510 INSECTS AFFECTING VEGETATION 



2. Keep the ants out of the trees if possible. This is a diffi- 

 cult matter in large fig orchards, but where a man only has one or 

 two trees on his lot and these are not in contact with any building 

 or fence, it can be done. Perhaps the best way is by wrapping the 

 tree trunks with something the ants will not cross, as fly paper or 

 ant tape. Of course, this material would have to be renewed after 

 every rain. 



3. In planting the trees, use those varieties which are not 

 particularly subject to the rot, unless there is some more important 

 reason for using the others. (La. E. S. B. 132.) 



CITRUS DISEASES. 



Foot Rot. This is clearly marked and not likely to be con- 

 founded with any other disease. It is confined to the crown and 

 main roots of the tree, extending a foot or so above the ground and 

 downward along the roots. Its presence is first indicated by an 

 exudation of gum, which forms in drops on the bark covering the 

 diseased spot. Further examination at this time reveals a brownish 

 coloration of the outer cortex and a decayed condition of the inner. 

 The affected areas emit a fetid odor similar to that from a decaying 

 orange. All plants, when attacked by a disease, strive to overcome 

 it, and this the orange tries to do by cutting off the affected portion 

 by a wall of new tissue similar to that formed around an ordinary 

 wound. Following this, the bark covering the spot dries up, breaks 

 away from the adjoining parts, and drops off. The wood is then 

 found to be decayed for a short distance beneath. 



Though the tree still continues to bear fruit, its appearance is 

 far from healthy; the leaves become yellow, the twigs and young 

 branches die, and the whole tree assumes an unthrifty appearance. 

 Where the affected tree can be seen from a distance, it stands out in 

 marked contrast to its neighbors. 



Fortunately all varieties of citrus stock are not in the same 

 degree subject to this dreaded disease. In order of footrrot resist- 

 ance they stand about as follows: Sour orange, Citrus bigaradia; 

 pomelo, C. decumana; rough lemon, C. sp.; lemon, C. limonum; 

 sweet orange, C. aurantium. Roughly, we may class the first three 

 as decidedly resistant, the last two as very much subject to the dis- 

 ease. It is pre-eminently a disease of the sweet stock. We are un- 

 able to place (7. trifoliata definitely, but would venture the opinion 

 that it possesses considerable merit in power of resistance as well as 

 in so many others. 



Cattle-penning; deep-setting; a wet, soggy-soil condition; the 

 USG of rank, organic nitrogenous fertilizers; planting in localities 

 underlaid with hard-pan; faulty drainage; a shaded condition of 

 the soil, and many similar circumstances and practices have been 

 given as the cause of foot-rot. While it is not probable that the 

 disorder is due to any of these, there is no doubt that they have a 

 deleterious effect on the general health of the tree, and so act as a 

 predisposing cause. A healthy, vigorous tree has all the chances in 

 its favor for withstanding the inroads of disease, and any decrease 

 in its vitality simply gives its enemies an opportunity to gain a foot- 



