Beneficial insects, such as natural enemies, are important to agro‐ecosystem functioning and thus agricultural production. Parasitoids and predators can provide sustainable long‐term solutions to ...pest problems (biological control), reducing the need for expensive and sometimes polluting pesticide applications. When several species of beneficial insects are present, their pest control actions may be additive, synergistic, or disruptive. One form of disruptive interaction between parasitoids and predators is direct interspecific contest for access to individual pests (the resource to be exploited). This study evaluated behavioural interactions between brood‐guarding wasps, Goniozus nephantidis (Muesebeck) (Hymenoptera: Bethylidae), which are known to engage in intra‐specific contests, and a predatory bug, Cardiastethus exiguus (Poppius) (Hemiptera: Anthocoridae), which attack the same pest species, Opisina arenosella (Walker) (Lepidoptera: Oecophoridae), a major pest in coconut production systems. Dyadic parasitoid–predator and predator–predator contests were staged to determine the factors that influence the behaviours within, and outcomes of, such interactions. Parasitoids were aggressive towards predators, sometimes killing them, but predators were not aggressive towards parasitoids. Biting and stinging only occurred when there was a host larva present. In the absence of the parasitoid that had oviposited onto a host, predators often consumed the parasitoid’s eggs. Egg consumption sometimes occurred when the parasitoid was present. Intra‐specific competition between pairs of predators was also evaluated: adults were aggressive towards each other, but interactions were not fatal. Biting was more common when there was no prey larva present. When a larva was present, predators were observed feeding simultaneously. We conclude that direct parasitoid–predator interactions are likely to influence pest population dynamics, possibly reducing the overall suppression of O. arenosella by its natural enemies.
Behavioural interactions were evaluated between brood‐guarding wasps – Goniozus nephantidis (Hymenoptera: Bethylidae) – and predatory bugs – Cardiastethus exiguus (Hemiptera: Anthocoridae) – which both attack a crop pest – Opisina arenosella (Lepidoptera: Oecophoridae). Parasitoids were aggressive towards predators, sometimes killing them, but predators were not aggressive towards parasitoids. Predators often consumed the parasitoid’s eggs. Predators were aggressive towards each other, but interactions were not fatal. Direct parasitoid–predator interactions are likely to reduce pest suppression by natural enemies.
Coconut palm (
Cocos nucifera
) infestation by
Opisina arenosella
(Lepidoptera: Oecophoridae) in the Indian subcontinent may occur in November to May each year in the same or adjoining areas of ...plantations. Parasitoids of
O. arenosella
may also be consistently present at these times. During other periods, pests and/or parasitoids could be maintained on intercrops that are commonly grown throughout the year. Field surveys of 54 intercrop species in Kerala, India, found that
O. arenosella
attacks banana, but not others, while laboratory screening showed that
O. arenosella
can mature on jack fruit, cashew and oil palm. Larvae of 20 lepidopteran species found on intercrops were screened for use by
Goniozus nephantidis
(Hymenoptera: Bethylidae), a larval parasitoid of
O. arenosella
, which oviposited on two species but its offspring failed to mature. Thirteen intercrop herbivore species were screened for use by
Brachymeria nosatoi
(Hymenoptera: Chalcididae), a pupal parasitoid of
O. arenosella
, which completed development on the pyralids
Herculia nigrivita
,
Syllepte derogata
and
Psara basalis
. Further, connectance trophic webs were compiled using prior field records of coconut, 33 species of intercrops, 58 species of lepidopteran herbivores and 29 species of primary parasitoids. Both laboratory and literature evidence suggests that populations of
O. arenosella
are unlikely to be maintained by feeding on intercrops or strongly influenced by direct competition with other lepidopterans but are likely to be affected by sharing parasitoids. Intercrop herbivores have clear potential for maintaining parasitoids of
O. arenosella,
and we recommend thirteen plant species as intercrops that should aid in conservation biocontrol.
Two‐ to three‐day‐old male Drosophila melanogaster flies were irradiated with 1, 2, 4, 6, 8, 10, 20, 25, 30, 40 and 50 Gy doses of gamma radiation. The longevity and rate of development were observed ...for three successive generations to assess the impact of irradiation. The mean lifespan of irradiated flies was significantly increased at 1, 2 and 8 Gy, while it was vice versa for high doses at 30, 40 and 50 Gy. Paternal irradiation had an impact on F₁ generation, with significantly increased mean longevity at 2 (female), 4, 6, 8 and 10 and decreased mean longevity at 40 and 50 Gy (male and female). Significant increase in the longevity was observed in the F₂ generation of the 8 (male and female) and 10 Gy (male) irradiated groups, while decreased longevity was observed in F₂ female progeny at 40 Gy. In the case of F₃ progeny of irradiated flies, longevity did not show significant difference with the control. Paternal exposure to radiation had a significant impact on the mean egg to adult developmental time of the F₁ generation; it was shortened at 2 Gy and extended at 25, 30, 40 and 50 Gy compared to the control. Mean development time at 30, 40 and 50 Gy was significantly increased in the F₂ generation, while there were no significant changes in the F₃ generation. The present study concludes that the effect of acute gamma irradiation on longevity and “egg to adult” development time of D. melanogaster may persist to following generations.
Abstract
Understanding the composition and dynamics of ecological communities is challenging because of the large number of organisms present and their numerous interactions. Among agricultural ...systems, intercropping considerably increases the complexity of communities compared to monocultures and alternative host plants can influence insect pest damage. Using literature records, we construct and analyse connectance trophic webs of date palm (
Phoenix dactylifera
) agro-ecosystems, including and excluding intercrops. Estimates of connectance (community complexity) are relatively low and little affected by consideration of intercrops. Plant–herbivore overlap is relatively high, suggesting that herbivores are typically not specialists. Herbivore–natural enemy overlap is greater when intercrops are considered, suggesting that diffuse apparent competition regulates pest populations. We pay particular attention to how trophic web structure might affect
Batrachedra amydraula
(Lesser date moth), an important economic pest. Records indicate it having 15 species of natural enemies and sharing 9 of these with other herbivores; these may maintain populations of natural enemies when the moth is seasonally rare, contributing to pest suppression. The estimated potential for apparent competition between the lesser date moth and other herbivores is higher when intercrops are considered. The consequent expectation of less severe infestations in plantations that are intercropped compared to monocultures matches empirically derived reports. Further, comparing results obtained from the literature on one country (Oman) and from 15 Middle Eastern countries, we find that community metric estimates are relatively little affected by the geographical scale considered. Overall, our results suggest that literature-based trophic web construction can provide an efficient and robust alternative, or in addition, to direct empirical methodologies and that the presence of intercrops will contribute to major pest suppression via indirect apparent competition.
The rationale of the present study was to isolate and identify endophytic fungi from endemic medicinal plants in Eastern Ghats and screened for antimicrobial potential of isolated fungal crude ...extracts. A total of 329 endophytic strains were isolated from 600 infected leaves and stem cuttings of endemic plants. The diversity and species richness was analyzed statistically and found to be higher in leaf segments than in stem segments. From isolated fungal strains,
was identified using molecular identification methods and selected as the most potent plumbagin-producing endophytic strain. Further the isolation and structural characterization of endophytic fungal plumbagin (5-hydroxyl-2-methylnaptalene-1,4-dione) was purified and confirmed through spectroscopy analysis. The molecular weight was determined as
188 in positive mode by ESI-MS, which confirmed to be plumbagin which potentially inhibited all tested pathogens, therefore the endophytic fungal plumbagin from the current study possesses important biological activities against pathogens.
The environment exposed to radionuclide faces detrimental effects of ionizing radiations and these radiations can damage DNA by inducing genotoxicity in living organisms. The gamma radiation induced ...genotoxicity was evaluated by employing Single cell gel electrophoresis (comet) assay in the foragers of Apis mellifera ligustica by exposing to different doses (1 to 60 Gy) of gamma radiation. DNA damage was measured as the percentage of comet tail DNA. The results showed a dose dependent increase and post irradiation time (1-24 h) dependent decrease in % tail DNA level in bee foragers. A significant increase in DNA damage was observed in all the samples and the extent of damage was proportional to the dose of gamma radiation received by the bees except in those treated with the lower doses (1, 5 and 10 Gy) of gamma radiation. The highest amount of DNA damage was recorded at 1 h post-irradiation which decreased gradually with time, that is, at 3 h and 6 h post-irradiation. However, there were no significant differences in the % tail DNA of bees of 12 h and 24 h post irradiation. The present study shows gamma radiation induced DNA damage in foragers of A. m. ligustica and also the comet assay is a suitable technique for detection of gamma radiation induced DNA damage.
In the effect of robust industrialization and rapid augmentation of a number of fleets, there has been a huge rise in the fossil fuel consumption. Tremendous increase in global warming threatens the ...ecological balance of the earth. Based on the recent sorts of hardship about the fuel, researchers are profoundly pondered over the field of renewability, environmentally friendly and economically doable. In recent decades biodiesel fuel becomes the center of attraction among researchers since it is renewable, bio degradable, non-noxious, eco-friendly and sustainable. This review paper highlights and reviews the properties of prosperous variety of the biodiesel fuels derived from non-edible feedstocks which are termed as third generation biodiesel and its effects on the performance and emissions of the diesel engines. It was observed that the physicochemical properties of the biodiesel differ based on the types of feedstocks and also have a considerable effect on the potential performance of engine and dynamic characteristics of emission level. Also, the usage of biodiesel commonly leads to a reduction in noxious pollutants like carbon monoxide, unburnt hydrocarbon and particulate matter with an obvious increase in fuel consumption and NOx emission. This review provides a prospective strategy for the researchers for enhancing the engine performance and emission characteristics by using the third generation biofuels and its blends with the productive marvelous outcomes.
‘Fuel Stability’ is one of the most significant properties of biodiesel, which insists the biodiesel stability during prolonged storage period. Poor resistance to oxidation process is the main hurdle ...for biodiesel commercialization in the global fuel market. Biodiesel degradation by the products yielded from oxidation process may deprive the fuel properties and obviously engine performance. Dosage of synthetic antioxidants is an appropriate method for improving the fuel stability of biodiesel. The present research work investigates the effects of tert-butyl hydroquinone (TBHQ) antioxidant additive concentrations on the oxidation stability, long-term storage stability and thermal stability of Calophyllum inophyllum biodiesel. Fourier Transform Infra-red (FTIR) spectroscopy was used to characterize the oxidation variability of biodiesel, following the FTIR spectrum regions of CH and OH bonds for various concentrations of TBHQ. Dosage of TBHQ at 1000ppm concentration (B100A3) with pure biodiesel enhances the oxidation stability by 94.658%, storage stability by 14.466% and thermal stability by 37.269%; meanwhile further dosage of antioxidant deteriorates the formation of hydrophobic and hydrophilic clusters between antioxidant and biodiesel compounds, which is characterized through FTIR spectrum. It is concluded that by dosing 1000ppm of TBHQ antioxidant with Calophyllum inophyllum biodiesel could enhance the storage period.
In the rapidly growing global energy consumption, diesel engines play the key role. Usage of diesel fuel contributes to harmful air pollution exhausted from combustion chamber. To overcome these ...serious issues, the biodiesel extracted from many feedstocks have been studied and implemented for the past few decades. The combustion characteristics of diesel are not same as the biodiesel blends due to the discrepancy in physio-chemical properties of biodiesel. Enormous studies have been focused on inadequate combustion profiles of biodiesel in compression ignition engines. This review paper analyzes the previous researches concerning the consequences of proposed effective strategies including the variation in engine operating parameters like fuel injection timing and injection pressure for enhancing combustion characteristics of biodiesel implementation. This study focuses its light on the advancement and retardation methods of injection timing and injection pressure to treat the engine combustion indicators such as in-cylinder pressure, peak cylinder pressure, heat release rate, ignition delay period and combustion duration, finally a comparative evaluation has been developed and the relevant reasons for the variation of combustion characteristics have been conversed. The review concludes that the advancement in injection timing and higher injection pressure are best in amplifying the combustion phenomena of biodiesel fuelling.
This research paper aims at investigating the performance, emission and combustion characters of diesel engine with 20% volume concentrations of animal fat based biodiesel (AFO20), waste cooking oil ...biodiesel (WCO20), camphor oil (CMO20) and also including pure diesel fuel (D100). The peak cylinder pressure and heat release rate of biodiesel was about 4.82% higher and 13.49% lower than those of diesel fuel on average respectively. Start of combustion of alternate blends happened at earlier crank angles compared to base fuel. Combustion duration of all alternate fuel blends is higher than those of diesel at all load conditions. While fuelling CMO20, AFO20 and WCO20, the NOx concentration in the emission shows 7.52%, 10.352% and 16.405% increment respectively with the biodiesel addition to diesel. However, significant reduction in NOx of about 43.8% was observed for camphor oil - diesel blend when compared to other biodiesel blends. The correlation between NOx emission level and in-cylinder temperature was premeditated by a novel procedure using thermal imager. The result shows that the increase in in-cylinder temperature contributed to the augmentation in NOx concentration.
•Effect of alternate fuels on engine characteristics has been studied.•AFO, WCO and CMO are used as alternate fuels in this investigation.•CMO and WCO show the lowest and highest NOx emission respectively among the blends.•NOx emission increased with increase in in-cylinder temperature for all blends.•Novel procedure of NOx analysis by thermal imager has been proposed.
PDF
