Mosaik fleckigkeit, Chlorose und Stippenflecktigkeit bei Apfeln, Birnen und Quetten
Phytopath Zeitschr 8(3): 285-296
The bitter pit disease of apples is apparently a type of virus disease and virus chlorosis. Juice taken from bitter pitted apples of one var. was able to cause mosaic mottling on leaves of another healthy var. when introduced mechanically. A disease with symptoms similar to those caused by the mosaic on apple was noticed also on pear trees. The disease is characterized by a mottling of the leaf blade. On older fruit-bearing trees, chlorosis is the only visible symptom on the leaves, the severity varying greatly with var. and climatic conditions. The disease expresses itself frequently in a shedding of the newly set fruit, only a few specimens reaching maturity. These remaining fruits later have a speckled appearance. The specks are dark green and of various depths. It was demonstrated that the chlorosis and mosaic mottling of the leaves and the shedding of the young fruit are symptoms of the same disease. The development of mosaic on quince was again found to be very similar to that on apple and on pear. Differences in its development in the 3 cases were generally only noticeable with older trees, and then only to a slight degree. This striking similarity together with the fact that the virus coming from pear and quince was transmissible to apple led the author to conclude that it is one and the same virus which causes this disease (expressed as mosaic, chlorosis and stippling) in the 3 cases.