Host behaviour and its influence on foraging and acceptance by the solitary parasitoid wasp,Venturia canescens (Hym: Ichneumonidae)

Behavioural interactions between the solitary koinobiont parasitoid,Venturia canescens, and two of its hosts,Plodia interpunctella andCorcyra cephalonica, were investigated. The response of both hosts to simulated antennation using a two-haired brush was examined over instars 3 (L3) to 5 (L5). YoungP. interpunctella larvae predominantly adopted escape tactics (writhe, trash) whereas L5P. interpunctella usually froze after the stimulus was applied. L3C. cephalonica larvae were more aggressive (headrear, flick) thanP. interpunctella in response to the application of the stimulus, but olderC. cephalonica responded less aggressively than in earlier instars. AlthoughV. canescens readily jabbed its ovipositor at both hosts after antennation,P. interpunctella was considerably more susceptible to parasitoid attack thanC. cephalonica, irrespective of size in the final (L5) instar.C. cephalonica, the larger, more aggressive host, actively resisted parasitism whereasP. interpunctella responded much more passively after parasitoid contact. Parasitoids examined and jabbed their ovipositors at dead hosts, but this behaviour was not sustained, implying that host movement stimulates parasitoid attack. On patches containingV. canescens, L5C. cephalonica andP. interpunctella, mostP. interpunctella larvae responded by freezing after parasitoid contact.P. interpunctella that froze usually avoided parasitism, whereas larvae that attempted to escape by crawling were pursued with vigour byV. canescens and usually parasitized. Irrespective of behaviour after parasitoid contact,C. cephalonia displayed more aggressive behaviour and had much greater success in warding off parasitoid attack. Host acceptance byV. canescens is clearly affected by the size and species of the host it attacks. The influence of host defensive behaviour is discussed in relation to the evolution of parasitoid counter-defences and oviposition strategies.     

Host preferences ofTrichogrammatoidea bactrae fumata (Hym.: Trichogrammatidae) an egg parasitoid of leafrollers (Lep.: Tortricidae)

Trichogrammatoidea bactrae fumata Nagaraja is a naturally occurring egg parasitoid of some leafrollers in New Zealand kiwifruit orchards. The parasitoid showed a distinct preference for younger host-eggs ofEpiphyas postvittana, in which it achieved a higher rate of successful development. Such a preference is not as apparent withCtenopseustis obliquana. Host-species preference experiments found that the parasitoid rarely attackedPlanotortrix octo, and successful wasp emergence from parasitised eggs of this host was low.Epiphyas postvittana was the preferred host whenT. bactrae fumata was reared on this species. When reared onC. obliquana, the parasitoid showed no preference forE. postvittana orC. obliquana.     

Consequences of mixed species infestation on the searching behavior and parasitism success of a larval parasitoid

When two herbivore pest species are potential hosts of a single parasitoid species, two questions arise. Firstly, which host is preferable for mass rearing in terms of later parasitoid performance, and secondly, how do parasitoids perform in mixed herbivore situations after colony establishment? We tested Hyssopus pallidus, a gregarious parasitoid of two major pests of apple, Cydia (Grapholita) molesta and Cydia pomonella, before and after landing on apples infested by one of the two Cydia species. Pre-alighting host preference was tested in a Y-tube olfactometer setup, and parasitism success in a contact bioassay. To gain information on parasitoid performance throughout the growing season, different fruit growth stages were used. Irrespective of the host they had developed on, the parasitoids showed similar olfactory preferences when given a dual choice between infested and healthy fruits, and they did not discriminate between fruits infested by C. molesta and C. pomonella. Responsiveness was generally high, especially late in the season close to harvest. Both hosts are parasitized regardless of the host the parasitoid female had developed on, and no differences in parasitism rates or number of offspring were noted for the two hosts offered. Results were consistent for all apple growth stages tested. In conclusion, mass rearing of this parasitoid can be carried out on either host, without limiting the future efficacy of the bio-control agent. Similarly, established colonies are expected to develop further on both hosts without any bias in host preference.     

Parasitoid hymenopterans of Costa Rica: Geographical distribution of the species associated with fruit flies [Diptera: Tephritidae]

The geographical distribution of the parasitoid species associated with fruit flies in Costa Rica is presented. In a study of 319 fruit samples infested with larvae of fruit flies, collected from 135 localities, 8 parasitoid species were recovered from 11.0% of the fruit samples. Two species are considered to be indigenous, two were introduced for the biological control ofCeratitis capitata (Wiedemann) in this country, at least 3 unidentified species of eucoiline cynipoids and one species of uncertain origin was found for the first time. The identified parasitoids were:Doryctobracon crawfordi (Viereck) (indigenous),D. areolatus (Szépligeti) (indigenous),Biosteres longicaudatus Ashmead (introduced),Aceratoneuromyia indica (Silvestri) (introduced) andTrichopria sp. (indigenous?). The introduced species were more frequently associated withAnastrepha spp. than withC. capitata. The need for systematic monitoring of populations of released parasitoid species is suggested.     

Genetic analysis of an introduced biological control agent reveals temporal and geographic change,with little evidence of a host mediated shift

The evolution of introduced biological control agents is largely un-explored. Although much is theorized, there is little empirical evidence quantifying the evolutionary dynamics of a biocontrol agent after release into a new environment. In this study we use Diachasmimorpha tryoni, a purposefully introduced biocontrol agent of Ceratitis capitata, to model and quantify spatial, temporal, and host-related evolutionary patterns. This parasitoid has undergone a host shift in its introduced environment, Hawaii, to the gall forming weed biocontrol agent, Eutreta xanthochaeta, an interaction likely mediated by competition for C. capitata with the egg-larval parasitoid Fopius arisanus. To elucidate potential evolutionary patterns we analyzed microsatellites and sequence data extracted from Hawaii and Australian population clusters defined by Structure, in Genepop, Canoco, and IBDWS. Our analysis revealed structuring of Hawaiian D. tryoni populations as defined by significant historic influences related to temporal structure, geographic space, host guild, and augmentative releases. The host-shift parasitoids were not genetically distinct from other Hawaii populations. There were small changes in microsatellite DNA at the population level, but only between Australia and Hawaii populations, not at the host level. These results show that D. tryoni has not undergone host-mediated evolution since introduction to Hawaii, despite the fact that they have expanded their host range in Hawaii to include the gall-forming E. xanthochaeta. To our knowledge this is the first study to quantify genetic differentiation of a biological control agent over geographic space and time using contemporary and museum specimens.     

New techniques of rearingAnagrus flaveolus [Hym.: Mymaridae], an egg parasitoid of the brown planthopper

A small cage was designed to study the biology and behavior ofAnagrus flaveolus Waterhouse, an important egg parasitoid of the brown planthopper,Nilaparvata lugens (Stal), a pest of rice. A method of rearing moderate numbers of parasitoids on planthopper eggs in the laboratory was developed. Though the mymaridAnagrus flaveolus Waterhouse, a common egg parasitoid of rice planthoppers and leafhoppers all over Asia, reduces pest populations, its biological control potential has largely been overlooked because of its minute size and the lack of suitable techniques to study and rear it in the laboratory.Ôtake (1968, 1969) described some techniques to study the development, longevity and fecundity of a related speciesAnagrus nr.flaveolus Waterhouse. The cages described herein are much simpler to build and more efficient to use compared with those developed earlier. Rearing this important parasitoid in large numbers in the laboratory has not been done before.     

Chaetomymar gracile Sp. N. andC. lepidum [Hymenoptera: Mymaridae]: Egg parasitoids of a cicadellid injurious toCitrus in South Africa

Chaetomymar lepidum Annecke & Doutt is recorded for the 1 st time as an egg parasitoid of the injurious cicadellid,Penthimiola bella, onCitrus, andC. gracile sp. nov. is described from the same host.     

Classical biological control ofaleurocanthus spiniferus (Hem.: Aleyrodidae), on citrus in Southern Africa

The spiny blackfly,Aleurocanthus spiniferus (Quaintance), is a citrus pest in parts of Mpumalanga, South Africa, and in Swaziland. The leaves, fruit and branches of infested trees are usually covered with sooty mould and a reduction in tree vigour and production is experienced. Classical biological control ofA. spiniferus by the parasitoid,Encarsia cf.Smithi (Silvestri) (Hym.: Aphelinidae) is reported with a significant reduction in numbers ofA. spiniferus. The parasitoid dispersed successfully from isolated trees growing in home gardens andA. spiniferus was virtually eliminated up to 0,8 km from the nearest point of release within 10 months. A mean of 72.9% parasitism was reached. In 8 months,E. cf.smithi statistically reduced theA. spiniferus in parts of a commercial orchard where it was released, reaching 82.4% parasitism.     

Biology and host preference of Selitrichodes neseri: A potential biological control agent of the Eucalyptus gall wasp,Leptocybe invasa

Selitrichodes neseri (Hymenoptera: Eulophidae) is a parasitoid of the invasive gall-forming wasp Leptocybe invasa (Hymenoptera: Eulophidae), which has caused serious damage to Eucalyptus plantations in many parts of the world. S. neseri is a recently discovered parasitoid considered to be a potentially important biological control agent of L. invasa. The aim of this study was to provide the first basic data on the biology of S. neseri, which is essential for its application in biological control. S. neseri was shown to be a biparental ectoparasitoid. Observation from dissected galls indicated that the parasitoid developed on late larvae, pupae and callow adults, although development did occur in a range of gall ages. Observed nominal parasitism in captivity ranged from 9.7% to 71.8%. Adult S. neseri specimens, fed with honey-water and galled Eucalyptus leaves, survived an average of 26 days at 26 °C. The average developmental time from oviposition to emergence was 19.3 days ± 0.2 days. There was no pre-oviposition period. A single female produced a maximum of thirty-nine offspring, with a maximum of ten per day. Dissection of the ovaries showed that twelve ovarioles were present. The sex ratio of S. neseri observed in this study was 1:3.43 males:females. Galls of native insects most closely related to L. invasa and to galls of similar morphology to L. invasa-induced galls, were not suitable for S. neseri oviposition. S. neseri showed considerable potential as a biological control agent of L. invasa due to its relatively short developmental time, long adult life span when supplemented with carbohydrates, ability to utilize a range of gall ages and the fact that it has a high level of host specificity.     

Effects of genetic variability and habitat of Qualea parviflora (Vochysiaceae) on herbivory by free-feeding and gall-forming insects

• Background and Aims Differences in the chemical and physical traits of plants caused by both genetic and habitat characteristics may influence attack by herbivores. Leaves of Qualea parviflora (Vochysiaceae), a common tree of different habitats in the Brazilian Neotropical savannas (cerrado), are susceptible to severe attack by herbivorous free-living and gall-forming insects. Attack by free-living and gall-forming insects within and between populations of Q. parviflora were examined and it was determined to what extent genetic variability (detected by RAPD markers), phenotypic characteristics of the plants and habit traits influence the number of free-living and gall-forming insect species and individuals attacking the plants, and the intensity of attack.• Methods On four occasions in 2000, leaves were sampled from ten individual trees in each of three types of vegetation in the cerrado: campo sujo, cerrado sensu stricto and cerradão at the Ecological Station of Pirapitinga (ESP), in Três Marias, north-western Minas Gerais, Brazil. Genetic variability was detected by RAPD markers, and concentrations of nutrients, phenols and tannins, sclerophylly and pre-dawn water potential of leaves were measured. Water and nutrient contents in the soil below each tree characterized the habitat. The free-living and gall-forming herbivorous insects were determined.• Key Results Of 69 RAPD markers analysed, 41 were polymorphic and were used for analyses of genetic variability of Q. parviflora. Most of the variability occurred within habitats, accounting for 97·65 % of the genetic variability. Plants in the cerrado sensu stricto and campo sujo were the most similar. There were no significant associations between genetic similarity and the chemical and physical traits of Q. parviflora, or with habitat, nor was there significant correlation between phenotypic and habitat traits. Increasing concentrations of tannins and sulphur, C : N ratio and sclerophylly correlated with increasing percentage of leaf area damaged by herbivores. Decreased sclerophylly, concentration of tannins and C : N ratio, and increased concentration of nutrients in leaves correlated with increased severity of attack by gall-forming insects.• Conclusions Nutrient concentration in the soil had more influence, indirectly, on free-feeding insects than did composition of Q. parviflora leaves. However, gall-forming insects are affected more by leaf quality, attacking fewer sclerophyllous leaves, with larger nutrient but smaller tannin concentrations.Key words: Cerrado, genetic variability, gall attack, herbivory, insect galls, plant quality, Qualea parviflora, RAPD, Vochysiaceae     

Development and encapsulation of the endoparasitoid,Microplitis croceipes (Hym.: Braconidae), in six candidate host species (Lep.)

Encapsulation and development of the endoparasitoid,Microplitis croceipes (Cresson), were studied in six atypical lepidopteran host species whose usual host isHelicoverpa zea (Boddie). The candidate hosts examined were: the fall armywormSpodoptera frugiperda (J. E. Smith); the beet armyworm,Spodoptera exigua (Hübner); the cabbage looper,Trichoplusia ni (Hübner); the greater wax moth,Galleria mellonella (L.); the Indian meal moth,Plodia interpunctella (Hübner); and the diamondback moth,Plutella xylostella (L.). BothS. exigua andT. ni were completely unsuitable forM. croceipes development due to the high rate of eggs that were encapsulated within three days after parasitism. Encapsulation inS. frugiperda included mainly parasitoid eggs and was first detected six days after parasitization at 25°C and two days at 30°C. Encapsulation inG. mellonella occurred only in the larval stage of the parasitoid. InP. interpunctella, parasitoid larvae reached the 3rd stadium, but none of them pupated. OnlyS. frugiperda andG. mellonella supported successful development ofM. croceipes from egg to adult. The percentage of parasitoids reaching the adult stage in these hosts was higher at 30°C than at 25°C (13% vs. 4% inS. frugiperda, and 21% vs. 3% inG. mellonella, respectively). However, these percentages were too low to substitute them as a more economical host for rearingM. croceipes. This biological information will be useful in additional laboratory studies directed toward reducing the rate of encapsulation (e.g., manipulation of host rearing temperature) to increase production ofM. croceipes on these hosts.     

Trophic cascades initiated by fungal plant endosymbionts impair reproductive performance of parasitoids in the second generation

Variation in plant quality can transmit up the food chain and may affect herbivores and their antagonists in the same direction. Fungal endosymbionts of grasses change the resource quality by producing toxins. We used an aphid-parasitoid model system to explore how endophyte effects cascade up the food chain and influence individual parasitoid performance. We show that the presence of an endophyte in the grass Lolium perenne has a much stronger negative impact on the performance of the parasitoid Aphidius ervi than on its aphid host Metopolophium festucae. Although the presence of endophytes did not influence the parasitism rate of endophyte-naïve parasitoids or their offspring’s survival to adulthood, most parasitoids developing within aphids from endophyte-infected plants did not reproduce at all. This indicates a delayed but very strong effect of endophytes on parasitoid performance, which should ultimately affect plant performance negatively by releasing endophyte-tolerant herbivores from top-down limitations.     

Longevity and development of the egg-parasitoid,Cheiloneurus pyrillae [Hymenoptera: Encyrtidae] at different combinations of temperature and relative humidity

Out of the 2 important physical factors like temperature and relative humidity, the former plays significant role in affecting the survival of adults and development of immature stages ofCheiloneurus pyrillae Mani which is an important egg parasitoid of the sugarcane leaf hopper (Pyrilla perpusilla Walker) in India. Average longevity of males and females of this parasitoid decreased from 2.47 to 0.81 days and from 4.95 to 0.84 days, respectively when the test temperature was increased from 15 to 35±1.5°C. Similarly, its mean developmental period was found to reduce from a maximum of 45.87 to a minimum of 10.12 days when the rearing temperature was increased from 15 to 30±1.5°C. The parasitoid could not be reared at or above 32.5±1.5°C because its immature stages failed to withstand this temperature. These informations will be helpful in maintaining the mass culture ofC. pyrillae in the laboratory.     

Development of Microplitis bicoloratus on Spodoptera litura and implications for biological control

Microplitis bicoloratus Chen (Hymenoptera:Braconidae:Microgastrinae), a new species of Microplitis Förster from China, is a solitary endoparasitoid of the larvae of the cotton leafworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). This parasitoid is the first to be successfully reared and evaluated in the laboratory as a potential agent for the biological control of S. litura in China. Oviposition, immature development, and the effects of parasitism on the development of S. litura were studied. In long-term oviposition trials, females laid eggs on S. litura larvae for up to 10 days; oviposition was heavily skewed toward the first few days, with approximately one third of the eggs laid on day 1 and over 50% laid by day 3. This rapid oviposition rate increases the potential for biological suppression of host populations because the likelihood of mortality for the parasites from exposure to detrimental environmental factors or generalist predators increases with time. Immature development of the parasitoid in its host only required 7 days: eggs hatched within 24 h, the first instar larva required 2 days, the second instar larva needed 3 days, and the third instar larvae exited the host and pupated in 1 day, at 27±1°C, 60–80% relative humidity and a 12:12-h (long day) photoperiod. The development of the parasitized hosts was disrupted. When the parasitoid larvae finished development, the body weights of host larvae were significantly reduced regardless of which host instar was parasitized. Our results suggest that M. bicoloratus has considerable potential as a biological control agent for S. litura.     

Toxicity and kinetics of spinosad in different developmental stages of the endoparasitoid <Emphasis Type="Italic">Hyposoter didymator</Emphasis> (Hymenoptera: Ichneumonidae) and its host <Emphasis Type="Italic">Spodoptera littoralis</Emphasis> larvae (Lepidoptera: Noctuidae)

The toxicity of spinosad was evaluated using the RaPID Assay^® Spinosad immunosorbent assay in different developmental stages of the parasitoid, Hyposoter didymator, and in its host, fourth-instar larvae of the cotton leafworm Spodoptera littoralis. Spinosad was applied directly to pupae and adults of H. didymator (ingestion or topical application) or to the immature stages of the parasitoid via the host larvae. Low amounts of spinosad were recovered from S. littoralis host larvae after topical treatment, and the compound was mainly retained in the hemolymph. Amounts of spinosad detected in third-instar larvae of H. didymator, pulled out from the hemolymph of parasitized S. littoralis larvae, were 85 pg (3.57 ng a.i./g body weight) in dead larvae, and 82 pg (3.42 ng a.i./g body weight) in alive individuals. After topical treatment of H. didymator cocoons, most of the compound was retained in the silken cocoon, preventing contamination of the pupa. Also in the parasitoid adults, relatively low amounts of spinosad were accumulated in the body overall, but half of all the insecticide recovered was found in the ovaries. The kinetic results obtained help to better understand the toxicity of spinosad in the complex S. littoralis–H. didymator, and to ascertain the compatibility between spinosad and the parasitoid for optimizing the control of lepidopteran pests.     

Mass rearing the tachinid fly argyrophylax basifulva,a parasitoid of the greater coconut spike moth [Tirathaba spp.] [Lep.: Pyralidae]

Argyrophylax basifulva (Bezzi) (Tachinidae) has proved to be an effective parasitoid in the control of Greater Coconut Spike Moth (Tirathaba complexa Butler) in Fiji. However, its use elsewhere has been hampered by difficulties in its mass rearing, particularly in obtaining matings. Techniques for rearing the fly that overcome these problems are given in this publication.     

Serratia marcescens as a rapid indicator of Microctonus hyperodae oviposition activity in Listronotus maculicollis and potential application of the technique to host-specificity testing

Listronotus maculicollis (Dietz) (Coleoptera: Curculionidae) is a potential novel host of the braconid parasitoid Microctonus hyperodae Loan, but initial studies have shown that levels of parasitism are lower than in the natural host L. bonariensis (Kuschel). A novel bacterial indicator test was used to determine whether the lower level of parasitism was due to behavioural factors, lack of oviposition, or host resistance. The incidence of ovipositor penetration by the parasitoid M. hyperodae into adult L. maculicollis was measured by immersing the ovipositor of the parasitoid in the facultative pathogen, Serratia marcescens Bizio. Adult weevils were then exposed to parasitoids for up to 72 h and rapid mortality used as an indicator of oviposition penetration. Survival was assessed after six days and surviving weevils were dissected and examined for parasitoid larvae. Mortality among L. maculicolis exposed to parasitoids treated with S. marcescens was significantly higher (P<0.001) than the controls but significantly lower (P<0.001) than in the natural host, L. bonariensis. Dissection of weevils exposed to uncontaminated parasitoids revealed that parasitism in L. maculicolis was significantly (P<0.001) less than parasitism in L. bonariensis. Serratia marcescens-induced mortality plus parasitism of surviving weevils in the parasitoid plus bacteria treatments produced a similar overall effect. Application of bacteria to the parasitoid ovipositor provided a rapid, simple test for ovipositor penetration, which shows potential for separation of behavioural and physiological defence mechanisms in parasitoid/host range studies.     

Predator and parasitoid attacking ant-attended aphids: effects of predator presence and attending ant species on emerging parasitoid numbers

Interaction between a predator and a parasitoid attacking ant-attended aphids was examined in a system on photinia plants, consisting of the aphid Aphis spiraecola, the two ants Lasius japonicus and Pristomyrmex pungens, the predatory ladybird beetle Scymnus posticalis, and the parasitoid wasp Lysiphlebus japonicus. The ladybird larvae are densely covered with waxy secretion and are never attacked by attending ants. The parasitoid females are often attacked by ants, but successfully oviposit by avoiding ants. The two ants differ in aggressiveness towards aphid enemies. Impacts of the predator larvae and attending ant species on the number of parasitoid adults emerging from mummies per aphid colony were assessed by manipulating the presence of the predator in introduced aphid colonies attended by either ant. The experiment showed a significant negative impact of the predator on emerging parasitoid numbers. This is due to consumption of healthy aphids by the predator and its predation on parasitized aphids containing the parasitoid larvae (intraguild predation). Additionally, attending ant species significantly affected emerging parasitoid numbers, with more parasitoids in P. pungens-attended colonies. This results from the lower extent of interference with parasitoid oviposition by the less aggressive P. pungens. Furthermore, the predator reduced emerging parasitoid numbers more when P. pungens attended aphids. This may be ascribed to larger numbers of the predator and the resulting higher levels of predation on unparasitized and parasitized aphids in P. pungens-attended colonies. In conclusion, a negative effect of the predator on the parasitoid occurs in ant-attended aphid colonies, and the intensity of the interaction is affected by ant species.     

Mycoflora of stored rice in relation to the biological control of Sitophilus oryzae by Anisopteromalus calandrae

In this study, we determined the effect of controlling rice weevils on the mycoflora of stored brown rice by using Anisopteromalus calandrae (Howard), a parasite of the rice weevil. The mycoflora in brown rice with the parasitoid was similar to that without the parasitoid; however, the dominant mold species differed. Without the parasitoid, Aspergillus candidus Link and Penicillium islandicum Sopp were the dominant species, whereas Aspergillus penicilloides Speg. and P. islandicum were dominant when the parasitoid was present. The difference appeared to be due mainly to the difference in the grain moisture content with and without the parasitoid. A. candidus was the dominant species in the communities without the parasitoid and was not observed when the weevils were suppressed. P. islandicum dominated or co-dominated regardless of the presence of the parasitoid which suggested that P. islandicum is tolerant to low grain moisture content or is positively affected by the presence of the rice weevil.     

The window of vulnerability and its effect on relative parasitoid abundance

Summary. 1. The length of time that a gall-forming midge, Rhopalomyia califomica , was vulnerable to attack by four parasitoid species was measured in the field at two locations.
2. The midge had a restricted window of vulnerability to each of the parasitoid species, but similar windows of vulnerability were found at the two sites.
3. A stage-structured model was used to illustrate that the length of the vulnerable window should have no effect on the fraction parasitized by a single parasitoid species if that species is the only parasitoid attacking the host in a coupled host-parasitoid interaction. However, the length of the window of vulnerability can have a positive effect on the fraction parasitized by a species in competition with other parasitoid species.
4. The length of the window of vulnerability can help explain the relative field abundance of four of the common parasitoid species of R.californica.