DISEASES OF PLANTS. 451 



scab, silver scurf, and buckskin. Studies were also made of the red rot of sugar 

 cane (Colletotrichum falcatum), of the spore stages of the brown fungus of 

 the whitefly, which is described as new under the name of /Egerita wcbberi 

 (E. S. R., 23, pp. 655, 758), and of a species of scaly fungus from Lecanium on 

 Piniis ta'da. 



The stem-end rot is a disease only recently observed on neni-ly all varieties of 

 citrus fruits in Florida, but is now reported from 20 localities with its focus 

 of infection in Volusia, Lake, and Orange counties. It has caused damage 

 ranging from 5 to 30 per cent of the fruit in infected groves. The fruit first 

 softens and becomes slightly depressed around the stem end without any 

 change in the color of the rind. The rot proceeds inward along the fibers of 

 the rag, and then outward into the pulp cells. At first there is no discoloration 

 of the rind and pulp, but as the softening continues the rind turns a dull 

 brown and the rag and pulp cells disintegi'ate, causing the entire fruit to become 

 soft and mushy. The rot usually occurs on full-sized ripening fruit after it 

 has dropped or has been picked, but may begin while the fruit is still on the 

 tree. It also develops on fruit which is apparently perfectly sound when 

 packed. Pure cultures have been isolated from the interior of diseased grape- 

 fruit, sweet and sour oranges, and from tangerines. Inoculation tests with 

 pure cultures and with pieces of diseased tissue produced typical stem-end rot 

 in the sound fruit, mainly of oranges, after an incubation period of al)out 2 

 weeks. These inoculation experiments showed that under laboratory condi- 

 tions the infection of sound oranges may occur not only through the cut ends of 

 stems up to 3 in. long, but also through the epidermis of the fruit and through 

 the calyx, and that infection of oranges and lemons may occur in water either 

 from cultures, pieces of diseased orange tissue, or infected soil. 



A description of gummosis and distinctions between it, scaly bark, and foot 

 rot are given, and the following methods of treatment are suggested: Either 

 scrape off the diseased bnrlc and paint the surface with a carbolineum mixture 

 consisting of 1 gal. of carbolineum and 1 gal. of water in which 1 lb. of whale-oil 

 soap has been dissolved, or peel off the bark over the diseased area without 

 injuring the underlying wood and cover the wound with a grafting wax con- 

 sisting of 6 oz. of alcohol, 1 lb. of resin, 2 oz. of tallow, and 1 oz. of spirits of 

 turpentine. 



A further test of the methods of controlling scaly bark, previously noted 

 (B. S. R., 23, p. 446), showed that in the main the recommendations therein 

 given still hold good, but certain modifications are suggested, the line of treat- 

 ment depending upon the condition of the trees and of the grove as a whole. 

 If the disease is of recent appearance in the locality and is confined to 2 or 3 

 trees in a grove, the infected trees should be cut back to the stump and treated 

 as previously suggested. If the disease is of long standing in a grove in which 

 the trees are still looking fairly well, a thorough pruning out and spraying 

 with Bordeaux mixture will effectually check its growth. When the trees are 

 badly diseased, showing much dead wood and weakened limbs covered with 

 scaly bark spots and spongy bark, they must be headed back in December and 

 January, cutting out all the foliage and small branches and leaving only the 

 body and larger limbs; the entire surface should then be painted with the car- 

 bolineum solution. 



An extended study of citrus scab or verrucosis has been made, the results 

 of which will be published later. In the spraying experiments for controlling 

 this scab it was found that trees sprayed with Bordeaux mixture in November 

 and again the following March were entirely free from the disease. The use 

 of a carbolineum emulsion even up to 25 per cent in strength was less effective 

 than the Bordeaux mixture. 



