BULLETIN 924, IT. S. DEPARTMENT OF AGRICULTURE. 



associated with rust-mite control is strong evidence that rust mites 

 might be largely concerned in the causation of the condition that is 

 generally recognized as wither-tip tear-stain. 



Table I. — Effect of various sprays on the control of tear-stain on grapefruit. 



191/ 



Jan. 29 



Mar. 23 



Apr. 7 



May 2 and 22.. 



June 



1918. 

 February (final count of 

 1,000 fruits), tear- 

 stained, per cent. 



Plat designation and spray application. 



No. 1, 



Bordeaux 

 mixture. 



3-4-50. 

 3-4-50. 

 3-1-50. 

 3-4-50. 



Not 

 sprayed. 



No. 2, 

 Burgundy 

 mixture. 



3-31-50.... 

 3-34-50.... 

 3-3V-50.... 

 3-34-50.... 



Not 

 sprayed. 



No. 3, 

 Bordeaux 

 mixture. 



3-4-50 



3-4-50 



3-4-50 



Lime-sulphur, 



1-40. 

 Lime-sulphur, 



1-66. 



1.3 



No. 4, 

 lime- 

 sulphur. 



1-40 



1-40 , 



1-40 



Not 



sprayed. 

 do 



No. 5, 

 lime- 

 sulphur. 



1-40.... 



1-40 



1-40.... 

 1-40.... 



1-66 



No. 6. 



Not sprayed. 

 Do. 

 Do. 

 Do. 



Lime-sulphur, 

 1-66. 



25.9. 



a The excessive number of tear-stained fruits on the plat sprayed with Bordeaux mixture may be 

 explained by the fact, quite frequently noted, that rust mites become unusually abundant on trees sprayed 

 with that material. The injury did not resemble Bordeaux russet, but was similar in every respect to the 

 tear staining on plat 6. 



A part of a grove of grapefruit was sprayed experimentally in June, 

 1919, using 3-4-50 Bordeaux mixture for plat 1 and 1-66 lime-sulphur 

 solution for plat 2. Plat 3 was an unsprayed check. This grove had 

 not been sprayed previously that season. At the end of July the 

 fruit in plat 2 was free from tear staining, but numerous tear-stained 

 specimens were observed in plats 1 and 3. The fruit on these plats 

 ripened and was harvested in February, 1920, with no increase of tear- 

 stain over that observed in July, 1919. This indicates that one appli- 

 cation of weak lime-sulphur solution applied at a time suitable for 

 rust-mite control in that grove was equally effective for the control 

 of tear-stain, while the standard strength of Bordeaux mixture applied 

 at the same time did not reduce this blemish. (PI. II, fig. 2.) 



Other experimental data obtained during the past four years 

 show without exception similar results. 



The conclusion of Yothers (11), based on numerous extensive 

 experiments to control rust mites in various parts of Florida, is 

 that bright fruit — i. e., fruit free from rust-mite injury — is invariably 

 free from tear-stain as well. (PI. II, fig. 1.) 



Growers generally throughout the Florida citrus belt have accom- 

 plished commercial control of tear-stain whenever they have con- 

 trolled rust mites by following the spraying schedules established 

 for these pests. 



Definite observations in commercial groves show clearly the 

 following facts: (1) Where rust mites are naturally absent tear- 

 stain is not observed; (2) where rust mites occur and are successfully 

 controlled tear-stain is also controlled; (3) where rust mites are 



