Parasitoid Of Diamondback Moth Research Articles

The effects of a naturalized weed, Lepidium virginicum, on the development and behaviors of the diamondback moth and its natural enemies in Hawaii

Weeds can play numerous important roles in pest suppression in agroecosystems. These include influencing the host searching behaviors of herbivorous pests and their natural enemies and providing shelter and alternative food sources for predators and parasitoids. Virginia pepperweed, Lepidium virginicum, is a widespread naturalized weed in Hawaii and can often be found in and around agricultural fields. It is a member of the Brassicaceae family and is a known host plant of the diamondback moth (DBM), Plutella xylostella. In this study, we found that DBM preferentially oviposit on L. virginicum (vegetative stage) when presented with a choice of cabbage. Using laboratory and semi-field trials, we investigated the responses of the natural enemies of DBM to the vegetative stage of L. virginicum and cabbage infested with DBM larvae. When DBM-infested plants were placed in the field for 48 h, more spiders and parasitized DBM larvae were recovered from the L. virginicum than from cabbage. In laboratory choice experiments, we demonstrated that the dominant DBM parasitoid species in Hawaii (Cotesia vestalis) oviposited in more host larvae on L. virginicum compared to cabbage, though this had no particular benefit for parasitoid development (adult size and sex ratio). Our findings suggest that the presence of L. virginicum in cabbage agroecosystems could be beneficial by serving to divert DBM oviposition away from cabbage and promoting predator and parasitoid populations.

Targeting diamondback moths in greenhouses by attracting specific native parasitoids with herbivory-induced plant volatiles.

We investigated the recruitment of specific parasitoids using a specific blend of synthetic herbivory-induced plant volatiles (HIPVs) as a novel method of pest control in greenhouses. In the Miyama rural area in Kyoto, Japan, diamondback moth (DBM) (Plutella xylostella, Lepidoptera: Plutellidae) larvae are an important pest of cruciferous crops in greenhouses, and Cotesia vestalis (Hymenoptera: Braconidae), a larval parasitoid of DBM, is found in the surrounding areas. Dispensers of HIPVs that attracted C. vestalis and honey feeders were set inside greenhouses (treated greenhouses). The monthly incidence of DBMs in the treated greenhouses was significantly lower than that in the untreated greenhouses over a 2-year period. The monthly incidences of C. vestalis and DBMs were not significantly different in the untreated greenhouses, whereas monthly C. vestalis incidence was significantly higher than monthly DBM incidence in the treated greenhouses. Poisson regression analyses showed that, in both years, a significantly higher number of C. vestalis was recorded in the treated greenhouses than in the untreated greenhouses when the number of DBM adults increased. We concluded that DBMs were suppressed more effectively by C. vestalis in the treated greenhouses than in the untreated greenhouses.

Spatiotemporal distribution and impact of diamondback moth parasitoids in the Dakar Niayes in Senegal

Conservation biological control, which fosters the optimal use of indigenous natural enemies, is a promising way for reducing pesticide reliance in horticultural systems. The objective of this study is to determine the distribution of parasitoid species, their parasitism rates on pest populations in relation to environmental conditions in the main Senegalese market garden area (Niayes). To do this, one hundred and sixteen cabbage plots, distributed in the Niaye segmented into three areas, along a South-North transect, are chosen. These plots were observed during four crop seasons from October 2012 to May 2014. Pest larvae were counted every three weeks using 24 randomly chosen cabbage plants per plot. Four hymenopteran parasitoid species were identified; Oomyzus sololowskii (Kurdjumov), (Eulophidae), Brachymeria sp. (Chalcididae), Apanteles litae Nixon and Cotesia vestalis (Haliday) both Braconidae. The percentage of parasitism varied between the plots, the geographical locations and the sampling period. O. sokolowskii and A. litae species were predominant and were affected by the growing season. The species distribution in the three sampling areas revealed that O. Sokolowskii was more efficient during the cold dry season, whereas A. litae was more efficient during the hot dry season. These results aim at identifying conditions favorable to the regulation of populations of cabbage moth by natural enemies. Parasitoids can play a promising role as biological control agents in Senegal. In order to do this, studies such as these must be carried out and the results communicated to farmers who often misunderstand the primordial role that natural enemies can play in pest control. Keywords : Cabbage, parasitism percentage, dry season, West Africa, Plutella xylostella .

Efficacy of aqueous extracts of black alder (Alnus glutinosa GAERTN.) and black elderberry (Sambucus nigra L.) in reducing the occurrence of Phyllotreta spp., some lepidopteran pests and diamondback moth parasitoids on white cabbage

AbstractThe insecticidal and antifeedant effects of aqueous extracts from two common plants (black alder Alnus glutinosa and black elderberry Sambucus nigra) on the occurrence of flea beetles (Phyllotreta spp.), as well as lepidopteran pests like the diamondback moth Plutella xylostella, small white butterfly Pieris rapae, large white butterfly Pieris brassicae, cabbage moth Mamestra brassicae and the Plutella xylostella parasitoid complex were investigated on white cabbage in 2008-2009. Aqueous extracts of black elderberry Sambucus nigra significantly reduced numbers of flea beetles Phyllotreta spp., eggs of Pieris rapae and P. brassicae, and larvae and pupae of Plutella xylostella on the cabbage. The aqueous extract of Alnus glutinosa was less effective. Parasitoids had the greatest impact on reducing numbers of diamondback moth: the dominant species was Diadegma fenestralis. The smallest number of parasitoids was reared from pupae collected from plots where the cabbages had been sprayed with the Sambucus nigra extract.

Situation of the Diamondback Moth (DBM), Plutella xylostella and Its Parasitoids in the Cauliflower Fields of Tehran

Aims: The diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) is one of the most important pests of cruciferous plants. Amongst the most important factors to reduce this pest population are parasitoids. The aim of present study was to Identify the parasitoids of the diamondback moth (DMB), computating the density of DBM stages and its parasitoids and their performance in different cauliflower fields of Tehran. Also the objective of this study was to elucidate the reactions of DBM parasitoids to host density. Correlation between different larval densities and parasitism rate of DBM parasitoids were calculated using a recall method in field conditions. Place and Duration of Study: Place – Department of Plant protection, Faculty of Agricultural Sciences, Shahed university, Tehran, Iran. Duration – June, 2011 to November, 2012. Methodology: Sampling was carried out every two weeks from late June until early November. From each field 20 plants were selected. All larval instars and pupae on each Original Research Article Annual Research & Review in Biology, 4(3): 473-486, 2014 474 plant were collected, and were counted and recorded separately for each field. Also, collected DBM larvae and pupae were kept on the host plant under controlled conditions (60 ± 5% RH, 27 ± 2 C and 14L:10D photoperiod). In order to do recall of larval parasitoids, different densities of 5, 15, 25 and 35 larvae were placed on each plant. For each density five plants were considered as five replication. Analysis of variance (ANOVA) was used to analyze the data on numbers of DBM larvae and pupa in different regions as well as the mean number of parasitoids and parasitism rate. The means were compared at the 5% level of significance using the Duncan studentized range test. Results: In all studied areas, the larvae, pupae and the total number of larvae and pupae were determined as 3.05, 2.26 and 7.54 (per plant), respectively. The percentage of parasitism by D. anurum, C. plutellae and O. sokolowskii in all regions and total parasitism by these three species were determines obtained as 12.67, 10.29, 13.27 and 36.23% per plant, respectively. Conclusion: The number of larval and pupal stages based on unit density, was significantly different between all experimental regions and Shahed university station. The highest percentage of parasitism was caused by D. anurum in Tehran. Spraying did not reduce the DBM population in some fields in Tehran, but repeated spraying caused a reduction in the activity of the parasitoids of DBM.

Selecting the right parasitoid for the environment in classical biological control programmes: the case of Diadegma semiclausum (Hymenoptera: Ichneumonidae) and Plutella xylostella (Lepidoptera: Plutellidae) in the Kofele highland of Ethiopia

The careful selection of parasitoids with a track record of success in similar environmental conditions may increase the likelihood of effective biocontrol. Diamondback moth (DBM) population and level of parasitism were assessed for three years prior to the release of Diadegma semiclausum (Hellén) in June 2008. Thereafter, the DBM population and severity of crop damage and the occurrence of D. semiclausum and indigenous DBM parasitoids were monitored by monthly surveys during the main production season of June to December for three years. Before release, DBM numbers fluctuated between 4.2 and 11.2 per plant and parasitism ranged between 6.5 and 24.7%. DBM density declined to 2.8, 0.9 and 0.7 per plant whilst parasitism levels increased successively to 21, 39 and 38% in 2008, 2009 and 2010, respectively. A significant shift in parasitoid guild was observed after D. semiclausum release: it comprised 18.6, 80.3 and 88.6% of total parasitism in the first, second and third year, respectively. The decline of DBM density following the release of the introduced parasitoid and its establishment will ensure production of Brassica spp. without pesticide use against DBM in the affected area.

Influence of cabbage resistance and colour upon the diamondback moth and its parasitoid Oomyzus sokolowskii

AbstractHost plant resistance and biological control are vital integrated pest management tools against the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), but to date no study has investigated this system including the DBM parasitoid Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae). We examined oviposition and development of P. xylostella exposed to two commercial cabbage cultivars (green ‘Chato de quintal’ and red ‘Roxo’) and possible effects upon O. sokolowskii. Under free‐choice tests, DBM females laid significantly more eggs on plants of the green cabbage, even though several population growth parameters showed that DBM developed better on the red cabbage. Furthermore, a laboratory free‐choice test with artificially green‐ and red‐painted kale leaf discs demonstrated a similar oviposition preference pattern, with green colour being preferred over red colour. The preference was apparently visually mediated; olfactometer tests showed similar attraction of moths to both green and red cultivars in choice and non‐choice tests. Host plant cultivar had no statistically significant effect on female parasitoid behaviour towards DBM larvae, nor on parasitoid numbers or longevity. Moreover, wasps parasitizing DBM larvae reared on the green cultivar developed more quickly and in larger numbers per parasitized larva. Thus, feeding on green cabbage rather than red does not hinder, and potentially even enhances, control of DBM by O. sokolowskii. On a practical level, these results suggest that intercalating green cabbage cultivars as a trap crop might help protect more profitable red cultivars in growing fields.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and ( Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and ( Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

Diadromus pulchellus in North America: field release against leek moth and new characters to distinguish it from Diadromus subtilicornis, a native diamondback moth parasitoid

We report successful overwintering of Diadromus pulchellus in North America (Ontario) following introduction of this species from Europe to control the leek moth, Acrolepiopsis assectella, a recently established alien species. Field rearing revealed that the native Diadromus subtilicornis emerged only from diamondback moth, Plutella xylostella, whereas D. pulchellus was reared almost exclusively from leek moth. The single D. pulchellus reared from diamondback moth was anticipated because host range studies found this species could develop on both leek moth and diamondback moth in the laboratory, although, it had not been previously reported from diamondback moth in the field in Europe. DNA barcoding of specimens of both Diadromus spp. confirmed their species status and novel morphological characters are presented to distinguish D. pulchellus from D. subtilicornis. In addition, DNA from specimens of D. subtilicornis from Europe clustered with DNA from specimens across Canada, confirming that it is a single Holarctic species. Finally, a new host association for D. subtilicornis is recorded from the dame's rocket moth: Pseudoplutella porrectella.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n -heptanal, α-pinene, and ( Z )-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R )-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n -heptanal, α-pinene, and ( Z )-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R )-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

Starvation and herbivore-induced plant volatiles affect the color preferences of parasitic wasps

Using light-emitting diode spotlights, we examined the responses of Cotesia vestalis, a parasitoid of diamondback moth (DBM), Plutella xylostella larvae, with different hunger level to different chromatic cues. Naive satiated female wasps showed no significant preference for either green, yellow, orange, or red spotlighted areas over a control area with background fluorescent light. When starved for 2 h, female wasps preferred yellow and green light over the control area, but not orange or red light. We also tested the effects of DBM-larvae-induced cabbage-plant volatiles, which attract female wasps, on wasp responses to green versus yellow light. In control experiments with no plant volatiles, starved wasps showed no color preference. However, when synthetic volatiles were present, the wasps preferred green over yellow light. We concluded that both hunger level and herbivore-induced plant volatiles were important factors affecting the response of parasitic wasps to light of different color.

Plant Resistance Affects the Olfactory Response and Parasitism Success of Cotesia vestalis

Understanding the factors influencing host-selection behavior of parasi- toids is essential in studies on host-parasitoid ecology and evolution, and in combin- ing sustainable strategies of pest management, such as host-plant resistance and biological control. The effects of host-plant resistance on the olfactory response and parasitism success by Cotesia vestalis, a parasitoid of diamondback moth (Plutella xylostella) larvae were examined. Here, it was demonstrated that host-plant resistance can strongly influence foraging behavior and parasitism success of the parasitoid. In olfactometer experiments, C. vestalis did not differentiate between crucifer plant types with similar levels of susceptibility or resistance to P. xylostella but showed a strong preference for susceptible compared with partially-resistant host plants. The influence of previous oviposition activity varied with the host-plant type experienced by the parasitoid. In cage experiments, C. vestalis preferred to parasitize P. xylostella larvae on a susceptible plant compared with larvae on a partially resistant host plant when exposed to hosts for 24 h. However, this preference appeared to be transitory, and was not found after 96 h exposure. The present study suggests that combining partial host-plant resistance with biological control by C. vestalis for the control of P. xylostella may in some circumstances be antagonistic and negatively affect para- sitism success.

Effects of larval densities and the duration since larval infestation on the host-searching behavior of Diadegma semiclausum, a parasitoid of diamondback moth larvae on plants

The host-searching behavior of Diadegma semiclausum, a parasitoid of diamondback moth (DBM) larvae, was studied in a wind tunnel. Wasps flew preferentially to a cabbage plant, freshly infested by 1 DBM larva, or one freshly infested by 10 DBM larvae, than to an intact plant. There was no significant difference between wasps’ responses to plants infested by different DBM larvae densities. We also found that the duration since the last infestation by 10 DBM larvae (1 or 3 days) negatively affected the attractiveness of infested plants. We also studied the time wasps spent searching for larvae on a cabbage plant (residence time). The wasps spent ca. 400 s on a plant freshly infested by 1 larva. Residence time was significantly longer (ca. 1,200 s) on a plant freshly infested by either 5 or 15 DBM larvae. Residence time of D. semiclausum on a plant freshly infested by 5 DBM larvae was significantly longer than on a previously infested plant (1 or 3 days after the last infestation). These results showed that host densities on a plant and the duration since their last infestation affected the host-searching behavior of D. semiclausum.

Reproductive fitness of <i>Diadegma semiclausum</i> Hellen (Hymenoptera Ichneumonidae) in response to host density

Diadegma semiclausum is an important larval parasitoid of diamondback moth (DBM) Plutella xylostella The present study investigated the reproductive fitness of D semiclausum females in response to host densities of 5 and 30 DBM larvae per cabbage seedling per day Both the number of hosts parasitised and the number of female progeny produced over the life of the parasitoid were significantly greater in the 30 than the 5 host density (hosts parasitised 60131 versus 12015 and female progeny produced 6710 versus 122) (P

Developmental responses of the diamondback moth parasitoidDiadegma semiclausum(Hellén) (Hymenoptera: Ichneumonidae) to temperature and host plant species

Effects of constant rearing temperature and the plant species fed upon by its hosts were investigated for several developmental parameters of Diadegma semiclausum (Hellén), an important parasitoid of the diamondback moth, Plutella xylostella (L.). Temperature had highly significant effects on all developmental parameters measured, and effects were usually both linear and quadratic with increasing temperature. Host plant species, comprising Brassica napus L., Brassica rapa L. ssp. pekinensis and Brassica oleracea L. var. capitata, also affected development of the parasitoid, and significant interactions were observed between plant species and rearing temperature for all developmental parameters measured. Development of D. semiclausum occurred successfully on all host plant species tested for the temperature range of 10 to 25°C. However, when its P. xylostella hosts consumed leaf tissue of B. napus, no specimens survived to pupate at 30°C, whilst pupation and adult eclosion occurred at 30°C on B. rapa ssp. pekinensis and B. oleracea var. capitata. At high ambient temperatures, such as those characteristic of tropical or subtropical regions (especially at low elevations) or regions that undergo temperature increases due to climate change, P. xylostella is predicted to occur at a higher range of temperatures than its biocontrol agent, D. semiclausum. Effects of high temperatures are expected to be more profound on the parasitoid for some host plants than others, with greater developmental limitations for the parasitoid on B. napus than on B. rapa or B. oleracea.

Application of synthetic herbivore‐induced plant volatiles causes increased parasitism of herbivores in the field

AbstractWe previously reported that Cotesia vestalis (Hymenoptera, Braconidae), a parasitoid of diamondback moth (DBM) (Plutella xylostella; Lepidoptera, Plutellidae) larvae, was attracted to volatiles from crucifer plants infested by moth larvae kept in a desktop acrylic box, and that a blend of four DBM‐induced plant volatiles was responsible for this attraction. In this study, using a specially designed dispenser to release the four compounds, we demonstrated that the wasp was attracted to intact komatsuna plants (Brassica rapa var. perviridis). The experiments were performed in a climate‐controlled room, which was approximately 1000 times larger than the acrylic box used previously. Similarly, using the dispenser in the field, C. vestalis females were attracted to intact komatsuna plants with the dispenser from a distance of three metres. We also examined the effect of the volatile blend on the incidence of parasitism of DBM larvae in the field. Three small containers containing DBM‐infested komatsuna plants with dispensers, and three control containers containing only infested plants (control) were arranged in two lines running perpendicular to a komatsuna field in which both DBM larvae and C. vestalis populations were maintained, at distances of 12, 30 and 70 m. The results showed that the incidence of DBM parasitism was significantly higher in containers containing dispensers than in the control containers, suggesting that the blend could potentially be applied to DBM control in agroecosystems.

Population dynamics of the diamondback moth Plutella xylostella L. (Lepidoptera: Yponomeutidae) in the Sydney Region of Australia

The population dynamics of the diamondback moth (DBM), Plutella xylostella L. (Lepidoptera: Yponomeutidae) was investigated at three farms on the Western side of the Sydney Basin, Australia, from November 2003 to October 2004. Adult populations were monitored fortnightly by counting the number that was trapped on yellow sticky traps, which peaked around November to December (summer) in all three farms, with virtually no trap catches in the winter months (June-August). The seasonal trend of adult DBM showed a higher number per trap in summer, ranging from 34.5-41.7 compared with the other seasons. Larval and pupal densities were highest in summer (2.0-4.0 and 3.3-5.1 per plant, respectively), while the lowest numbers were recorded in winter. Rainfall had a significant impact on the DBM populations. The activity (numbers and parasitism) of the DBM parasitoid Diadegma semiclausum Héllen (Hymenoptera: Ichneumonidae) was recorded in all three farms, with the population showing a synchrony with that of the DBM. The highest number of parasitoids per trap (36.8-53.8) was recorded in summer compared with the other seasons. Parasitism was highest in the non-sprayed farm (56.3%) in summer compared with 16.4% and 31.5% in the other farms which have been sprayed with insecnticides. Canonical correspondence analysis showed environmental variables accounting for 11.2% of the variability in the insect data, out of which 83.9% was explained along the first canonical axis.© 2010 International Formulae Group. All rights reserved.Keywords: Diamondback moth, Plutella xylostella, Diadegma semiclausum, parasitism, brassica

Occurrence of Diadegma semiclausum, a parasitoid of diamondback moth in lowlands of Syria

The parasitoid, Diadegma semiclausum (Hymenoptera: Ichneumonidae) is one of the most effective parasitoids of diamondback moth (DBM) in the highlands (> 1600 m above sea level) of Asia. A Diadegma population from the lowland areas of Homs, Syria (about 203–487 m above sea level) was examined to determine if it differs at the species-level from the D. semiclausum and other Diadegma populations present in different countries using molecular diagnostic tools. Phylogenetic analysis based on the neighbor-joining method using the mitochondrial cytochrome oxidase I (COI) and the nuclear internal transcribed spacer 2 (ITS2) sequences grouped the Homs (Syria) Diadegma population with D. semiclausum populations from other countries. The results suggest that D. semiclausum occurs in the lowland conditions in Homs (Syria), where the temperature is higher. The Homs (Syria) strain did not show any variations in the parasitism when the parasitized host (DBM) larvae were exposed to varying temperatures for 24 h. It could not survive when the parasitized DBM larvae were continuously reared at 35 °C; however it inflicted significantly higher parasitism when the parasitized DBM larvae were reared at day and night temperatures of 35 °C and 20 °C, respectively. Preliminary results indicate that the D. semiclausum strain from Homs (Syria) possesses some level of heat tolerance, which could be exploited for successful management of DBM in the tropical lowlands.