The biology and phenology of the citrus whitefly, Dialeurodes citri, on citrus in the Coastal Plain of Israel

The citrus whitefly, Dialeurodes citri (Ashmead) (Homoptera: Aleyrodidae) ( CWF), is a polyphagous citrus pest, originating in S. E. Asia, which was fi rst discovered in the Western Galilee region of Israel in 1975. The larval instars of CWF secrete honeydew, and the sooty mould fungus, which develops on the honeydew, causes damage to the tree and its fruit. In observations made in Israel between 1987 and 1991 CWF usually completed three generation s per year, although a small proportion of the population had two or four g enerations. From October to April a combination of shortened photoperiod an d reduced temperature arrest the development of CWF in the fourth larval in star. The average length of the life cycle from egg to adult emergence was 65 days in the first generation (April-June), 52 days in the second generat ion (July-August) and 8 months in the third generation (September-April). U nder laboratory conditions of L16: D8 and 25 degrees C, the mean developmen tal time was 54 days, and the duration of the egg, first larval instar, sec ond larval instar, third larval instar, fourth larval instar and putative p upa (red eyes) were 12.1, 6.5, 5.5, 7.6, 18, and 4.7 days, respectively. Ad ults prefer to lay their eggs on young, fully developed citrus leaves, but also oviposit on older leaves. The inner region and shaded sides of the tre e are preferred for oviposition.