19 
_ of the fruits. The fruits developed are very prone to split and drop 
| prematurely. In the first stage of the disease either the stained fruit, 
_ or the stained, dying twigs must be present to determine with cer- 
| tainty the presence of the malady. Trees affected with the disease may 
_ grow for years and show only one of these characters; in other cases 
_ all the symptoms may be present, but to a very slight extent, so that 
_ eareful search must be made to find them. ‘As the disease progresses 
the brown staining of the fruit and twigs becomes more abundant 
and the dying back of the twigs occurs all over the tree; eruptions form 
on the young and old twigs; nodal swellings, due to the gum pockets, 
_ become very abundant; and the tree assumes the dense foliage and reg 
ular outline described above. In this stage of the disease many fruits 
set, but they usually turn yellow, become stained, split, and fall before 
maturity, only a few, if any, reaching full size. Soon the gum erup- 
| tions extend to the old limbs and these die back. The rank new growth 
becomes limited to the center of the tree; here branches grow luxu- 
) riantly for a time, only to become stained and die back later. The tree 
then assumes the ragged appearance described above (PL IV). In this 
stage no fruits set, and, indeed, the tree has become so sick that no 
flowers are formed. This disease is not accompanied by profuse bloom- 
ing, as is the case in blight; on the contrary, the tendency is to produce 
very little bloom. If the disease is allowed to continue unchecked the 
trees will ultimately cease to grow and finally die. 
Cause.—The cause of die-back is not yet thoroughly understood. 
For several years experiments have been under way to determine 
| whether various fertilizers may not produce the malady. Experiments 
have also been conducted in the laboratory with water cultures. In 
these experiments various forms of pure chemical manures were 
employed, the amounts used being under absolute control. From the 
| results of these experiments and from extensive field observations in 
| many parts of the State it seems highly probable that the disease is 
| caused by malnutrition. In most cases it is probably induced by exces- 
) Sive use of organic nitrogenous fertilizers. As before stated, trees near 
| stables, chicken houses, privies, etc., are very commonly affected by the 
i) disease. Heavy applications of cotton-seed meal, dried blood, ov other 
) highly nitrogenous organic fertilizers are frequently followed by the 
appearance of the trouble. Groves fertilized continuously with organic 
i fertilizers rich in nitrogen are usually more or less affected with the 
jmalady, depending upon the quantity of fertilizer used. Whether the 
chemical marures, such as nitrate of soda or sulphate of ammonia, when 
| used in excessive quantities, will finally produce the disease, is yet ques- 
}tionable, but all evidence indicates that they will not. In several 
experiments the excessive quantities of chemical manures used killed 
i the trees outright, although no signs of the disease appeared. 
A form of the disease known as soil die-back is very common and is 
very evidently independent of the action of any fertilizer. Certain 
