THE AVOCADO 63 



In the earlier stages the surfaces may show a fuzzy, whitish growth 

 the fruiting parts of the fungus. The surfaces of older spots are darker 

 in color and frequently covered with a dark webby fungous growth. 

 On young shoots and twigs the spots appear more elevated, small, 

 oval, dark purplish brown to black, and have comparatively smooth 

 surfaces. This same type of spot is observed on the fruits. 



"It is plainly evident that the avocado scab fungus is none other 

 than Cladosporium citri, which causes citrus scab. The two fungi 

 agree in structure and growth habits, and both are parasitic on citrus. 



44 Only tentative control measures for avocado scab can be sug- 

 gested at the present time. Spraying with Bordeaux mixture for the 

 disease in the nursery has given good results in some cases, in others 

 less satisfactory. If the new growth can be protected while it is 

 putting out, the disease may largely be avoided. The sprayings 

 should be made when the foliage begins to put out, and continued until 

 the leaves are nearly developed. The 1 1 50 Bordeaux mixture may 

 be applied at intervals of ten days or two weeks, or often enough to 

 keep the young foliage well protected. The fungus develops more 

 rapidly during cool weather where moist conditions are provided. 

 Shade and a crowded condition of the trees also seem to favor the 

 development of the scab." 



Many growers in southern Florida who have planted the 

 Trapp avocado have been troubled by the trees dying back 

 following the production of a heavy crop of fruit. Krome 

 of Homestead has given this subject much study, and writes 

 as follows regarding it in the 1916 Report of the California 

 Avocado Association : 



" Avocado trees of the West Indian race, when in good condition of 

 growth, are prone to put on a tremendous bloom from which a setting 

 of fruit is apt to result so heavy as to be entirely beyond the carrying 

 capacity of the tree. Following this abnormal effort there is often a 

 period of apparent exhaustion during which the tree seems to realize 

 that it has 'bitten off more than it can chew,' and to be seeking the 

 best method to recoup from its over exertion. This is a critical time 

 in the life history of the tree and calls for intelligent handling on the 

 part of the grower. If left to its own devices the tree will endeavor 

 to carry the over crop, draining upon its reserves until its vitality has 

 been seriously impaired. Evidences of this condition are usually very 

 apparent. The tree drops a large portion of its leaves, the younger 

 branches change in color from a dark green to a saffron yellow and no 

 new growth is put on. Lack of sufficient foliage to provide proper 



