Optimized timing of IPM treatments against pear psylla (Cacopsylla pyri) based on a temperature driven population dynamics model

Abstract: Pear suckers (Cacopsylla sp. or pear psylla) (Hemiptera, Psyllidae) are widely considered to be the most important pest in pear orchards. They are mostly feared by growers because of their secreted abundant honeydew colonized by sooty mould fungi causing blackening of leaves, shoots and fruits. Sustainable control of pear psylla relies on their natural suppression by beneficial arthropods and a well-tuned integration of crop protection treatments. However, population dynamics of pear psylla are complex with their presence in pear trees throughout the whole year in 4-5 consecutive generations in commercial pear growing in Northwestern Europe. Conversely, main beneficial arthropods like predatory bugs (Anthocoris sp.) and earwigs (Forficula auricularia L.) are only present at certain periods as active psyllid predators on pear shoots and foliage. In order to achieve a maximal control efficacy on the pear psylla population and a minimal side-effect on their natural enemies, we followed a modelling approach to optimize IPM treatment schedules. A temperature driven model forecasting the dynamics and populations structure (eggs/larvae/adults) of pear psylla was used to optimize timing of control sprays targeting a specific life stage of the pest. In addition, impact on beneficial populations was minimized by avoiding non-selective treatments on vulnerable life stages using a similar population dynamics forecasting modeling approach. This model-based strategy for an improved sustainable control of pear psylla was tested in multiple field trials. The outcomes of these field validation trials are presented and discussed, providing valuable insights in model driven integrated pest management in commercial fruit growing.