Pear psyllids, insects of the genus Cacopsylla, specialize in feeding on Pyrus tree species. The primary pear psyllid species affecting European pear orchards are Cacopsylla pyricola, Cacopsylla pyri, and Cacopsylla pyrisuga. These species exhibit varied life cycles that contribute to their impact on pear cultivation. C. pyrisuga is the only univoltine species, producing one generation per year, and alternates between deciduous and evergreen hosts. Adults migrate to pear orchards in spring to reproduce, laying eggs exclusively on Pyrus species, then die after mating and oviposition. Young psyllids develop into adults from April through June, emigrate to conifers, and return to pear orchards the following spring.
Conversely, C. pyricola and C. pyri are multivoltine species with multiple generations per year and does not necessarily alternate between hosts. They overwinter in a reproductive diapause as winterform morphotypes. At the end of winter, these winterforms lay eggs on pear trees, giving rise to summerforms, which can have four to six generations per season depending on the region and temperature.Pear psyllids cause significant damage to pear crops, including "pear russet" characterized by fruit markings from psyllid honeydew and sooty mold. Immature psyllids excrete large quantities of honeydew, leading to blotches or streaks on the pear fruit surface, resulting in downgraded harvests. Pear psyllids also vector "pear decline," a serious disease caused by a phytoplasma that infects the phloem of host plants, leading to severe declines in pear tree health. This disease is prevalent in North America, Europe, Africa, and Asia. Despite resistant rootstocks, 20-30% of pear psyllids in North America and Europe still carry the phytoplasma, with the highest infection rates in overwintered psyllids. Currently, no effective control agents or cures exist for phytoplasma diseases, making the control of insect vectors crucial. This thesis explores manipulating psyllid behavior with infochemicals and visual cues to reduce feeding and oviposition in pear orchards. The study focuses on the impact of host plant-borne volatiles, non-host odors, and visual cues on the behavior of C. pyricola, C. pyrisuga, and particularly C. pyri, as there is limited knowledge about the chemical ecology of pear psyllids. The study investigates the effect of visual cues on C. pyri's color preference to develop specific traps combined with attractive compounds. Choice assays with different LED wavelengths show that C. pyri prefers green LEDs (532 nm and 549 nm) over yellow, orange, and red LEDs. Field trials with newly developed sticky traps coated in transparent-colored PVC sheets matching the preferred LED wavelengths confirmed that green traps (525 to 537 nm) attracted significantly more pear psyllids than red or transparent traps. Besides, the number of bycatches of beneficial insects in the green traps was very low compared. These results highlight the importance of color in psyllid attraction for developing effective trapping strategies. Additionally, the study examines volatile organic compounds (VOCs) emitted by pear trees to identify signals influencing pear psyllid host plant preference. Electroantennography showed that female pear psyllids detect pear tree volatiles, influencing their olfactory-based preferences.