A serious epidemic of stolbur on celery

A 3-year study was carried out in a geographically and ecologically isolated area of north-east Italy with a long tradition in horticulture, where a severe epidemic of stolbur phytoplasma occurred. Among cultivated vegetables, celery was the most susceptible to the disease. In the farms surveyed, Convolvulus arvensis a natural host of the phytoplasma and the vector Hyalesthes obsoletus were plentiful. Groups of H. obsoletus individuals transmitted the pathogen to celery and grapevine under controlled conditions. Other species of insects, shown by PCR to host the phytoplasma, did not transmit it. The surveyed area is a closed ecological niche with high infection pressure and represents a primary example of how an epidemic of phytoplasma can develop among cultivated plants.