Morimoto, R. 1976 A study of the biological control of Comstock mealybugs, Pseudococcus comstocki Kuwana.. Review of Plant Protection Research 9: 72-89.

Notes: Pseudococcus comstocki (Kuw.) has become the pest most regularly occurring in apple and pear orchards in Japan because of the destruction of its natural enemies by the frequent application of organochlorine and organophosphorus insecticides. The author describes the results of studies since 1962 on methods of using natural enemies alternative to the normal one of releasing large numbers of beneficial insects at one time and allowing them to multiply naturally, since this multiplication does not occur in areas where chemicals are applied frequently. The best method appears to be to release parasites repeatedly for control over a short period only, as if the parasites were a 'biotic insecticide'. From a comparative study of nine species of natural enemies of P. comstocki (a list of which is given), it was concluded that the most suitable for the purpose was Pseudaphycus malinus Gah., which had a short oviposition period, attacked adults and immature stages of Pseudococcus comstocki but no other species, had good host-finding ability, and showed little interference between individuals of its own species. The parasites were released by pinning sheets of paper bearing parasitised mummified mealybugs produced in the laboratory to the fruit trees; about 2000 adult parasites emerged/sheet, and three sheets were usually required for each moderately infested apple tree and two sheets/pear tree. The best time for application of the sheets proved to be during the second and third nymphal instars of the pest in the spring; this method was found to control even heavy infestations in orchards if used for two successive seasons, and chemical applications could be reduced gradually from the third season onwards. Since Pseudaphycus malinus is very susceptible to chemical insecticides, these should not be applied within 10 days before or 15 days after releasing the parasite. Ants, especially Lasius niger (L.), that nest in infested fruit trees and tend Pseudococcus comstocki for its honeydew, were found to cover up the mealybugs with grains of earth and wood chips to prevent parasitism; if such ants are present, they must therefore be eradicated before the parasites are released.