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DIE-BACK. 



Die-back manifests itself by a number of striking characters. The 

 foliage becomes very dark green, the vigorous growth remains angular 

 and immature and frequently becomes strongly recurved, and the tips 

 turn up slightly, forming S-shaped curves In the spring trees affected 

 with this disease start out a very vigorous growth, which may con- 

 tinue for several moaths. Finally a reddish brown resinous substance 

 exudes on the twigs, forming the so called die-back stain, which is very 

 characteristic, and they begin to die back This death of tissues may 

 include the entire new growth or only a portion of it. Under the bark 

 of the young limbs gum pockets form and burst out, causing large, 

 unsightly eruptions on the twigs. 



Larger gum pockets frequently form at the nodes, producing large 

 swellings. If a tree is badly affected no fruit is formed ; if moderately 

 affected an abundance of fruit sets, but the larger portion of this 

 turns to a lemon-yellow colour before half grown, becomes stained by the 

 characteristic reddish exudations like that occurring on the branches, 

 and prematurely falls. Fruit which hangs on the tree till nearly ripe 

 is large and coarse and is frequently stained. It usually splits and 

 falls before thoroughly ripe. The fruit on a slightly affected tree is 

 very large and coarse, with very thick, rough rind. Much of it is ren- 

 dered unsalable by the reddish die-back stain. It is very prone to split 

 and fall before mature. 



Frenching, or variegation of the foliage, frequently accompanies die- 

 back and seems to be a symptom of the disease. The very dark green 

 colouration which some growers believe to be an indication of a healthy 

 grove, may, on the contrary, denote a condition verging on die-back. 

 A lighter green would probably indicate better general health. 



DIE-BACK A DISEASE OF INDIGESTION. 



Die-back appears to be a form of indigestion, due to an overfed con- 

 dition of the plant. It occurs apparently wherever excessive quantities 

 of nitrogenous manures from organic sources are applied or become avail- 

 able to the plant. Trees near closets or barns or in barnyards almost 

 invariably have die-back. When chickens roost on a tree for any length 

 of time, so that the droppings fall on the soil beneath, the disease usually 

 results. Many cases are known to the writer where it has apparently 

 been caused by excessive applications of cotton-seed meal, blood and 

 bone, barn manure, etc. Indeed, all organic manures in excessive quan- 

 tities appear to give rise to it. If organic fertilizers are used they must 

 therefore be applied with considerable caution to avoid an excess. No 

 safe rule can be given as to the amount of manure that can be used with 

 safety ; this depends upon the size and condition of the tree, previous 

 treatment, and soil conditions. 



Whether the chemical manures, nitrate of soda and sulphate of am- 

 monia, will produce the disease if used in excessive quantities, is ques- 

 tionable. We have not been able to learn of any instance where this has 

 occurred. Several cases are known where nitrate of soda was used of 

 sufficient strength to cause the leaves to fall without producing any sign 

 of this disease. Frequently the method of cultivation has considerable 

 to do in causing die-back, excessive cultivation appearing to aggravate 

 it very greatly. 



