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

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