DISTRIBUTION OF APPLE PROLIFERATION DISEASE IN ORCHARDS WITH INTEGRATED AND CONVENTIONAL PESTICIDE PROGRAMS

Authors:	G. Krczal, K. Bliefernicht
Keywords:	Apple proliferation/spread/insecticide programs
Abstract: In the south of Germany (Pfalz) an increased number of trees with early red fall coloration was observed in autumn 1989, a disease symptom that may be caused by the apple proliferation agent. In order to determine the percentage of infected trees, samples of all suspected trees in a number of orchards with integrated and conventional pesticide programs were examined with the DAPI-test. The investigation yielded the following results: There was an overall incidence of apple proliferation at about 3% (range of 0 to 12%), irrespective of the insecticide program applied. There is no strong correlation between early red fall coloration and disease incidence. Trees with red leaf symptom showed AP-infection from 0 to 100 %. There is indication that infestation level depends on the variety.
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