Key Parasitoids Research Articles

Natural Increases in Parasitoid and Predator Abundances and a Shift in Species Dominance Point to Improved Suppression of the Sorghum Aphid Since Its Invasion into North America

Melanaphis sorghi (Theobald) (Hemiptera: Aphididae), commonly called the sorghum aphid, is an invasive pest of sorghum (Sorghum bicolor) (L.) in North America. It was first observed in 2013 along the Gulf Coastal Plains ecoregion of Texas, Louisiana (USA), and Mexico, where it quickly established itself as an economically important pest within a few years. This ecoregion contains an established complex of aphid natural enemies, including both predators and parasitoids. In the decade since its invasion, indicators of increased suppression observed across six years and five locations from south to north Texas were as follows: (1) aphid abundances trending downwards across the years, (2) overall natural enemy abundances trending upwards during the same time period, and (3) a key parasitoid and coccinellid species increasing in dominance. Two key taxa, Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae) and six species of coccinellids (Coleoptera: Coccinellidae), were likely responsible for the majority of the pest’s suppression. In light of these findings, the importance of monitoring and stewarding natural enemies of invasive insect pests is discussed as part of a comprehensive strategy to measure and reduce the impact of a pest invasion in large-scale agroecosystems.

Sawfly Sex Pheromones: Analysis of Their Impact on Pine Odor Attractive to Egg Parasitoids

Pinus sylvestris trees are known to efficiently defend themselves against eggs of the herbivorous sawfly Diprion pini. Their direct defense against eggs is primable by prior exposure to the sex pheromones of this species and their indirect defense involves attraction of egg parasitoids by egg-induced pine needle odor. But it is unknown whether exposure of pine to D. pini sex pheromones also affects pine indirect defense against sawfly eggs. In this study, we investigated the influence of exposure of P. sylvestris trees to the sex pheromones of D. pini on indirect defense mediated by egg parasitoids. Behavioral assays with Closterocerus ruforum, a key parasitoid of sawfly eggs, revealed no significant attraction to odor from egg-free pines pre-exposed to pheromones. Chemical analyses of odor from egg-free pines showed no pheromone-induced change in the emission rates of the known key terpenoids promoting parasitoid attraction. Further comparative analyses of odor from egg-laden pines pre-exposed to the sex pheromones and of odor from egg-laden pines unexposed to pheromones neither revealed significant differences in the emission rates of terpenoids relevant for parasitoid attraction. The results suggest that a pheromone-induced or pheromone-primed, egg-induced pine indirect defense seems to be redundant in addition to the known pheromone-primable pine direct defense against the eggs and the known egg-inducible indirect defense.

Assessing the effectiveness of selected reduced-risk insecticides and malathion on blueberry gall midge (Diptera: Cecidomyiidae) and key parasitoids

The blueberry gall midge, Dasineura oxycoccana, is a major blueberry pest in Florida and North America, primarily controlled with insecticides. However, their efficacy on D. oxycoccana and impact on natural enemies are poorly documented. We compared the effects of seven reduced-risk insecticides with malathion on larval and adult D. oxycoccana in laboratory bioassays. Acetamiprid showed the highest larval mortality, similar to malathion. Imidacloprid was effective after 2 h, while spirotetramat was effective after 3 h. On adults, cyantraniliprole and acetamiprid were as effective as malathion. Flupyradifurone began showing comparable lethality at 3 h, while spirotetramat, imidacloprid, and tolfenpyrad began inducing comparable mortality 6 h post-application. The same insecticides were evaluated for their effects on D. oxycoccana and their key parasitoids in two southern highbush blueberry plantings in North-central and Central Florida. A wetter-spreader adjuvant was added to spirotetramat as a ninth treatment. Spirotetramat + adjuvant effectively reduced adults and larval densities by up to 100% in the first year and adults by 59% and larvae by 56% in the second year. Acetamiprid reduced adult densities by 65% in 2019. Spinetoram reduced adults by 77% and larvae by 100% in 2019, while flupyradifurone reduced adults by 77% and larvae by 37% in 2020. These insecticides had minimal adverse effects on Platygaster spp. and overall parasitoid densities for both years. Based on these findings, there is potential for incorporating spirotetramat + adjuvant, flupyradifurone, spinetoram, or acetamiprid into a strategic rotational program with minimal impacts on natural enemies of D. oxycoccana.

Compatibility of Bioinsecticides with Parasitoids for Enhanced Integrated Pest Management of Drosophila suzukii and Tuta absoluta.

Drosophila suzukii and Tuta absoluta are successful biological invaders of agroecosystems. Their integrated pest management (IPM) programs involve the release and/or conservation of natural enemies. Among these, Ganaspis kimorum is a major Asian parasitoid of D. suzukii and has been introduced as a classical biological control agent of this pest in Europe and North America, while Necremnus tutae is a key fortuitous parasitoid of T. absoluta in the Mediterranean region. Bioinsecticides represent key alternatives to chemicals for controlling both pests. This study investigated the potential compatibility of both parasitoids with Beauveria bassiana, Bacillus thuringiensis, garlic essential oil (EO), and spinosad, in comparison to two synthetic insecticides, cyantraniliprole and chlorantraniliprole. The results showed that combining each of the tested insecticides with G. kimorum slightly increased pest mortality compared to the insecticide alone. Necremnus tutae had a significant additive effect on host mortality when combined with insecticides. Beauveria bassiana and B. thuringiensis were most compatible with both parasitoid species. Both garlic EO and chlorantraniliprole impaired the survival of immature N. tutae and showed sublethal toxicity on the reproductive and non-reproductive behaviors of N. tutae. Spinosad exhibited high acute toxicity on both juvenile and adult parasitoids of both species. Overall, these findings provide useful insights into insecticide selectivity toward two key parasitoids and offer new knowledge on the potential of combining natural enemies and bioinsecticides for optimized IPM.

Topical and field‐tested residual effects of globally used insecticides on the parasitoid Tamarixia radiata released against the Asian citrus psyllid, Diaphorina citri

AbstractTamarixia radiata (Waterston) (Hymenoptera: Eulophidae) is the key parasitoid of the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), in several citrus‐producing regions of the world. Chemical control is common to suppress ACP. Insecticides from globally used classes of insecticides for controlling ACP were tested on its primary parasitoid, T. radiata. Evaluations included dose–response of dimethoate, fenpropathrin, and imidacloprid in a topical application and lethal and sublethal effects from residues of imidacloprid, fenpropathrin, horticultural mineral oil (HMO), pyrethrin, and spirotetramat at 1, 3, and 7 days after application (DAA) of sprays on citrus trees in the orchard. The parasitism potential of the females that survived insecticide exposure was evaluated on untreated nymphs of ACP developing on citrus shoots and untreated parasitoid females were evaluated on nymphs treated with insecticides. In the topical application, imidacloprid was 8× more toxic to T. radiata than dimethoate and fenpropathrin. The lethal effect of the residues from imidacloprid and fenpropathrin sprays was more detrimental than other insecticides. Parasitoid mortality from 1‐ to 3‐day‐old residues averaged 90–96% for imidacloprid, 83–94% for fenpropathrin, 38–77% for pyrethrin, 43–44% for HMO, and 17–33% for spirotetramat. Parasitism by females that survived insecticide exposure was reduced by 71–88% from fenpropathrin, 28–59% from pyrethrin, 31–55% from imidacloprid, 44–4% from spirotetramat, and 39–11% from HMO compared to untreated females. The lethal and sublethal effects of all insecticides on T. radiata were significantly reduced at 7 DAA, suggesting a lower impact on its establishment and performance if releases are made after a week from spray application.

Diet source-dependent functional response of key parasitoids of <i>Spodoptera frugiperda</i> (J.E. Smith, 1797) (Lepidoptera, Noctuidae)

Foods derived from plants are important sources of food for natural enemies and influence several functions of their existence, including reproduction. The objective of the current study was to assess the effect of different sources of food and host densities on the oviposition efficiency of key parasitoids of Spodoptera frugiperda. The experiment was set up under laboratory conditions in a completely randomized block design with three factors namely parasitoids (four), feeding (groundnut pollen, soybean nectar, honey, starved as control) and host densities (five), a total of 80 treatments. There were five replications for the experimental design while the experiment was repeated four times, a total of 20 replications for each treatment. Results showed that the functional response of adult parasitoids was influenced both by food sources and host densities. Soybean nectar worked the best like honey, followed by groundnut pollen. Soybeans and groundnut may therefore have agroecological interests beneficial for mass rearing to promote key parasitoids as biological agents to control S. frugiperda. As for the host densities, the minimum and maximum of the parasitized host were obtained respectively with the densities of 20 and 100 eggs per female for T. remus, 20 and 80 eggs for Trichogramma sp. and C. insularis and 5 to 50 larvae for C. marginiventris. Taking into account the interesting results obtained which would be favourable to the rapid multiplication of parasitoids, tests in real environments are necessary to test the influence of the main environmental factors on the performance of said parasitoids.

Nontarget impacts of insecticide-based population control of eastern spruce budworm (Lepidoptera: Tortricidae) on nontarget caterpillar communities and parasitism

Abstract Narrow-spectrum insecticides are currently used to control populations of spruce budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae), in eastern Canada. However, these could have nontarget impacts on other caterpillars – some of which may serve as alternative or alternate hosts to key parasitoids – that are also susceptible to control tactics. This study was conducted to determine how the insecticides, Bacillus thuringiensis variety kurstaki (Btk) and tebufenozide, used to control spruce budworm populations, impact caterpillar communities and associated parasitism rates. Post-treatment field sampling of caterpillars was conducted in 2018 and 2019 in New Brunswick, Canada, at sites treated with either Btk or tebufenozide and at control sites. Caterpillar species richness and abundance, community structure, and parasitism rates were assessed using molecular analyses for 659 collected caterpillars. We found that insecticide applications had no significant impact on abundance, species richness, or parasitism rate relative to the measurements made in the control sites. Nonetheless, a significantly higher caterpillar abundance and lower parasitism rate occurred in Btk-treated sites than in tebufenozide-treated sites. Overall, however, Btk and tebufenozide treatments did not negatively affect the non-budworm caterpillar community under the present conditions of low caterpillar densities, suggesting that parasitoids have alternative and alternate hosts after treatments that target the spruce budworm.

Pteromalid fauna (Hymenoptera, Pteromalidae) in oilseed rape (Brassica napus L.) fields in Bulgaria – species composition and perspectives for biological control

Parasitoid wasps belonging to the family Pteromalidae are widespread and abundant members of the insect communities in the temperate regions of the world. As many other chalcids do, pteromalids serve as natural enemies of the pests in various crops and play an important role in the biological control of these harmful insects. Here we present the results of a field study in Bulgaria which was focused on the diversity of family Pteromalidae in ten oilseed rape fields. All samples were collected by sweep netting on the border line or inside the crop field. A total of 93 pteromalid specimens belonging to 26 taxa were gathered. The most abundant genus was Mesopolobus – 67% of the sampled pteromalids. The most numerous species in the samples was Mesopolobus morys – a well-known key parasitoid of the cabbage seed weevil, Ceutorhynchus obstrictus, in Europe. One species – Halticoptera patellana, is recorded for the first time in Bulgarian fauna. Clearfield oilseed rape fields had relatively higher parasitoid abundance and richness than the fields treated by conventional technology. In the present work we discuss the overall species composition of Pteromalidae obtained from the studied areas and present our point of view on the perspectives for biological control of oilseed rape pests.

English

The objective of this article is to review the knowledge on Spodoptera frugiperda and the possible management strategies against the pest to identify research areas for its integrated management.  A review of the literature shows that S. frugiperda (Lepidoptera: Noctuidae) has been causing considerable damage to maize and many other crops since its detection in several African countries and it is one of the most destructive pests to have entered Africa in the 21st century. Several control methods have been developed against this pest ranging from the use of synthetic plant protection products to agroecological and biological controls. The biology, distribution and control methods of the pest are well documented. However, Integrated Management of the pest remains a major challenge; the main control is chemical. Innovative research on biological and ecological control methods will help to overcome the constraints and promote sustainable management of the pest. Very few scientifically proven alternatives adapted to the African context exist. This gap needs to be filled by further research considering aspects such as the inventory of local natural enemies, the performance of key parasitoids and the potential of local entomopathogens for sustainable and integrated management of the pest. Key words: Spodoptera frugiperda, natural enemies, integrated management.

Modelling the Potential Geographic Distribution of Two Trissolcus Species for the Brown Marmorated Stink Bug, Halyomorpha halys.

Simple SummaryThe brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), native to Asia, has been accidentally introduced to Europe and North America, where it has become a key pest by feeding on numerous important crops. Although H. halys has not yet established in Australia, there is a general consensus that this is only a matter of time, and thus, it is prudent to investigate management options. Previous studies have modelled the potential distribution of H. halys and one of its principal natural enemies, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae). Here, we developed a similar model of the potential distribution of Trissolcus mitsukurii (Ashmead), which is a primary parasitoid of H. halys in Japan, and which was introduced to Australia in the 1960s to control another introduced pest. We used the three models to examine the overlap in the projected distributions of both T. mitsukurii and T. japonicus with H. halys, and to assess the potential for the two Trissolcus species to help mitigate the impacts of H. halys in its global adventive range.The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is native to northeast Asia. It was accidentally introduced to Europe and North America, where it has become a key pest, feeding on many important crops. Previous eco-climatic niche modelling indicates that H. halys could expand its distribution vastly, and numerous border interceptions of this pest in many countries, including Australia and New Zealand, indicate that it would be prudent to prepare for its eventual arrival. Similar niche modelling was used to assess the potential distribution of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), the key parasitoid of H. halys in China. Trissolcus mitsukurii (Ashmead) is one of the main parasitoids of H. halys in Japan. It is known to have existed in Australia since the early 20th century and was also specifically introduced to Australia in the 1960s, and it has now also invaded Italy. We used CLIMEX to model the climatic niche of T. mitsukurii to estimate its global potential distribution. We found that T. mitsukurii should be able to significantly expand its range globally, and that there is a significant degree of overlap in the projected ranges of T. mitsukurii, T. japonicus and H. halys. From a biological control perspective, this implies that the two Trissolcus species may be able to help mitigate the potential impacts of H. halys.

Global Habitat Suitability of Spodoptera frugiperda (JE Smith) (Lepidoptera, Noctuidae): Key Parasitoids Considered for Its Biological Control.

Simple SummaryThe fall armyworm (FAW), Spodoptera frugiperda has now become a pest of global importance. Its introduction and detection in Africa in 2016, and subsequent introduction and spread into Asia and Australia, has put several millions of food producers and maize farmers at risk. Not all pest management strategies are sustainable. Biological control with the use of parasitoid wasps is one of the durable and environmentally sound options. The present study was initiated to predict the habitats of high establishment potential of key parasitoids of FAW in South America, which might prove to be effective as classical biological control agents of FAW in regions where it is an invasive species under current and future climate scenarios. The prospective parasitoids are the following: Chelonus insularis, Cotesia marginiventris, Eiphosoma laphygmae, Telenomus remus and Trichogramma pretiosum. The results demonstrate overlapping habitat suitability areas of the pest and the parasitoids, suggesting promises for biological control options for the management of FAW under current and future climate scenarios.The present study is the first modeling effort at a global scale to predict habitat suitability of fall armyworm (FAW), Spodoptera frugiperda and its key parasitoids, namely Chelonus insularis, Cotesia marginiventris, Eiphosoma laphygmae, Telenomus remus and Trichogramma pretiosum, to be considered for biological control. An adjusted procedure of a machine-learning algorithm, the maximum entropy (Maxent), was applied for the modeling experiments. Model predictions showed particularly high establishment potential of the five hymenopteran parasitoids in areas that are heavily affected by FAW (like the coastal belt of West Africa from Côte d’Ivoire (Ivory Coast) to Nigeria, the Congo basin to Eastern Africa, Eastern, Southern and Southeastern Asia and some portions of Eastern Australia) and those of potential invasion risks (western & southern Europe). These habitats can be priority sites for scaling FAW biocontrol efforts. In the context of global warming and the event of accidental FAW introduction, warmer parts of Europe are at high risk. The effect of winter on the survival and life cycle of the pest in Europe and other temperate regions of the world are discussed in this paper. Overall, the models provide pioneering information to guide decision making for biological-based medium and long-term management of FAW across the globe.

Overwintering parasitism is positively associated with population density in diapausing larvae of Chilo suppressalis

The suppression of overwintering population is essential in integrated pest management, but little is known about the biological mortality factors that reduce the overwintering density of Chilo suppressalis. Here, we examine the parasitism of overwintering larvae, and assume that key parasitoids strengthen the over-wintering population suppression. The natural parasitism incidence and related dominant parasitoids in overwintering larvae were investigated in two successive winters, in 2015–2016 and 2016–2017. Parasitism rates were also assessed in larvae collected from 15 different counties in 2016. The results showed that the parasitism incidence and dominant parasitoids in overwintering C. suppressalis larvae were significantly different for different sampling dates and sites. Overwintering larvae of C. suppressalis were mainly parasitized by Cotesia chilonis, and less often by Eriborus sinicus and Microgaster russata. Regression analysis indicated that the natural incidence of parasites in overwintering C. suppressalis larvae was positively correlated with the over-wintering larval density. The current work provides support for overwintering pest management strategies by showing the effectiveness of parasitoid communities as a bio-mortality factor for suppressing overwintering density.

Establishment in an Introduced Range: Dispersal Capacity and Winter Survival of Trissolcus japonicus, an Adventive Egg Parasitoid.

The herbivorous brown marmorated stink bug, Halyomorpha halys, has spread globally, and one of its key parasitoids, Trissolcus japonicus, has recently been detected in the pest’s introduced range. For an exotic natural enemy to impact its targeted host in a novel environment, it must disperse, locate hosts, and potentially be redistributed to susceptible sites. Through intentionally releasing T. japonicus across four Oregon eco-regions, we investigated an introduced parasitoid’s dispersal capacity in urban sites and in two perennial crops, hazelnut and raspberry. In a second paired field and laboratory study, we investigated T. japonicus survival in different plant materials. Within three days of release, adult T. japonicus located host egg masses at 45% of sites and, one year later, were detected at 40% of release sites. Areas where released wasps survived winter were mostly urban or semi-natural. In commercial crop release experiments, we recovered the highest percentage of wasps in raspberry within 5 m of the release site but found no statistical difference in dispersal distance with some wasps dispersing up to 50 m. Adult parasitoids survived up to 16 weeks outdoors in the winter, with greater survival over time in bark compared to leaf litter. Wasp survival remained above 50% over the course of a simulated winter environment without precipitation. Our work affirms the continuation of H. halys parasitism by T. japonicus in novel environments and provides insight into the high population sizes necessary to survive winter and locate host egg masses the following season.

Interaction Between Two Leafminer Parasitoids, Halticoptera arduine (Hymenoptera: Pteromalidae) and Diglyphus isaea (Hymenoptera: Eulophidae), in the Management of Liriomyza huidobrensis (Diptera: Agromyzidae).

Liriomyza spp., leafminer flies (Mik; Diptera: Agromyzidae), are economically important quarantine pests that puncture and mine leaves and fruits of various horticultural crops worldwide, affecting yield and trade. Halticoptera arduine (Walker; Hymenoptera: Pteromalidae), a key parasitoid from the pests' areas of origin in South America, was introduced as a potential alternative management strategy. Prior to H. arduine release, its potential interactions with the dominant local ectoparasitoid, Diglyphus isaea (Walker; Hymenoptera: Eulophidae), were assessed. Halticoptera arduine and D. isaea were released in single, sequential and simultaneous combinations on Liriomyza huidobrensis (Blanchard; Diptera: Agromyzidae) to evaluate possible effect on the parasitism rate, reproduction and host mortality. The combination of both parasitoids did not significantly affect the specific parasitism rates of either of them, an indication that H. arduine and D. isaea can coexist. Parasitism rates of the exotic H. arduine were significantly superior to the indigenous D. isaea in all release combinations except when both species were released simultaneously. While 50 individuals of D. isaea resulted only in 21.23 ± 2.1% parasitism, 50 parasitoids composed of 25 H. arduine and 25 D. isaea caused 53.27 ± 4.99%. Both parasitoids further induced significant nonreproductive host mortalities. Both parasitoids' F1 progenies sex ratios were female-biased in all parasitoid release combinations except in single release of D. isaea with a balanced sex ratio. The improvement in D. isaea's sex ratio induced by the presence of H. arduine suggests a synergetic effect on D. isaea's reproductive performance. The introduction of H. arduine in horticulture production systems may therefore improve natural control of Liriomyza leafminers in East Africa.

Residual toxicity of emamectin benzoate and chlorantraniliprole on Eupelmus tachardiae howard-A key parasitoid of lac insect Kerria lacca (kerr)

Residual response of emamectin benzoate and chlorantraniliprole against Eupelmus tachardiae Howard (Hymenoptera: Encyrtidae)-a key parasitoid of lac insect, Kerria lacca (Kerr) was assessed under laboratory conditions by exposing the adults on residual film of insecticides. Emamectin benzoate caused 0–14.44% mortality within 1 hr of exposure, 27.5–38.99% mortality within 3 hr, 53.61–96.67% mortality within 18 hr and 100% mortality within 24 hr of exposure except at a very low concentration (0.00025%). Whereas, no mortality with chlorantraniliprole was observed after 1 hr of exposure and within 3 hr of exposure only 3.33 and 8.61% mortality was at 0.0056 and 0.0074% concentration, respectively, which is the recommended dose in lac ecosystem for the management of lepidopteran pests. Within 24 hr of exposure, 30.20–65.31% mortality was observed with concentrations of chlorantraniliprole as against 19.68% in control. Based on mortality within 24 hr of exposure it can be inferred that the emamectin benzoate is relatively more toxic than the chlorantraniliprole. Relatively less toxicity of chlorantraniliprole to this parasitoid species might be attributed due to specificity of this insecticide.

Landscape diversity and crop vigor outweigh influence of local diversification on biological control of a vineyard pest

AbstractThe influence of local and landscape habitat diversification on biological control of the Western grape leafhopper (Erythroneura elegantula Osborn) by its key parasitoids Anagrus erythroneurae S. Trjapitzin & Chiappini and Anagrus daanei Triapitsyn was studied in wine grape vineyards. At the landscape scale, Anagrus rely on alternative host species in non‐crop habitats outside of the vineyard to successfully overwinter, while at the local scale vineyard diversification can provide resources, such as shelter and floral nectar, which improve parasitoid performance. In a two‐year experiment, plots with and without flowering cover crops were compared in vineyards representing a gradient of landscape diversity. While the cover crops did attract natural enemies, their populations were unchanged in the crop canopy and there was no difference in parasitism rate, leafhopper density, crop quality, or yield. Vineyards in diverse landscapes had higher early‐season abundance of Anagrus spp., which was linked to increased parasitism and decreased late‐season populations of E. elegantula. Leafhopper densities were also positively associated with crop vigor, regardless of landscape or cover crops. Flowering cover crops did increase abundance of some natural enemy species as well as parasitism rate in vineyard landscapes with intermediate levels of diversity, indicating a local × landscape interaction, although this did not lead to reductions in E. elegantula densities. These findings indicate that, in this agroecosystem, landscape diversity mediates and in many ways outweighs the influence of local diversification and that E. elegantula densities were regulated by a combination of biological control and crop vigor.

The activities of generalist parasitoids can be segregated between crop and adjacent non-crop habitats

Non-crop habitat adjacent to crops may be important for enhancing the activity of natural enemies in crops. However, it is not always clear whether natural enemies that are active in non-crop habitats actually contribute to pest suppression in adjacent crop habitats. We hypothesised that parasitic wasps that utilise the same hosts can be segregated between crop and non-crop habitats in an agro-ecosystem. We tested this hypothesis using the light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), in vineyards and adjacent native vegetation. We experimentally measured the parasitism rate of larval E. postvittana at six and eight sites in both vineyards and the adjacent native vegetation in two consecutive years. Wild larval Tortricidae were also collected at each experimental site to assess their diversity and related parasitoids. Parasitised hosts were then identified using a PCR-based protocol to examine the parasitoids’ host ranges. The parasitoid Therophilus unimaculatus (Turner) (Hymenoptera: Braconidae) was most active in non-crop native vegetation, whereas Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) parasitised the most larvae in vineyards. Parasitism of E. postvittana by D. tasmanica was higher on grape than on plantain, which indicates that host plants influence activities in different habitat. Both species shared the same range of tortricid hosts. Overall, our results indicate the two key parasitoids that attack E. postvittana differ in their pattern of habitat use. The native vegetation adjacent to crops may not enhance the activity of some natural enemies for pest control in an agricultural ecosystem.

Host Plant Associations of Anagrus spp. (Hymenoptera: Mymaridae) and Erythroneura elegantula (Hemiptera: Cicadellidae) in Northern California.

Anagrus erythroneurae S. Trjapitzin & Chiappini and Anagrus daanei Triapitsyn are the key parasitoids of the western grape leafhopper (Erythroneura elegantula Osborn) in northern California vineyards. Erythroneura elegantula overwinters as an adult in reproductive diapause. To successfully overwinter, Anagrus spp. must locate an alternate leafhopper host that overwinters in an egg stage that they can parasitize. These alternate leafhopper hosts are thought to be primarily located in the natural habitats surrounding vineyards. This study identifies the noncrop host plants utilized by Anagrus spp. not only during the overwintering period but throughout the entire year, as well as the leafhopper species associated with these host plants. Over a 2-yr period, Anagrus spp. and leafhoppers were sampled from numerous plants in natural and cultivated habitats surrounding vineyards. Results from this study confirm previously known Anagrus spp. host plants, but also identify new host plant species. Some of the host plants harbored Anagrus spp. year-round while others were utilized only during certain periods of the year. Leafhoppers associated with Anagrus spp. host plants may potentially serve as the alternate host utilized by Anagrus spp. on these plants, but this was not confirmed in the current study. Records of E. elegantula demonstrate their cyclical movement between the vineyard floor (winter), temporary noncrop hosts (spring/fall), and the grape vine canopy (summer).

Singing on the wings! Male wing fanning performances affect female willingness to copulate in the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Braconidae: Aphidiinae).

Lysiphlebus testaceipes (Hymenoptera: Braconidae: Aphidiinae) is a generalist endoparasitoid attacking more than 100 aphid species. In L. testaceipes, wing fanning is a main male courtship display evoked by a female-borne sex pheromone. However, no information is available on the characteristics and behavioral role of male fanning during courtship in this parasitoid. Here, the courtship behavior of a wild strain of L. testaceipes was quantified and the male wing fanning performances were analyzed through high-speed video recordings and examined in relation to mating success. Courtship sequence of wild L. testaceipes did not substantially differ from that previously reported for other populations mass reared on aphids. We observed that the male courtship duration did not affect mating success. However, video analysis revealed that the males producing high-frequency fanning signals achieved higher mating success over those that display low-frequency fanning. Wing fanning before successful and unsuccessful courtship differed in amplitude of wing movements and alignment toward the mate, highlighting that frontal courtship positively influence the female mating decisions. This study increases knowledge on sexual behavior in a key parasitoid of aphids, highlighting the importance of wing fanning among the range of sensory modalities used in the sexual communication of L. testaceipes. From a practical point of view, this information is useful in L. testaceipes-based biocontrol strategies, since it can help to establish parameters for quality checking of mass-reared wasps over time.

Could Brassica rapa, Brassica juncea and Sinapis alba facilitate the control of the cabbage seed weevil in oilseed rape crops?

A two-year small plot experiment was performed to test whether (1) other plants in the cruciferous family: Brassica juncea (L.) Czern. and Sinapis alba L. are more attractive to the cabbage seed weevil (Ceutorhynchus obstrictus (Marsham)) than turnip rape (Brassica rapa Metzg.) and oilseed rape (Brassica napus L.); (2) the host plant species affects the oviposition preferences of parasitoid species attacking the cabbage seed weevil. According to our results oilseed rape had the highest pest infestation. The parasitism rate was highest on B. juncea and B. rapa. Thus, we can assume that wild relatives of oilseed rape plants can support the presence of hymenopteran natural enemies of pests in the field. The parasitism rate was surprisingly high, up to 85.4% on B. juncea. In addition to the key parasitoids of C. obstrictus, species from the family Mymaridae were also found. The species composition of parasitoids differed between investigated plant species, suggesting that the physical or volatile characteristics of closely related plant species affect the behavioural responses of C. obstrictus parasitoids and therefore could be used to enhance the natural enemy complex.