Management of pear decline caused by 'Candidatus Phytoplasma pyri' in Hungary

Pear decline caused by 'Candidatus Phytoplasma pyri' is a serious disease in Hungary. The disease up to now has occurred sporadically without causing very serious damages. Recently, several 4-5 years old intensive pear orchards in Eastern-Hungary were severely infected with a disease symptomatologically similar to pear decline (PD) caused by 'Ca. P. pyri'. The affected varieties were Abate Fetel, Williams and Conference grafted on quince C and BA29 rootstocks. To detect if 'Ca. P. pyri' was associated with this pear disease and with its putative vector (Cacopsylla pyri), diseased shoots and psyllas were tested with PCR. The amplified DNA products were digested with SspI and SfeI restriction enzymes. The results indicate that the likely vector of phytoplasma associated with PD in Hungary is C. pyri. In the last two years psyllas were collected every two weeks for PCR assays, and groups of 25 to 100 individuals were caged for 4 weeks on healthy pear seedlings. More than 40% of the investigated winterform psyllas were positive in PCR. The new first and second generations were much less infected. Shoot infections with 'Ca. P. pyri' were detected from the end of July. To obtain commercially acceptable fruits in Hungary, pear psylla must be controlled with insecticides. For psylla control oil and Vertimec are used in Hungary. This later chemical is absorbed into the leaf tissue and kill psyllids very efficiently. In field trials, it has provided 4-5 weeks of protection under normal growing conditions. A second Vertimec application was made just prior to a late June population increase. After this spray, egg and nymph populations were back down to negligible levels. Practically, it was possible to control pear decline by controlling the vector of the disease.