Overwintering of the San Jose scale on stone fruit in Northern Italy

A monitoring programme was carried out in Emilia-Romagna during winter 1998-99 to establish the developmental stage of overwintering Quadraspidiotus perniciosus (Comstock) (Homoptera: Diaspididae) specimens in Northern Italy, mainly on stone fruit. Some stone fruit orchards and one pear orchard (used for comparison) were sampled. Samples were collected at the end of the autumn and three times during winter. Alive San Jose scale specimens were removed and slide mounted. Microscopic observations were conducted to asses developmental stage and stylet development. According to data collected, the most of specimens spend the greatest part of the winter in the first stage. Only at the end of the winter specimens begins to develop, quite quickly towards the second and adult stage. No significant differences have been observed between the different crops. Data on the phenology of this pest are very useful in choosing control strategies mainly based on IGR application during winter.