Biology, seasonal population fluctuation and distribution of the Cottony cushion scale Icerya purchasi Maskell (Hom: Margarodidae) in east of Mazandaran province, Iran

The cottony cushion scale Icerya purchasi Maskell is a polyphagous pest which has beendistributed all around the word including Iran. The pest attacks to citrus and many other plants. The biology of I. purchasi at laboratory conditions (21.7°C, 75 R. H. and 10:14 L:D) and its seasonal population fluctuations in two citrus orchards located in Sari (North of Iran) were studied during 2003 - 2005. Samples were taken weekly from 10 trees in each orchard. Three 10cm twigs were taken randomly from each tree in each sampling occasion and number of adults and nymphs were recorded in laboratory. The mean number of eggs per female was 295. 7 with incubation period of 9. 1 days. Developmental period of the 1st, 2nd and 3rd instars was 19.5, 26.5 and 56.2 days respectively. Adults were observed from April to March. Three peaks of nymphs occurred in July, November and February and three for adults in May, August and February. According to these data, it is estimated that I. purchasi overwinters in all stages specially the 2nd instar nymphs. The investigation showed that the cottony cushion scale distributed throughout the east of Mazandaran from Behshahr to Noor.