Melon Fly Research Articles

Bioefficacy of entomopathogenic Aspergillus strains against the melon fly, Bactrocera cucurbitae (Diptera: Tephritidae)

Three Aspergillus strains were isolated from naturally diseased adults of the melon fly Bactrocera cucurbitae Coquillett (Diptera: Tephritidae) collected from Hainan Province, China. Then laboratory bioassays were carried with A. flavus (BC-22 and BC-D-1) and A. tamarii strains (BC-212) against B. cucurbitae. The results indicated that conidial suspensions (1 × 108 conidia/ml) of the three strains exhibited high toxicity against the adults of B. cucurbitae and low insecticidal activity to the eggs, larvae and pupae. Furthermore, the virulence of three strains (BC-22, BC-D-1 and BC-212) for the adults was compared; the LT50 values were 6.05, 5.81 and 4.91 days with 1 × 108 conidia/ml, respectively. After 8 days after inoculation, the LC50 values were 12.00 × 105, 1.15 × 105 and 0.28 × 105 conidia/ml, respectively. Undiluted culture supernatant of the three strains had less bioefficacy to B. cucurbita compared to use of the conidia suspension. The three strains, especially BC-212, showed a faster colony growth, higher germination rate and sporulation. These results indicated that the A. tamarii BC-212 strain was the better one to consider for the control of melon flies. In conclusion, Aspergillus species could be candidates for fly control as pest control agents. To our knowledge, this is the first report on A. flavus and A. tamarii strains pathogenic to B. cucurbitae.

Attraction of wild‐like and colony‐reared Bactrocera cucurbitae (Diptera:Tephritidae) to cuelure in the field

AbstractThe attraction of wild tephritids to semiochemical‐based lures is the ideal basis for trap network design in detection programmes, but in practice, mass‐reared colony insects are usually used to determine trap efficiency. For Bactrocera cucurbitae Coquillett, a lower response by wild males compared with colony‐derived individuals, usually used to estimate attraction parameters, could mean that the sensitivity of detection networks targeting this pest is reduced. We describe the results of mark–release–recapture experiments with wild‐ and colony‐derived B. cucurbitae males in a grid of cuelure‐baited traps within a macadamia nut orchard in Hawaii Island designed to quantify the attraction of cuelure to each fly type. For colony males, we estimate a 65% probability of capture at 27 m, intermediate with previous estimates on the attraction of methyl eugenol to Bactrocera dorsalis Hendel (36 m) and trimedlure to Ceratitis capitata Wiedemann (14 m) at the same site. Results suggest similar response over distance by wild‐derived B. cucurbitae compared with colony in the field, but there may be qualitative differences in response between wild and colony based on very low response of wild males in a standard bioassay of attraction. For both fly types, the estimates of attraction in the smaller of two grid sizes tested were lower than for the larger spacing, suggesting trap competition was a factor at an intertrap distance of 75 m. Dispersal patterns within the grid were generally to the south for the colony‐derived males and more variable for the wild‐derived males. In neither case was the direction of recapture correlated with the prevailing direction of the wind.

Disruption of Darna pallivitta (Lepidoptera: Limacodidae) by Conventional and Mobile Pheromone Deployment.

Identification of the Darna pallivitta (Moore) pheromone component n-butyl (E)-7,9-decadienoate (E7,9-10:COOn-Bu) has made it possible to investigate communication disruption to control this lepidopteran pest. Conventional communication disruption trials showed marked decreases in the mean number of male moths captured in E7,9-10:COOnBu-treated fields compared with control fields. For traps baited with E7,9-10:COOnBu, percent disruptions were 94.4% and 92.1% for septa (1 g pheromone/ha, 1-wk trial duration) and spirals (6 g pheromone/ha, 8-wk trial duration) respectively. For traps baited with virgin female moths, percent disruption was 73.3% using septa disruptors (1 g pheromone/ha, 1-wk trial duration). Mobile communication disruption using Bactrocera cucurbitae (Coquillett) as carriers for E7,9-10:COOn-Bu was evaluated in the following three areas: fly survivorship, attraction of male moths to treated flies, and moth disruption in a small-scale field trial. Topical application of E7,9-10:COOnBu showed no significant decrease in survivorship at 50 and 80 µg/fly. However, decreased survivorship was observed at 100 µg/fly and linear regression showed E7,9-10:COOnBu dose was significantly correlated with B. cucurbitae survivorship. Traps containing honey–pheromone-fed flies attracted and caught D. pallivitta over a 1-wk period, demonstrating the attractiveness of the carrier. Releasing E7,9-10:COOnBu-fed B. cucurbitae (∼2 g pheromone/ha, 1-wk trial duration) resulted in significantly reduced trap catches in treatment fields compared with control fields on the first 2 d of the field trial. Percent disruptions were 84.7% (day 1) and 56.0% (day 2). These results suggest that both conventional communication disruption and mobile communication disruption have potential to control D. pallivitta.

Weathering and Chemical Degradation of Methyl Eugenol and Raspberry Ketone Solid Dispensers for Detection, Monitoring, and Male Annihilation of Bactrocera dorsalis and Bactrocera cucurbitae (Diptera: Tephritidae) in Hawaii.

Solid male lure dispensers containing methyl eugenol (ME) and raspberry ketone (RK), or mixtures of the lures (ME + RK), and dimethyl dichloro-vinyl phosphate (DDVP) were evaluated in area-wide pest management bucket or Jackson traps in commercial papaya (Carica papaya L.) orchards where both oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, Bactrocera cucurbitae (Coquillett), are pests. Captures of B. dorsalis with fresh wafers in Jackson and bucket traps were significantly higher on the basis of ME concentration (Mallet ME [56%] > Mallet MR [31.2%] > Mallet MC [23.1%]). Captures of B. cucurbitae with fresh wafers in Jackson and bucket traps were not different regardless of concentration of RK (Mallet BR [20.1%] = Mallet MR [18.3%] = Mallet MC [15.9%]). Captures of B. dorsalis with fresh wafers, compared with weathered wafers, were significantly different after week 12; captures of B. cucurbitae were not significantly different after 16 wk. Chemical analyses revealed presence of RK in dispensers in constant amounts throughout the 16-wk trial. Degradation of both ME and DDVP over time was predicted with a high level of confidence by nonlinear asymptotic exponential decay curves. Results provide supportive data to deploy solid ME and RK wafers (with DDVP) in fruit fly traps for detection programs, as is the current practice with solid TML dispensers placed in Jackson traps. Wafers with ME and RK might be used in place of two separate traps for detection of both ME and RK responding fruit flies and could potentially reduce cost of materials and labor by 50%.

Efficacy of some botanicals as insecticides on the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera : Tephritidae)

Efficacy of methanolic extracts of different indigenous plant parts, such as the leaves and barks of neem (Azadirachta indica); leaves of basil (Ocimum basilicum), mahua (Madhuca indica), lantana (Lantana camara), eucalyptus (Eucalyptus globulus), surjokonna (Spilanthes acmella) and flowers of golden shower (Cassia fistula), rosy periwinkle (Catharanthus roseus) and orchid (Mokara charkuan) were tested against the oviposition behavior of the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera : Tephritidae). Most effective botanicals as attractants were observed in C. fistula and M. indica. In choice test, the percentage of B. cucurbitae pupae emerged were 0.0 in the leaves and barks of A. indica, 0.22 in flowers of M. charkuan, 1.43 in leaves of O. basilicum, 2.68 in leaves of L. camara, 6.83 in flowers of C. roseus, 5.51 in leaves of S. acmella, 13.27 in leaves of E. globules, 19.99 in flowers of C. fistula and 14.09 in leaves of M. indica. In nochoice test, the respective percentages of B. cucurbitae pupae emerged were 0.0, 2.19, 2.29, 11.68, 10.65, 12.34, 7.73, 6.76, 13.66 and 15.16 for the leaves of A. indica, bark of A. indica, in flowers of M. charkuan, in leaves of O. basilicum, in flowers of L. camara, in flowers of C. roseus, in leaves of S. acmella, in leaves of E. globules, in flowers of C. fistula and in leaves of M. indica. Phytochemical screening of the methanolic crude extracts of the botanicals showed that M. indica was strongly positive for steroid; C. fistula were strongly positive for alkaloid, flavonoids and glycoside and M. charkuan was weakly positive for carbohydrates, alkaloid and steroid.Bangladesh J. Zool. 41(1): 105-112, 2013

English

Fruit flies are regarded as one of the most devastating pest of fruits and vegetables on earth planet. Generally chemical control is implemented for their control but it poses lot of eco-environmental concerns so the emphasis is now turning towards eco-friendly management practices.  Bio-control is an efficient and environmentally sound approach and augmentation is primarily focus on classical biological control program. In this study, eight sub-sterilizing doses of 0, 20, 30, 40, 50, 60, 70 and 80 were tested against Bactrocera zonata and Bactrocera cucurbitae pupae. The results showed that radiation prolong the duration of pupal stage and hatching is reduced by applying radiation. This also shows that when the quantity of the radiation increases, the adult emergence decreases. This study could be very useful in exploiting the potential host for longer period of time for culturing their pupal parasitoids.      Key words: Sub sterilizing doses, radiation, fruit flies and emergence.   &nbsp

Field Evaluation of Melolure, a Formate Analogue of Cuelure, and Reassessment of Fruit Fly Species Trapped in Sydney, New South Wales, Australia.

In Australia, tephritids are usually attracted to either cuelure or methyl eugenol. Methyl eugenol is a very effective lure, but cuelure is less effective likely due to low volatility. A new formate analogue of cuelure, melolure, has increased volatility, resulting in improved efficacy with the melon fruit fly, Bactrocera cucurbitae Coquillett. We tested the efficacy of melolure with fruit fly species in Sydney as part of the National Exotic Fruit Fly Monitoring programme. This monitoring programme has 71 trap sites across Sydney, with each trap site comprising separate Lynfield traps containing either cuelure, methyl eugenol, or capilure lure. In 2008, an additional Lynfield trap with melolure plugs was added to seven sites. In 2009 and 2010, an additional Lynfield trap with melolure wicks was added to 11 trap sites and traps were monitored fortnightly for 2 yr. Capture rates for melolure traps were similar to cuelure traps for Dacus absonifacies (May) and Dacus aequalis (Coquillet), but melolure traps consistently caught fewer Bactrocera tryoni (Froggatt) than cuelure traps. However, trap sites with both a cuelure and melolure traps had increased capture rates for D. absonifacies and D. aequalis, and a marginally significant increase for B. tryoni. Melolure plugs were less effective than melolure wicks, but this effect may be related to lure concentration. The broader Bactrocera group species were attracted more to cuelure than melolure while the Dacus group species were attracted more to melolure than cuelure. There is no benefit in switching from cuelure to melolure to monitor B. tryoni, the most important fruit fly pest in Australia.

Effects of autodisseminated Metarhizium guizhouense PSUM02 on mating propensity and mating competitiveness of Bactrocera cucurbitae (Diptera: Tephritidae)

We investigated the effects of inoculation by Metarhizium guizhouense PSUM02 on mating propensity and mating competitiveness of Bactrocera cucurbitae, with a view on pest management. On day 4 postinoculation, the M. guizhouense-treated male flies had significantly lowered mating propensity and mating competitiveness, while the treated female flies had reduced mating propensity on day 4 and reduced mating competitiveness on day 5. The mating propensity and competitiveness of treated male and female flies then further declined until death. Kaplan–Meier survival analysis of treated male and female flies gave average survival times (AST) of 6.2 ± 0.2 and 5.4 ± 0.3 days in the mating propensity assay, and about 5.0 ± 0.1 and 4.4 ± 0.2 days in the mating competitiveness assay. The AST of untreated flies ranged from 12.8 ± 0.1 to 14.7 ± 0.2 days for comparison (observation up to 15 days). Untreated flies had decreased AST and mating characteristics when exposed to contact with treated male flies, indicating transmission of the fungal infection by such contact also to untreated male flies. Surprisingly, contact with treated female flies did not affect the AST of untreated males or females in the same cage. These results corroborate the potential for pest control by autodissemination with treated male flies, which transmit the fungus to a healthy population better than the treated female flies.

Parasitism, emergence, and development of Spalangia endius (Hymenoptera: Pteromalidae) in pupae of different ages of Bactrocera cucurbitae (Diptera: Tephritidae).

The wasp Spalangia endius Walker (Hymenoptera: Pteromalidae) is a major parasitoid of the pupae of fruit flies, which are a common agricultural pest. An understanding of this intricate host–parasitoid interaction could provide basic information necessary for the sustainable integrated biological control of fruit flies. In this study, we investigated the effect of S. endius on different-aged pupae of the melon fly Bactrocera cucurbitae Coquillett by using choice and nonchoice tests under laboratory conditions. We showed that S. endius females oviposited, and their progeny successfully developed, in different-aged pupae of B. cucurbitae regardless of the method of exposure. There was an oviposition preference for 3–5-d-old pupa. The highest mean percentage parasitism occurred on 4- and 5-d-old hosts, followed by 2- and 3-d-old hosts. The average development time for both males and females was significantly longer in 6–7-d-old hosts than in the younger host stages. Adult females that developed from younger host pupae (2–5-d old) were significantly heavier than those from older host pupae (6–7-d old), and they also lived longer. The sex ratio (proportion of females) of the parasite progeny decreased with an increase in host age. Host mortality also decreased gradually as the pupal age increased. The differences in development time, body weight, and longevity between females and males were significant. These results suggest that S. endius is a good candidate for the biological control of B. cucurbitae.

Implementing a spinosad-based local bait station to control Bactrocera cucurbitae (Diptera: Tephritidae) in high rainfall areas of Reunion Island.

Three species of fruit flies cause serious damage to cucurbit crops on Reunion Island: Bactrocera cucurbitae (Diptera: Tephritidae) (Coquillett 1899), Dacus ciliatus (Loew 1901), and Dacus demmerezi (Bezzi 1917). To control them, a program of agroecological management of cucurbit flies has been implemented based on the application of Synéis-appât, especially spot sprays on corn borders. However, the high rainfall on Reunion Island limits the long-term efficiency of the bait; in addition, this method cannot be used for large chayote trellises, because corn borders cannot be planted around them. The aim of this study was to design a bait station adapted to prevailing conditions on Reunion Island. An ‘umbrella trap’ tested in Taiwan was used as a reference to compare its efficacy with our local bait station. Experiments were conducted in field cages on B. cucurbitae to test different characteristics of bait stations and to construct one using local materials. Results were validated in the field. The attractiveness of the bait station was related mainly to the color of the external surface, yellow being the most attractive color. The efficacy of the bait station with respect to fly mortality was found to be linked to the accessibility of the bait, and direct application of Synéis-appât on the bait station was found to be the most efficient. In the field, B. cucurbitae were more attracted to the local bait station than to the umbrella trap, while the two other fly species displayed equal attraction to both trap types. Our local bait station is a useful alternative to spot sprays of Synéis-appât and is now included in a local pest management program and is well accepted by farmers.

Role of phenolic acids and enzymes of phenylpropanoid pathway in resistance of chayote fruit (Sechium edule) against infestation by melon fly, Bactrocera cucurbitae

AbstractMelon fly is a serious pest of cucurbits all over the world causing huge losses to yield. However, the only exception is the chayote fruit (Sechium edule) that shows resistance to melon fly infestation. Studies on culture of melon fly indicated the absence of plant traits resisting oviposition on chayote fruit. However, the melon fly was unable to complete its life cycle successfully on chayote showing that factors inhibiting larval development in melon fly could be attributed to biochemical constituents. Studies were, therefore, carried out to compare the biochemical responses of chayote, a melon fly resistant species and bitter gourd, a susceptible species to melon fly infestation with regard to the levels of phenolic acids and activities of the enzymes of phenylpropanoid pathway (PPP) leading to synthesis of lignin. The resistant chayote exhibited significantly higher accumulation of lignin associated with higher activities of phenylalanine ammonia‐lyase (PAL), tyrosine ammonia‐lyase (TAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD). On the contrary, the susceptible bitter gourd recorded lower activities of PAL, CAD and POD and a decreasing trend of TAL during infestation associated with a lower lignin content. The monomer composition of lignin in the resistant chayote showed twofold higher level of guaiacyl (G) and syringyl (S) units compared to susceptible bitter gourd and the G/S ratio during infestation increased in chayote while decreasing in bitter gourd. The levels of PPP intermediates, p‐coumaric acid was higher in chayote while p‐hydroxy benzoic acid, a chemo‐attractant, was higher in bitter gourd. Incorporation of p‐coumaric acid in the larval diet strongly inhibited larval growth even as p‐hydroxy benzoic acid promoted growth confirming the direct role of p‐coumaric acid in conferring resistance to chayote. The level of salicylic acid, a signal molecule involved in induction of defence response, was higher in chayote compared to bitter gourd. Chayote also exhibited higher level of activity of POD in the phloem exudates compared to bitter gourd. The higher concentration of sugars in exudates of chayote might act like signalling molecules causing activation of plant genes, especially of the phenylpropanoid biosynthesis pathway and possibly produce an osmotic effect inducing resistance against the melon fly. Thus, the study revealed that the resistance in chayote to melon fly infestation is a complex, multi‐layered process in which the activities of PPP enzymes generating phenolic intermediates leading to lignin biosynthesis and the composition of exudates appear to play significant roles. Besides, the study also indicated that different forms of lignin might play a role in the resistance of chayote against melon fly infestation.

Assessment of Navel Oranges, Clementine Tangerines, and Rutaceous Fruits as Hosts of Bactrocera cucurbitae and Bactrocera latifrons (Diptera: Tephritidae).

Export of Citrus spp. fruits may require risk mitigation measures if grown in areas with established tephritid fruit fly (Diptera: Tephritidae) populations capable of infesting the fruits. The host status of Citrus spp. fruits is unclear for two tephritid fruit fly species whose geographic ranges have expanded in recent years: melon fly, Bactrocera cucurbitae (Cocquillett), and Bactrocera latifrons (Hendel). In no choice cage infestation studies, B. latifrons oviposited into intact and punctured Washington navel oranges (Citrus sinensis [L.] Osbeck) and Clementine tangerines (C. reticulata L. var. Clementine), but eggs rarely developed to the adult stage. B. cucurbitae readily infested intact and punctured tangerines, and to a lesser extent punctured oranges, but did not infest intact oranges. Limited cage infestation and only a single literature report of field Citrus spp. infestation suggest that risk mitigation of Citrus spp. for B. latifrons is not needed. Risk mitigation options of Citrus spp. for B. cucurbitae, including heat and cold treatments and systems approaches, are discussed.

Melon Fly, Bactrocera cucurbitae (Diptera: Tephritidae), Infestation in Host Fruits in the Southwestern Islands of Japan Before the Initiation of Island-wide Population Suppression, as Recorded in Publications of Japanese Public Institutions.

Bactrocera cucurbitae (Coquillett) is a tephritid fruit fly native to the Indo-Malayan region. Its distribution, though, has extended to include Africa, temperate Asia, and a number of Pacific islands. It became established in Japan in 1919 in the Yaeyama Islands and spread north in the Southwestern Islands of Japan. It was subsequently eradicated from these islands by an eradication program that extended from 1972 to 1993. As part of an effort to develop a worldwide database on the status of fruits as hosts of melon fly, the infestation data gathered from host fruits collected in this eradication program, before the initiation of suppression activities, are summarized here. Bactrocera cucurbitae infestation was documented in 24 plant taxa of four plant families (Caricaceae, Cucurbitaceae, Moraceae, and Solanaceae), with the following four new hosts identified: Ficus erecta Thunb., F. pumila L. (Moraceae), Solanum erianthum D. Don (Solanaceae), and Zehneria liukiuensis Jeffrey ex Walker (Cucurbitaceae).

Bio-efficacy of neem and other botanicals for melon fruit fly (Bactrocera cucurbitae) management

Melon fruit fly (Bactrocera cucurbitae) is pest on various cucurbitaceous plants and fruits. To explore the pesticidal property of indigenous plants against fruit fly, pupal dipping in 2 and 5% concentration of six plants was accomplished for 1 minute in the laboratory. Temperature was maintained at 32±3°C and relative humidity (RH) at 75 ± 10 per cent. Kaner, Thavetia peruviana was found best in preventing adult emergence and causing mortality of pupae upto 70.70% and 86.20% at 2 and 5% concentrations, respectively. Parthenium and NSKE at 5% were also found promising. The sequence of efficacy of different botanicals with respect to lesser number of adult emergence was Thavetia peruviana 5% > Parthenium hystrophorus 5%> NSKE 5% > Datura latifolia 5%> Cuscuta reflexa 5% > Pongamia pinnata 5%.

Developmental Biology of Zeugodacus cucurbitae (Diptera: Tephritidae) in Three Cucurbitaceous Hosts at Different Temperature Regimes.

Fruit flies are key pests of cucurbits in many parts of the world, including Tanzania. Developmental biology of Zeugodacus cucurbitae (Coquillett) has been determined across temperature regimes in some cucurbitaceous hosts, in limited geographies. This study was conducted to determine duration and survival rates of immature stages of Z. cucurbitae in three cucurbitaceous hosts, at different temperature regimes. It was hypothesized that temperature and cucurbitaceous hosts influence duration and survival of immature stages of Z. cucurbitae. We conducted experiments in the environmental chamber set at 75 ± 10% RH and a photoperiod of 12:12 (L:D) h, at temperatures of 20, 25, and 30°. Our results showed that duration and survival of immature stages of Z. cucurbitae differed significantly among the temperature regimes but not among the hosts. Egg incubation period as well as larval and pupal stages were significantly longer (P < 0.0001) at low temperature in all three hosts Likewise, survival rate of all immature stages were significantly higher (P < 0.0001) at higher than lower temperatures. The three hosts, cucumber (Cucumis sativus), watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai), and pumpkin (Cucurbita pepo) did not significantly affect duration or survival rates of immature stages of Z. cucurbitae. The low developmental thresholds were estimated at 15.88, 13.44, and 12.62 for egg, larva and pupa, respectively. These results further confirm that Z. cucurbitae is well adapted to warm climate, which dominates many areas of Tanzania.

Evaluation and Efficacy of Pest Management Modules for cucur-bits against Fruitfly,Bactrocera cucurbitae(Coquillett) in Andaman

Fruit fly (Dacus cucurbitae) is a major pest of cultivated cucurbits. Among cucurbits, incidence was more in bitter gourd and ridge gourd as compared to other cucurbitaceous veg-etables. IPM module has been developed for the successful management of cucurbit fruit fly. Integrated Pest Management (IPM) module com-prising of installation of cue-lure baited traps @ 50 traps/ha for mass trapping, weekly clipping of infested fruits, foliar spray of aqueous leaf ex-tracts of Morinda citrifolia @ 100g/l and foliar spray of spinosad 45SC or imidacloprid 17.8SL @ 0.3ml/l alternately at 15 days interval was found effective with respect to less fruit damage due to fruit fly (9%) and maximum fruit yield (10.75 t/ha) in bitter gourd as compared to un-treated control (39.3% fruit damage and fruit yield 5.53 t/ha). The same trend was also noticed in ridge gourd also. IPM module was found bet-ter with respect to less fruit damage (5.9%) and maximum fruit yield (7.59t/ha) in ridge gourd. The yield in untreated control plots was recorded 3.46t/ha. IPM module for cucurbit fruit fly gave higher cost benefit ratio of 1: 3.35 in IPM and 1: 2.30 in non-IPM fields of bitter gourd and 1: 1.99 in IPM and 1: 1.23 in non-IPM fields of ridge gourd, respectively. IPM module for cucur-bit fruit fly gave higher incremental cost benefit ratio of 1: 3.35 in IPM and 1: 2.30 in non-IPM fields of bitter gourd and 1: 1.99 in IPM and 1: 1.23 in non-IPM fields of ridge gourd, respectively. By using these management practices, application of synthetic insecticides can be reduced and low-er the risk to people, wildlife and the environ-ment.

Novel toxicity of Bacillus thuringiensis strains against the melon fruit fly, Bactrocera cucurbitae (Diptera: Tephritidae).

Bactrocera cucurbitae (melon fruit fly) is one of the most detrimental vegetable-damaging pests in Bangladesh. The toxicity of Bacillus thuringiensis (Bt) has been reported against a few genera of Bactrocera in addition to numerous other insect species. Bt strains, harbouring cry1A-type genes were, therefore, assayed in vivo against the 3(rd) instar larvae of B. cucurbitae in this study. The biotype-based prevalence of cry1 and cry1A genes was calculated to be 30.8% and 11.16%, respectively, of the test strains (n=224) while their prevalence was greatest in biotype kurstaki. Though three indigenous Bt strains from biotype kurstaki with close genetic relationship exhibited higher toxicity, maximum mortalities were recorded for Btk HD-73 (96%) and the indigenous Bt JSc1 (93%). LC50 and LC99 values were determined to be 6.81 and 8.32 for Bt JSc1, 7.30 and 7.92 for Bt SSc2, and 6.99 and 7.67 for Btk HD-73, respectively. The cause of toxicity and its variation among the strains was found to be correlated with the synergistic toxic effects of cry1, cry2, cry3 and cry9 gene products, i.e. relevant Cry proteins. The novel toxicity of the B. thuringiensis strains against B. cucurbitae revealed in the present study thus will help in developing efficient and eco-friendly control measures such as Bt biopesticides and transgenic Bt cucurbits.

Hierarchical Analysis of Variation in the Mitochondrial 16SrRNA Gene among Five Different Insect Orders

Nucleotide sequences from a 500 bp region of the 16SrRNA gene were analyzed for ten insect pests of five different orders to examine the patterns of variation within the gene fragment and the taxonomic levels for which it showed maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. Among them, partial 16SrRNA gene was amplified in ten insects of five different orders. As previously reported for many holometabolous insects, the 16SrRNA gene data is reported here for 5 different orders were highly AT-rich and exhibited strong site-to-site variation in substitution rate. The partial 16SrRNA genes of five out of ten insects were reported first time. Primers were made from blasting 2 different genera of the order Diptera. These primers were proven to be universal as it amplified the partial 16SrRNA gene in ten different insects across five different orders, Diptera, Coleoptera, Heteroptera, Lepidoptera and Hymenoptera. Later, a phylogenetic tree was also constructed for understanding and analyzing the relation of above five orders. This study resulted in unusual findings which were as follows: All the species of Drosophila of order Diptera were evolutionary more closely related to Dysdercus koenigii of order Heteroptera than Bactrocera cucurbitae of Drosophilan order, Diptera in terms of partial 16SrRNA gene sequence. Similarly, Spodoptera litura and Helicoverpa armigera belonged to same family Noctuidae whereas Pieris brassicae belonged to family Pieridae. All belonged to order Lepidoptera. The results showed that Spodoptera litura in terms of partial 16SrRNA gene sequence was evolutionary more close to Pieris brassicae than Helicoverpa armigera.

A novel polysaccharide in insects activates the innate immune system in mouse macrophage RAW264 cells.

A novel water-soluble polysaccharide was identified in the pupae of the melon fly (Bactrocera cucurbitae) as a molecule that activates the mammalian innate immune response. We attempted to purify this innate immune activator using nitric oxide (NO) production in mouse RAW264 macrophages as an indicator of immunostimulatory activity. A novel acidic polysaccharide was identified, which we named “dipterose”, with a molecular weight of 1.01×106 and comprising nine monosaccharides. Dipterose was synthesized in the melon fly itself at the pupal stage. The NO-producing activity of dipterose was approximately equal to that of lipopolysaccharide, a potent immunostimulator. Inhibition of Toll-like receptor 4 (TLR4) led to the suppression of NO production by dipterose. Furthermore, dipterose induced the expression of proinflammatory cytokines and interferon β (IFNβ) and promoted the activation of nuclear factor kappa B (NF-κB) in macrophages, indicating that it stimulates the induction of various cytokines in RAW264 cells via the TLR4 signaling pathway. Our results thus suggest that dipterose activates the innate immune response against various pathogenic microorganisms and viral infections. This is the first identification of an innate immune-activating polysaccharide from an animal.

A comparison of polyphenolic content, antioxidant activity and insecticidal properties of Jatropha species and wild Ricinus communis L. found in Mauritius

ObjectiveTo evaluate the phytochemical, antimicrobial and insecticidal properties of different Jatropha species and Ricinus communis (castor) (R. communis) growing in Mauritius. MethodsQualitative and quantitative methods were used for the determination of the presence of phytochemicals in the crude plants solvent extracts. The antimicrobial sensitivity (disc diffusion method) and Antibacterial activity (MIC-microdilution method) of 13 microorganisms were studied. The insecticidal properties of the crude solvent extracts against larvae of two insects, Bactrocera zonata and Bactrocera cucurbitae (Diptera, Tephritidae), which cause important economic losses to local fruits were also demonstrated. ResultsEthyl acetate was proved to be a good solvent for extraction. Jatropha multifida showed very interesting activity against Bacillus algicola and Staphylococcus epidermis. Both R. communis and Jatropha multifida were proved to be very effective as biopesticide against different types of insect larvae. ConclusionsThis study was able to demonstrate that Jatropha species as well as R. communis growing in Mauritius possess antimicrobial, phytochemical and insecticidal properties.