Bracon Brevicornis Research Articles

Making a healthy choice: Tactical host selection behaviour of a parasitoid wasp

Abstract Host selection behaviour plays a pivotal role in determining the success of parasitoids, especially in environments where host quality varies. In heterogeneous environments, parasitoids frequently encounter hosts that are infected. We conducted experiments to ascertain whether the ecto‐parasitoid Bracon brevicornis can differentiate between healthy caterpillars and those infected with Bacillus thuringiensis (Bt) and examined the implications of this host selection behaviour. In an olfactometer choice assay, B. brevicornis avoided Bt‐infected Spodoptera litura hosts. In a no‐choice assay, the female parasitoid displayed a lower paralysis rate on infected hosts, indicating a strong selection behaviour. Furthermore, we explored the impact of infection duration by exposing female wasps to larvae infected for 24, 48 and 72 h with Bt. Both choice and no‐choice assays demonstrated that female B. brevicornis refrains from ovipositing on infected larvae, regardless of the infection duration. Direct exposure to Bt through consumption did not affect the fitness of the tested parasitoid wasp. However, post‐24‐h Bt infection, host larvae showed an increased total hemocyte density, particularly high phagocytic cell numbers, and enhanced melanization, rendering the host larva unsuitable for parasitoid development. Taken together, our study underscores that parasitoids exhibit robust host selection behaviour by actively avoiding infected hosts. This insight is valuable for devising new pest control strategies in agriculture that safeguard beneficial parasitoids.

PARASITISATION POTENTIAL OF EGG AND LARVAL PARASITOIDS AGAINST LESSER WAX MOTH Achroia grisella F. (LEPIDOPTERA: PYRALIDAE) UNDER STORED CONDITION

The study conducted to evaluate the parasitisation potential of egg (Trichogramma chilonis Ishii) and larval parasitoids (Bracon brevicornis Wesmael and Apanteles galleriae Wilkinson) on the developmental stages of lesser wax moth, Achroia grisella F. The results indicated that a maximum parasitisation of 46.67% was noticed on egg masses released with seven pairs of T. chilonis, with an overall mean of 28.89 % and also the adult emergence was recorded about 59.49 %. Among the two larval parasitoids taken, the per cent parasitisation of lesser wax moth larvae by A. galleriae was maximum (38.68% overall mean) than by B. brevicornis (33.14%) with a mean adult emergence of 71.16% and 64.78% respectively.

Impact of Some Gamma-Irradiated Hosts on Bracon Brevicornis Wesmael Parasitism and Production

Impact of Some Gamma-Irradiated Hosts on Bracon Brevicornis Wesmael Parasitism and Production

The Compatibility of Natural Enemies and Botanical for Management of Earias vittella (Fabricius) (Lepidoptera: Nolidae) and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Bhendi Ecosystem

Aims: The current study was conducted to know the compatibility of natural enemies and botanical for management bhendi fruit borers in the bhendi field.
 Study Design: Randomized Complete Block Design (RCBD).
 Place and Duration of Study: Experiment conducted during 2019-20 and 2020-21 at ICAR- National Bureau of Agricultural Insect Resources, Hebbal, Bengaluru, Karnataka, India. 
 Methodology: Two field tests were conducted at the entomological research farm, ICAR-NBAIR Bengaluru, Karnataka, India, to know the compatibility of the natural enemies (Trichogramma chilonis Ishii (Hymenoptera:Trichogrammatidae) , Chelonus blackburni (Cameron) and Bracon brevicornis (Wesmael) (Hymenoptera: Braconidae) and botanical (Neem oil 0.5%) for management of E. vittella and H. armigera on bhendi. Arka Nikita (IIHR) bhendi variety was used for the two trials with different treatments in four replication. The release rates of parasitoids were decided based on the previous parasitic potential studies.
 Results: In the first trial, among the treatments, a combination of T. chilonis + C. blackburni + B. brevicornis and C. blackburni + B. brevicornis recorded the lowest pooled mean larval population reduction over pre-treatment count of E. vittella and were on par with each other, recording 40.19% and 37.27%, respectively followed by T. chilonis + B. brevicornis (31.28%), C. blackburni (30.90%), B. brevicornis (28.64%), Neem oil 0.5% (27.71%), Neem oil 0.5% + B. brevicornis (25.46%) and T. chilonis (25.32%). A similar trend was also observed in combination of T. chilonis + C. blackburni + B. brevicornis and C. blackburni + B. brevicornis against H. armigera, which accounted for 47.19% and 37.22% of reduction over pre-treatment count in the respective treatment combination of parasitoids. The next best treatments were T. chilonis + B. brevicornis (28.21%), C. blackburni (26.56%), B. brevicornis (22.21%), Neem oil 0.5% (20.37%), T. chilonis (17.31%) and Neem oil 0.5% + B. brevicornis (16.07%)
 Conclusion: From this study we recommend that, for bhendi fruit borers management, release of parasitoids like T. chilonis + C. blackburni + B. brevicornis at 50,000+1000+1000 adults/ha, respectively in bhendi field starting from 35 DAS at 15 days’ intervals of duration, two-time release of parasitoids is enough later, they have augmented and reduce the population of fruit borer larvae effectively.

The Parasitic Potential of Bracon brevicornis Wesmael and Chelonus blackburni (Cameron) (Hymenoptera: Braconidae) on the Age of Earias vittella (Fabricius) (Lepidoptera: Nolidae) and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Laboratory Conditions

Aims: The current study was carried out to investigate the parasitic potential of density of two important parasitoids against the age of two important bhendi fruit borer pests.
 Study Design: Completely Random Design (CRD).
 Place and Duration of Study: The study was conducted during 2019-20 and 2020-21 at bio control laboratory of National Bureau of Agricultural Insect Resources (ICAR) Hebbal, Bengaluru (Latitude: 13.097221 Longitude: 77.568291) by adopting standard methodology and materials.
 Methodology: An experiment was designed to examine the effects of parasitoid densities of Bracon brevicornis and Chelonus blackburni on the host age (different instars) larvae of fruit borers two important fruit borers by checking the the percent parasitization. The second, third, and fourth instar larvae of E. vittella were introduced separately at different ratios of Bracon brevicornis parasitoids and host viz., 1:10, 2:10, 3:10, 4:10, and 5:10. Mated female parasitoids were utilised in all cases, and the experiment was carried out in a glass jar of 18 x 12 cm, using the sandwich approach. [1] with four replications. After 24 h, the larvae were observedand the percent parasitization was calculated. The same parasitoids were used for thesecond, third, fourth, and fifth instars larvae of H. armigera. 
 To examine the parasitic potential of C. blackburni, another experiment was conducted with various ratios of its adults and eggs of E. vittella and H. armigera by adopting the procedure of Swamiappan and Balasubramanian [2]. The parasitoid and host eggs were maintained at a ratio of 1:100, 2:100, 3:100, 4:100, and 5:100 with four replications. The observation of percent parasitization was recorded after the egg incubation period.
 Results: The parasitic potential studies showed that the parasitoid host ratio of 5:10 (100%) was the best for E. vittella (II, III and IV instar larvae) with the highest parasitization followed by 4:10 (96.83 %), 3:10 (85.08 %), 2:10 (61.71 %) and least parasitization was observed in 1:10 parasitoid host ratio (52.71 %). Similarly, for H. armigera (II, III, IV and V instar larvae) parasitoid host ratio of 5:10 was recorded the highest parasitization (96.75 %), followed by 4:10 (93.69 %), 3:10 (84.11 %), 2:10 (64.75 %) and least parasitization was observed in 1:10 parasitoid host ratio (45.07 %)
 The parasitic potential of C. blackburni revealed that the 5:100 parasitoid host ratio resulted in the maximum parasitization of 64.75% against E. vittella, followed by 4:100 (60.50%), 3:100 (52.55%), 2:100 (38.27%), and 1:100 (25.60%). Similarly, for H. armigera, parasitization was highest at a parasitoid host ratio of 5:100, followed by 4:100 (64.50%), 3:100 (58.25%), 2:100 (43.45%), and 1:100 (28.50%).
 Conclusion: The parasitoids: host ratio of 5:10 for B. brevicornis and 5:100 for C. blackburni is optimal for managing the bhendi fruit borer complex at the IV instar level.

Management of Fall Army Worm <i>Spodoptera Frugiperda</i> (J E Smith) in South Asia-Current Status and Future Strategies

Fall armyworm (FAW) Spodoptera frugiperda (J E Smtih) is a native of the neotropics and it has invaded Nigeria region of Africa in 2016 and reached India in May 2018. Since then it has spread to most of the South and Southeast Asian countries, Australia and recently reached New Zealand and some South Pacific islands. Even though FAW has many hosts in its native region, the population that reached Africa and spread to Asia and Oceania prefers maize the most. In its biology, the capability of adults to fly more than 100 km in a night, females laying eggs in clusters of 100 or more to a maximum of 2,000 eggs in five days of their lifetime, later instar larvae becoming cannibalistic, pupating in soil, not diapausing and inability to survive at temperatures below 10oC, offers a unique opportunity to devise an effective management strategy. The IPM package for maize incorporating management of FAW involve: seed treatment with a systemic insecticide to protect young plants up to three weeks after planting; release of egg parasitoids Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) and Telenomus remus (Hymenoptera: Platygastridae) immediately after finding FAW moths caught in the pheromone traps in the field; and release of larval parasitoids Bracon (Habrobracon) hebetor, and Bracon (Habrobracon) brevicornis (Hymenoptera: Braconidae) and treating with bio- and botanical pesticides, when whorl damage in observed.

Oviposition Preference and Performance of a Specialist Herbivore Is Modulated by Natural Enemies, Larval Odors, and Immune Status.

Insect herbivores frequently must balance host plant quality and the risk of attack by their natural enemies when making oviposition decisions. Yet, which factor is more important remains unresolved in plant-insect ecology. Here, we report the oviposition preference and larval performance of the brassicaceous specialist Plutella xylostella, in the context of plant quality (cabbage Brassica oleracea vs. mustard B. juncea) and associated natural enemies. Despite the greater larval weight and adult lifespan on cabbage, ovipositing females strongly preferred mustard. Both the egg parasitoid Trichogrammatoidea bactrae and the larval ectoparasitoid Bracon brevicornis are more likely to attack P. xylostella that feed on cabbage; thus, mustard represents enemy-reduced space from these two parasitoids. However, larval diet had no impact on the parasitism rate of specialist Cotesia vestalis. Feeding on mustard improved larval immune responses. The total hemocyte number, diversity, and phenoloxidase activity were higher in mustard-fed larvae which increased their survival against the entomopathogen, Bacillus thuringiensis. Interestingly, host plants altered the larval body odor profile. Mustard-fed larvae emitted allyl isothiocyanate (AITC) and butyl isothiocyanate (BITC) while cabbage-fed larvae emitted dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS) that served as short-range cues for larval parasitoids. For B. brevicornis, host body odor guided oviposition choice was crucial as their fitness was affected by the host larval diet. Although C. vestalis showed a clear preference towards volatiles emitted by mustard fed larvae, their fitness was unaltered. Taken together, our results illustrate that P. xylostella prefers to lay eggs on mustard plants providing enemy-reduced space from some, but not all, natural enemies.

Effect of Adult Nutrition at Different Concentrations on Reproduction and Longevity of <i>Bracon brevicornis</i>, Larval Parasitoid of Coconut Black-Headed Caterpillar

Coconut black-headed caterpillar (<i>Opisina arenosella</i>) or BHC is one of the main coconut palm defoliators in many Asian countries, including Malaysia, where it was discovered in 2017. Since then, an effort has been made to manage the pest by the use of larval parasitoids, started with a study on the effects of sucrose diet on reproduction, longevity and parasitism of a naturally occurring parasitoid known as <i>Bracon brevicornis</i> (Hymenoptera: Braconidae). The aim of this study was to determine the optimal sucrose concentration for improving its rearing technique. Two experiments were conducted, i.e., a) reproductive performance study; and b) longevity study. In each study, different sucrose concentrations were tested on mated females in five (5) replications. Feeding on 20% sucrose concentration resulted in significantly (P<0.05) highest fecundity (82.4 ± 0.9), hatchability (100%), pupation, fertility (82.7%) and longest reproductive period (12.8 ± 0.3 days) of <i>B. brevicornis</i> among treatments. Meanwhile, 40% sucrose was able to prolong its adults’ lifespan (20.6 days). Adults fed on 20% sucrose had the highest parasitism (33.4±0.6 host larvae), despite the fact that 30% sucrose had no statistically significant difference. Thus, this study suggested that 20% sucrose could be suitable to increase fertility and parasitism by <i>B. brevicornis</i>. However, additional research on its effect on behaviours is necessary to acquire a better knowledge of its efficiency in the field.

Crop diversification for sustainable management of leaf webworm, Nausinoe geometralis Guenee of Jasmine (Jasminum sambac L.)

A field trial to investigate the effect of diversifying crops in jasmine ecosystem to manage leaf webworm incidence, revealed that there was a significant reduction in the pest incidence and infestation in intercropped plots as compared to jasmine sole crop. The data indicated the supremacy of marigold in reducing the incidence of the pest as well as attracting more natural enemy population, bagging the credit of eco-feast crop. Marigold recorded significantly the lowest mean incidence of 15.58%, followed by onion (16.03%) and coriander (16.43%) compared to jasmine as sole crop (2.17%). The population of natural enemies viz., coccinellids, chrysopids, preying mantises and spiders were more recorded in marigold intercropped jasmine with 8.70, 3.60, 4.40, 5.30 nos/five plants respectively. Moreover, the emergence of the larval parasitoids, Bracon brevicornis and Phanerotoma hendecasiella were more encountered in jasmine intercropped with marigold than sole jasmine crop. The pest defender ratio was highest in jasmine + marigold (1:3.50) and the order falls as jasmine + coriander (1:3.05) and jasmine + gingelly (1:2.34).

Bracon wasps for ecological pest control-a laboratory experiment.

Biological control of pest insects by natural enemies may be an effective, cheap and environmentally friendly alternative to synthetic pesticides. The cosmopolitan parasitoid wasp species Bracon brevicornis Wesmael and B. hebetor Say (Hymenoptera: Braconidae) use lepidopteran species as hosts, including insect pests like Ephestia kuehniella or Ostrinia nubilalis. Here, we compare the reproductive success of both Bracon species on E. kuehniella in a laboratory experiment. We asked (1) how the reproductive success on a single host larva changes with temperature, (2) how it changes with temperature when more host larvae are present and (3) how temperature and availability of host larvae influence the efficacy of Bracon species as biological control agents. In general, differences between B. brevicornis and B. hebetor have been small. For rearing both Bracon species in the laboratory on one host larva, a temperature between 20–27 °C seems appropriate to obtain the highest number of offspring with a female-biased sex ratio. Rearing the braconid wasps on more than one host larva revealed a higher number of total offspring but less offspring per host larva on average. Again, highest numbers of offspring hatched at 27 °C and the sex ratio was independent from temperature. Although no parasitoids hatched at 12 °C and only few at 36 °C, host larvae were still paralyzed. The efficacy of B. brevicornis was higher than 80% at all numbers of host larvae presented at all temperatures while the efficacy of B. hebetor was less than 80% at 12 °C and 27 °C at low numbers of host larvae presented. In conclusion, practitioners can use either B. brevicornis or B. hebetor at low and high temperatures and at varying host densities to achieve high pest control efficacy.

Performance of larval parasitoid, Bracon brevicornis on two Spodoptera hosts: implication in bio-control of Spodoptera frugiperda

Successful pest management using parasitoids requires careful evaluation of host-parasitoid interactions. Here, we report the performance of larval ecto-parasitoid wasp, Bracon brevicornis (Wesmael) on important agricultural pests, Spodoptera litura (Fabricius) and S. frugiperda (J.E. Smith). Biology of B. brevicornis was studied on different host instars under laboratory and cage setup. In no-choice assay, the parasitoid development was highest on fifth-instar S. litura larvae as the wasp laid ~ 253 eggs with 62% hatching, 76% pupae formation and 78% adult emergence. Similarly, these parameters were highest on fifth instar S. frugiperda larvae (293 eggs, 57% hatching, 80% pupae formation, 70% adult emergence). In two-choice assay, B. brevicornis preferred fourth or fifth over third instar larvae of both hosts. Successful parasitism depends on host paralysis and suppression of host immunity. B. brevicornis interaction downregulated cellular immunity of both hosts as shown by reduced hemocyte viability and spreading. The percent parasitism rate of B. brevicornis was unaltered in the presence of host plant, Zea mays in cage study. 76 and 84% parasitism was observed on fifth-instar larvae of S. litura and S. frugiperda, respectively. We evaluated the performance of B. brevicornis as a biocontrol agent on S. frugiperda in maize field. Our results show 54% average reduction in infestation after release of B. brevicornis. Taken together, we report the performance of B. brevicornis on important insect pests for the first time in laboratory and field conditions. Our findings indicate that B. brevicornis is a promising candidate for integrated pest management.

Bracon wasps for ecological pest control-a laboratory experiment.

Biological control of pest insects by natural enemies may be an effective, cheap and environmentally friendly alternative to synthetic pesticides. The cosmopolitan parasitoid wasp species Bracon brevicornis Wesmael and B. hebetor Say (Hymenoptera: Braconidae) use lepidopteran species as hosts, including insect pests like Ephestia kuehniella or Ostrinia nubilalis. Here, we compare the reproductive success of both Bracon species on E. kuehniella in a laboratory experiment. We asked (1) how the reproductive success on a single host larva changes with temperature, (2) how it changes with temperature when more host larvae are present and (3) how temperature and availability of host larvae influence the efficacy of Bracon species as biological control agents. In general, differences between B. brevicornis and B. hebetor have been small. For rearing both Bracon species in the laboratory on one host larva, a temperature between 20–27 °C seems appropriate to obtain the highest number of offspring with a female-biased sex ratio. Rearing the braconid wasps on more than one host larva revealed a higher number of total offspring but less offspring per host larva on average. Again, highest numbers of offspring hatched at 27 °C and the sex ratio was independent from temperature. Although no parasitoids hatched at 12 °C and only few at 36 °C, host larvae were still paralyzed. The efficacy of B. brevicornis was higher than 80% at all numbers of host larvae presented at all temperatures while the efficacy of B. hebetor was less than 80% at 12 °C and 27 °C at low numbers of host larvae presented. In conclusion, practitioners can use either B. brevicornis or B. hebetor at low and high temperatures and at varying host densities to achieve high pest control efficacy.

Bracon brevicornis Genome Showcases the Potential of Linked-Read Sequencing in Identifying a Putative Complementary Sex Determiner Gene.

Bracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis. It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read-based genome of B. brevicornis, complete with an ab initio-derived annotation and protein comparisons with fellow braconids, Fopius arisanus and Diachasma alloeum. We demonstrate the potential of linked-read assemblies in exploring regions of heterozygosity and search for structural and homology-derived evidence of the complementary sex determiner gene (csd).

Behavior and generation times of Bracon brevicornis (Wesmael) (Hymenoptera:Bracondae) reared on Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) and Galleria mellonella (Lepidoptera: Pyralidae)

The ectoparasitoid Bracon brevicornis (Wesmael) (Hymenoptera: Braconidae) attacks Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) in dry bolls during the late cotton season 2018. Observations on the behaviors, some biological aspects and life table parameters of B.brevicornis were studied on two hosts pests; P. gossypiella and Galleria mellonella under the laboratory conditions. Larval duration of B. brevicornis was 5.3 and 6.1 days on P. gossypiella and Galleria mellonella respectively, and pupal durations was 5.4 and 5.5 days when reared on full grown larvae of P. gossypiella and 5th instar larvae of G. mellonella, respectively. The Sex ratio for females: male was 0.7: 0.3 when parasitoid reared on P. gossypiella, while, it estimated by 0.45 female: 0.55 male, when parasitoid reared on G. mellonella. Parasitoid female and male longevity when reared on P. gossypiella was 17.03 ± 1.5 and 11.94 ± 1.8 days, respectively, while it was 18.25 ± 0.3 days/female and 11.4 ± 0.9 days/male, when reared on G. mellonella. The generation time of B. brevicornis lasted 14.0 days when reared on P. gossypiella and increased to 15.7 days when reared on G. mellonella. The increased in time estimated by 1.7 days when reared on G. mellonella. Life table data; showed that the net reproduction rate (R0) was 90.017 and 41.781 when reared on P. gossypiella and G. mellonella in a single generation. The calculated biological parameters (R0, GT and rm) indicated that hosts of P. gossypiella seem to be more favorable host for development and multiplication of B. brevicornis than G. mellonella host.

Impact of conventional insecticides on two bollworms and their indirect effects on the ectoparasitoid, Bracon brevicornis (Wesmael) (Hymenoptera: Braconidae)

BackgroundCotton bollworms such as Pectinophora gossypiella and Earias insulana are serious pests which destroy the cotton plant, and Bracon brevicornis is a parasitoid which attacked the larvae of bollworms.ResultsIn this study, experiments were performed to investigate and evaluate the toxicity of etofenprox and chlorpyrifos insecticides against newly hatched larvae of Pectinophora gossypiella and Earias insulana. Some biological aspects of compound effects on larval and pupal duration, percentage of mortality, and percentage of adult emergence which resulted from treated newly hatched larvae were studied. The results revealed that LC50 was 0.7 and 0.87 ppm when P. gossypiella was treated with etofenprox and chlorpyrifos, respectively, while LC50 was 0.09 and 0.73 ppm when E. insulana was treated with etofenprox and chlorpyrifos, respectively. The obtained results showed that the percentage of mean larval mortality was 65.0 and 63.0% for treated P. gossypiella, while it was 71.0 and 66.0% for treated E. insulana. The corresponding figure for pupal percentage mortality was 8.0 and 10.0% for treated P. gossypiella, but it was 5.0 and 2.0% for treated E. insulana, with etofenprox and chlorpyrifos, and a prolongation effect in larval and pupal development (total immature stage) resulted from treated both bollworms as follows: 35.5 and 32.4 days for treated P. gossypiella compared with 21.9 days in control and 34.7 and 23.2 days for treated E. insulana compared with 23.1 days in control. The indirect effect of etofenprox and chlorpyrifos on the total immature stage of Bracon brevicornis was 18.2 and 19.5 days compared with 14.3 days in control when B. brevicornis parasitized on P. gossypiella larvae while it was 19.8 and 20.6 days compared with 15.2 days when B. brevicornis parasitized on E. insulana larvae.ConclusionThe life cycle of B. brevicornis after parasitism on P. gossypiella and E. insulana larvae treated with etofenprox and chlorpyrifos were increased than the control larvae.

Field evaluation of biocontrol agents and biopesticides against spotted pod borer, Maruca vitrata (Geyer) on lablab

Microplot field trial was conducted from March to May 2017 to assess the efficacy of various biopesticides, pathogen, predator and parasitoid against M. vitrata on lablab (var. Co Gb 14). The experiments were carried out in a randomized block design (RBD) with nine treatments and three replications. Results revealed that spinosad 45% SC @ 75 ml ha-1 was significantly superior to all other treatments by recording a cumulative mean population reduction of 72.58 per cent. The next in the order of efficacy were emamectin benzoate 5% SG @ 200 ml ha-1 (65.16 %) &gt; sequential application of emamectin benzoate (200 ml ha-1) + Bracon brevicornis (2000 adults ha-1 released after fortnight) (63.70%) &gt; emamectin benzoate (100 ml ha-1) + B. brevicornis (1000 adults ha-1) @ half the dose each (62.06 %) &gt; azadirachtin 0.03% @ 2.5 L ha-1 (39.33 %) &gt; B. brevicornis @ 2000 adults ha-1(32.77 %) &gt; Crude suspension of B. bassiana (Bb 112) @ 108 Spores ml-1 (25.95 %) &gt; Xylocoris flavipes @ 40,000 adults ha-1 (20.22 %).

Plant Volatiles Modulate Immune Responses of Spodoptera litura

Plants emit a specific blend of volatiles in response to herbivory and these volatiles, which often attract predators and parasitoids function as an indirect plant defense. The impact of plant volatiles in shaping herbivore defenses is unclear. Here, we report that specific plant volatiles induce immune responses in the polyphagous herbivore, Spodoptera litura. We characterized the hemocyte profile and established their functional significance with respect to ontogeny and exposure to specific plant volatiles. Fifth instar larvae showed the highest number and hemocytes diversity. We characterized seven different types of hemocytes, of which granulocytes performed phagocytosis, oenocytoids showed melanization activity, and plasmatocytes along with granulocytes and oenocytoids were found to be involved in encapsulation. Among the six volatiles tested, exposure to (E)-β-ocimene caused the highest increase in total hemocytes number (THC) followed by linalool and (Z)-3-hexenyl acetate exposure. Although THC did not differ between these three volatile treatments, circulating hemocytes diversity varied significantly. (E)-β-ocimene exposure showed higher number of plasmatocytes and phenol oxidase activity. The interaction of the parasitic wasp Bracon brevicornis with (E)-β-ocimene exposed larvae was poor in terms of delayed paralysis and lower egg deposition. In choice assays, the wasp showed clear preference towards control larvae indicating (E)-β-ocimene treatment renders the host unattractive. Hemocyte profiles post-parasitoid exposure and (E)-β-ocimene treatment were similar indicating cue-based priming. When challenged with Bacillus thuringiensis, linalool exposure resulted in the highest survival as compared to other volatiles. Our results show that specific HIPVs can modulate cellular immunity of S. litura, revealing a new role for HIPVs in tri-trophic interactions.

Evaluation of the Biological Parameters of the Interaction the Parasitoid, Bracon brevicornis Wesmael (Braconidae: Hymenoptera) vs. Four Different Hosts under the No-Choice Situation

Bracon brevicornis Wesmael (Braconidae: Hymenoptera) is a generalist idiobiont ecto-parasitoid that parasitizes a wide range of Lepidoptera. In the present context, our study aimed to examine under laboratory conditions the effect of host size on the biological parameters of parasitoids B. brevicornis for efficient laboratory rearing of that parasitoid. Under the no-choice situation, we compared biological parameters of this parasitoid wasp on four host species belonging to the Lepidoptera, viz. Pectinophora gossypiella (Gelechiidae) and Earias insulana (Noctuidae) as small size hosts, Helicoverpa armigera (Noctuidae)and Spodoptera littoralis (Noctuidae) as large size hosts. The biological parameters of the parasitoid on P. gossypiella or E. insulana (Small size) in most case proved to have a significant effect on their egg-adult developmental stages compare to its interaction vs. H. armegra or S. littoralis host (large size). The hosting on P. gossypiella or E. insulana the parasitoid produced excellent paralyzing and parasitism capacities but this capacity was less efficient on large size hosts and they received a significantly lower number of eggs as compared to H. armegra or S. littoralis which they received a good number of eggs. No variation was observed considering the egg-to-adult development time of B. brevincornis parasitizing P.gossypiella (small size) and S. littoralis (large size), but the lowest egg-to-adult development time was observed on H. armegra (large size). The biochemical analysis showed that the larger size hosts contained more resources for the growing the parasitoid, this was reflected only on fecundity. The other biological parameters: hatchability, longevity, lifetime and the percentage of hosts producing parasitoid offspring and sex ratio were not dependent on host size regardless of parasitoid generation. The results indicate that the parasite's behaviour of B.brevicornis can develop under no-choice situation equally successfully on both small and large size host.

Toxicity of some new and conventional insecticides on Trichogramma chilonis Ishii and Bracon brevicornis Wesmael under laboratory condition

Toxicity of some new and conventional insecticides on Trichogramma chilonis Ishii and Bracon brevicornis Wesmael under laboratory condition

Toxicity of some new and conventional insecticides on Trichogramma chilonis Ishii and Bracon brevicornis Wesmael under laboratory condition

Toxicity of some new and conventional insecticides on Trichogramma chilonis Ishii and Bracon brevicornis Wesmael under laboratory condition