Laboratory, semi-field and field studies to evaluate the effect of pesticides on psyllids

Abstract: Cacopsylla pyri and C. melanoneura are considered important pests for pear and appleorchards in north Italy: the first caused direct damages on pear plants while the second isinvolved in transmission of apple proliferation phytoplasma. Every year several insecticides arerequired in order to control these psyllids. Data obtained from laboratory, semi-field bioassaysand field trials are important to develop new IPM strategies. The present work reports threemethods to evaluate the effect of pesticides on psyllids. A baseline was determined for C. pyri.The used method consisted in treating pear leaves by immersion into pesticide solutions, andrearing larvae of C. pyri on holding cells. The mortality of psyllids was assessed after 72 hours.The efficacy and the persistence of pesticides were then evaluated by semi-field bioassays.Overwintering adults and young instars of C. melanoneura were put on treated potted appleplants, which were isolated with cloth cages, at three different timing (1 hour, 7 and 14 days afterthe pesticide treatment). Adult survival was recorded after 1, 3 and 7 days after their exposure tothe pesticide, while young instar survival was recorded 7 days after they were placed on plants.Finally pesticides were evaluated in field trials to assess both efficacy and side-effects. Theexperimental design was based on randomized blocks in a commercial apple orchard. Beatingmethod was used to assess the overwintering adult survival of C. melanoneura, while samples ofshoots and leaves were collected to count the number of eggs and young instars of psyllids and toassess the presence of beneficials.