Survival,development and reproduction of Euseius finlandicus (Oudemans) (Acari: Phytoseiidae) fed on various kinds of food substances

Laboratory experiments were conducted to investigate the effect of diet on the biology of the phytoseiid mite, Euseius finlandicus (Oudemans). The predatory mite was able to develop and reproduce better when fed on the eriophyid mites, Aceria olivi (Zaher and Abou-Awad), Aceria dioscoridis (Soliman and Abou-Awad) and Cisaberoptus kenyae (Keifer). The developmental time of immature stages was the shortest when fed on motile stages of eriophyid mite species, followed by the spider mite, Tetranychus urticae Koch, and then pollen grains of Ricinus communis L., Phoenix dactylifera L. and Helianthus annuus L. Total egg production was highest when the predator fed on A. olivi, A. dioscoridis and C. kenyae recording at the rate of 51.0 50.0 and 43.84 eggs/female, respectively, but lowest on pollen grains, R. communis, P. dactylifera and H. annuus at the rate of 11.96, 5.3 and 2.0 eggs/female, respectively. But, the reproduction was nil on the tetranychid mite, T. urticae. Also, sex ratio of the progeny favoured females, when the predatory mite was reared on the eriophyid preys. E. finlandicus recorded the highest intrinsic rate of increase (r_m?=?0.31 females/female/day) when fed on A. dioscoridis, followed by (0.30 and 0.23 females/female/day) when fed on A. olivi and C. kenyae, respectively. In contrast, the lowest intrinsic rate of increase (r_m?=??0.31) was noted when fed on H. annuus pollen grains. The eriophyid mite, as a prey, recorded the shortest developmental time and highest oviposition rate of E. finlandicus.     

The antagonistic/synergistic effects of some medicinal plant essential oils,extracts and powders combined with Diatomaceous earth on red flour beetle,Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

Abstract

Red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is a prominent pest of stored products particularly cereal flour. Since resistance of this pest to common chemical insecticides is well documented, we were examined the synergistic/antagonistic interaction between Satureja hortensis L., Trachyspermum ammi L., Ziziphora tenuior L., Cuminum cyminum L. and Foeniculum vulgare Miller essential oils, ethanolic extracts and powders with Diatomaceous earth (DE) against T. castaneum adults under laboratory conditions at 27 ± 1 °C, 65 ± 5% RH and continuous darkness. We assayed repellency of ethanolic extracts and essential oils of mentioned plants on the pest. Results showed that DE had high toxicity to the pest. Plant essential oils and ethanolic extracts (except ziziphora) synergized the performance of DE. Nevertheless, plant powders elicited antagonistic effects (except ziziphora that exhibited synergistic effect). The most repellent EO and extract was cumin which exhibited mean repellency value on adult insect equivalent to 92.58 and 51.47%, respectively.     

Control of apple blue mould disease with Torulaspora delbrueckii in combination with Silicon

In this study, Torulaspora delbrueckii alone and in combination with silicon were evaluated for the control of apple blue mould disease caused by Penicillium expansum. In vitro, the antagonistic effects of T. delbrueckii in controlling mycelial growth of P. expansum on potato-dextrose-agar (PDA) in dual cultures, and the growth of P. expansum alone with cell-free metabolites and volatile components of T. delbrueckii were assayed. In vitro, to evaluate the direct effect of silicon on mycelial growth of pathogen, silicon at different concentrations (0.2, 0.4, 0.6, 1 and 2% (wt./vol.)) was added to PDA medium. Silicon at 0.6% (wt./vol.) and above concentrations completely inhibited the mycelial growth of P. expansum. However, it had no significant effect on population dynamics of yeast in vitro and in apple wounds. In vivo, silicon at 0.2 and 1% (wt./vol.) in combination with antagonistic yeast (1 × 10⁸ cell/ml) was a more effective approach to reduce the lesion diameter of blue mould decay of apples than the application of silicon or T. delbrueckii alone at 20 and 4°C, respectively.     

The effect of different salts (heavy metals) on the mycelium growth of Nematophagus fungi

Environmental pollution in addition to direct damage on plant growth, with the destruction of biological control agents, causes indirect damage to plants. The aim of this research was to study the effects of different concentrations (0, 500, 1000, 1500 and 2000 ppm) of heavy metals including Ag, Co, Cu, Fe, Hg, Mn, Pb and Zn on the mycelial growth and to assess the fungicidal or fungistatic effects of these salts on five Nematophagus fungi including Trichoderma harzianum (T8), Trichoderma virens (T21), Trichoderma hamatum (T9), Pochonia chlamydosporia var. chlamydosporia and Arthrobotrys oligospora. The results show that Ag, Co, Cu, Fe and Hg could stop the mycelium growth of all fungi, but Mn, Pb and Zn cannot inhibit the growth of these fungi completely. Among the first group, Hg and Cu stopped the growth of fungi even in 500 ppm. Among these metals that inhibit the growth of fungi, Cu has fungistatic effect and others have fungicide effect. The experiment was conducted in vitro condition, using potato dextrose agar (PDA) under complete randomised design with four replications. The data of mycelium growth were recorded at seven days after inoculation at 25 ± 2°C.     

Characterisation of Bacillus thuringiensis mutant highly producing melanin pigment and active against potato tuber moth

The bacteria Bacillus thuringiensis mutant is highly producing melanin pigment with increased ultra violet resistance and insecticidal activity against the potato tuber moth Phthorimaea operculella (Zeller). The results showed that the high decrease of crystal protein formation rate ranged from 100% (B.t.EMS-M2 and B.t.EMS-M6) to 91.82% (B.t.EMS-M9). The EMS–UV-induced mutants (B.t.EMS–UV-2h-1, B.t. EMS–UV-2h-2, B.t.EMS–UV-2h-3, B.t.EMS–UV-2h-5, B.t.EMS–UV-4h-1, B.t.EMS–UV-4h-3 and B.t.EMS–UV-6h-2) showed 100% decrease in the crystal protein formation. Results also showed that the growth rate of B. thuringiensis isolates was detected by measuring the light absorption of culture broth (BP media at pH 8) at the wavelength of 600 nm. The absorbance values of the standard melanin were 2.055 and 0.134 at wavelengths of 226.5 and 602 nm, respectively. This means that the maximum absorbance at wavelength was 226.5 nm, this result is similar to that of the synthetic melanin which has the absorbance of 226 nm. Our experiments detected that the pigment extracted from the mutant isolate B.t.EMS-M3 (EMS-induced mutant) gave the maximum value of absorbance (2.615) at wavelength of 227.5 nm that was similar to standard melanin which gave absorbance value about 2.055 at a wavelength of 226.5 nm. This may be due to the genetic alterations that happened to the mutant isolates due to the mutation by EMS or/and UV irradiation.     

Differentiation of the causal pathogen of onion white rot Sclerotium cepivorum isolates by using the APIZYM system

The APIZYM system of detection of enzymes was proven to be useful in the differentiation of 15 European and Egyptian isolates of S. cepivorum, the incitant of onion white rot. The tested isolates produced alkaline phosphatase, esterase (c4), esterase lipase (c8), leucine arylamidase, valinearylamidase, trypsine, α-chymatrypsin, acid phosphatase, naphthol-AS-B1-phosphohydrolase, ß-galactosidase, ß-glucutronidase, α-glucosidase, ß-glucosidase and N-acetyl-ß-glucosaminidase and did not produced lipase (c14), crystine arylamidase, trypsine, ß-glucutronidase, α-mannosidase and α-fucosidase. According to enzyme activity, isolates can be divided into four groups (G). The differences between groups were in the activity of the enzymes α-chymotrypsin and α-glucosidase. The tested European isolates and the Egyptian isolates No.6 of the pathogen were in G1 and G2; however the rest of the Egyptian isolates were in G3 and G4.     

Molecular characterization of European and Egyptian isolates of Sclerotium cepivorum,the incitant of onion white rot

Abstract

The tested European and Egyptian isolates of Sclerotium cepivorum were able to infect Giza 6 onion cultivar causing white rot disease with a different degrees of disease severity (ranging from sever to weak). The pattern of esterase isozymes produced by the tested isolates of the pathogen showed two main bands (arrows) which were different in density. Such differences in density of bands were present in every run and therefore appear to be indicators for differences among the tested isolates. Analysis of the protein pattern of the tested isolates of the pathogen indicated that the tested isolates had major proteins of a molecular weight of 52, 36, 23 and 16 kDa. Variation between isolates was detected by presence of bands of low molecular weight. Isolate Nos. 1, 4, 5, 7, 8, 9, 10 and 13 had a band at 17 kDa, whereas isolate Nos. 2, 3, 6, 11, 12, 14, and 15 had a band at 20 kDa. Using RAPD analysis to evaluate the genetic diversity of the tested isolates indicated that the tested field population of the pathogen was genetically heterogeneous but shared a number of common bands with molecular weights ranging from 650 to 2500 bp. Based on the DNA banding pattern the tested isolates can be assigned to seven genetically different groups. All tested isolates produced a band at 2500 bp except isolate No. 7. No correlation was exibited between patterns esterase isozmes, protein and DNA patterns of S. cepivorum isolates and their virulence or geographical origin.     

A review on digestive TAG-lipases of insects

Digestion in insects is a multi-step process to afford nutritional requirements of biological activities. The process starts with nervous stimuli and continues with biochemical activities of digestive enzymes as well as several pumps to digest and absorb the obtained molecules. Carbohydrases, lipases and proteases are the three main digestive enzymes involved in digestion process. Lipases seem to be very important not only for digestive role but also for esteratic activity so that some experts consider lipases as the Class 3 of general esterases. Digestive lipases divided into different groups based on their biological roles namely triacylglycerol lipases, phospholipases and two types of phosphatases. Briefly, triacylglycerol lipases (TAG-lipases) are the hydrolysing enzymes that affect the outer esteric links of triacylglycerols in ingested food. Phospholipases including PLA2 and PLA1 remove phosphatide fatty acids attached to the Position 2 and Position 1. Finally, Alkaline and acid phosphatases are the enzymes that hydrolyse phosphomonoesters under alkaline or acid conditions, respectively. In this review, presence and physiological role of digestive TAG-lipases are explained and their possible importance will be discussed in insect.     

Activity of digestive proteinases and carbohydrases in the alimentary tract of the fig leaf roller,Choreutis nemorana Hübner (Lepidoptera: Choreutidae)

.The fig leaf roller or Fig-tree Skeletoniser, Choreutis nemorana (Lep.: Choreutidae), is a destructive pest of fig trees found in some fig-growing areas of Iran. The larvae feed on the upper level of leaves, near the main vein. In this study, digestive carbohydrases including α-glucosidase, β-glucosidase, α-galactosidase, β-galactosidase and proteinases including trypsin, chymotrypsin and elastase were investigated. The results showed that the carbohydrases were present in the alimentary tracts of the pest. Optimum pH for α-glucosidase and β-glucosidase activity was at pH 6.0 and 7.0, respectively. Maximum activity of α-galactosidase and β-galactosidase occurred at pH 6.0. Total proteolitic activity against the substrate azocasein was optimally occurred at pH 10.0. The greatest activity of trypsin, chymotrypsin and elastase was determined at pH 10.0, 11.0 and 11.0, respectively. Zymogram analyses using nitrocellulose membrane revealed two trypsin isoforms in which one of them was completely inhibited by Soybean Kunitz inhibitor and the other was notably inhibited.