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Biological parameters of the onion thrips, Thrips tabaci Lindeman were studied on the following onion (Allium cepa L.) cultivars: Nasik Red Plus N-53, Onion Dr-301 (Krishna), Onion White, and Nasik Red, at 25±1oC and 65±5% RH. Signifi cant (p < 0.05) diff erences were found in the life stages and fertility life tables on diff erent cultivars except in the pupal stages. More information about the biological parameters of T. tabaci on onion cultivars can help in designing Integrated Pest Management programs for onion thrips.
The wettable powder was prepared on the basis of aerial conidia of two isolates of the entomopathognic fungus, Beauveria bassiana. Viability and pathogenicity of conidia products were evaluated against the second-instar larva of Thrips tabaci in four cases; Conidial-product Maintained in Refrigerator (CMR), Conidial-product Maintained in Laboratory (CML), New Formulated Conidia (NFC) and New Conidia without formulation (NC). Analysis of corrected seven-day total mortality data revealed that there were significant differences among these product-cases in their pathogenicity to thrips larvae. Recorded mortality rates for CMR, CML, NFC and NC showed that the pathogenicity of CML was lower compared to three other cases for both isolates. In the next step, inorganic salts (MgCl2, NH4PO4, KH2PO4, MgSO4 and NaCl) were added at a rate of 0.1 M into the both CMR and CML products. Bioassay results indicated that caused total mortality of thrips larvae increased with adding of salts. Our results showed that applied carriers and salts have positively effected preserving of conidia viability and pathogenicity to the second-instar larva of the onion thrips.
Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a major pest of greenhouse crops in Iran. It is one of the major limiting factors affecting yield of cucumber. A study on the biology of this pest was carried out in laboratory condition (25±1°C, 70±5% RH and 16:8 h (L: D) photoperiod) on cucumber (var. Soltan) in 2007. This survey showed that T. tabaci completed the life cycle from 18 to 21 days. Duration of life cycle including egg, L1, L2, prepupa, pupa and adult was 2.82±1.33, 1.95±1.42, 4.12±0.92, 1.03±1.44, 1.97±0.91 and 14.4±3.13 days. Females could produce about 26.82±5.56 eggs. Thrips sex ratio progeny revealed no presence of males, since only females emerged. Knowledge on the biology of this insect pest would contribute to a better understanding of the relationships between the crop and the environment, and knowledge on this insect pest biology would allow establishing control strategies in a future integrated pest management program (IPM).
Studies on the relative toxicity of different bio-rational insecticides against second instar larvae and adults of onion thrips, Thrips tabaci were carried out on Experimental Farm and in the laboratory, Faculty of Agriculture, University of Suez Canal. Eight insecticides Dipel 2x, BioFly, Agrin, BioGuard, Spinosad, Neemix, Mectin and Match were all evaluated for their relative toxicity towards T. tabaci with recommended dose, half of recommended dose and quarter of recommended dose in the laboratory and only recommended dose under field conditions. Spinosad was the most toxic among the tested insecticides followed by Mectin, Match and Agrin when used against thrips adults. The respective values of LC50 of those insecticides were 0.048 cm/l, 0.070 cm/l,0.079 cm/l and 0.137 g/l. Also, Spinosad was the most effective insecticide against second instar larvae followed descendingly by: Agrin, Match and Dipel 2x. Toxicity index values at LC50 level show such superior efficiency of Spinosad (100%) when applied against adults and second instar larvae of onion thrips under laboratory conditions. All insecticides under field conditions caused reduction of infestations of thrips. For the residual effect post application, all insecticides gave significant reductions in thrips numbers at the 21 day post treatment except for: Agrin and Match. Spinosad, Mectin, Neemix and BioFly gave the best control and continued to suppress thrips populations till 21 days after treatment. Spinosad was non harmful and Dipel 2x, Agrin were slightly harmful, BioGuard was significantly harmful whereas BioFly, Match and Mectin were very harmful to Orius albidipennis.
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