Investigation of biology, dynamism and distribution of cottony cushion scale, Icerya purchasi Maskell in Mazandaran province.

Cottony cushion scale, Icerya purchasi Maskell is one of the most important pests of citrus orchards in Mazandaran province and the east of Guilan province The samples were taken from 10cm of the end of twigs (30 samples in weekly samplings). The results indicated that the pest has 2 generations in a year. The first nymphal instars of the first generation emerge in the late of May and the population peak occurs in the late of June. In the second generation, the first nymphal instars emerge in September and the population peak occurs the late of September. The egg sacs were often observed in May and September. Population of the pest is high in intensive orchards especially Palestine sweet lemon cultivar. Different cultivars of citrus are hosts of cottony cushion scale. Cottony cushion scale occurs in Amlash(Kohneh gooyeh, Abbas govabar and Otaghvar), Kelachay(Hasanvareh and Reza mahaleh), Langroud(Leilakooh, Parshkooh and Malat), Chaboksar(Miandeh), Ramsar(Sefidtamashk, Sadatshahr and Katalom), Tonekabon(Khoram abad and Zangsha mahaleh), Chalous(Zavat), Nashtaroud (Dinarsara and Polsara),Abbas abad(Hasandeh) and Salman shahr(Danial) cities. Infested orchards in Sefidtamashk, Khoram abad,Hasanvareh ,Ghasem abad and Miandeh are more than other regions. The biology of cottony cushion scale I. purchasi was studied in natural conditions, in the west of Mazandaran province and also in laboratory conditions (75 and quot;b5% RH. and 25 and quot;b1 C and quot;a ).The results indicated that Eggs hatch into crawlers in 9 and 12 days in laboratory and natural conditions, respectively. The crawlers are red with black legs and antennae. They settle along leaf veins and begin to produce a cottony substance. The second instar nymph emerge from the white molt shell after 16 to 18 days. The amount of cottony substance increases with age. The third-instar scales have the long hairs grouped in tufts and emerge after 20 days. Third instar nymphs move to branches and trunks. The adults may be found on branches or on the trunks of trees. The adults are red to orange with black legs and antennae. Cottony cushion scale completes its life cycle in 75 days in summer. It takes 60 days in laboratory conditions. The pest has 2 generations in a year. The insect hibernates as second instar nymph and adult female under leaves. The average fecundity in the west and the east of Mazandaran province 645 and 450,respectively. The average fecundity in laboratory conditions is 410. The egg production takes almost 12 days in summer, whereas it takes almost 15 days in laboratory conditions.