LT50 Values Research Articles

Initial efficacy of pyrethroids, inert dusts, their low-dose combinations and low temperature on Oryzaephilus surinamensis and Sitophilus granarius

In this study, initial efficacy of three pyrethroids, two inert dusts and their low-dose combinations were investigated on adults of Sitophilus granarius and Oryzaephilus surinamensis at laboratory conditions. The insects were exposed to treatments on concrete surface. The LC25 values of the pyrethroids and LD25 values of the inert dusts were estimated and used for determining their combination effects. Mortality of insects was recorded 48 h after treatments. The effect of a low temperature, −18 °C was also assessed on both species. Exposure times to −18 °C were 15, 18, 22, 27, 33 and 40 min for S. granarius and 10, 12, 15, 19 and 23 min for O. surinamensis in main experiments. The treated insects were kept in the laboratory conditions for 24 h after cold treatments, then the mortalities were recorded. The LC50 values estimated for deltamethrin, lambda-cyhalothrin and fenvalerate on S. granarius were 45.08, 43.34 and 465.00 mg ai/L; and on O. surinamensis were 0.65, 1.83 and 81.36 mg ai/L, respectively. The LD50 estimated for zeolite on S. granarius was 10.32 g/m2; and kaolin was not effective on this species. The LD50 values estimated for zeolite and kaolin on O. surinamensis were 7.7 g/m2 and 12.0 g/m2, respectively. Mortalities caused by deltamethrin + zeolite and lambda-cyhalothrin + zeolite combinations on S. granaries were 80.0% and 63.3%, respectively. The effects of combinations of the pyrethroids and zeolite or kaolin on O. surinamensis were also significantly higher than sum of their individual effects. It means the effects of these combinations were synergistic. The LT50 values estimated at −18 °C were 33 min for S. granarius and 16 min for O. surinamensis. The results obtained from this study can be used as basic and preliminary information for practical control programs of these pests in stored products.

Synthesis of Cordyceps fumosorosea-Biochar Nanoparticles and Their Effects on Growth and Survival of Bemisia tabaci (Gennadius)

Nanotechnology can offer an environmentally sustainable alternative to synthetic chemicals for pest management. Nano-formulations of different microbial pest control agents have been effective against several insect pests. Synthesis of Cordyceps fumosorosea-biochar (BC) nanoparticles and their bio-efficacy against Bemisia tabaci was observed during this study. The characterization of C. fumosorosea-BC nanoparticles through different analytical techniques showed successful synthesis of nanoparticles. UV spectroscopy showed a characteristic band of surface plasmon between 350 and 400 nm; SEM images confirmed the synthesis of spherical shaped nanoparticles; X-ray diffractogram showed strong peaks between 2θ values of 20°–25°; and atomic force microscopy (AFM) analysis revealed particle size of 49.151 nm. The bioassay studies demonstrated that different concentrations of C. fumosorosea-BC nanoparticles caused significant reduction in hatchability of B. tabaci eggs as well as survival of immatures emerging from treated eggs when compared with controls. The results also revealed that C. fumosorosea-BC nanoparticles were highly pathogenic against 2nd and 3rd instar nymphs and pupae of B. tabaci having LC50 values of 6.80, 7.45, and 8.64 ppm, respectively. The LT50 values for 20 ppm concentration of C. fumosorosea-BC nanoparticles against 2nd and 3rd instar nymphs, and pupae of B. tabaci were 3.25 ± 0.29, 3.69 ± 0.52, and 4.07 ± 0.51 days, respectively. These findings suggest that C. fumosorosea-BC nanoparticles can potentially be used in biorational B. tabaci management programs.

UJI EFEKTIVITAS EKSTRAK ETANOL DAN METANOL KULIT PISANG KEPOK (Musa acuminata-xbalbisiana) PADA LARVA NYAMUK Aedes aegypti

Dengue fever is caused by Aedes aegypti mosquitoes. Using of synthetic larvicides has been so many impact on resistance and can damage the environment. Therefore, naturl larvaside by using ethanol and methanol extracts from kepok banana peel (Musa acuminata-xbalbisiana) againts the death of larvae of Aedes aegypti instar III and IV. This research wasexperimental, with concentration of ethanol extract and methanol treatment of 0,5%, 0,75%, 1%, 2,5%, 5%, kontrol positif dan kontrol negatif controls in five replicaions. Larval mortality is calculated after the first 6 hours of death for up to 24 hours. Larvicidal activity data were analyzed with the Kruskal-Wallis test and probit test to find the LC50 value. The results of the study obtained the value of LC50 in ethanol extrack of kepok banana peels at 3,264% and methanol at 2,681%. LT50 values in the best ethanol and methanol extracts were obtained at a concentration of 5% of 12,136 hour and 12,979 hour.

π‐Extended Carbazole Derivatives as Host Materials for Highly Efficient and Long‐Life Green Phosphorescent Organic Light‐Emitting Diodes

High-performance organic light-emitting diodes (OLEDs) that use phosphorescent and/or thermally activated delayed fluorescence emitters are capable of realizing 100 % electron-to-photon conversion. The host materials in these OLEDs play crucial roles in determining OLED performance. Carbazole derivatives are frequently used as host materials, among which 3,3-bis(9H-carbazol-9-yl)biphenyl (mCBP) is often used for lifetime testing in scientific studies. In this study, the π conjugation of the carbazole unit was expanded to enhance OLED lifetime by designing and developing two benzothienocarbazole (BTCz)-based host materials, namely m1BTCBP and m4BTCBP. Among these host materials, m1BTCBP formed a highly efficient [Ir(ppy)3 ]-based OLED with an operational luminescence half-life (LT50 ) of over 300 h at an initial luminance of approximately 12000 cd m-2 (current density: 25 mA cm-2 ). The LT50 value at 1000 cd cm-2 was estimated to be about 23 000 h. This performance is clearly higher than that of mCBP-based OLEDs (LT50 ≈8500 h).

Film seeds coating with hexane extracts from Illicium verum Hook.f. and Syzygium aromaticum (L.) Merrill & Perry for controlling Callosobruchus maculatus (F.) and Callosobruchus chinensis L.

The application of film seed coating with some plant extracts against stored insect pests was an alternative approach for insect protection instead of using chemical insecticides. The overuse of insecticides has contributed to both human health and environmental problems. The hexane extracts of Illicium verum (HS) and Syzygium aromaticum (HC) were evaluated against bruchid beetles (Callosobruchus maculatus and Callosobruchus chinensis). The insecticidal activities and enhancing seed germination after being coated by various concentrations of extracts, purified fraction (PF) of extracts, standard chemicals of PF, fipronil insecticide (FI), and coating agent groups were evaluated after stored. Both HS and HC at 3% concentrations were more effective against C. maculatus than C. chinensis with LT50 values of 1.60-1.90 and 3.44-3.62 h, respectively. They could also kill those insects with a higher number than that of standards. The HS and HC could inhibit the progeny population of those insects over 95.6% with no significant difference compared to the FI group. The eugenol standard was the most effective and completely inhibited the emergence compared with trans-anethol standard and PFs. The seed that was coated with 1% of HS and stored at 4 °C for 6 months showed no effect on seed germination with no significant difference between FI and control groups. The application of 1% of HS incorporated in the film seed coating against bruchid beetles and did not affect seed germination quality after 6 months. © 2021 Society of Chemical Industry.

Anti-oxidant, pediculicidal and pesticidal activities of leaves of Rhinacanthus nasutus (Linn) grown in Sri Lanka

Rhinacanthus nasutus is an ethnomedical plant used in the traditional system of medicine for treating skin diseases. As no adequate studies available on R. nasutus grown in Sri Lanka, this study aimed on exploring anti-oxidant, anti-parasitic and pesticidal activity of leaves of the plant. Antioxidant capacity of the crude extract of leaves was evaluated using DPPH free radical scavenging assay and FRAP assay using ascorbic acid and FeSO4.7H2O as the standards respectively. Pediculicidal efficacy was carried out against head lice using 0.0010% (w/v) methanolic, ethyl acetate and aqueous extracts of leaves by following modified filter paper diffusion bioassay. Pesticidal activity of leaves was evaluated using modified filter paper contact bioassay against mealybugs, P. marginatus, resides on papaw and guava trees. The IC50 value of DPPH assay was found to be 514.3 μgmL-1 and FRAP value was found to be 594.33±2.93 μmol Fe2+/g in anti-oxidant assay. The LT50 (median Lethal Time) values for 0.0010% (w/v) concentration of methanolic, ethyl acetate and aqueous extracts were 263, 347 and 676 min respectively in pediculicidal assay. LC50 (50% mortality) value was found to be 0.0011% (w/v) after 240 minutes whereas LT50 values of 0.0020% (w/v) of methanol, ethyl acetate and aqueous fractions of R. nasutus for adult were found as 31, 124 and 189 hours and for nymph were 14, 18 and 29 hours respectively in pesticidal assay. Accordingly, methanolic extract was effective in controlling nymph stage of mealybug life cycle than adults with the LC50 of 0.0015% (w/v) within 14 hours. This study confirmed promising pediculicidal and pesticidal activity and significant anti-oxidant capacity of leaves of R. nasutus.
 Asian J. Med. Biol. Res. December 2020, 6(4): 754-760

Entomopathogenic Fungal Screening against Two Spotted Spider Mites, Tetranychus urticae Koch in Tomato and Broad Mite, Polyphagotarsonemus latus (Banks) in Chilli

Background: Entomopathogenic fungi are microorganisms that specifically infect and often kill insects and other arthropods. Most are non-pathogenic to plants and relatively non-toxic to humans and animals. Use of fungal entomopathogens can be an alternative to insecticides and could help in bio-intensive pest management. The current study aimed to study the pathogenicity of entomopathogenic fungal isolates against two Spotted Spider Mites, Tetranychus urticae Koch in tomato and broad Mite, Polyphagotarsonemus latus (Banks) in chilli. Methods: An extensive survey for the natural occurrence of entomopathogenic fungi on insects and mites was made in different agro climatic regions of Tamil Nadu during 2013 and 2014. Survey revealed the occurrence of two entomopathogenic fungi viz., Beauveria bassiana (Balsamo) Vuillemin and Metarhizium flavoviride Gams and Rozsypal var. minus. Laboratory experiment was conducted to evaluate the pathogenicity of fourteen isolates of Beauveria bassiana, Metarhizium anisopliae and Lecanicillium lecanii against Tetranychus urticae and Polyphagotarsonemus latus. Result: In opposition to T. urticae, the Beauveria bassiana isolate Bb 112 showed the highest toxicity of all the other isolates tested, with low LC50 value of 0.6 x106 spores ml-1 and LT50 of 92.60h. Against P. latus, Bb 112 had high virulence with low LC50 value of 0.3x106 spores ml-1 and LT50 value of 92.32h. Hence, there is potential for use of entomopathogenic fungi in the field conditions as an alternate control method in combating the insect pests and other arthropod pests since they are considered natural mortality agents and are environmentally safe.

Response of citrus to freezing tolerance differs depending on genotypes and growing conditions

Global warming is contributing to extreme weather events such as abnormally colder weather, but there is lack of information on the freezing tolerance of citrus grown in Korea. Therefore, it is necessary to prevent damage from the cold in advance, by acquiring information on the critical temperature at which 50% injury (LT50) occurs for citrus varieties grown in Korea. Electrolyte leakage (EL) and tetrazolium chloride (TTC) analyses were performed to determine LT50 values and estimate the freezing tolerance for citrus varieties cultivated in Korea. We also investigated which factors such as genotype, environmental condition (e.g., in vitro, in vivo), cultivation condition, and wind speed affect the LT50 value in citrus. The LT50 value measured in the EL and TTC analyses of the ‘Haryejosaeng’ mandarin indicated it had better resistance to the cold than the citrus hybrids. The LT50 value in the in vitro experiments was lower than for the in vivo experiments, but there was little difference among the genotypes. Some factors, such as cultivation condition and wind speed, affected the LT50 values. The flavonoid levels, total polyphenol content, and antioxidant activity were affected by exposure to freezing temperatures, which was not related to the change in freezing tolerance level.

Bio-efficacy, persistence and residual toxicity of different insecticides against jassid Empoasca kerri (Pruthi) infesting soybean

An investigation was undertaken to study the bio-efficacy, persistence and residual toxicity of different insecticides viz., chlorantraniliprole 0.004 per cent, ethion 0.100 per cent, triazophos 0.050 per cent, indoxacarb 0.010 per cent, emamectin benzoate 0.001 per cent, quinalphos 0.050 per cent and profenophos 0.100 per cent against Empoasca kerri (Pruthi) infesting soybean at the Research Farm of Department of Agril. Entomology, College of Agriculture, Latur (MS). The overall results concluded that all the insecticides under investigation were significantly superior over untreated control in minimizing the population of E. kerri. Among the treatments, profenophos 0.100 per cent was found to be the most effective insecticide in minimizing the population of E. kerri on soybean (3.83 and 2.60 jassids per three leaves) followed by quinalphos 0.050 per cent (4.03 and 2.90 jassids per three leaves), triazophos 0.050 per cent (4.47 and 3.50 jassids per three leaves), chlorantraniliprole 0.004 per cent (5.03 and 3.60 jassids per three leaves), indoxacarb 0.010 per cent (7.20 and 5.00 jassids per three leaves), emamectin benzoate 0.001 per cent (7.40 and 5.40 jassids per three leaves) and ethion 0.100 per cent (7.67 and 5.50 jassids per three leaves) after first and second sprays, respectively. The highest grain yield was achieved by chlorantraniliprole 0.004 per cent (34.87 q per ha) while quinalphos 0.050 per cent (1:19.72) exhibited highest incremental cost benefit ratio. The results on residual toxicity of different insecticides against E. kerri infesting soybean indicated that profenophos 0.100 per cent and quinalphos 0.050 per cent illustrated highest persistent toxicity index (PT) (864.67 and 873.18 and; 815.74 and 822.85, respectively) and LT50 values (6.80 and 7.02 and; 5.91 and 6.11 days, respectively) against E. kerri after first and second sprays as compared to other insecticides.

Insecticidal Potential of Indigenous Flora of Soon Valley against Asian Citrus Psyllid Diaphorina citri Kuwayama and Cotton Aphid Aphis gossypii Glover

Diaphorina citri Kuwayama (Psyllidae: Hemiptera) and Aphis gossypii Glover (Aphididae; Hemiptera) are destructive sap-feeding pests of citrus and cotton, respectively. This study assessed the toxicity potential of indigenous flora of Soon valley and surrounding salt range (Punjab, Pakistan) against D. citri and A. gossypii. Among acetone extracts of 40 plant species, the extracts of Mentha longifolia (L.) Huds., Melilotus officinalis (L.) Pall., Nerium indicum Mill., Datura alba L. and Salvia officinalis L. showed highest psyllid mortality (i.e. 93, 91, 89, 88 and 81%, respectively). Bioassay with most effective extracts further revealed that the most toxic extracts were S. officinalis, N. indicum and M. longifolia with LC50 values of 18.59, 20.27 and 20.73%, respectively. Similar trend of toxicity was observed in case of their LT50 values. These results suggest the putative effectiveness and further biochemical characterization of these plant extracts for the management of D. citri and A. gossypii and other sap-feeding insect pests.

Pathogenicity of Beauveria bassiana (Bb 112) against sucking insect pests of tomato and brinjal and its relative safety to honeybees

Pathogenicity test performed against Thrips tabaci, Ferrisia virgata in tomato, Bemisia tabaci and Scirtothrips dorsalis in brinjal in laboratory experiments, revealed that oil formulation of B. bassiana, (Bb 112) was highly virulent with the lowest LC50 values of 0.23 × 106 spores ml−1, 0.34 × 106 spores ml−1, 1.62 × 106 spores ml−1 and 0.46 × 106 spores ml−1, respectively. Time mortality response of tested insect pests in brinjal, showed the LT50 values for T. tabaci, F. virgata in tomato, B. tabaci and S. dorsalis in brinjal, as 98.06, 95.23, 106.30 and 115.83 h, respectively at 108 spores ml−1.

Evaluating the freeze tolerance of bermudagrass genotypes

AbstractBermudagrasses (Cynodon spp.) are commonly used in golf courses, athletic fields, and home lawns in the transitional climatic region of the United States. Winterkill, however, is a major concern for bermudagrasses grown in this region. Controlled environment testing is a reliable method to evaluate freeze tolerance contributing to the selection of freeze tolerant genotypes. Therefore, this study was designed to test the freeze tolerance of two elite experimental genotypes, OKC1873 and OKC1406, along with two industry standards (‘Tifway’ and ‘Tahoma 31’), by exposing them to various freeze temperatures (−4 to −14 ℃) in a controlled environment. The freezing test was replicated in time, and the mean lethal temperature to kill 50% of the population (LT50) for each genotype was determined. Tifway (freeze‐sensitive standard) had an LT50 value of −7.0 ℃. The genotype OKC1873 (−7.2 ℃), was in the same statistical group as Tifway. Tahoma 31 was the best‐performing genotype with the lowest LT50 value of −9.1 ℃. The genotype OKC1406 (−8.8 ℃) was in the same statistical group as Tahoma 31. Top‐performing experimental genotypes will move on for further screening in replicated field trials for future consideration for commercial release based on qualities such as improved freeze tolerance, desirable turfgrass quality, and sufficient disease resistance.

Insecticide Susceptibility Status of Wild Population of Phlebotomus kandelakii and Phlebotomus perfiliewi transcaucasicus Collected from Visceral Leishmaniasis Endemic Foci in Northwestern Iran.

Background: Phlebotomus kandelakii and Phlebotomus perfiliewi transcaucasicus sand flies are the vectors of visceral leishmaniasis in Iran. The aim of this study was to evaluate the susceptibility of Ph. kandelakii and Ph. perfiliewi transcaucasicus, collected from an endemic focus of visceral leishmaniasis (VL) in the northwest of Iran, to different selected insecticides.Methods:Sand flies were collected from the villages of Meshkinshahr and Germi Counties using light traps and aspirators from May to October 2019. The sand flies were identified as Ph. kandelakii and Ph. perfiliewi transcaucasicus using standard identification keys. Susceptibility test was carried out against DDT (4%), Malathion (5%), Propoxur (0.1%) and Lambda-cyhalothrin (0.05%) according to the WHO standard method. MedCalc statistical software was employed to calculate LT50 and LT90 and to compare the chances of sand flies surviving the exposure to the studied insecticides.Results:A total of 1,278 female specimens were used for the susceptibility tests. Out of which 1,063 samples were used for the test and 215 for the control group. The estimated LT50 values for DDT (4%), Malathion (5%), Propoxur (0.1%), and Lambda-cyhalothrin (0.05%) for Ph. kandelakii were 15.1, 13.4, 15.4 and 5.8 minutes respectively, and for Ph. perfiliewi transcaucasicus were 11.9, 15.6, 15.9 and 5.8 minutes respectively.Conclusion:This susceptibility studies revealed different LT50 values for different insecticides efficient against Ph. kandelakii and Ph. perfiliewi transcaucasicus. The regular monitoring for the resistance of Ph. kandelakii and Ph. perfiliewi transcaucasicus sand flies seems necessary in diseases control programs in this area.

Determination of the Yield Quality and Winter Durability Characteristics of Some Bread Wheat (Triticum aestivum) Genotypes in Pasinler and Erzincan Locations

Bread wheat is the most important plant species used in human nutrition and most of the daily protein and calorie needs of people are met from this plant. 13 advanced bread wheat lines, 1 candidate for registration and 6 bread wheat varieties have been compared in terms of yield, number of spikes per square meter, 1000 grain weight, hectoliter weight, plant height, protein ratio, zeleny sedimentation value and 3 different (-17, -19 and -21 °C) cold level parameters in this study. Durable genotypes were determined according to the LT50 value (the degree when 50% of the plants perish with cold stress). As a result of the observations, it was noted that lines 1, 2, 3, 4, 5, 8 were superior in terms of resistance to cold and line 10 displayed superiority in terms of yield compared to the other varieties. It is concluded that these lines may be suitable variety candidates for wheat cultivation in the region. Furthermore, it has been concluded that it is important to include cold test studies in breeding programs in regions like the East Anatolia Region where harsh winters prevail.

Bio-efficacy, persistence and residual toxicity of different insecticides against soybean pod borer Helicoverpa armigera (Hubner) infesting soybean

The studies on the bio-efficacy, persistence and residual toxicity of different insecticides viz., chlorantraniliprole 0.004 per cent, ethion 0.100 per cent, triazophos 0.050 per cent, indoxacarb 0.010 per cent, emamectin benzoate 0.001 per cent, quinalphos 0.050 per cent and profenophos 0.100 per cent against Helicoverpa armigera (Hubner) infesting soybean were conducted at the Research Farm of Department of Agril. Entomology, College of Agriculture, Latur (MS). The overall result revealed that all the insecticidal treatments were significantly superior over untreated control in minimizing the larval population of H. armigera infesting soybean. Among the treatments, chlorantraniliprole 0.004 per cent was found to be the most effective insecticide in reducing larval population of H. armigera on soybean (1.22 and 1.44 larvae per mrl) followed by emamectin benzoate 0.001 per cent (1.33 and 1.78 larvae per mrl), indoxacarb 0.010 per cent (2.22 and 1.89 larvae per mrl), quinalphos 0.050 per cent (2.41 and 2.00 larvae per mrl), profenophos 0.100 per cent (3.67 and 2.22 larvae per mrl), triazophos 0.050 per cent (3.78 and 2.67 larvae per mrl) and ethion 0.100 per cent (4.11 and 2.78 larvae per mrl) after first and second spray, respectively. The highest soybean yield was achieved by chlorantraniliprole 0.004 per cent (34.87 q per ha) while quinalphos 0.050 per cent (1:19.72) registered highest incremental cost benefit ratio. The results on residual toxicity of different insecticides against H. armigera infesting soybean indicated that chlorantraniliprole 0.004 per cent and emamectin benzoate 0.001 per cent illustrated highest persistent toxicity index (PT) (953.68 and 913.48 and; 885.64 and 875.80, respectively) and LT50 values (7.93 and 7.78 and; 7.06 and 7.09 days, respectively) against third instar larvae of H. armigera after first and second spray as compared to the other insecticides.

Bio-efficacy, persistence and residual toxicity of different insecticides against girdle beetle, Obereopsis brevis (Swedenborg) infesting soybean

An investigation was undertaken to study the bio-efficacy, persistence and residual toxicity of different insecticides viz., chlorantraniliprole 0.004 per cent, ethion 0.100 per cent, triazophos 0.050 per cent, indoxacarb 0.010 per cent, emamectin benzoate 0.001 per cent, quinalphos 0.050 per cent and profenophos 0.100 per cent against Obereopsis brevis (Swedenborg) infesting soybean at the Research Farm of Department of Agril. Entomology, College of Agriculture, Latur (MS). The result revealed that all the insecticidal treatments were significantly superior over untreated control in minimizing the per cent plant infestation due to O. brevis. Among the treatments, chlorantraniliprole 0.004 per cent was found to be the most effective insecticide in minimizing infestation due to O. brevis on soybean (6.10 and 3.77 per cent per mrl) followed by ethion 0.100 per cent (6.52 and 4.58 per cent per mrl), triazophos 0.050 per cent (7.33 and 4.60 per cent per mrl), indoxacarb 0.010 per cent (7.44 and 4.63 per cent per mrl), emamectin benzoate 0.001 per cent (7.44 and 5.11 per cent per mrl), quinalphos 0.050 per cent (7.59 and 5.33 per cent per mrl) and profenophos 0.100 per cent (8.55 and 5.99 per cent per mrl) after first and second sprays, respectively. The highest grain yield was achieved by chlorantraniliprole 0.004 per cent (34.87 q per ha) while quinalphos 0.050 per cent (1:19.72) documented highest incremental cost benefit ratio. The results on residual toxicity of different insecticides against O. brevis infesting soybean indicated that chlorantraniliprole 0.004 per cent and ethion 0.100 per cent illustrated highest persistent toxicity index (PT) (851.86 and 817.14 and; 833.80 and 827.96, respectively) and LT50 values (6.48 and 6.14 and; 6.48 and 6.10 days, respectively) against early instar grubs of O. brevis after first and second sprays as compared to the other insecticides.

Effect of high-temperature extracted plant material fume against southern cowpea weevil (Callosobruchus chinensis L.) (Coleoptera: Bruchidae) as a non-chemical novel fumigation technique

BackgroundFumes from high-temperature heated plant leaves containing volatile phytochemicals generated from Lantana camara, Cinnamomum zeylanicum, Azadirachta indica and Ocimum sanctum were tested for their insecticidal activity against adult southern cowpea weevil (Callosobruchus chinensis L.) and their F1 progeny production/emergence. Volatile phytochemicals containing fume was generated using a flameless dry heat extraction method similar to pyrolysis combustion without air supplement at 180 ± 5 °C. Insect mortalities were assessed up to 72 h after exposure to the different treatments of fumigation by plant-fume and control.ResultsAll volatile plant-fume samples contained average of 16.3 ± 1.5% O2 and 5.8 ± 0.5% CO2 in the test jars. The F1 progeny emergence was estimated 30 days after treatment. After 36 h of exposure, L. camara showed the highest toxicity against C. chinensis, followed by O. sanctum, A. indica and C. zeylanicum, with LT50 values of 7.3, 9.4, 14.7 and 20.6 h, respectively. The volatile phytochemical containing plant-fume generated by A. indica and C. zeylanicum produced LT99 values that were not significantly different (P > 0.05) from each other. The F1 adult emergence from treated mungbean (Vigna radiata L.) samples was significantly inhibited by L. camara and A. indica volatile plant-fume compared to C. zeylanicum fume. However, plant-fume generated from all four plants exhibited effective direct toxicity and F1 progeny inhibition of more than 86%.ConclusionFrom the study, it can be concluded that volatile plant-fume treatment was highly lethal to C. chinensis and significantly reduced F1 progeny emergence. Therefore, phytochemicals obtained from thermal extraction technique can be used as an alternative technique to chemical fumigation of stored mungbean.

The Potential Role of Photosensitizers in Fight against Mosquitoes: Phototoxicity of Rose Bengal against Culex Pipiens Larvae

Background: Thecommon house mosquito, Culex pipiens, is abundant in Egypt and act as a vector of pathogens of medical and veterinary importance. Aim: The present study aimed to compare the toxic effect of rose bengal a photosensitizer to that of chlorpyrifos, a commercially available larvicide against the early 3rd larval instar of Cx. pipiens. Methods: We compare the toxic effect of rose Bengal exposed to sunlight from 10 am to 4 pm to that of chlorpyrifos, against the early 3rd larval instar of Cx. pipiens. Results: Treatments revealed dose-dependent mortality, reaching 100% after treatment with rose bengal for 6 hrs and 90.6% for chlorpyrifos for 24 hrs. Six hours post-treatments, the LC50 of rose bengal and chlorpyrifos were 4.9x10-6 and 4.9x10-4, respectively; while the LC95 were 2.0x10-3 and 4.0x0-3, respectively. Based on the LC50 values of chlorpyrifos as a reference substance, rose bengal was found 100 times more potent than chlorpyrifos. The LT50 of rose bengal ranged from 34.8 to 1.1 hrs post-treatment with1×10-6 M and 1×10-2, respectively. The LT50 values of chlorpyrifos ranged from 3065.9 to 6.1 hrs after subjecting to 1×10-4 M and 1×10-3, respectively. Conclusion: It could be concluded that rose bengal could be used to prevent mosquito bites and their associated diseases as an alternative to traditional insecticides and an eco-friendly larvicide.

Probit and Logit analysis: Multiple observations over time at various concentrations of biopesticide Metarhizium anisopliae strain

A study was done to assess the goodness of fit of the regression lines using the data of silkworm larvae (J12 x C12 race) killed by various concentrations of M. anisopliae and LC71 of Metarhizium. anisopliae at different time intervals (hr) applying probit and logit function. The data were transformed before analysis using probit and logit transformations of proportion kill and with and without a logarithmic transformation of predictors. Analysis showed that the LC50 value were 5.969×106, 6.000×106, 7.250 and 7.235 spores mL-1 for probit, logit, log-probit and log-logit, respectively. The LT50 values were 204.247, 204.381, 2.304 and 2.305 hr for probit, logit, log-probit and log-logit, respectively. Significant Chi-square value indicates the necessity of heterogeneity factor for correction of variances under all functions. Residual deviance values were lower at the log-probit (2.826 for concentration and 0.292 for time) and log-logit (2.406 for concentration and 0.440 for time) models with higher p-values (≥ 0.587) compared to probit and logit model. In our study, p-values was higher (p>0.05) with lower residual deviance in log transformed data which indicated that the log-probit and log-logit models could best fit to the mortality data of silkworm larvae when the both concentration and time were as predictors. Results indicated that the log-transformation of predictors would be best for describing the mortality values of insects by concentration of Metarhizium. anisopliae and under different time values. However, it requires more précised complete datasets and good knowledge of statistics of samples values along with the conversion of results of probit and logit analyses back to original units before coming into concrete application of these analytical inferences into practice.

Combining insect pathogenic fungi and a pheromone trap for sustainable management of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a key invasive pest of maize and other crops in Africa. Entomopathogenic fungi play an important role in regulating the immature stages of this invasive pest as opposed to synthetic pesticides that are hazardous to human, environment and biodiversity. To tackle the adult stage of the pest (the moth) and to improve on the application strategy of the fungal-based biopesticides, this study evaluated the effect of various entomopathogenic fungi isolates on S. frugiperda moths. Twenty-two isolates (16 Metarhizium anisopliae and 6 Beauveria bassiana) were screened in the laboratory to assess their pathogenicity and virulence against S. frugiperda moths. The compatibility of the most pathogenic isolates with S. frugiperda pheromone FALLTRACT lure, the horizontal transmission of the inoculum among S. frugiperda moths, and the effect on oviposition were also determined under laboratory conditions. All 22 fungal isolates screened were pathogenic to the moths, but the mortality varied significantly among the isolates (P < 0.0001) seven days post-treatment. Beauveria bassiana ICIPE 621 and M. anisopliae ICIPE 7 outperformed all the other isolates by causing 100% mortality of the moths with the lowest LT50 values of 3.6 ± 0.1 and 3.9 ± 0.0 days, respectively. Both isolates were also found compatible with FALLTRACT lure, as the lure had no effect on the conidial germination in the laboratory. Male and female moths were able to horizontally transmit conidia of both fungal isolates to untreated moths, causing high mortality of S. frugiperda in ‘donor’ and ‘recipient’ groups. In addition, the oviposition, hatchability of eggs and longevity of larvae were significantly affected on the fungal infected females. Although single moths still retained high conidial numbers 72 h post-inoculation, the number of conidia decreased with time. These results suggest that ICIPE 7 and ICIPE 621 could be used in combination with S. frugiperda pheromone in an autodissemination approach to suppress S. frugiperda population.