Transmission of pear decline by using naturally infected Cacopsylla pyri L.

The spread of pear decline (PD) disease in an orchard in northeastern Italy and the role of the vector Cacopsylla pyri (L.) in the spread of the disease were investigated. From 1993 to 1995, about 90% of pear trees showed symptoms like those of PD. Using the DAPI technique, the presence of phytoplasmas in stems and roots of the affected trees was demonstrated. Every month, from May to October, 1995, C. pyri adults were collected from the orchard and then tested for phytoplasma by exposure to pear seedlings. Every month a group of 200 insects was tested on six pear seedlings. In January, 1996 after an adequate winter chilling period, the inoculated test plants were transferred to a greenhouse under controlled environmental conditions. Five months later, symptoms referable of PD were observed on three out of 36 inoculated pear seedlings. All three symptomatic plants were inoculated in July. Using the DAPI technique and PCR analyses the three symptomatic pear seedlings were found to be PD infected; no phytoplasmas were detected in the inoculated asymptomatic test plants or in the negative controls.