514 INSECTS AFFECTING VEGETATION 



Gradually the larger branches are embraced, water sprouts develop 

 only to become affected and die. Eventually the tree succumbs. 



Die-back is not, so far as known, a fungous disease, no spores nor 

 any thing of the sort having been found connected with it. It ap- 

 pears rather to be a disorder brought about by a variety of circum- 

 stances, and the external marks of the disease are to be regarded as 

 an indication of a deranged condition of the whole tree. In certain 

 localities it seems to be brought about by the presence of hard-pan 

 in proximity to the surface. Again, the condition seems to be due 

 to a wet, poorly aerated soil. But perhaps the most prolific source of 

 the trouble is the use of fertilizers unsuitable to the orange tree. 

 Now, whether we should make a distinction in die-back as induced 

 by these several causes, it is difficult to say. 



Many instances have come under the observation of the writer, 

 of the occurrence of the disease where trees were planted in ground 

 previously used in growing vegetables, and which was heavily ferti- 

 lized with blood and bone and cotton-seed meal. Then, too, in some 

 localities the spaces between the tree-rows have been used for grow- 

 ing vegetables, the same fertilizers applied as in the cases just men- 

 tioned, and with the same deplorable effect on the orange trees. 

 The disease has been observed in groves regularly fertilized with rank 

 nitrogenous fertilizers, and trees standing near and receiving nutri- 

 ment from stables, closets and hencoops are generally affected. The 

 general conclusion reached by all observers during the past fifteen 

 years or more has been for the most part to the effect that the exces- 

 sive use of organic nitrogenous fertilizers will cause die-back, and the 

 matter has been pretty thoroughly discussed in the horticultural 

 papers of the state. 



These consist for the most part in removing conditions and dis- 

 continuing practices which induce the disease. Make a thorough 

 study of the soil and the methods of fertilizing. In some places, 

 with trees growing on hard-pan, the following plan was adopted 

 and they made a complete recovery : The trees were cut back, lifted 

 from the ground, the hard-pan removed, either by blasting or pick- 

 ing it out, and the trees reset. The remedy for trees growing in 

 damp ground consists in paying proper attention to drainage and 

 fertilizing. (Fla. E. S. B. 53). 



Sooty Mold. This is widely distributed throughout the State. 

 It occurs as a sooty-black covering on the leaves, fruits, and twigs of 

 many plants, and is intimately associated with various insects. In 

 Florida it follows Lecanium oleoe on Nerium oleander and Persea 

 Carolinensis; Aphis gossypii on the orange, egg-plant, and many 

 other herbs, shrubs, and trees; Lecanium hesperidium, Ceroplostes 

 Floridensis and Aleyrodes citri on the orange. In short, it may be 

 said that it is found with all the scale and allied insects which exude 

 honey-dew in any considerable quantities. 



The fungus is a saprophyte, and is dependent upon this honey- 

 dew for its sustenance. The insects already referred to are gregari- 

 ous in their habits. Consequently, the honey-dew accumulates in 

 considerable quantities on various parts of the plant, and in this 



