44 CALIFORNIA CITRUS CULTURE. 



cultivation, usually consequent upon the cementing lime carbonate in 

 the water used in irrijMtion. Cultivating at different depths will tend 

 to break this up and relieve the trees. Dynamite will break up the 

 deep or natural hardpan. The trio of remedies for physiological ills 

 is right irrigation, cultivation and fertilization. 



Exanthema Florida Die-Back. 



(PIG. 22.) 



This disease is not well understood. The ends of the branches die; 

 frequently tufts of small twigs develop from supernumerary buds; the 

 bark roughens and shows lines of brown excrescence ; gum pockets form 

 near the attachment of the leaves; the fruit is imperfect and often pale 

 yellow and insipid, and gum forms in the fruit close about the core; 

 dark green leaves appear, which, though they would seem to indicate 

 health, are really the result of the disease. It is claimed that gravelly 

 soils with coarse gravel for subsoils, or soils underlaid with hardpan 

 promote this disease, as do large applications of stable fertilizer on such 

 soils, especially if the trees have previously lacked plant food. As 

 above advised, good care and removing the cause when possible is the 

 only known cure. 



Gummosis Gum Disease. 



Mr. H. S. Fawcett has shown that gum disease is often fungoid. The 

 gum is an incident. Fungoid attack of the bark is the real disease. It 

 affects all kinds of citrus trees, but lemons suffer most. Gum exudes at 

 various places, but in case of lemons, most at the crown near or at the 

 place where the bud was inserted. Injuries, improper irrigation and 

 earth compacted about the spot where the bud was inserted are enough 

 to cause the disease. It is best to have the bud above the earth and 

 avoid running water about the crown. 



Mr. Fawcett has produced gum disease of the lemon by inoculations 

 with the decaying bark; also from cultures. He finds two distinct 

 forms, both produced by common molds of the packing-house. In one, 

 the brown rot fungus (Pythiacystis citrophthora) , the decay of the 

 inner and outer bark is almost coincident, and the diseased bark remains 

 hard, while in the other, gray fungus (Botrytis vulgaris), the outer 

 bark decays before the inner, and all becomes soft. The cure for both 

 is Bordeaux paste. (See Monthly Bulletin, Vol. 2, No. 8, page 601, 

 August, 1913.) 



Ps orosus Scaly Bark. 



(FiG. 23.) 



This trouble, not found in the lemon, is described in its name. The 

 cause may be improper aeration or irrigation. When serious it is often 



