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The predacious miteTyphlodromus pelargonicus El-Badry preyed on the different developmental stages of the two spotted spider miteTetranychus urticae Koch. The development was quickest and the number of prey consumed was highest when individuals were maintained on eggs compared with nymphs or adult female stages. The predator was able to develop and reproduce on the eriophyid miteEriophyes dioscoridis. Soliman & Abou-Awad, nymphs of the tobacco whiteflyBemisia tabaci (Genn.) and pollen grains ofPhoenix dactylifera andRicinus communis. The average number of eggs/♀/day was 1.4, 0.7, 1.2 and 0.9 on eriophyid, whitefly,Ph. dactylifera andR. communis respectively.

When females of the predacious mite Phytoseius finitimus Ribaga ingested dicofol and avermectin with the prey Eriophyes dioscoridis Soliman & Abou-Awad, the egg production sharply decreased after 120 h in the former, while continued at a lower rate in the later respectively. Dicofol was moderately toxic when ingested, although, avermectin caused mortality increased by increasing the time of exposure to treated prey. Few immatures reached maturity when fed on treated prey with dicofol, contrasting better development and less immature mortality on avermectin treated prey. Zusammenfassung Untersuchungen uber die Uberlebensrate, Reproduktion und Entwicklung der rauberischen Milbe, Phytoseius finitimus (Acari, Phytoseiidae) nach Futterung mit Dicofol- und Avermectin-behandelten Beutetieren Bei weiblichen Raubmilben von Phytoseius finitimus, die uber die Beutetiere (Eriophyes dioscoridis) Dicofol und Avermectin aufnahmen, konnte man beim ersten Praparat eine deutliche Abnahme der Eiproduktion ab 120stundiger Fraszeit feststellen. Beim zweiten Praparat blieb die Eiproduktion auch bei langerer Fraszeit erhalten, allerdings auf niedrigerem Niveau. Wahrend bei zunehmender Futterungszeit mit Avermectin-behandelten Beutetieren die Wirkung auf die Raubmilbe anstieg, zeigte Dicofol diesbezuglich unterschiedliche Wirkungen. Wenige Tiere erreichten das erwachsene Stadium, wenn sie wahrend ihrer Entwicklung mit Dicofol-behandelten Beutetieren gefuttert wurden, dagegen zeigte sich bei Avermectin eine vergleichsweise bessere Entwicklung und geringere Mortalitat wahrend der Entwicklung.

The gall mite Eriophyes dioscoridis Soliman & Abou-Awad was much more sensitive to avermectin than to fenvalerate. On the other hand, the predacious mite Phytoseius finitimus Ribaga was more tolerable to avermectin than to fenvalerate. Residues of avermectin showed a longer activity on E. dioscoridis and a shorter one on P. finitimus, whereas fenvalerate showed the opposite. Avermectin was able to penetrate through the roots and killed mites in galls on stem at concentrations as low as 0.063 ppm. None of the gall individuals suffered mortality with fenvalerate or control treatments.

Laboratory studies revealed that the acarid mite,Tyrophagus casei Oudemans is an adequate diet for development and reproduction of the stigmaeid mite,Agistemus exsertus Gonzalez. A combination of pollen grains of castor beanRicinus communis L. andT. casei is a sufficient plant-animal diet for the development and reproduction of the phytoseiid mite,Amblyseius gossipi Elbadry. When the later predator was restricted to such animal prey it developed to the adult stage, but females failed to lay eggs.