438 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



more elongated the apple. This elonga- 

 tion is seen in apples grown near large 

 bodies of water, which lower the temper- 

 ature at this season of the year, and in 

 seasons when the temperature is low, 

 owing to seasonal fluctuations. This In- 

 fluence is also seen in the form of apples 

 on different parts of the tree. Those in 

 the lower north portion are more elon- 

 gated than those from the warmer, upper 

 south portion. 



The attainment of the highest quality, 

 appearance and keeping quality is very 

 largely dependent on the warmth and 

 length of the growing season. This may 

 be measured with a fair degree of satis- 

 faction for the apple-growing regions of 

 North America by an average of the mean 

 temperatures for the months of March to 

 September inclusive. This is called the 

 mean summer temperature, and gives 

 temperatures ranging from 52 to 72 de- 

 grees. Factors determining the mean 

 summer temperature in a given orchard 

 are latitude, elevation, site and aspect, 

 soil, culture, prevailing winds and sun- 

 shine. 



A summer mean too low for a variety 

 will result in greater acidity, increased 

 insoluble solids, greater astringency, less 

 coloration, decreased size, scalding in 

 storage. 



A summer mean too high for a variety 

 results in uneven ripening, premature 

 dropping, rotting on the trees, poor keep- 

 ing quality, lack of flavor, mealiness, less 

 intense color, decreased size. 



The accompanying map (p. 436) shows 

 the distribution of the Ben Davis with the 

 northern limit of hardiness. 



APPLE DISEASES 



Alternaria Decay 



A decay of apples caused by a species of 

 Alternaria was first described from Colo- 

 rado by Longyear. This fungus entered 

 the apple at the blossom end and pro- 

 duced a cob-webby growth of mycelium 

 around the seeds. An Alternaria has 

 been found a number of times associated 

 with apple decays. This fungus usually 

 occurs on injured places such as the blos- 



som end injured by insects or broken 

 places in the skin. Associated with other 

 fungi this Alternaria forms a rather 

 thick, dry covering of mycelium over the 

 injured place. The fungus does not usual- 

 ly penetrate very deeply in such cases 

 but when ripe apples are inoculated from 

 pure cultures, it is found to be capable 

 of causing a complete decay. This fungus 

 alone has been reisolated a number of 

 times from decaying apples which had 

 been inoculated, thus proving that it 

 caused the decay. The apple decay Al- 

 ternaria differs sufficiently from a species 

 of the same genus which has been found 

 repeatedly on dead spots in apple leaves 

 and on dead parts of other plants so that 

 the two fungi can be distinguished readi- 

 ly in culture. The Alternaria from apple 

 leaves has not been found to cause de- 

 cay of the fruit upon inoculation. 



W. J. Morse 



Apple Tree Anthracnose 



Neofabraea malicorticis (Cordley) 

 Jackson 



H. S. J.\CKS0N 



The apple tree anthracnose is, with 

 the possible exception of the apple scab, 

 the most serious fungus disease with 

 which apple growers in the Northwest 

 have to deal. In general, the disease is 

 characterized by the formation of dark 

 colored sunken cankers in the bark of 

 the younger branches. These are most 

 abundant on branches under two or three 

 inches in diameter, but are not uncom- 

 monly found on branches of larger size. 



When they occur on older branches hav- 

 ing a thick bark, the cankers may not 

 always penetrate entirely to the wood. 

 Usually, however, the bark in the mature 

 cankers is found to be entirely dead, the 

 cambium destroyed and the sap wood dis- 

 colored to a limited extent. 



Deyelopmeut of tlie Cankers 



By close observation one may find the 

 young cankers beginning to develop 

 commonly early in November. It is 

 possible that in seasons of early fall rain 

 they may begin to appear much earlier. 



They begin their development as small 

 reddish brown spots in the bark. These 



