Acrolepiopsis Assectella Research Articles

Oviposition and feeding preference of Acrolepiopsis assectella Zell. (Lep., Acrolepiidae)

Abstract: The leek moth, Acrolepiopsisassectella (Zell.), is a recently discovered exotic species in eastern Ontario and western Quebec. This Allium spp. (Asparagales, Alliaceae) specialist can cause up to 40% crop damage. A no‐choice experiment was used to determine the relationship between oviposition behaviour and larval survival of the leek moth as the phylogenetic distance from the preferred host Allium ampeloprasum var. porrum L. increased. Results indicate that oviposition preference and larval survival of the leek moth declined as the phylogenetic distance from the preferred host increased. These results support the conclusion that the leek moth is a specialist feeder on closely related Allium spp. although the strength of this preference may decline as the motivation to oviposit increases. This may indicate that the leek moth is able to use closely related novel hosts as temporary refuges if the preferred host plant is unavailable.

Efficacy of Steinernema feltiae against the leek moth Acrolepiopsis assectella in laboratory and field conditions

The susceptibility of larvae of the leek moth, Acrolepiopsis assectella Zeller (Lepidoptera: Acrolepiidae) to different concentrations of an autochthonous strain of Steinernema feltiae (Rhabditida: Steinernematidae) was examined in laboratory experiments using Petri dishes. The efficacy of this strain in pots and field experiments was also evaluated. High mortality (80%–100%) of leek moth larvae was observed when these larvae were exposed to low concentrations (3 × 103 to 1 × 104 IJs/m2) of S. feltiae under laboratory conditions. Foliar application of 30,000 IJs/leek in pot experiments caused a 98% reduction in leek moth larvae. Field experiments showed a 87.7% reduction of leek moth larvae with the nematode treatment, significantly higher than the 22% reduction with the Bacillus thuringiensis treatment. The efficacy of the treatments with S. feltiae in relation to the microhabitat of the leek moth larvae between the interfolded leaves of the leek is discussed.

Taxonomic review of the leek moth genusAcrolepiopsis(Lepidoptera: Acrolepiidae) in North America

AbstractThe North American species ofAcrolepiopsisare reviewed and include six described species:A. assectella(Zeller),A. californicaGaedike,A. heppneriGaedike,A. incertella(Chambers),A. leucoscia(Meyrick), andA. reticulosa(Braun).Acrolepiopsis liliivoraGaedike is considered a junior synonym ofA. californica(new synonymy).Acrolepiopsis assectella, commonly known as the leek moth, is a recently invasive alien species in North America and a pest of the plant genusAllium, including leek, onion, garlic, and related cultivated plants. A key to species based on adults is provided, diagnostic characters including male and female genitalia are illustrated, and geographical distribution, host plants, and larval feeding pattern and damage (where known) are given. Diagnostics and illustrations are presented also forA. sapporensis(Matsumura); known as the Asiatic onion leafminer, it is very similar toA. assectellaand is an invasive alien species present in Hawaii, though not in North America. Adult diagnostic characters of the genusAcrolepiopsis, the family Acrolepiidae, and the superfamily Yponomeutoidea are also provided and illustrated. DNA barcoding data (short sequences of the mitochondrial cytochromecoxidase I gene) obtained for five of the six species revealed interspecific differences averaging 8.1%, whereas intraspecific variation was ≤ 0.16%, and provided unequivocal species separation matching morphology-based identifications.

Responses of ovipositing moths to host plant deprivation: life history aspects and implications for intercropping

Abstract1. When considering intercropping as a strategy to reduce pest oviposition, knowledge about the insect’s oviposition behaviour is very important. Physiological effects on the insect because of difficulties in finding a suitable oviposition site may also be important.2. In the present study, the effects that delays in access to host plants have on lifetime fecundity on diamondback moth and leek moth were examined. The ability to postpone egg laying, fecundity and lifetime oviposition are discussed in relation to intercrop/cover crop as a strategy to reduce oviposition on crop plants.3. When faced with host plant deprivation, the diamondback moth is relatively more dependent upon host plant stimuli for the onset of egg production. By contrast, leek moth is able to postpone egg production for a longer time. There even appeared to be a tendency for leek moth females to extend their lifetime when faced with host plant deprivation.4. We conclude that leek moths have the ability to postpone production of eggs and lay them later in life when finally encountering host plants after a period of host plant deprivation. Therefore, the use of intercropping as a strategy to reduce oviposition is questionable. For such an insect, use of a trap crop might be a better option because the female will lay her eggs in the trap crop and not get the opportunity to lay them later in life when finally encountering crop plants.

Consequences for a specialist insect and its parasitoid of the response of Allium porrum to conspecific herbivore attack

Recent studies on the leek Allium porrum L. demonstrate that a sharp increase in the release of volatile and nonvolatile sulphur compounds occurs in response to attack by the specialist phytophage, the leek moth Acrolepiopsis assectella (Zeller). The consequences of that response on the developmental capacity and behaviour of the leek moth and on the host-searching behaviour of the parasitoid hymenoptera Diadromus pulchellus Wesmael have been studied. No immediate adverse effect on larval development is seen, but the duration of male development is significantly longer. In addition, an almost 20% decrease is observed in the number of oocytes produced by adult females that developed on attack-damaged leek plants. Leek moths do not avoid damaged plants system- atically. On attacked plants, larvae tend to consume more and females to lay more eggs, although the latter tendency disappears after intensive attack. Concerning host-searching by D. pulchellus, the data indicate that females make use of the induced leek response. Parasitoids are attracted more strongly to attacked plants than to undamaged plants and mechanically damaged plants. The results of this study in a tritrophic system involving a biannual plant suggest a complex defence system combining direct and indirect mechanisms. Sulphur compounds may act by reducing second-generation pests, thereby preventing the specialist insect population from exploding at the expense of the leek.

Role of Caterpillar Silk Thread in Location of Host Pupae by the Parasitoid Diadromus pulchellus

Diadromus pulchellus is a solitary ichneumonid parasitoid. Its only known host is the pupa of Acrolepiopsis assectella, a specialist herbivore of Allium species. D. pulchellus females parasitize A. assectella pupae within 48 h after the caterpillars spin their cocoon and begin to pupate. Having observed that the cocoon produced by the leek moth caterpillar stimulates parasitoid egg-laying and that caterpillar leaves a silk thread, we studied the hypothesis that silk thread might be involved in host-finding by the parasitoid. Behavioral tests showed that when D. pulchellus females encounter a host silk thread, they change directions, follow the thread, and quickly locate the host. These findings show that pupal parasitoids can use signals produced by their hosts at the developmental instar preceding the one that they parasitize.

Increased Sulfur Precursors and Volatiles Production by the Leek Allium porrum in Response to Specialist Insect Attack

To defend themselves against herbivory, plants use a variety of direct and indirect strategies involving induced increases in secondary substances. Species of the Allium genus (Alliaceae), such as the leek Allium porrum (L.), produce nonprotein sulfur amino acids derived from cysteine, i.e., alk(en)yl-cysteine sulfoxides that are precursors of volatile thiosulfinates and disulfides. These defend most species including the specialist leek moth, Acrolepiopsis assectella. We determined by measuring the increase in the sulfur precursor propyl-cysteine sulfoxide (PCSO) if production of this precursor is induced in response to moth attack and mechanical wounding. The concentration of PCSO was determined by HPLC in 2- or 6-mo-old leeks after attacks of various intensity either by the specialist leek moth or by a generalist moth, Agrotis ipsilon. Injury-induced release of sulfur volatiles was measured by GC/MS after the attacks. Results showed an increase in the production of sulfur compounds in both the precursor and volatile form, occurring only in association with intensive attacks by leek moths. The increase in sulfur precursors also led to an increase in the release of sulfur volatiles. This induced response may provide an effective defense strategy against the plant's main natural enemy, both directly and indirectly by attracting entomophagous insects.

How a specialist and a non‐specialist insect cope with dimethyl disulfide produced by Allium porrum

AbstractDamaged Allium plants produce and release sulfur allelochemicals, presumably to prevent insect herbivory. Defensive sulfur compounds, particularly dimethyl disulfide (DMDS), are highly toxic for non‐adapted species. The toxicity of DMDS in these insects is due to disruption of the cytochrome oxidase system of their mitochondria. The purpose of this study was to compare susceptibility to DMDS in a specialist and a non‐specialist insect of Allium plants, i.e., Acrolepiopsis assectella Zeller (Lepidoptera: Acrolepiidae) and Callosobruchus maculatus Fabricius (Coleoptera: Bruchidae) a specialist insect of Leguminosae. Results showed that A. assectella larvae are less susceptible to DMDS than C. maculatus adults. This bruchid becomes more tolerant after a first exposure to 0.2 µl l−1 of DMDS, with second‐exposure toxicity depending on the time lapse between exposures. Higher second‐exposure tolerance could be due to selection and detoxification. To answer this question, the activity of glutathione S‐transferase (GST), a key enzyme in the detoxification system, was analyzed after DMDS exposure of C. maculatus adults and larvae and of A. assectella larvae. Exposure to DMDS increased GST activity in C. maculatus adults and larvae. This finding implies that induced GST is involved in C. maculatus tolerance to DMDS. Exposure to DMDS had no effect on GST activity in A. assectella. Adaptations underlying A. assectella tolerance to sulfur compounds are discussed.

The Acrolepiopsis assectella silk cocoon: kairomonal function and chemical characterisation

Two soluble sericin-like polypeptides, B1 and B2, from leek moth ( Acrolepiopsis assectella) cocoons trigger host-acceptance behaviour in the parasitoid, Diadromus pulchellus (Proc. Roy. Soc. London B 269 (2002) 1879). We found that these polypeptides were particularly cysteine-rich and lost their ability to trigger host-acceptance behaviour after being denatured and purified. This suggests that inter-disulphide bonds and the secondary structure of B1 and B2 are important for their biological activity. We also isolated six insoluble polypeptides (or polypeptides of low solubility) from A. assectella cocoons. At least four of these polypeptides triggered host-acceptance behaviour. The strongest responses were observed with P22, a light-chain fibroin or a seroin-peptide, and P100, a sericin-like polypeptide that is probably more strongly associated with the silk core than are B1 and B2. In conclusion, several polypeptides from different parts of the A. assectella silk-cocoon (the insoluble core and coating of the silk thread) are able to elicit host-acceptance behaviour in D. pulchellus females. These polypeptides belong to different silk protein families and are used as kairomones by this specialist parasitoid.

The cypovirus Diadromus pulchellus RV-2 is sporadically associated with the endoparasitoid wasp D. pulchellus and modulates the defence mechanisms of pupae of the parasitized leek-moth, Acrolepiopsis assectella.

Diadromus pulchellus is a solitary endoparasitoid wasp that parasitizes the pupae of the leek-moth, Acrolepiosis assectella (Lepidoptera). Hitherto, every individual D. pulchellus from France that has been investigated was infected by an orthoreovirus, DpRV-1, and an ascovirus, DpAV-4. Recently, a new strain of D. pulchellus, established from a French field population, was found to be able to develop on leek-moth pupae, but lacked both DpRV-1 and DpAV-4. However, all these wasps were infected with a new cypovirus, DpRV-2. This cypovirus is transmitted to the A. assectella pupae at each wasp oviposition and is replicated mainly in the gut cells of the parasitized pupae. DpRV-2, like the ascovirus DpAV-4, is able to inhibit the defence reaction of A. assectella pupae and so contributes to the parasitic success of D. pulchellus wasps.

Trap cropping effect on oviposition behaviour of the leek moth Acrolepiopsis assectella and the diamondback moth Plutella xylostella

AbstractThe potential of trap cropping as a pest control strategy was explored for two specialist moth species, where oviposition behaviour determines larval distribution. Oviposition behaviour was studied at three different scales: Individual plants in the laboratory, small scale field experiments with and without cages, and medium scale field trials. The study insects were the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), a specialist on Brassica species and the leek moth, Acrolepiopsis assectella (Z.) (Lepidoptera: Acrolepiidae), a specialist on Allium species. The diamondback moth preferred Indian mustard, Brassica juncea (L.) over white cabbage, B. oleracea var alba (L.). The leek moth did not show preference when offered leek, Allium porrum (L.) and chives, A. schoenoprasum (L.). However, the leek moth did prefer to oviposit on plants of a larger biomass over smaller plants. In both the small scale and the medium scale field studies the trap crops reduced the number of eggs laid on the primary crop. The total number of eggs laid in the monoculture and the trap crop treatments were the same in the small scale field cage study, but the females distributed their eggs differently. More eggs were laid on trap crops compared with primary crops and this pattern was also validated in the medium scale field trials. In this study only the direct effects of trap cropping were considered. Indirect effects of vegetation diversity such as enhancement of natural enemies could potentially increase the efficacy of trap cropping.

Effects of the Diadromus pulchellus ascovirus, DpAV-4, on the hemocytic encapsulation response and capsule melanization of the leek-moth pupa, Acrolepiopsis assectella

DpAV-4 is a symbiotic ascovirus found in natural populations of the solitary endoparasitoid wasp Diadromus pulchellus. The female wasp injects this virus into the pupae of the leek-moth Acrolepiopsis assectella during oviposition. The ascovirus replicates in the pupal tissues and the consequent lysis of the cells occurs synchronously with egg hatching and the development of the wasp larva. We show here that encapsulation and capsule melanization were activated when minute nylon monofilaments were implanted into the hemocoel of non parasitized leek-moth pupae and that encapsulation and melanization were inhibited in pupae parasitized by D. pulchellus. When the pupae were infected by DpAV-4, melanization of the nylon monofilaments was abolished, but a capsule was still always formed. These results indicate that DpAV-4 is a free virus able to alter the defence system of the parasitized host so as to improve the development of the parasitoid wasp, D. pulchellus.

Food experience on the predatory behavior of the ant Myrmica rubra towards a specialist moth, Acrolepiopsis assectella.

Entomophagous insects are often repelled by the secondary compounds of the plants eaten by their prey. These compounds, therefore, take on a defensive role for the phytophagous species that sequester them. Given that numerous entomophagous species are capable of learning, the effects on the foraging behavior of a repeated experience were investigated in the predatory ant Myrmica rubra. The sulfur amino acids methyl-cysteine sulfoxide (MCSO) and propyl-cysteine sulfoxide (PCSO) produced by Allium plants were identified in caterpillars of the leek moth Acrolepiopsis assectella. Three behavioral studies were carried out, with or without prior familiarization with caterpillars reared either on leek or on an artificial diet containing no Allium compounds. In choice tests with the two types of caterpillars, unfamiliarized ants displayed a preference for caterpillars reared on the artificial diet, but this preference disappeared or was reversed in both young and old ants after familiarization.

Effect of temperature on development and activity periods of the leek moth Acrolepiopsis assectella Zell. (Lep., Acrolepiidae)

Effects of temperature on egg, larval and pupal developmental times of the leek moth were examined at five constant temperatures ranging from 12 to 20°C. Using this data, a linear degree‐day model for the leek moth was developed. The model gave the threshold temperature of Th=6°C, and 630 degree‐days were required above the threshold temperature, to complete the development of the leek moth. To validate the model in the field, flight activity during the summers of 1998 and 1999 was studied using pheromone traps. If the summer is warm the leek moth can have two generations per year in Sweden, but the probability of completing two generations within leek plantations is very limited. The likelihood of the leek moth becoming a pest is highly dependent on access to alternative host plants for the first generation of leek moths.

Effect of Intercropping on Oviposition and Emigration Behavior of the Leek Moth (Lepidoptera: Acrolepiidae) and the Diamondback Moth (Lepidoptera: Plutellidae)

We compared the effect of intercropping on oviposition and emigration behavior of two related specialist moth species. The effect of height of the intercrop species (red clover) on oviposition was studied in field cages, using the leek moth, a specialist on Allium species, and the diamondback moth, a specialist on Brassica species. The moths were also evaluated in an open field experiment. Emigration of both moths was studied in the laboratory and in the field in cages with host plants, red clover (nonhost), host plant and red clover, and bare soil. The possible influence of noncontact stimuli was also studied in the laboratory. The leek moth laid the same amount of eggs in monoculture as in intercroppings with high and low clover. White cabbage intercropped with high clover received fewer eggs of the diamondback moth compared with a cabbage monoculture. Intercropping with low clover did not reduce the amount of eggs laid. Intercropping did not appear to affect the emigration of either the leek moth or the diamondback moth. Leek moths were less likely to emigrate than diamondback moths during the first 4 h of the study. We conclude that diamondback moth may be more likely to be controlled by intercropping than leek moths.

Frequency and viability of diploid and haploid male offspring of mated females of solitary endoparasitoid Diadromus pulchellus

Sex determination in the order Hymenoptera is based on arrhenotoky, hymenopteran males are usually haploid and females diploid. Males of the Ichneumonidae Diadromus pulchellus, solitary endoparasitoid of A Acrolepiopsis assectella pupae, are normally haploid, but diploid males are present in a natural population and can be obtained in an experimental population. The future of an ovocyte laid by mated females of the solitary endoparasitoid D. pulchellus was characterised by six probabilities related to the sex and development of the ovocyte. The probabilities of fertilisation of female ovocyte ( k 1) or non-fertilisation ( k 3) showed that an inseminated female functioned as a unmated female for half of the time (since k 1 = 0.492 and k 3 = 0.455) with the probability of fertilisation of male ovocyte, k 2, equal to 0.053.The survival probabilities of each type of ovocyte showed that an ovocyte had a high probability of developing up to the adult stage, although the difference between the calculated sex ratios at laying (males/females = 1.032) and at emergence (0.90) revealed a slight reduction in the number of haploid sons. The probabilities of fertilisation and of viability of all the ovocytes laid by each of the 33 mated females were analysed by an ascending hierarchical classification of Euclidean distances and by an analysis of their principal components. The 33 mothers were distributed into four distinct sub-groups characterised by a sex ratio varying from an exclusive presence of females to an exclusive presence of males. Our hypothesis was that this distribution in four sub-sets could not simply result from the random nature of the sample.

Effects of sulfur-containing precursors of Allium secondary metabolites on behavior and physiology of Diadromus pulchellus, a specialist parasitoid of Acrolepiopsis assectella

Diadromus pulchellus, a monophagous parasitoid of the leek moth, Acrolepiopsis assectella, a specialist of plants in the Allium genus, was raised on four series of chrysalids coming from four diets: leek leaves (LL), an artificial diet with (D + L) or without (D − L) leek powder, and an artificial diet plus 1% methyl-cysteinesulfoxide, a precursor of characteristic sulfur volatiles (D + P). Various behavioral and physiological responses by the parent parasitoids and the progeny were studied. No differences were observed in behavior among the four series. The higher precursor concentration observed in LL and in D + P than in D + L and D − L was responsible for a lower emergence ratio and higher egg production in LL and D + P. The consequences of these variations are discussed in relation to narrowness of the tritrophic system. The fact that sulfur volatiles favorable to behavior arise from nonvolatile sulfur precursors, having negative effects on physiology, can also contribute to the maintenance of the system.

Polypeptides of Acrolepiopsis assectella cocoon (Lepidoptera: Yponomeutoidea): an external host-acceptance kairomone for the parasitoid Diadromus pulchellus (Hymenoptera: Ichneumonidae)

Contact kairomones are essential for host-acceptance behaviour by female parasitoids. In the solitary endoparasitoid wasp, Diadromus pulchellus, this behaviour depends mainly on compound(s) in the cocoon of their host, Acrolepiopsis assectella pupae. Extracts of empty cocoons and polypeptides extracted from cocoons were tested in acceptance behaviour assays using cotton fibre lures bearing extracts. Extractions with solvents of increasing polarity indicated that the active compounds were polar, while SDS–PAGE showed that four glycopolypeptides contained enough information to trigger host-acceptance behaviour in female wasps. This kairomonal activity was found to be due to the protein moieties, and was independent of any glycosylation. These four glycopolypeptides might be two variants of two soluble sericin-like polypeptides differing in their degree of glycosylation.

Behavioural and olfactory variations in the leek moth, Acrolepiopsis assectella, after several generations of rearing under diverse conditions

AbstractThree strains of the leek moth, Acrolepiopsis assectella, were compared: two reared on leek leaves (Allium porrum) for which generations 10 to 12 (L) or generation 2 (G2) were used, the third one (D) reared on an artificial diet incorporating leek powder, for which generation ca 140 was examined. The walking behaviour (L and D) and the antennal responsiveness (L, G2 and D) were compared between individuals subjected to leek leaf odour and 4 volatiles identified in these leaves: 2 specific sulphur ones (dipropyl thiosulphinate and dipropyl disulphide) and 2 ‘general green leaf volatiles’ (cis‐3‐hexen‐1‐ol and trans‐2‐hexen‐1‐ol). The walking behavioural thresholds to leek odour, dipropyl thiosulphinate, and cis‐3‐hexen‐1‐ol were lower for L than for D females. The chemoanemotactic responses to dipropyl disulphide are almost identical, and trans‐2‐hexen‐1‐ol has nearly no activity. Accordingly, the olfactory sensitivity (assessed by EAG) to sulphur volatiles and cis‐3‐hexen‐1‐ol was higher for L and G2 females than for D ones. The threshold for thiosulphinate was at a concentration (v/v) of 4 ×10−4 M/l for D females, 4 × 10−5 M/l for L females and 4 × 10−8 M/l for G2 ones. It may be hypothesised that laboratory rearing conditions cause variations in the thresholds of antennal sensitivity and walking behaviour to specific and more efficient leek volatiles. This may result from the selective pressures experienced by the larvae reared in the laboratory.

Transfer, Perception, and Activity of Male Pheromone of Acrolepiopsis assectella with Special Reference to Conspecific Male Sexual Inhibition

In the leek moth, Acrolepiopsis assectella, the male, stimulated by a calling female, produces a sexual pheromone that is active on the female. The male-produced pheromone blend contains eight alkanes previously isolated from the male hair-pencils. We used EAG techniques to study the effect of the pheromone on females reared on leek or on artificial diet and on males reared on leek. The optimal stimulation duration appeared to be 1.6 sec exposure to the pheromone or components. The concentrations tested on the antenna were of the order of 1012 molecules/cm3. The hair-pencil extract tested was of an estimated concentration of around 109 molecules/cm3. The antennal responses are expressed relative to responses to a standard, amyl acetate, but also as an absolute value. Generally, females reared on artificial diet and males reared on leek responded better than females reared on leek. Of the alkanes tested, those present in hair-pencils gave higher responses, with hexadecane always giving the strongest response. A possible inhibiting activity of male leek moth pheromone on the sexual behavior of conspecific males was investigated. The behavior of sexually stimulated males was observed in the presence of other males, hair-pencil extracts, and different compounds either pure or in a mixture. The experiments established that in this species, male pheromone inhibits wing fluttering duration of conspecific males. This inhibition was obtained not only with fluttering males as a source of pheromone but also with all the alkanes tested. The inhibition was due to hair-pencil chemicals, particularly if these were perceived by olfaction plus contact. Wing fluttering increased the inhibitory activity of male-derived alkanes.