518 INSECTS AFFECTING VEGETATION 



conspicuous, the disease is usually not noticed until the markings 

 have attained some size. It shows up in its matured condition on 

 the fruit at any time from May to July. Only young, succulent 

 tissue is attacked by the disease. As the fruit approaches maturity, 

 it becomes immune to attack. 



Since melanose begins to develop on the fruit in the early spring, 

 measures for its prevention must be carried out at that time. It has 

 been found that the disease can be controlled by the use of either 

 Bordeaux mixture or ammoniacal solution of copper carbonate. 

 They should be first applied about two weeks after the bloom has 

 fallen; and again about a month later. In case periods of cold 

 occur late in the spring, a third spraying should be made a month 

 later still. 



Russeting and Tear-Streaking Caused by Withertip Fungus. 

 This fungus has become a serious parasite in citrus groves during the 

 last fifteen years. Previous to this time its occurrence in Florida 

 was well known to botanists, but no serious damage occurred from it. 

 Its manifestations in the grove are quite various, but only that form 

 having the appearance of russeting will be discussed here. (Fla. 

 E. S. B. 108). 



Russeting and tear-streaking can nearly always be traced back 

 for their beginning to a small dead spur or sprig. The fungus lives 

 in this dead spur or sprig. Water from rains, and moisture follow- 

 ing heavy dews, collect in drops on these sprigs or spurs, and the 

 drops, when they fall, carry with them numerous fungus spores. 

 These spores come in contact with the epidermis of the fruits, and 

 germinate, causing minute lesions on the epidermis too small for 

 complete infection and production of anthracnose. It requires con- 

 siderable time for withertip russeting to appear. It has not been 

 observed to occur until the fruit has nearly matured. Tear-streak- 

 ing may be produced at any time after the fruit has begun to color, 

 and on late varieties while they are still green. Withertip russeting 

 and tear-streaking (or streaking), being caused by the presence of 

 fungus, can be prevented by the use of a fungicide. Bordeaux mix- 

 ture and ammoniacal solution of copper carbonate are excellent for 

 this purpose. The grower must be prepared to fight scale insects, 

 however, when he uses these fungicides in his grove. In many cases 

 the loss from russeting and tear-streaking will be less than the cost of 

 applying the fungicide and of following that with the insecticides 

 for destroying scale insects. 



(1) The proper time to begin preventive work for withertip 

 russeting and tear-streaking is in July, when all dead and weakened 

 wood should be pruned out and destroyed. This reduces the amount 

 of fungus spores to a minimum and saves the costly work of 

 spraying. 



(2) Spray with ammoniacal solution of copper carbonate as 

 soon as russeting from withertip fungus becomes apparent. Repeat 

 in three weeks or a month, especially if rains have occurred in the 

 meantime and the fruit is continuing to russet. (See Anthracnose.) 



