APPENDIX. 



195 



often confused with the unfruitfulness resulting- from self-sterility, are (1) 

 heavy wood-growth, (2) the attack of fungi on the blossoms, (3) frosts, (4) un- 

 favorable weather during the blooming season. It should also be said that a 

 tree is not self-sterile when it does not blossom. This bulletin does not at- 

 tempt to tell why trees do not bloom, except that it is generally due to poor 

 management. The only thing which concerns us now is why trees which 

 blossom full do not set a reasonable amount of fruit. 



BLOSSOMS MAY DROP BECAUSE OF HEAVY WOOD-GROWTH. 



Young trees generally set little or no fruit the first few years, when they 

 are growing fast, although they may blossom full. With most varieties this 

 early dropping of the blossoms occurs only two or three sea- 

 sons, but Northern Spy and a few other varieties of apples 

 are often unfruitful ten to thirteen years from this cause. 

 Older trees may show the same results if stimulated too highly 

 with nitrogenous fertilizers. The logical remedy is to check 

 this excessive growth of wood by withholding nitrogen or by 

 putting the orchard into sod for a few years. 



The direct cause of this unfruitfulness is not known. The 

 stamens and pistils are usually well developed and pollen may 

 be produced in abundance. Since young trees drop their blos- 

 soms as badly in a mixed orchard, where other pollen is avail- 

 able, as when alone, the trouble probably lies more with the 

 pistils than with the pollen. 



Up to this limit of excessive growth there is a fairly con- 

 stant relation between the vigor of a tree and its productive- 

 ness. Lack of vigor causes much more unfruitfulness than 

 excessive vigor. If a tree is unhealthy or dying because of 

 poor nourishment, few of its blossoms are strong enough to 

 set fruit. The same results may follow if the tree is ex- 

 hausted by overbearing. 



BLOSSOMS MAY BE KILLED BY FUNGL 



If the weather is warm and wet in early spring, condi- 

 tions are favorable for the growth of fungi, and it sometimes 

 happens that fruit blossoms are "blasted" by the early growth 

 of these parasites. The common brown-rot fungus often kills 

 peach blossoms and may seriously decrease the setting of jn red fruit buds 

 fruit. It is probable that this fungus sometimes attacks ofKoya'^-pricot. 

 plum and cherry blossoms also. Apple and pear scab may kill the blossoms, 

 but often it kills the young fruits soon after they are set. Wherever spraying 

 is practiced faithfully, the killing of fruit blossoms by fungi need not occur, 

 especially if one thorough apiilication is made to the trees before the buds 

 open. The killing of pear blossoms by blight, however, cannot be prevented 

 by spraying. The blossoms on Kiefer and LeConte trees are especially liable 

 to be destroyed by the growth of blight microbes, which are carried from 

 flower to flower. The only way to prevent this loss is to have no blighted 

 trees in or near the orchard. 



72 — Winter in- 



