New infestation outbreaks of Panonychus ulmi Koch (Acari: Tetranychidae) in apple orchards of North-West Italy
Abstract: The fruit tree red spider mite, Panonychus ulmi, has been a major pest in almost all fruit growing regions of the world, due to the negative effects of chemical sprays on natural enemies, until integrated pest management became widespread. Indeed the reduction of insecticide applications allowed the biocoenosis of antagonists, to control the red spider mite. In cases of use of certain insecticides this mite again became a local problem. In 2003 and 2005 in North-West of Italy inexplicable spread of infestations of this mite both on apple and peach orchards has been recorded. Our studies conducted in 2006, 2007 and 2008 assessed that Panonychus ulmi Koch (Acari: Tetranychidae) is still the main species in the orchards of north-west Italy and Amblyseius andersoni (Acari: Phytoseiidae) is its main antagonist. Hypothesis of an involvement of grass chemical control in infestation outbreaks of red spider mite was not confirmed and, it seems that it can be excluded as a cause of red spider mite infestation outbreaks.