TEAR-STAIN OF CITRUS FRUITS. 



present and are not controlled tear-stain occurs and usually varies 

 proportionately with the severity of the rust-mite attack; (4) rust- 

 mite russet and wither-tip tear-stain develop simultaneously 



Usually in Florida a small proportion of late citrus blooms occur 

 in June. Fruits from such blooms develop after the normal rust- 

 mite period and almost invariably ripen free from tear staining 

 unless rust mites happen to become abundant during the following 

 winter or early-spring months. 



CULTURAL WORK. 



Fungi are admittedly capable of producing tear-streak patterns 

 on the host; for example, Phomopsis citri is known definitely to 

 produce melanose injury in distinct tear streaks on various citrus 

 fruits. Consequently a careful study was made to determine the 

 frequency of the occurrence of Colletotrichuin gloeosporioides or 

 other fungi in typical wither-tip tear-stain areas. 



In preliminary tests made during the fall of 1918 oranges and 

 grapefruit were selected that showed typical wither-tip tear-stain, 

 as well as fruit affected with rust-mite russet which shaded off into 

 tear-stain. Usually 30 cultures were made from each fruit, 10 each 

 from areas selected as follows: (1) Typical rust-mite russet, (2) 

 typical tear-stained streaks or slightly discolored areas on fruits show- 

 ing no streaking, and (3) normal areas not discolored. The fruits 

 were washed 1 minute in 1-1,000 mercuric-chlorid solution and 

 afterwards thoroughly rinsed in sterile water. Bits of tissue were 

 then removed with flamed instruments to sterile Petri dishes and 

 covered with melted corn-meal agar. These cultures were allowed 

 to grow five days at room temperature. The results of this pre- 

 liminary culture test are found in Table II, the percentages being 

 based on the number of the bits of tissue used in each test. 



Table II. — Culture tests for the isolation of Colletotrichum gloeosporioides l from normal 

 and affected parts of orange and grapefruit rind. 



Series. 



Number 

 of fruits. 



Bits of 



tissue 



cultured. 



Colletotri- 

 chum 



gloeospori- 

 oides. 



Miscel- 

 laneous 

 organ- 

 isms. 



No 

 growth. 





17 

 16 

 19 



170 

 160 

 190 



38.2 



21.1 



6.2 



18.8 

 19.3 

 15.7 



43.0 





59 6 





78.1 







1 The use of the name CMetotrichum gloeosporioides in the culture data of this publication merely follows 

 established custom and is without prejudice as to the proper designation of the organism. Any Colletot- 

 richum showing characteristic growth on corn-meal agar was recorded as this species. 



It thus appears that Colletotrichum gloeosporioides is recovered 

 in rather low percentage from tear-streaked areas, that it is present 

 to some extent in normal as well as badly russeted areas, and that 

 the frequency of occurrence varies directly with the degree of injury. 



