No. 6. DEPARTMENT OF AGRICULTURE. S71 



a good oxygen supply favor general decaj^ organisms. We know 

 that a fence post will usually rot because of the same conditions, 

 more rapidly near the surface of the ground than above or below. 

 1 am sure that in some cases winter injury is primarily responsible 

 for the trouble with the apple trees. In a few instances I have 

 found the blight bacterium present as the cause of the extensive 

 death of the bark ; and I have also found other organisms associated 

 with the trouble, such as the fungus of Black Kot, the wood rotting 

 Schizophyllum, and the root rotting Aimillaria. In the Far West, 

 some hold that arsenic injury to bark is responsible for a somewhat 

 similar, although apparently not identical condition. And there 

 are cases where imjH'oper painting of trunks has caused trouble. 

 But when all these things are considered, I am not satisfied in my 

 own mind that I can satisfactorily account for half of the so-called 

 Collar Kot that I have seen. 



Though we can not yet speak certainly about its causation, we 

 ought to take precautions against its possible spread. In hunting 

 borers in orchards affected with collar rot, free use should be made 

 of disinfecting solution on all wounds and tools. Close watch should 

 be kept for the first signs of the trouble, and the affected area cut 

 out as thoroughly as may be, lea\'ing the live bark with a smooth 

 edge for healing. The cut surface should be washed with bichloride 

 of mercury or strong lime-sulphur as a disinfectant, and the sur- 

 face painted with pure lead and oil paint or tar. When the ex- 

 posed surface is large, and above ground, a coating of grafting 

 wax will prevent drying out, and promote healing. Diseased trees 

 should be prevented from carrying a full crop of fruit, and atten- 

 tion should be paid to securing proper soil moisture and aeration 

 and fertilization. Judicious reduction of foliage by summer prun- 

 ing would doubtless be helpful. 



We come next to those constitutional disorders that we call 

 physiological diseases. They are not caused by organisms of any 

 sort ; they result from derangements of the normal y)hysiological 

 functions of the plant parts, usually due to unfavorable environ- 

 mental conditions. Our knowledge of them at present is meagre; 

 and from their nature control measures are unfortunately of limited 

 applicability. Such troubles are Fruit Pit (perhaps more usually 

 known as Baldwin Spot, although this term is also sometimes con- 

 fusingly applied to Fruit Spot mentioned above), Watery Core, 

 Watery Apex, Sun Scald, Sticky Skin, and probably Jonathan Spot. 

 Fruit Pit shows rather large, vagirely outlined, slightly depressed 

 spots, that suggest finger print bruises. Under these the flesh is 

 dead for some distance, and later the surface becomes dead and 

 l»rown. Frequently affected areas can be found in the interior of 

 the flesh. The cause is supposed to be lack of sufficient moisture at 

 certain periods in fruit development, especially sudden changes from 

 wet to very dry conditions. It may be that tillage methods can 

 be so developed as to equalize the soil water supply sufficiently to 

 reduce this trouble to a minimum. 



Watery Core and Watery Apex seem to be different forms of the 

 same trouble. Continued deficiency of water may cause the cell 

 sap to reach such high concentration as to kill the living substance, 

 and there is a consequent diffusion of sap into the small spaces 



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