English: The insect of the photo, Cacopsylla pruni is the natural vector of the phytoplasma, European stone fruit yellows phytoplasma (ESFY), which causes the yellow rot of the stone fruit.

Phytoplasma transmission occurs through the insect that feeds by sucking the phloem sap of the Prunus spp plants. Cacopsylla pruni takes phytoplasma during feeding bites on infected plants, becoming in turn infectious a few weeks after acquisition. C. pruni makes only one generation a year and winters as an adult. At the end of winter the re-immigrant adults go to the primary host (preferably blackthorn) on which they lay the eggs of the new generation. The juvenile forms develop in about three weeks to then give rise to the adults of the year who migrate to the wintering sites.

The juvenile forms that feed on an infected host, become in their turn already infectious, but it seems that they are mainly re-immigrant adults at the end of winter to have an important role in the epidemiology of the disease. (Macrophotography of the insect, insect size 4 mm.)