Wasp Infestation Research Articles

A genetic bottleneck in populations of a New Zealand endemic ant associated with density of an invasive predatory wasp

Predation by invasive species can reduce the effective population size of native species, which may cause increased levels of genetic drift resulting in a loss of genetic diversity. The magnitude of these effects appears likely to be related to invader abundance. In the Fuscospora beech forests of New Zealand, dispersal of the most abundant ant species, Prolasius advenus (Fr.Smith) (Hymenoptera: Formicidae), coincides with the peak abundance of the invasive predatory wasp Vespula vulgaris (L.) (Hymenoptera: Vespidae). Dispersing winged ant queens can comprise more than 25 % of the wasps’ diet. We hypothesised that the predation of wasps on queen ants could increase genetic drift on ant populations when wasps were at high density, which would erode genetic diversity and potentially fitness. We used six microsatellite markers to examine genetic diversity, population genetic structure and to test for evidence of a genetic bottleneck in P. advenus populations from seven sites with varying levels of wasp infestation. Populations of ants at high wasp densities showed evidence of a genetic bottleneck, which we suggest is the result of intense predation on dispersing queens by Vespula wasps. The seven sites examined were broadly divided into two distinct populations with some evidence of either limited admixture or derivation from a common ancestral population. Our results are consistent with a short term effect of high levels of predation by an invasive species with long-term implications for the recipient species.

Mega-trap-plots: a novel method of Sirex woodwasp management on Pinus radiata plantations in Chile

Sirex noctilio is one of the most important invasive pests that affect Pinus radiata plantations in Chile. Its management is based on a biological control complex, the most important component of which is the nematode, Deladenus siricidicola. However, in some areas, S. noctilio populations attain epidemic levels and no effective control methods exist to reduce large populations in a short period. In this study, we evaluated a novel method called mega-trap-plots (MTPs), which consist of an area of 1 ha with trap trees, which were debilitated in four different months (from November to February) with the purpose of reducing the Sirex wasp population through harvesting of trees attacked. The main objective was to reduce the potential population of S. noctilio, by evaluating four periods or months of MTP installation to maximise the colonisation of trap trees by wood wasps. The results showed that the MTPs that were installed from November to January had the highest wood wasp infestation, which was coincident with the flight period of the insect. The trap trees were clearly attractive to S. noctilio females up to 90 d following their establishment. The MTPs that were established in November concentrated a potential population of 57 901 females of S. noctilio, which represents a population 5.4 times greater than that in the control, with 10 701 females. The population of S. noctilio attracted between November and January shows that the use of MTPs is an effective system for the management of wood wasps on plantations with a high level of infestation and thereby can reduce their spread and the attack of new trees within the same forest compartments.

Agro‐ecosystem services and dis‐services in almond orchards are differentially influenced by the surrounding landscape

1. The simultaneous influence of specific habitats on agro‐ecosystem services, dis‐services, and their interactions are largely unknown. Natural and semi‐natural habitats surrounding cropland may support ecosystem services and dis‐services and their net balance is important to guide decision‐making in agriculture.2. It was tested how natural and semi‐natural habitats surrounding almond orchards in Israel influence: pest control services by parasitoids, pest predation dis‐services by the Almond wasp, and seed predation dis‐services by granivorous birds. The latter could provide sanitation services when consuming almonds infested by Almond wasps after harvest.3. Seventeen almond orchards were surveyed, surrounded by varying percentages of natural and semi‐natural habitats. We harvested almonds to identify Almond wasp infestation and parasitoid abundance, monitored bird‐feeding marks, and observed birds.4. Almond wasp predation was positively influenced by semi‐natural habitat and highest at orchard edges. Parasitoid abundance was not influenced by natural or semi‐natural habitats. Granivorous bird abundance was negatively influenced by semi‐natural habitats but did not influence bird seed predation of harvestable or overwintered almonds.5. Natural habitats did not influence the studied ecosystem services or dis‐services in almond orchards in Israel. Therefore, protecting natural habitats for conservation is not necessarily disadvantageous for farmers. Semi‐natural habitats increased insect pests, but no direct link to services or dis‐services by birds was observed. Therefore, a more holistic approach by accounting for several services and dis‐services and their connection to different habitat types to manage agriculture more sustainably is advocated.

Infestation of Quadrastichus erythrinae Kim (Eulopidae: Hymenoptera) an invasive pest on Erythrina spp, a popular standard for black pepper (Piper nigrum) in Idukki district in Kerala, India

Black pepper is an important spice crop grown in Kerala state. Idukki and Wayanad districts contribute major share in production of this spice crop. More than 80 percent of pepper vines grown in this area are trailed on Erythrina spp. A survey has been conducted to ascertain the severity of gall wasp infestation in Erythrina spp. The total number of locations and black pepper gardens covered during the survey include 6 blocks and 37 panchyats in Idukki district of Kerala state. E. variegata (dense thorn) could be rated as moderately resistant (Scale 2- 25% infestation and less) and E. variegata (white thorn) as less susceptible (Scale 3 - 25 to 50 % infestation). The reaction of different types/species of Erythrina to EWG has revealed that the infestation was higher in black thorn type of E. variegata where in the infestation was 75 to 100 percent. Chakkupallam, Erattayar, Kanchiyar of Kattappana panchayats recorded maximum infestation since the pepper growers used black thorned type of E. variegata as standards.

Invasion by the chestnut gall wasp in Italy causes significant yield loss inCastanea sativanut production

The Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera Cynipidae) is an invasive species in chestnut forests and orchards in many parts of the world. 2 Nuts produced by the European chestnut (Castanea sativa Miller) are important in human food and culture, and as a component in food webs in forest ecosystems. 3 Severe infestations are reported to reduce nut yield, although precise data are lacking because of large natural year-to-year variability in yield. 4 The recent colonization of chestnut orchards in north-eastern Italy, where nut yield has been continuously and precisely recorded for several years, offered an opportunity to calculate the impact of gall wasp infestation level on yield. 5 The nut yield of C.sativa chestnut trees was negatively related to the gall wasp infestation level, with losses as high as 80% being reported when the number of current-year galls was above six galls per 50-cm twig. 6 Yield losses can be explained by direct and indirect factors related to gall formation, and a fuller understanding of the mechanisms involved could identify possible mitigation measures.

Interventi per la gestione dei castagneti invasi dal cinipide

Abstract: The rapid spread of the Chinese gall wasp (Dryocosmus kuriphilus Yasumatsu) in Italian chestnut growing areas is causing new criticisms. In this context, in addition to a clear plant suffering due to the wasp infestation, the dangerous recurrence of chestnut blight and the sudden spread of Gnomoniopsis sp., a coloniser of galls but also the etiological agent of nut brown rot, must be considered. Therefore, it is very important to increase the plants’ vigour and prevent their decline. Preliminary experiments were carried out in different Italian regions between 2010 and 2011. Organic plant fertilizers were applied to plants showing middle or high defoliation levels caused by the wasp attacks. The observations carried out during the growing season indicate a good vegetative restart in the treated plants compared to the untreated controls, in all the situations and independently of the fertilizers applied. Most of the treated plants (between the 75% and the 100%) showed an evident improvement in the canopy vegetation, while the untreated controls were always classified in the worse classes of crown condition. These preliminary results highlight the efficacy of this kind of treatments for infested chestnut stands. This strategy, which is based on the preliminary evaluation of the plant vigour (following the proposed scale of attack severity and lack of foliage), consists in a manuring treatment at vegetative restart, which can be repeated in the following years in dependence on the results obtained. Moreover, pruning may be suggested only to manage the development of plants showing a definite recovery. The gall wasp pullulation requires new management strategies aimed at preserving the chestnut orchards, in order to avoid the chestnut cultivation to be marginalized or abandoned.

Gnomoniopsis associated with necrosis of leaves and chestnut galls induced by Dryocosmus kuriphilus

Chestnut (Castanea spp.) is a very important crop in the Monti Cimini area (Viterbo, Italy) which is seriously infested with the key pest, chestnut gall wasp Dryocosmus kuriphilus (Speranza et al., 2009). In May 2009 such seriously infested chestnut plants in the Monti Cimini area were found with necrotic leaves and galls. Lesions on leaves were irregular and variable in size, lemon green to amber in colour with green margins. Initially, galls were olive green then became dark brown. Inside the galls larvae of chestnut gall wasp were dead. Tissue from the edge of lesions was surface-sterilized using 1% sodium hypochlorite, rinsed in sterile distilled water and aseptically cut in 5–10 pieces not exceeding 5 × 5 mm, plated on potato dextrose agar (PDA) in Petri dishes containing an antibiotic solution (0·2% streptomycin sulphate) and incubated at 20 ± 3°C. Light brown fungal colonies were observed after 1 week close to the tissue and numerous orange slimy masses of conidia were observed on the culture surface. The colonies were regular in outline with a clear and thinner margin. Conidia were oval to oblong, sometimes slightly obovoid, straight or curved and measured 5·5–8·0 μm × 2·0–3·0 μm (mean = 6·8 × 2·5 μm, n = 210). The fungus was identified at Centraalbureau voor Schimmelcultures (CBS, Utrecht, The Netherlands) as an undescribed species from the genus Gnomoniopsis. Identification was based on both DNA sequencing (ribosomal ITS) and morphology (GenBank Accession Nos. EU254851, EU254854, EU254855). The pathogenicity of the fungus was tested in the Tuscia University experimental farm using freshly isolated cultures. Ten chestnut galls were inoculated, after slight pinprick injury, with an aqueous suspension containing 2 × 106 spores/mL and incubated in clean cheesecloth covered with Parafilm. Control-injured galls were sprayed with sterile distilled water and incubated in the same manner. Control plants did not show any disease symptoms 60 days after inoculation. In contrast, the fungus produced characteristic blight symptoms on 90% of the inoculated galls. Similar blight symptoms were observed on chestnut twigs inoculated with 4 mm discs of 7-day-old PDA cultures. Isolations from these lesions confirmed the presence of a fungus identical to Gnomoniopsis. Although chestnut leaf blight has been reported to be caused by some species of the genus Gnomonia (Sogonov et al., 2008), this appears to be the first record of a fungus in the genus Gnomoniopsis associated with the necrosis of chestnut galls caused by Dryocosmus kuriphilus. This Gnomoniopsis sp. has not been reported in Italy on non gall-infested leaves of chestnut trees (Cristinzio, 1986). The relationship between the necrotrophic propensity of Gnomoniopsis and chestnut gall wasp infestation is under investigation. The authors would like to thank the Regione Lazio (Italy) for financial support.

Characterization of a Lamellocyte Transcriptional Enhancer Located within the misshapen Gene of Drosophila melanogaster

Drosophila has emerged as an excellent model system in which to study cellular and genetic aspects of hematopoiesis. Under normal developmental conditions and in wild-type genetic backgrounds, Drosophila possesses two types of blood cells, crystal cells and plasmatocytes. Upon infestation by a parasitic wasp or in certain altered genetic backgrounds, a third hemocyte class called the lamellocyte becomes apparent. Herein we describe the characterization of a novel transcriptional regulatory module, a lamellocyte-active enhancer of the misshapen gene. This transcriptional control sequence appears to be inactive in all cell types of the wild-type larva, including crystal cells and plasmatocytes. However, in lamellocytes induced by wasp infestation or by particular genetic conditions, the enhancer is activated and it directs reporter GFP or DsRed expression exclusively in lamellocytes. The lamellocyte control region was delimited to a 140-bp intronic sequence that contains an essential DNA recognition element for the AP-1 transcription factor. Additionally, mutation of the kayak gene encoding the dFos subunit of AP-1 led to a strong suppression of lamellocyte production in tumorous larvae. As misshapen encodes a protein kinase within the Jun N-terminal kinase signaling pathway that functions to form an active AP-1 complex, the lamellocyte-active enhancer likely serves as a transcriptional target within a genetic auto-regulatory circuit that promotes the production of lamellocytes in immune-challenged or genetically- compromised animals.

PRELIMINARY REPORT ON THE SEGREGATION OF RESISTANCE IN CHESTNUTS TO INFESTATION BY ORIENTAL CHESTNUT GALL WASP

In 1995, h y brid chestnuts were planted in North Carolina, (southern U.S.A.), where the introduced insect Oriental Chestnut Gall Wasp (D,vocos'Inu.s hiiuiphi/us) is present. Of the 93 trees planted. 53 survived 12 years and were evaluated for the presence of Oriental Chestnut Gall Wasp infestation. Among the survivors, 11 had no wasp galls and 25 had few galls. Because the female parents were all susceptible, the genes controlling resistance to infestation cannot be cytoplasmic. Numbers of trees with little or no infestation suggest that genetic control ma be a single, dominant nuclear gene. If this is true, resistance can easily be transferred into timber chestnuts and orchard chestnut cultivars. INTRODUCTION Oriental Chestnut Gall Wasp, Drvocosmus ki.iriphi/us. (Payne et al.. 1976) has now spread from the state of Georgia in the southern United States, where it was introduced in 1974, to most of the southern growing area of chestnut trees in the United States, and to Cleveland, OH in north-central U.S. (Fig. 1) (Stehli, 2003, 2006). There is apparently nothing to stop it moving north, throughout the native range of American chestnut trees. Eggs are laid in leaf and flower buds, and the resulting galls kill the leaves and flowers and sometimes result in death of the trees. No pesticides are registered for control of this insect. Allegheny (American) chinquapin, Caslanea nimiJa, and Chinese chinquapin, C. Henrri, seem to be resistant to infestation (AnagnoStakis. 1998), and all other species of Castanea are susceptible to infestation. Breeding experiments were therefore begun to study the genetic control of this resistance, and to produce Ca.sia,iea that can survive in the presence of the insect for both forest and orchard plantings. In 1995, hybrid chestnuts were planted in the state of North Carolina. in cooperation ith the U.S. Forest Service, to test the trees for resistance to infestati � w on in an area where

A novel virus isolated from the aphid Brevicoryne brassicae with similarity to Hymenoptera picorna-like viruses

A novel virus, Brevicoryne brassicae virus (BrBV), has been identified in the cabbage aphid using a method based on the random amplification of encapsidated RNA. The complete sequence of the RNA genome of BrBV has been determined. The positive-strand genomic RNA is 10 161 nt, excluding the 3' poly(A) tail, and contains a single open reading frame (positions 793-9744) encoding a putative polyprotein of 2983 aa. The N-terminal part of the polyprotein shows similarity with the structural proteins of iflaviruses. The C-terminal part possesses consensus sequences of the helicase, cysteine protease and RNA-dependent RNA polymerase similar to those of iflaviruses and other picorna-like viruses. The highest sequence similarity observed was with iflaviruses from honeybee and an endoparasitic wasp. Replication and transmission of BrBV was not dependent on endoparasitic wasp infestation of the aphids.

Epidemiological and bacteriological aspects of mastitis associated with yellow-jacket wasps (Vespula germanica) in a dairy cattle herd.

The German wasp, Vespula germanica has been observed to injure teats of dairy cows, causing lesions that are associated with clinical and subclinical mastitis. The presence of skin lesions on the teats, caused by the wasps, was recorded in a dairy cattle herd located in the Samaria foothills during July-October 1999. Wasp-inflicted injuries were found in 43.6% (58 of 133) of the adult cows and 1.4% (one of 71) of the first-calving cows. They were located in 42.4% of cows (n = 25) on all quarters, 18 cows (30.5%) had lesions on the front quarters and 27.1% (n = 16) of cows on the hind quarters only. Clinical and subclinical mastitis were diagnosed in 61% (36 of 59) and 28.8% (17 of 59), respectively, of the injured adult and first-calving cows. The most common bacterial isolates from the mastitic cows were Staphylococcus aureus 45.1% (n = 14), Streptococcus dysgalactiae 16.1% (n = 5), Streptococcus spp. 19.4% (n = 7) and others 13.9% (n = 5). The loss of milk production was estimated at 300 kg milk for each cow injured by wasps and exhibiting clinical mastitis. An increase in the bulk-milk somatic cell count, from 186 x 103 at 1 month prior to the outbreak to a peak of 1200 x 10(3) in the post-outbreak month, was noted. The culling rate reached 13.6% (eight of 59) of the affected cows. In summary, the considerable economic losses caused by the wasp infestation resulted from decreased milk production and a decline in milk quality, culling of affected cows, and increased demand for use of drugs and veterinary care.

THE CHALCID SEED WASP, MEGASTIGMUS NIGROVARIEGATUS HYMENOPTERA: TORYMIDAE, ON ROSA RUGOSA THUNB. IN NOVA SCOTIA

AbstractTwo naturalized populations and two planted populations of Rosa rugosa Thunb. were studied with respect to chalcid seed wasp infestation. Megastigmus nigrovariegatus Ashmead was found in hips from planted R. rugosa in Halifax and Dartmouth, Nova Scotia, but not from bushes at naturalized sites. The percentage of infested hips at the Halifax and Dartmouth locations was 26 and 31%, respectively. The percentage of infested achenes within a single hip varied widely from 3 to 79% at the Halifax site and 7 to 60% at the Dartmouth site.Adult emergence was over 75% successful when achenes were over 2 mm in diameter but less than 15% for smaller achenes. The exit hole on the achene faced the outer wall of the hip. Adults emerged later in Nova Scotia than in the United States and between 59 and 72% were female. More than one adult wasp was observed ovipositing on a single hip.

Figs (Ficus spp.) and fig wasps (Chalcidoidea, Agaonidae): hypotheses for an ancient symbiosis

Figs and their pollinating fig wasps are dependent on one another for propagation of their own kinds. The wasps reproduce by ovipositing through the styles of female flowers within the closed fig receptacles (syconia). About half of the female flowers within the syconia of monoecious figs have styles which are longer than the ovipositors of the wasp, and they will therefore produce seeds rather than wasp larvae. Since a longer ovipositor would enable a wasp to reach more ovules and deposit more eggs, the question arises at to why longer ovipositors have not evolved. In an attempt to answer this question, four seemingly plausible hypotheses are examined but each is shown to be problematical in some way. Consideration is then given to a fifth hypothesis which proposes that ovipositor length is constrained by abortion of syconia with relatively few seed embryos and many agaonid larvae. It is argued first that this pattern of abortion will be selected during a sustained period of heavy wasp infestation because seeds will then become scarce relative to pollen-carrying wasps. Increased expenditure by the fig on seed production would therefore be favoured by natural selection. A greater expenditure on seeds would occur if young syconia with exceptionally heavy wasp infestations were dropped and the saved nutrients invested in syconia of a subsequent crop containing average levels of wasp larvae and seeds. Provided that the energy and nutrient cost of dropping young syconia is small, the selective advantage to the wasp of longer ovipositors is eliminated in this way. A stable coexistence of figs and wasps is therefore possible. The paper concludes by discussing two general predictions of the abortion hypothesis, and how these may be tested.