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Symptoms. — Die-back has probably more characteristic symptomg 

 than any known plant disease, principally among which are the 

 following : 



j|i>l. The ends of the very rapid growing shoots turn yellowish before 

 maturing, and finally become stained reddish brown in patches or 

 throughout. This appearance is caused by a deposit in the outer cells 

 of a reddiih-brown resin- like substance. This yellowing and staining 

 of the twigs, which is very general on the new growth all over the 

 tree, is followed by the dying back of the affected twigs for a short 

 distance, usually 3 to 6 inches. The reddish stain may occur on the 

 twigs back of the point to which they die, and, indeed, may spread in 

 irregular patches, more or less over the entire new growth. 



2. On the new growth (most frequently at the nodes, but sometimes 

 in the intern odes) there occur comparatively large swellings, caused by 

 gum pockets formed in the wood. These pockets frequently become 

 quite marked, 



3. Eruptions, caused by the bursting of the bark, very commonly 

 occur on new and old twigs. In such cases the tissue swells up, pro- 

 trudes from the rupture, and becomes stained by the reddish-brown, 

 resin-like exudation, which is so characteristic of the disease. These 

 eruptions are very numerous, and in badly affected trees many limbs, 

 from an inch in diameter down to the smallest, become thickly studded 

 with them. This character almost invariably accompanies the disease 

 and is present at all seasons of the year, so that it may probably be 

 regarded as the principal symptom. Trees may be slightly affected, 

 however, and not show this symptom. 



4. In diseased trees rapidly grown young shoots often droop in a 

 characteristic manner. After starting to push, the twigs gradually 

 bend downwards and the ends turn up a little, giving the twigs a 

 slightly S shaped curve. This however, is not always a symptom of 

 die-back, being occasionally seen in perfectly healthy trees. 



5. Young twigs frequently develop an abnormal number of buds in 

 the axils of the leaves, where, under normal conditions, only one or 

 two are formed. This over production of buds is often followed by a 

 gummy exudation at these points. Several of these buds from one 

 node may develop into branches, which in connection with the short 

 internodes, frequently give the new growth a somewhat fascicled ap- 

 pearance. This causes a dense foliage and after the new growth which 

 produces this fascicled appearance, has died back the tree takes om a 

 very regular appearance, as if it were clipped. This is very character- 

 istic of cases in the middle stage of the disease. In a later stage large 

 limbs die back, leaving around the trunk a dense growthof small water 

 aprouts with large leaves. These shoots in turn become stained with the 

 characteristic reddish-brown exudations and eruptions and finally die 

 back. In this stage of the disease, which is one of the last, the tree 

 presents a very ragged appearance, many of the large limbs being dead. 



6. The leaves on trees affected with die-back are rather larger and 

 generally longer and more pointed than those on healthy trees. This 

 symptom, however, is not very noticeable. 



7. The foliage of diseased trees is always a very dark green ; indeed 

 this colour, so much desired by some growers, indicates that the grove 

 is on the verge of showing the disease. 



