TEAR-STAIN OF CITRUS FRUITS. 11 



CONCLUSIONS. 



While the foregoing evidence is to the effect that tear staining of 

 Florida citrus fruits is caused by rust mites rather than by the fungus 

 CoUetotricJiwm gloeosporioides, as claimed by Rolfs, it must be admitted 

 that the writer may not have seen all types of this injury. However, 

 if a special type of tear staining caused by this fungus occurs in Florida 

 it must have been exceedingly rare during the past four years to have 

 escaped detection by the writer. The experimental and observational 

 data on the control of what has been regarded as wither-tip tear-stain 

 by investigators and Florida growers seems to be definite enough to 

 warrant the conclusion that practically all of the so-called wither-tip 

 tear-stain in Florida is caused by rust mites and can be readily con- 

 trolled by controlling these pests. 



SUMMARY. 



(1) Pure cultures from typically tear-stained fruit show that Col- 

 letotrichum gloeosporoides is not confined characteristically to the tear 

 streaks, but is even more prevalent on the larger russeted areas and is 

 almost invariably found on normalty colored areas. 



(2) Inoculations on grapefruit in various stages of development 

 with cultures of the fungus Colletotrichum gloeosporioides failed to pro- 

 duce tear streaks or other positive reaction. 



(3) Dead wood that might harbor Colletotriclbum gloeosporioides was . 

 found associated with not more than 10 per cent of the affected fruit. 



(4) It is impossible to distinguish by histological methods between 

 the ordinary rust-mite russet and so-called wither-tip tear-stain. 



(5) Rust mites were found very abundant in recently developed 

 tear-streak patterns on grapefruit. 



(6) Spring-bloom fruit on unsprayed trees usually becomes seriously 

 tear stained; June-bloom fruit on such trees usually ripens free from 

 these markings. 



(7) Copper sprays applied in the spring and not followed by rust- 

 mite applications of sulphur sprays tend to increase tear staining, 

 but when followed by rust-mite applications no appreciable amount 

 of tear staining develops. 



(8) When sulphur sprays are applied during the early spring, 

 which is usually too early for the best rust-mite control, and are not 

 followed by the regular rust-mite application tear staining is greatly 

 reduced. 



(9) When only the rust-mite applications are made, tear staining 

 is practically eliminated. 



(10) The same local and seasonal conditions of moisture and light 

 that favor rust-mite injury also favor tear-stain. 



(11) Practically all of the so-called wither-tip tear-stain in Florida 

 is associated with rust mites and can be readily controlled by con- 

 trolling; these mites. 



