PLANT DISEASES 255 



with the bordeaux and, while commercial results can be 

 secured, entire eradication is practically out of the question. 



There is a disease of lemons which is also called brown-rot, 

 but this is caused by a different fungus. As the name indi- 

 cates, the lemon turns brown after the disease has penetrated 

 the interior of the fruit. It is necessary in treatment 

 to spray the ground thoroughly with bordeaux mixture, 

 especially in the vicinity of the trees, for rain splashing 

 the ground may carry the spores to the fruit on the 

 lower part of the tree. The prevalence of this fungus is 

 one of the factors which make careful handling so neces- 

 sary, for wherever a slight bruise occurs, the spores are 

 able to gain access to the interior of the fruit and decay 

 quickly follows. 



The same fungus which causes the brown-rot of the fruit 

 is also responsible for a gum disease of the bark, which has 

 proved serious. This is now kept under control by budding 

 the lemon on such resistant forms as Florida sour stock and 

 by keeping the bud union well above the ground. When the 

 disease appears, it may be checked 

 by scraping off the injured bark 

 and then painting the affected 

 parts with a mixture of blue-stone 

 and lime. One pound of blue- 

 stone and two pounds of lime are 

 dissolved separately in three quarts 

 of water and the two solutions are 

 then mixed. 



366. Shot-hole fungus (Fig. 130) 



,. . , , FIG. 130. Shot-hole fungus. 



produces a disease in which small 



round discolorations or holes appear on the leaves and 

 fruit. The manner in which these are scattered suggests 

 the effect of a charge of shot from a shot-gun. A num- 

 ber of different species are responsible for the disease. 

 Like all other fungi, these must be treated before they gain 



