The pear psyllid (Psylla pyri) is one of the most important pests in pear orchards where it can inflict extensive economic damage.
When pear psyllids become active in spring, they first feed on young leaves and flowers. In summer they mainly feed on new shoots. Direct feeding damage such as growth inhibition and leaf malformation are less important than the secondary damage caused by excreted honeydew. Honeydew stains the fruit and branches black. This is a nightmare for many pear growers. In addition psyllids transmit viruses and weaken next season's flower buds. In this way not only the current harvest, but also next season's harvest can be in danger.
The pear psyllid hibernates as an adult. Early in the year this small pest becomes active. As soon as the average temperature is over 10° C for two successive days, mating takes place and the pear psyllid begins to lay its eggs. This usually takes place in early spring. In mid spring, the first larval stages are present in the crop. There are 5 larval stages and each year 3 to 4 generations of the pear psyllid develop. Climate plays an important role in the development rate. At an average temperature of 10° C, the pear psyllid takes almost 100 days to complete its life cycle. At an average temperature of 23° C, development takes only a month. Eggs are 0.3 mm long and change from white to yellow to orange. Larvae are orange-red to brown-black. As they age, larvae become less mobile and secrete more honeydew. After the 5th larval stage the pear psyllid sheds its skin and a 3mm, brown-black, winged adult is formed.