CITEIIS DTSEASER. 



109 



Fig. 21. — Spots on grapefruit leaves 

 cine to Plii/lhisfictd sp. 



A leaf spot (Fig. 21) due to an as yet undetermined fungus oc- 

 curs widespread, but on hardly more than a few leaves at a time 



The spots are brown, slightly 

 raised, plateau-like appear the 

 same on both leaf surfaces, and 

 vary in size up to one centimeter 

 in diameter. Their shape is cir- 

 cular to irregular. Larger and 

 older spots become gray at the 

 center with definite, raised brown 

 margins. 



A pecidiar condition of ter- 

 minal leaf clusters has been o1)- 

 served in grapefruit nursery 

 trees, in which all the leaves are 

 distorted, stunted, and one sur- 

 face (generally the back) glazed. 

 This is thought to be due to thrips injury. 



Spraying injury may assume several forms. Bordeaux causes 

 a burning of young unfolding tips, and on more fully developed 



leaves may produce a pitting 

 (Fig. 22). the pits corresponding 

 to the position of drops of spray 

 material respcnisible for the burn- 

 iiiL;. Limc-sulphui- m;iy cause in- 

 jiii-ies on fruit, with much the 

 a])pearance of aiitlu-aenose spots, 

 which fungus in fact generally 

 follows. 



Knots in the rind occur in 

 grapefruit, and jiossibly the or- 

 ange. They are characterized by 

 a slight raising of the skin, which 

 feels hard. Internally they show 

 as gum infiltrated areas. The 

 cause is not known. 



A common blemish on grape- 

 fruit consists of minute (a milli- 

 meter, more or less, in diameter), bi-own to bhu-k. sliglitly depressed 

 markings on the surface. The epidenti only is nft'ccted. but since 



Pk;. 22. — Spottiiio diu' t( 

 niixtiii-c. 



I '.or 



ileal IX 



