ON THE GEOGRAPHIC-DISTRIBUTION AND PREVALENCE OF THE APPLE PROLIFERATION PHYTOPLASMA IN LOW-INTENSITY ORCHARDS IN GERMANY

DAPI fluorescence microscopy, PCR amplification, and visual symptom as sessment were used to examine the geographic distribution of the apple proliferation phytoplasma in Germany. Emphasis was given to trees nev er or rarely treated with insecticides and grown in low-intensity orch ards. The survey revealed that the infested area extents further north than previously thought and that the northern range of distribution r uns from Osnabruck to Dresden. Another finding is that in large areas of Germany a high percentage of trees grown in low-intensity orchards is infected. This distribution range is considerably larger than the a rea where the disease usually is of economic importance. Thus, it: wou ld appear that the pathogen is much more prevalent in low-intensity or chards for juice and cider production than in high-intensity orchards. Possible reasons For these differences are discussed.