EGG-HARVESTING ALLOWS LARGE-SCALE REARING OF AMBLYSEIUS-FINLANDICUS (ACARI, PHYTOSEIIDAE) IN THE LABORATORY

An improved method to rear Amblyseius finlandicus (Oudemans) in the laboratory is described that allows large numbers to be produced. Mites developed faster and had a higher ovipositional rate when fed on pollen and reared on a bean (Phaseolus vulgaris L.) leaf substrate than when fed on pollen on an artificial arena. Two-spotted spider mites (Tetranychus urticae Koch) were an inferior food source for A. finlandicus mainly because of their profuse webbing. A. finlandicus was able to develop and reproduce on all 11 types of pollen tested although immature mortality was high on cedar (Cedrus sp.) pollen. Total number of mites increased almost 100-fold in three weeks on bean leaf substrate when eggs were collected and transferred (= egg-harvesting) in cotton tufts from the base colonies every two or three days to initiate new colonies. Only about a 13-fold population increase occurred when egg-harvesting was not employed, probably due to a combination of cannibalism and reduced fecundity. Egg-harvesting using cotton tufts is especially suitable for large scale rearing of species like A. finlandicus that are cannibalistic and/or lay fewer eggs with increasing population density. In addition, the phytoseiids Amblyseius reductus Wainstein and Anthoseius rhenanus (Oudemans) were reared successfully on pollen and spider mites using either leaf or artificial arenas. This is the first record of successful rearing of A. rhenanus in the laboratory and of A. reductus in the laboratory on pollen.