The effects of climatic conditions on seasonal population fluctuation of date palm scale Parlatoria blanchardi Targ. (Hem.: Dispididae)

Palatoria blanchardi Targ. is an important of date palm in Iran. The population was monitored monthly by leaf sampling during 4 years (2000-2004). Sample unit was 3 leaves that taken from 3 strata of the palm canopy of ten trees. Weather data (temperature and relative humidity) were obtained from Abadan meteorology station. Correlation analysis and sigmoid models including Monomolecular, Logistic, Gompertz, Weibull and Richard models were used to study the relationship between population density and weather parameters. Pest activities started in March and population increased by increasing of temperature and humidity. Result showed that there were three overlapping periods of activities in field. The first, second and third periods of activities started in April, September and December respectively. The first period was longest and the third period was shortest. There was significant correlation between population abundance and weather condition including temperature and relative humidity. The order of relative influences of climatic factors on seasonal population fluctuation showed that the effect of temperature was greater than the effect of relative humidity. The highest population occurred when temperature was between 16 º C and 24 º C and relative humidity was between 42 and 63 percent.