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The first spraying should be done just after most of the bloom 

 has shed. This may be followed by a second spraying 10 to 14 days 

 later, and by a third in three or four weeks after the second. Spray- 

 ing should be thorough, as only the thrips actually hit are killed. 

 This spraying will also kill any rust mites that should happen to be 

 present at this time of year. 



Sun Scald. This cannot be classed as a disease. It is an injury 

 resulting from some factors that are imperfectly understood. It is 

 generally supposed to be due to water on the fruit acting as a lens, 

 and by collecting the light rays developing enough heat to cause 

 injury. 



This affection appears on the fruit during the late summer or 

 early fall. It first shows as a premature yellowing of a spot near the 

 stem end that is fully exposed to the sun. The surface may be 

 pitted as though the oil glands had dried out. The spot is dry to 

 the feel, and holds heat in contrast to unaffected portions of the 

 fruit. 



This affection in itself is confined to the skin. But owing to 

 the weakening of the tissues that it produces, the fruit is attacked by 

 fungi at this point. They penetrate the rind and cause a discolora- 

 tion that may extend to the center of the fruit. Tangerines and 

 Satsumas seem to be more susceptible to this trouble than other citrus 

 fruits. No method of treatment has been developed, owing to lack 

 of exact knowledge as to the cause. 



Die-Back Markings. Die-back is one of the common diseases 

 of citrus trees. It is not due to any organism, such as a fungus or 

 an insect, but is caused by improper feeding conditions. Some of 

 the conditions known to aggravate the disease are : over-feeding with 

 organic nitrogenous fertilizers, such as stable manure, cottonseed 

 meal, and others; and unfavorable soil conditions, such as lack of 

 drainage, or a compact subsoil of hard pan, marl, or clay, that is too 

 near the surface. The disease is common upon certain lands in 

 Florida, such as the shell lands, the coquina lands, and the rocky 

 lands in the extreme southern part of the State. 



Die-back affects the fruit and young stems. The symptoms on 

 the stems are various. Fruits marked by die-back are usually 

 spoken of as ammoniated fruit. But this may be considered as a 

 misnomer since it gives the impression that the disease is due to too 

 much ammonia in the soil; whereas, the disease is related only to 

 certain forms of ammonia in the soil, namely, the organic forms. 



Die-back spots on the fruit are mostly confined to the epidermis. 

 They usually do not extend into the tissue beyond the depth of the 

 oil glands. They vary in size from small spots 1/16 on an inch in 

 diameter, to patches covering a large portion of the surface of the 

 fruit. The smallest spots are usually circular in outline and conical 

 in shape, and of a glossy brown or black color. The larger spots, 

 and patches are somewnat raised, with the surface irregularly 

 cracked. They vary considerably in outline; some resemble thrips 

 marks in this respect, and others cover the surface like rust-mite 

 russeting. 



