Tropical Fruits 137 



In the packing-house the use of disinfectants in the washer 

 prevents trouble; one pint of formaUn to 1250 gallons of 

 water, or 1 pound of copper sulfate to 625 gallons of water. 



Cottony-rot ^'^- (Sderotinia libertiana) . — The fungus on 

 lemons is identical with that of lettuce drop, and its mycelium 

 and sclerotia appear as described under that disease. The 

 decay spreads rapidly from fruit to fruit in storage, and the 

 loss is consideral^le. Twig, blossom, or seedling infection of 

 oranges or lemons, accompanied by gummosis, also occurs. 

 Disinfection of the fruit with 1/50 per cent solution of copper 

 sulfate is employed. 



Canker * ^^^-492 [Pseudomonas citri Hasse) . — • Citrus canker 

 is one of the most destructive diseases introduced into the 

 United States in recent years. Its nature was first pointed 

 out by Hasse in 1915. Before that time it was thought to be 

 caused by fungi and was confused with citrus scab. The 

 origin of the disease is obscure. It was first described from 

 the southernmost island of Japan in 1899 on navel oranges, 

 where it was undoubtedly introduced from South China. 

 About 1910-11 citrus canker was introduced directly from 

 Japan into Texas on the trifoliate orange and on nursery 

 stock. In a short time it was carried into other Gulf states 

 on infected plants, imported directly from Japan and in- 

 directly from Texas, so that by 1914 it had assumed the 

 aspects of an epidemic in certain parts of Florida, Alabama, 

 Mississippi, Louisiana, and Texas. About the same time 

 outbreaks were reported from two areas in the Transvaal, 

 South Africa, the Philippine Islands, and later from North 

 Australia; originating in impoi-tations from Japan. 



Citrus canker, while primarily a leaf spot, may attack parts 

 of the tree above ground. On the leaves, the young spots 

 usually appear on the under side as small, yellow, translucent, 

 oily pimples. Later they rupture to form brown, raised, 

 corky spots with an oily outline, and sometimes a wide, 

 yellow margin. The spots break through to the upper side 

 of the leaf. The young spots on the twigs and branches are 

 * Prepared by d. L. Peltier. 



