washington National Forest (GWNF), Augusta County, Virginia, and the Monongahela National Forest (MNF), Pocahontas County, West Virginia. Macrolepidopteran larvae were collected from canopy foliage and from under canvas bands placed around tree boles. A total of 115 macrolepidopteran species and 5,235 individual larvae were reared. Forty-two percent (2,221) of the larvae were gypsy moth, Lymantria dispar (L.) (Lymantriidae). A total of 43 primary and secondary (hyperparasitoid) hymenopteran parasitoid species were reared from 46 macrolepidopteran species. Hymenopteran families represented included Ichneumonidae (23 species), Braconidae (19), Eulophidae (6), Perilampidae (1), and Trigonalidae (1). We reared 41 and 28 parasitoid species from the GWNF and the MNF, respectively, with 19 species reared from both forests. Many parasitoid species were collected infrequently, suggesting that they are relatively rare on the sampled hosts. The introduced species Cotesia melanoscela (Ratzeburg) (Braconidae), and Euplectrus bicolor (Swederus) (Eulophidae) were among the most commonly reared parasitoids, the latter reared from native hosts. The four most commonly reared native parasitoids were Meteorus hyphantriae, Riley (Braconidae), Microplitis near hyphantriae (Ashmead) (Braconidae), Aleiodes preclarus Marsh & Shaw, and Euplectrus maculiventris (Westwood) (Eulophidae). A total of 53 new hymenopteran parasitoid-macrolepidopteran host records were documented. Results from this study will be used to evaluate long-term treatment effects of regional applications of Bacillus thuringiensis kurstaki, and the gypsy moth fungus Entomophaga maimaiga Humber, Shimazu & Soper on hymenopteran parasitoids of macrolepidopteran larvae.     

Parasitoid Wasps in Flower Heads of Asteraceae in the Brazilian Cerrado: Taxonomical Composition and Determinants of Diversity

This study provides the first survey of the parasitoid fauna reared in flower heads of Asteraceae in the Brazilian cerrado. We investigated the relative importance of herbivore richness and plant species commonness to differences in parasitoid species richness among the plant species. A total of 15,372 specimens from 192 morphospecies belonging to 103 genera of Hymenoptera were reared from the flower heads of 74 Asteraceae species. Chalcidoidea and Ichneumonoidea were the most common superfamilies, with Eulophidae and Braconidae as the main families of parasitoid wasps. Singletons and doubletons accounted for 45% of total parasitoid species richness. The number of parasitoid species per plant species ranged from 1 to 67, and the variation in parasitoid species richness among plants was mainly explained by the number of sites in which the plants were recorded. This study shows that there is a highly diversified fauna of Hymenoptera parasitoids associated with flower heads of Asteraceae in the Brazilian cerrado. Our findings suggest that the accumulation of parasitoid species on plants is mainly determined by the regional commonness of plant species rather than the number of herbivore species associated with the plants.     

Taxonomic Composition of Hymenopteran Parasitoid Assemblages from Agromyzid Leaf-miners Sampled in Central Argentina

This paper deals with the taxonomic composition of parasitoid assemblages reared from agromyzid leaf-miners of 28 species collected in Cordoba, Central Argentina. The relative representation of each parasitic family was estimated, taking into consideration their species richness and abundance. Sample size affected the total species richness in each complex, and also that of Eulophidae and Pteromalidae, indicating that not only size but also taxonomic structure of parasitic assemblages are influenced by sampling effort. 3 superfamilies and 5 families of Hymenoptera Parasitica were represented, with Eulophidae (Chalcidoidea) specifically and numerically dominant both in the total community of parasitoids and in the parasitic assemblages of individual hosts. Chrysonotomyia, Chrysocharis (Eulophidae), Halticoptera (Pteromalidae) and Phaedrotoma (Braconidae) were the most relevant genera in terms of number of species and number of specimens reared. The parasitoids obtained from samples taken in agroecosystems differed from the global spectrum of taxa mainly by showing a numerical dominance of Braconidae, despite a noticeable specific impoverishment of this family.     

Preliminary inventory of parasitoids associated with fruit flies in mangoes,guavas, cashew pepper and wild fruit crops in Benin

Fruit flies are pests of great economic importance due to their quarantine pest status and losses recorded in West Africa. An inventory of parasitoids associated with fruit flies in mangoes, guavas, cashew, pepper and major wild fruit crops was carried out in northern-central Benin in 2005, 2006, and 2008. Tephritid parasitoids reared from field-collected fruits belonged to three families: Braconidae (97.2%), Eulophidae (1.6%) and Pteromalidae (1.2%). Fopius caudatus (Szépligeti) accounted for 73.8% of all the parasitoids and therefore was the most abundant and widely distributed parasitoid. The parasitism rate was 7.7%, with the highest recorded in wild fruit crop habitat. Ceratitis cosyra (Walker) (77%) was the fly host most commonly reared from fruits that produced F. caudatus. The recently introduced pest Bactrocera invadens Drew Tsuruta and White was rarely parasitized and only by Pachycrepoideus vindemmiae (Rondani) (Hymenoptera: Pteromalidae) at this time. This is the first report of the inventory of one native parasitoid species from B. invadens in Africa, especially in West Africa.     

Species richness and parasitism in an assemblage of parasitoids attacking maize stem borers in coastal Kenya

Abstract. 1. Parasitoids were reared from four species of lepidopteran stem borer collected in maize in southern coastal Kenya from 1992 to 1999. The stem borers included three native species, Sesamia calamistis Hampson, Busseola fusca Fuller, and Chilo orichalcociliellus (Strand), and one exotic borer, Chilo partellus (Swinhoe). A total of 174 663 caterpillars was collected, of which 12 645 were parasitised.
2. Twenty-six primary parasitoid species were reared from the exotic borer, C. partellus , indicating a rapid accumulation of native parasitoids on the alien borer.
3. The three most abundant parasitoids were the larval parasitoids Cotesia sesamiae Cameron, Cotesia flavipes (Cameron), and the pupal parasitoid Pediobius furvus Gahan. The pupal parasitoid Dentichasmias busseolae Heinrich and the larval parasitoid Goniozus indicus Ashmead were also common. All used an ingress-and-sting method of attack.
4. Cotesia flavipes , introduced into Kenya in 1993, was found in all seasons from 1997 onwards, and has become the most abundant stem borer larval parasitoid in the area. A native congener, Cotesia sesamiae , appeared in all seasons from 1992 to 1999. Together, these two parasitoids accounted for 83.3% of the parasitised borers.
5. Thirty parasitoid species were recovered in Kilifi district, 27 in Kwale, and 15 in Taita Taveta. Parasitism was much greater in Taita Taveta district than in Kilifi or Kwale districts.     

Parasitoids and hyperparasitoids of Mythimna convecta (Walker) (Lepidoptera: Noctuidae) larvae infesting late-maturing maize in southern New South Wales

Abstract  After several reports of late-maturing maize in Murrumbidgee valley, southern New South Wales, Australia, being severely damaged by armyworm, five crops were surveyed for the presence of larvae in April 2003. Mythimna convecta Walker (Lepidoptera: Noctuidae) was the only species successfully reared from armyworm larvae collected in the field. Ninety-six per cent of armyworm larvae collected were parasitised. Five parasitoid species, Cuphocera sp. nr pilosa (Malloch), Ceromya horma (Malloch), Tritaxys scutellate (Macquart), Chaetophthalmus sp. (Diptera: Tachinidae) and Netelia sp. (Hymenoptera: Ichneumonidae) were reared from M. convecta larvae. Cuphocera sp. nr pilosa was the most frequently encountered parasitoid being reared from 83% of M. convecta larvae collected. Examination of maize plants at each collection site showed high numbers of tachinid puparia adhering to plants. Cuphocera sp. nr pilosa was the only species reared from these puparia. Of the Cu . sp. nr pilosa puparia collected, 23–83% were parasitised by five parasitoid wasps: Trichomalopsis sp. Crawford (Hymenoptera: Pteromalidae), Brachymeria sp. Westwood, Eupelmus sp. Dalman (Hymenoptera: Chalcididae), Perilampus sp. Latreille (Hymenoptera: Perilampidae) and a species belonging to the family Diapriidae.     

First record of a walnut shield bearer Coptodisca (Lepidoptera: Heliozelidae) in Europe

A leafminer of the Nearctic genus Coptodisca Walsingham (Lepidoptera: Heliozelidae), a species of potential economic interest, is reported for the first time from Europe, infesting the black (Juglans nigra L.) and the common walnut (Juglans regia L.). Mines were collected since September of 2010 in several sites of two Italian regions (Campania and Lazio). The species is rather similar to Coptodisca juglandella (Chambers), the only Coptodisca known to attack walnuts, but at present, an unambiguous identification cannot be provided because of the unsatisfactory characterization of this leafminer and congeneric species. Three generations were recorded per year and leafminers overwinter as mature larvae. The first adults emerged in May–June while mature larvae of the last generation started the overwintering in September. During the last generation of the year, infestation levels of leaves were 100% in all sampled localities. Several species of parasitoids were reared from infested mines, with specimens belonging to the genus Chrysocharis (Hymenoptera: Eulophidae) being the most frequent parasitoids.     

Intraspecific size variation in polyphagous parasitoids (Hym.: Parasitica), of leaf miners and its relation to host size

Wing and body lengths of polyphagous parasitoids of leafminers are analyzed in order to understand the relationship between host and parasitoid sizes. A distinct positive relationship was observed: within each parasitoid species, smaller individuals were reared from smaller hosts. There was no difference between idio-and koinobionts in sexual dimorphism, with females being significantly larger than males in both groups.     

The role of host plant species in the phenotypic differentiation of sympatric populations of Aleiodes nolophanae and Cotesia marginiventris

The ecology of parasitoids is strongly influenced by their host plant species. Parasitoid fitness can be affected by a variety of plant traits that could promote phenotypic differentiation among populations of parasitoids. Generalist parasitoids are expected to be more affected by plant traits (e.g., plant defensive traits) than specialist parasitoids. Data are presented on phenotypic differences of two braconid parasitoid wasps ovipositing on the same insect host species on two different host plant species. Adult mass, adult longevity, and percent parasitism are compared for the generalist parasitoid Cotesia marginiventris Cresson and the specialist parasitoid Aleiodes nolophanae Ashmead (both Hymenoptera: Braconidae) emerging from green cloverworms, Hypena scabra Fabricius (Lepidoptera: Noctuidae), feeding on two host plant species, alfalfa (Medicago sativa L.) and soybean (Glycine max L. Merr.) (both Fabaceae), at three locations. Specialist wasps that parasitized the green cloverworm on alfalfa had a significantly larger mass than the ones that parasitized the green cloverworm on soybean at the three study sites. Generalist wasps that parasitized green cloverworms on alfalfa had a larger mass than wasps parasitizing green cloverworms on soybean only at one of the study sites (i.e., Prince George's County, MD, USA). Similarly, both specialist and generalist wasps lived longer when parasitizing green cloverworms on alfalfa than when parasitizing them on soybean at only one of the study sites (i.e., Prince George's County). In Prince George's County, percent parasitism on alfalfa by the specialist parasitoid was higher than on soybean for three consecutive years and percent parasitism by the generalist parasitoid was the same on alfalfa and soybean every year. Thus, phenotypic differences among populations associated with different host plant species vary geographically (i.e., parasitoid phenotype associated with different host plant species differ at some sites while it is the same at other sites). The implications of geographic variation for biological control are discussed.     

Parasitic wasp assemblages associated with native and weedy plant species in an agricultural landscape

Abstract  The establishment and maintenance of suitable habitat on-farm or in the surrounding landscape can enhance the survival of beneficial parasitic Hymenoptera, thus improving the control of pest species. Both endemic and weedy non-crop plant species across a highly modified agricultural landscape supported species-rich and abundant parasitic wasp assemblages with diverse biology and host associations. It was also shown that isolated, recently planted, single-species stands of plants can rapidly accumulate diverse assemblages of parasitoids. Chalcidoidea was the most species-rich and abundant group, egg and larval parasitoids were the most speciose and abundant guilds, and parasitoids of herbivorous insects feeding on and inside plant tissue were the most species-rich and abundant functional groups. The hymenopteran assemblages associated with the majority of plant species were dominated by three parasitoid species: a Trichogrammatidae, a Scelionidae ( Telenomus sp.) and a Eulophidae ( Ceranisus sp.), all genera that contain many important biocontrol agents of pest Lepidoptera, Hemiptera and Thysanoptera. Results show that both native and weedy plant species may potentially provide an important reservoir of mobile parasitic wasps of benefit to crop protection.     

Species composition and population dynamics of leafmining flies and their parasitoids in Victoria

Abstract  Mined leaves were sampled from unsprayed sites in Victoria to record the range of leafminers and their parasitoids. Three agromyzid leafminers, Liriomyza brassicae (Riley), Liriomyza chenopodii (Watt) and Chromatomyia syngenesiae Hardy, and one drosophilid leafminer, Scaptomyza flava (Fallén), were collected, along with 15 parasitoids, mainly Eulophidae. The most common parasitoids were Hemiptarsenus varicornis (Girault) (42.5%), Diglyphus isaea (Walker), 14.6%, Closterocerus mirabilis Edwards & La Salle (10.5%), and Opius cinerariae Fisher (8.5%). Most parasitoids were collected from two or more leafminer hosts. Weekly collections from Chinese cabbage ( Brassica rapa var. pekinensis ) infested with L. brassicae and S. flava , and beetroot ( Beta vulgaris var. crassa ) infested with L. chenopodii were made over two seasons at Knoxfield, Victoria to assess the relative impact of these parasitoids on agromyzid fly populations in crops. A further two parasitoid species were identified at low densities. Hemiptarsenus varicornis and D. isaea were the most numerous parasitoids collected in both crops. A different sampling method in the second year showed that O. cinerariae made up 25% of the sample from Chinese cabbage and was probably more common than estimated in the first season. Control exerted by local parasitoids was high, with 100% control of L. chenopodii reached in beets within 1–3 weeks of mines appearing and 100% control of L. brassicae within 6 weeks.     

The spatio-temporal distribution dynamics of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Coleoptera: Curculionidae), and its larval parasitoids in canola in western Canada

Distribution patterns of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), and its larval parasitoids were investigated in commercial fields of spring canola (Brassica rapa L. and Brassica napus L.) in southern Alberta, Canada, from 2002 to 2004 in relation to developmental stages of its host plants. Adult weevils invaded fields along one or more fronts when crops were in bud to early flower. Significant clustering of adults along field edges in early stages of invasion was followed by more homogeneous distributions as canola reached the mid to late flowering and pod enlargement stages. Larval weevil distributions, as indicated by exit holes in siliques at the end of the season, were often aligned spatially with adult distributions, but they did not coincide in all regions of the fields. The primary ectoparasitoid species attacking weevil larvae comprised Necremnus tidius (Walker) (Hymenoptera: Eulophidae), and Trichomalus lucidus (Walker), Chlorocytus sp., and Pteromalus sp. (Hymenoptera: Pteromalidae). Parasitism rates increased from 0.1 to 5.0% over the three years of study. Parasitoid distributions were often, but not consistently, spatially associated with high densities of C. obstrictus larvae. Lack of close spatial alignment of parasitoids and their hosts probably reflects low parasitoid numbers in comparison with an abundant resource of weevil larvae, and a lack of co-evolutionary history between host and parasitoids. Some parasitoids invaded fields early in host plant development, at the same time that weevils invaded. Unfortunately the synchronous invasions of host and parasitoids indicate that insecticidal applications to reduce adult weevil infestations may be detrimental to these beneficial species.     

Effects of host instar and size on parasitization efficiency and life history parameters ofOpius dissitus

The braconid parasitoidOpius dissitus Muesebeck (Hymenoptera, Braconidae) produced 1.7 to 3 times more offspring when provided second and third instar leafminers (Liriomyza sativae Blanchard) as compared to first instars. Females arising from parasitization of different instars did not differ significantly in numbers of chorionated eggs in their ovaries at adult eclosion. Development time was prolonged by about two days when parasitoid oviposition occurred in first, as compared to third instar hosts. Parasitoid length was positively correlated with host weight (r²=0.75). Because only 7% of variation in host weight could be explained by host density, parasitoid length varied considerably among hosts reared at the same density. Longevity and lifetime fecundity of parasitoids were inversely related to the weight of their hosts.     

Native saltbush (Rhagodia spp.; Chenopodiaceae) as a potential reservoir for agromyzid leafminer parasitoids on horticultural farms

Australia has to date been spared the introduction of highly polyphagous invasive pest agromyzid leafminers; however, their arrival and spread should be considered imminent. To develop a pre-emptive control strategy to deal with exotic leafminer outbreaks the first step is to identify Australian leafmining flies, their plant hosts and their parasitoids to gain an understanding of their population dynamics. Native vegetation may be providing resources for beneficial parasitic wasps plus access to alternative hosts and refuge from disturbance. Here, two Australian endemic saltbushes ( Rhagodia candolleana and R. parabolica , Caryophyllales: Chenopodiaceae) have been investigated for their potential to act as reservoirs for endemic agromyzid hosts and their key parasitoids. Mined leaves of the two Rhagodia species were sampled on two commercial horticultural properties in the Virginia horticulture area on the Northern Adelaide Plains between September 2007 and April 2008. Leaf mines on both Rhagodia species were caused by an endemic leafminer species, putatively Phytoliriomyza praecellens Spencer (Diptera: Agromyzidae). Ten species of parasitoids (all Hymenoptera) emerged from R. candolleana mines and seven different species from R. parabolica mines, mainly from the family Eulophidae and with some Pteromalidae and Braconidae. Trigonogastrella Girault sp. (Pteromalidae), Zagrammosoma latilineatum Ubaidillah and Hemiptarsenus varicornis Girault (both Eulophidae) were the most abundant species on R. candolleana , whereas two Opius Wesmael spp. (Braconidae) were the most abundant species on R. parabolica . Findings from this survey suggest an opportunity to plant purpose-designed refuges that could play a role in conservation biological control as part of an Integrated Pest Management strategy developed prior to incursion of pest leafminers such as Liriomyza species.