530 INSECTS AFFECTING VEGETATION 



fairly firm at first, and the discoloration proceeds slowly from the 

 stem end in a more or less uniform circle, and does not extend in 

 bands. It causes a slow, and at first only slight, discoloration of the 

 center and inner peel and partitions, and the juice sacs often remain 

 unaffected for some time. The fruits, when entirely decayed, still 

 keep their form more or less, but do not turn black until dried up. 

 This rot is caused by a species of fungus hitherto undescribed. It at- 

 tacks all varieties of citrus fruits, and appears to gain entrance chiefly 

 at the stem end. It is most destructive when accompanied by scale 

 insects under the calyx next to the stem. 



The recommendations based on experiment and observation 

 during two seasons may be summarized as follows : 



(1). Pruning out and destruction of dead and diseased 

 branches. 



(2). The removal and destruction of all dropped and decayed 

 fruits. 



(3). Care at all stages of picking and handling to avoid infec- 

 tion from the fungus. 



(4). Keeping fruit at a low temperature in transit and in 

 storage. 



(5). Spraying with insecticides to keep scale insects from at- 

 tacking fruit. 



Diplodia Rot. In the early stage this rot shows as a patch about 

 the stem end similar to stem-end rot. The discoloration becomes 

 darker as the decay proceeds, and appears as dark wide bands corre- 

 sponding to the divisions between the segments. The fruit becomes 

 black as the decay advances and very light in weight. The rot often 

 advances quickly through to the blossom end, and a patch of discol- 

 oration shows there before all the peel is involved. The Diplodia rot 

 often starts also in thorn punctures or similar injuries. It is usually 

 accompanied by the exudation of a small amount of thin gum, or a 

 considerable amount of amber-colored sticky juice. This amber- 

 colored juice less frequently accompanies the stem-end rot. Many of 

 the characteristics of the two rots are so similar that for practical pur- 

 poses they may be classed together. The citrus fruits are much more 

 resistant to Diplodia rot than to stem-end rot. Diplodia rot appears 

 to be less common on immature fruits on the tree, and the fungus 

 causing it is less parasitic. The same line of treatment given for stem- 

 end rot holds good for Diplodia rot. 



Black Rot. This rot begins at the blossom (or stylar) end, 

 especially in navel oranges, but sometimes in other varieties if there 

 be a defect at the blossom end. The fruit attacked ripens prema- 

 turely with a deep red color. This decay causes a blackening along 

 the central core of the fruit where the segments meet and does not 

 soften the fruit so rapidly as the previous rots. The decay is more 

 confined to the interior of the fruit and is darker in color. The fun- 

 gus enters by means of slight imperfections at the blossom end, and 

 produces most of the decay under the skin. All diseased fruits should 

 be destroyed. (Ma. E. S. B. 108.) 



