Fenpropathrin, pyridaphenthion and Mitran, representatives of major insecticide classes, inhibited the fecundity of females of the two‐spotted spider mite Tetranychus urticae exposed to their sublethal residues either before or after they had matured. Moreover, the developmental rate of immatures was evidently extended, while the longevity of females was markedly shortened.
Zusammenfassung
Zur Wirkung von subletalen Konzentrationen einiger Insektizide auf die Fekundität und die Entwicklung von Tetranychus urticae Koch (Acarina, Tetranychidae)
Stellvertretend für die wichtigsten Insektizidgruppen wurden Fenopropathrin, Pyridaphenthion und Mitran ausgewählt, um die Auswirkung einer subletalen Dosis auf Tetranychus urticae zu untersuchen. Unabhängig davon, ob T. urticae im Larven‐ oder Adultstadium mit einem Insektizid behandelt wurde, ging die Fekundität zurück. Weitere Auswirkungen waren eine längere Entwicklungsdauer im Larvenstadium und eine deutliche Verkürzung der Lebensdauer der Weibchen.
The effect of prey species and the different stages of prey on the predatory efficiency and biology of the phytoseiid mites, Amblyseius gossipi ELBADRY and Typhlodromus mangiferus sp.n. was studied. It was found that feeding either predator on Tetranychus cucurbitacearum (SAYED) promoted faster development and a higher rate of oviposition than rearing on the twospotted spider mite, T.urticae (KOCH). Different stages of both prey species also produced different responses in the biological activities of these predaceous mitcs.Mites of the family Phytoseiidae have received much attention because of their reproductive potential and ability to regulate phytophagous mite populations.In Egypt, several studies have revealed that phytoseiids are widely distributed on different plantations and have a considerable role in biological control of acarine pests (ELBADRY & ELBANHAWY, 1968 ; ELBARDY et al., 1968 ;RASMY & ELBANHAWY, 1974 ; RASMY, 1977).The present study has been conducted on the effect of different stages of prey as well as prey species, i.e. Tetranychus urticae (KOCH) and T.cucurbitacearum (SAVED) on the biological activities of 2 phytoseiid mites, Typhlodromus mangiferus sp.n. and Amblyseius gossipi ELBADRY. The afore mentioned phytophagous mites are the most common tetranychid mites infesting different crops in Egypt.
METHODSLeaf discs of sweet potato, 6,5 cm 2 in area, were used as a substrate for rearing the phytoseiid mites. The leaf discs were kept in Petri dishes on water-saturated cotton. Newly hatched larvae of these mites were confined singly on the leaf discs.In a 1st series of experiments, 3 groups of 20 larvae each, of the predatory mite T.mangiferus were reared on 3 different stages of T.urticae; eggs, larvae and nymphs.
Our study established the histopathlogical effect of different dosages malathion on the third larval instar of Chrysomya megacephala. The concentration of malathion increased gradually during the larval stages reaching the maximum concentration in the third instar larvae.The midgut of third larval instar was studied using transmission electron microscope. The most significant alterations were increasing damage to the larvae midgut including columnar prominent ,fat vacuoles, atrophied microvilli. These results indicate that malathion retard larval development.
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