الفهرس 
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Abstract
The present study was conducted to evaluate the insecticidal efficiency and safety of zinc oxide and hydrophilic silica(NPs) against the mites Tyrophagus putrescentiae (T. putrescentiae),Caloglyphus berlesei (C. berlesei) on wheat flour and the insects Tribolium castaneum (T. castaneum) on wheat flour &Sitophilus oryzae (S. oryzae) on wheat grains and Callosobruchus maculatus (C. maculatus) on cowpea seeds. The results showed that, both zinc oxide (NPs) and hydrophilic silica (NPs) exhibited a significant toxic effect (P<0.5) against T. putrescentiae, C. berlesei, S. oryzae, C. maculatus at highest level while T. castaneum showed high resistance against the two tested materials. At the end of the experiment, mortality percentage of T. putrescentiae, C. berlesei, S. oryzae, C. maculatus and T. castaneum recorded 100, 100, 100 , 88.3and 38.3, respectively at the highest level used for each pest (1.5, 1.5, 2.5,0.6and 8) g/ kg of zinc oxide (NPs), respectively while for hydrophilic silica (NPs), mortality percentage of T. putrescentiae, C. berlesei, S. oryzae and C. maculatus and T. castaneum approached 100,100, 98.3, 81.6, and 58.3%, respectively at the highest level used for each pest (1. 1. 2. 0.3 and 8) g/ kg of hydrophilic silica (NPs), respectively. Both tested materials caused high reduction percentage in F1 progeny with C. maculatusand S.oryzae. As mentioned above T. castaneum was more resistant thus both tested materials caused slight reduction percentage in F1 progeny with T.casteneum and hence this insect excluded from the next experiments. As hydrophilic silica (NPs) is more effective than zinc oxide (NPs) in protecting wheat flour, wheat grains and cowpea seeds, so the residual toxicity experiment was carried out with hydrophilic silica only according to LC90(0.4 g/kg) on wheat and cowpea which tested for six months storage against adults of S. oryzae and C. maculatus, respectively and showed that C.maculatus was more sensitive than S. oryzae. In general, data indicated that, by Abbot’s method up to the third month (in wheat) and the fourth month (in cowpea) the mortality percentage was more or less 100 % after that the mortality percentage decreased down so it recorded 83.3, 63.3 and 35% for S. oryzae at 4th, 5th& 6th months, respectively. Meanwhile this percentage was 96.6, 78.3 and 63.3% for C. maculatus at 4th, 5th& 6th months, respectively. One exciting result from these experiments is that no fresh insect infestation is found in hydrophilic silica (NPs)-treated stored wheat and cowpea even up to 3 & 4 storage months respectively. Whereas, the decrease in the mortality percentage after three months (in case of wheat) and four months (in case of cowpea) could be attributed to the decline of efficacy of the used material(0.4 g/kg) of hydrophilic silica. In this study the components of wheat grains and cowpea seeds (moisture contents, crude protein, crude fat, total ash and total carbohydrates) of untreated and treated samples with LC90 of hydrophilic silica (NPs) after 6 months storage was carried out and results showed slight differences between the components of treated and untreated wheat and cowpea samples;either unchanged, increased or decreased. In this study, the following parameters were determined in wheat only as mentioned previously; it is the more economic crop.A simple, rapid and sensitive germination experiment in Petri dishes was conducted to evaluate the phytotoxicity of hydrophilic silica (NPs) on the stored grains. Germination percentage of wheat seeds stored for 6 months after treatment with LC90 of hydrophilic silica (NPs) recorded 100% in treated and 90% in untreated wheat seeds. Meanwhile, shoot and root length and root/shoot ratio as well as, the vigor index and pigments content (chlorophyll a, chlorophyll b, chlorophyll a + b, carotenoids)of treated wheat was slightly affectedcomparing with untreated wheat. Silicon element was estimated in wheat seedlings; untreated and treated with hydrophilic silica (NP) and stored for six months. The results reported the accumulation of silicon by treated seeds, so seedlings treated with hydrophilic silica (NPs) contained 5.15 % silicon in wheat grains while untreated seedlings contained 2.5% silicon. The histopathological examination of the male mice livers showed infiltration of inflammatory cells, hepatic architecture with binucleated hepatocytes, congested central veins were frequently seen with few mononuclear cells adherent to its endothelial lining and congested dilated portal venules were also observed in focal areas, hemorrhage (an escape of blood from a ruptured blood vessel)and infiltration of lymphocytes marginated chromatin in some nuclei. Histopathological assessment of the lung showed normal histoarchitecture and no difference in alveolar septa, bronchiolar and epithelium of the treated and untreated animals. The mechanism of nanoparticles phytotoxicity remains unclear. It was generally reported to be related to the NP species, test plants, concentration, chemical composion, surface modification and particle size.The toxicity symptoms generated by NPs must be investigated at the molecular level to better understand optimal methods for synthesis of NPs that would be more efficient for plant growth and developmentas well as safety on all living beings.