DISEASES OF CULTIVATED PLANTS 523 



The rind of die-back fruit frequently shows a great increase in. 

 thickness, and the fruit as a whole is coarse to the feel. This is sup- 

 posed to be due to a too rapid growth of the fruit arising from nitro- 

 gen stimulation. (Fla. E. S. B. 108.) 



Fruit that is severely affected with die-back will show a collec- 

 tion of a clear to brownish colored gum in the angles of the segments 

 next to the pith. This is conclusive evidence of the identity of the 

 disease, as this form of gumming is only known- to occur in fruits 

 affected with die-back. The fruit on a tree severely affected with 

 die-back is quite likely to become marked and to fall early. The 

 fruit that remains on the tree will color and ripen prematurely, and 

 is especially subject to splitting. The line of splitting usually de- 

 velops in the discolored patches. Die-back fruit is for the most part 

 insipid. It is unfit for shipping on account of the conspicuous 

 markings. The marking on the fruit is usually not accompanied 

 by any other disease that would confuse its identity. 



The safest treatment for die-back consists of the removal of the 

 conditions that are aggravating the disease, and the development of 

 more favorable conditions for the growth of the tree. If the disease 

 has arisen from the feeding of too much ammonia from organic 

 sources, such as dried blood, cottonseed meal, stable manure, and 

 others, this practice should be discontinued. Only fertilizers con- 

 taining inorganic forms of nitrogen, such as nitrate of soda, sulphate 

 of ammonia, or nitrate of potash, should be used. If the grove has 

 been heavily fertilized, much lighter applications should be made. 

 All cultivation should be discontinued, excepting such as is necessary 

 to conserve the moisture. The natural growth of grass and weeds 

 that comes on during the rainy season should be cut and removed 

 when it is mature. This treatment should continue until the grove 

 has entirely recovered. Under most conditions this will require 

 from one to several years. If the condition aggravating the disease 

 is the presence of a hardpan too near the surface, it must be broken 

 through. This may be accomplished either by the use of hand 

 implements or dynamite, according to its thickness. 



In case the water cannot be kept down by ditches where there is 

 lack of drainage, the tree rows should be ridged high. Lack of drain- 

 age sometimes occurs in localities that are high, owing to pockets 

 being formed by an irregular layer of hardpan. This may be deter- 

 mined by systematic borings. 



Where die-back occurs on shell or coquina lands, the land 

 should not be stirred. The grass and weeds should be mowed fre- 

 quently, and decaying vegetable matter should not be allowed to 

 accumulate. Such fertilizers as cottonseed meal, dried blood, guano, 

 stable manure and others should be avoided. This method of treat- 

 ment also applies to die-back when it occurs on the rocky lands in 

 the southern part of the State, excepting that cultivation is permis- 

 sible when it is necessary to conserve the moisture. 



Anthracnose. This disease, caused by Colletotrichum gloeos- 

 porioides, manifests itself by brown or dark-colored sunken patches 

 occurring in the skin of the fruit. The darkened spots may bo 



