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  • Author or Editor: H. HUSSEIN x
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Influence of various prey stages of the pest Tetranychus urticae Koch on survival, development, and reproduction as well as the life table parameters of the predacious mite Neoseiulus barkeri (Hughes) was studied under laboratory conditions. Neoseiulus barkeri females lived shorter (36.31 days versus 45.00), had a higher total fecundity (64.81 eggs female−1 versus 53.81 eggs female−1) and a higher daily fecundity rate (2.76 eggs female−1 day−1 versus 1.78 eggs female−1 day−1), and exhibited a higher intrinsic rate of increase (0.339 individuals female−1 day−1 versus 0.226 individuals female−1 day−1) and shorter generation time (11.60 days versus 15.70 days), at 28–30 °C, 70–75% RH under continuous fluorescent light, when reared on a diet of larvae rather than a diet on mixed nymph stages of T. urticae on raspberry leaf disks. The sex ratio of the progeny was strongly female biased recorded when female of N. barkeri fed on larvae and nymphs of T. urticae. The adult female of N. barkeri consumed daily an average of 25.0 larvae versus 82.0 eggs (24–48-h old) of T. urticae during its life cycle, while it was increased to 48.6 larvae versus 80.5 eggs (24–48-h old) daily during the adult stage. Neoseiulus barkeri failed to develop beyond the protonymphal stage when the predator offered eggs (0–24-h old) of T. urticae as food. Larvae of T. urticae proved to be the most favorable stage of T. urticae for N. barkeri, while the eggs (24–48-h old) were the least.

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The direct toxicity of three essential oils to females of the two spotted spider mite, Tetranychus urticae Koch, was tested in the laboratory. Wheat germ oil (Triticum vulgare Vill) was the most toxic essential oil to females of T. urticae, while clove oil (Eugenia caryophyllata Thumberg) was the least toxic one (LC50=0.995 and 2.82%, LC90=3.08 and 16.66%), respectively. Leaf discs treated with increasing concentrations of eucalyptus (Eucalyptus glabulus Labill.) and wheat germ oils showed a high percentage of repellency (90–100%), respectively. The oviposition deterrent indices (ODI) of eucalyptus and wheat germ oils were ranged (22–100) for T. urticae at concentration (1–4%), while this value was between (5–35%) in case of clove oil at the same above concentrations. Females of T. urticae suffered a significantly depression in reproduction when fed on painted kidney bean leaves with (1–4%) concentrations of each oil used in our studies. In contrast, at 0.25 and 0.5% concentrations, no significant differences was recorded between the total number of eggs deposited on treated leaves and control ones. Also, a high percentage of T. urticae mortality was recorded for wheat germ and clove oils during 10 days.

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The relationships between the predatory mites, Typhlodromus negevi Swirski and Amitai and Typhlodromips swirskii (Athias-Henriot) (both Acari: Phytoseiidae), and their prey, tobacco whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) were investigated to determine the effects of predation on intra-guild or extra-guild prey and predator preference. Life cycle characteristics of both predatory mites were measured when fed eggs and larvae of the other predator species and compared to data obtained when the predators were fed whitefly eggs. In addition, choice tests were conducted to determine if the predators had a preference for different prey/stage or not.Typhlodromips swirskii appears to be an important intra-guild predator on T. negevi juveniles because of a high predation rate and a preference for T. negevi eggs (intra-guild prey) over whitefly eggs (extra-guild prey) when offer a choice test. Typhlodromus negevi is also an intra-guild predator of T. swirskii juveniles; it has a lower predation rate than T. swirskii. Typhlodromips swirskii had a higher predation rate on B. tabaci eggs (extra-guild prey) than on T. negevi juveniles (intra-guild prey).Extra-guild prey was an equally good or better food source than intra-guild prey/stages for both predators, based on high oviposition rates and fast development times.The results of this study indicate a potential for mutual interactions between T. swirskii and T. negevi when used together in biological control of whitefly.

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Abstract  

A well performance Electrolytic Controlled Etching (ECE) unit has been designed and constructed in our laboratory. Low electric field strength of few volts and a 2 kHz wave signals has been applied across the electrodes that confined the 9 and 12 μm thick PET foils in the ECE unit. PET foils were exposed to fission fragments (FFS) using 252Cf source. The dependence of different measurable parameters such as FFS fluence (Φ), applied voltage (V), etching temperature (T) and etching concentration (C) on both track etch rate (V T) and breakthrough time (T B) have extensively been studied using the FFS-irradiated PET foils. Various empirical relationships connecting the results of the present work have been extracted. Moreover, the constructed ECE technique has proven to be an encouraged time saving method in the development of trusting measurements comparing with others that might involve expensive sophisticated tools.

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Abstract  

The formation of cationic astatine /I/-coordination compounds with selenium-containing neutral ligands is described. The detection of compound formation and first physico-chemical data on the characterization of this new group of At/I/-compounds were obtained by investigation of their electromigration behaviour in free electrolytes. Se-donors coordinate more strongly to At/I/ than ligands containing carbamide and thiocarbamide. This fact is proved by electromigrational studies on the exchange of N,N-ethyleneselenocarbamide, respectively N,N-ethylenethiocarbamide with iodide.

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The biology of Agistemus exsertus Gonzalez was studied to determine the suitability of different phytoseiid eggs as prey. The development was faster and reproduction was higher when A. exsertus fed on eggs of Amblyseius lindquisti Schuster and Pritchard, Neoseiulus cucumeris (Oudemans) and Amblyseius zaheri Yousef and El borolossy (6.57 days and 111.5 eggs; 6.71 days and 110.1 eggs and 6.93 days and 101.0 eggs) than that of Euseius scutalis Athias-Henriot, Neoseiulus barkeri (Hughes) and Amblyseius swiriskii Athias-Henriot (8.6 days and 63.1 eggs; 7.29 days and 52.0 eggs and 7.87 days and 37.7 eggs), respectively. A. exsertus consumed daily more N. barkeri and A. zaheri eggs (4.63 and 3.85) than other phytoseiid eggs, respectively. Deits of A. lindquisti, N. cucumeris and E. scutalis (eggs) provided the greatest female longevity and the least was in case of N. barkeri.

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Abstract  

The ion mobilities of [211At] At(I) in dependence on thiourea (tu) concentration, iodide concentration and a mixture of both ligands were measured by the electromigration method in free electrolytes. An equilibrium model was developed for the characterization of electromigration curves which permitted the calculation of stability constants and ion mobilities of the complexes [AtI], [AtI2], [Attu]+, [Attu2]+ and [AtItu] existing in these solutions. Ethanol and water served as solvents. The temperature was 298 K and the ionic strength was about 0.05 mol/dm3.

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Abstract  

The total mass attenuation coefficients, partial interaction and the effective atomic numbers (Zeff) of glass system (80−x)B2O3–10Al2O3–10SiO2xCaF2 (where x = 5, 10, 20, 25, 30, 35 and 40 mol %) have been calculated at photon energies 0.662 and 1.25 MeV using the WinXCom software on the basis of mixture rule. Results indicated that the total mass attenuation coefficients showed a decrease with increasing the CaF2 concentration, due to a decrease in Compton scattering probability, which gave a dominant contribution to the total mass attenuation coefficients for the studied glass samples at both energies. However, the photoelectric absorption and coherent scattering showed an increase with increasing the CaF2, concentrations at same energies. For a comparison, the total mass attenuation coefficients of the glass system had lower values at the energy 1.25 MeV than that at 0.662 MeV. Zeff was found to increase linearly with the increase of CaF2 concentrations. It was concluded that low CaF2 concentrations in glass system, under study, have Zeff close to that of human tissue and have higher total absorption coefficients at energy of 0.662 MeV than that at 1.25 MeV. These results are very useful in designing gamma radiation detectors using thermoluminescence technique. Therefore, it is recommended to use low CaF2 concentration of our glass system as good gamma detectors at energy of 1.25 MeV.

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O'Regan fixed point theorem is used to establish an existence result for the fractional order integral equation x(t) = g(t)+ ?Ia f(.,x(.))(t), t?[0,1], a ? 0, where the vector-valued function is nonlinear weakly-weakly continuous. Moreover, existence of weak solutions to the Cauchy problem  dx/dt = f(t, x (t)), t ? [0,1], x(0) = x0, is obtained as a corollary.

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Two parts of the plant Capparis aegyptia, leaves and fruits, were extracted successfully with 4 different solvents. These solvents namely n-hexane, diethyl ether, ethyl acetate and ethanol. These extracts were tested for their toxicity against eggs and adult females of the two-spotted spider mite, Tetranychus urticae Koch. Extracts of both parts of the plant, prepared from various solvents were affected the behavior, toxicity and fecundity of females under laboratory conditions. Ethyl acetate extract of leaves and fruits was the most potent extract tested against eggs and adult females of T. urticae. In contrast, ethanol extract of fruits was the least effective extract against both tested stages. The egg stage was less susceptible to most different extracts of both parts of C. aegyptia. Leaf discs treated with LC50 concentration of various extracts showed a high percentage of repellency in case of ethanol extract from leaves and fruits (86.67 and 96.42%), respectively. Treated females with LC50 concentration of different extracts showed a higher remarkable percentage of mortality as well as a reduction in the total number of eggs laid during 15 days with fruit extracts than that with leaves extract.

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