CITRUS scab: its cause and control. 



29 



fcions were made with a power outfit developing about 300 pounds 

 pressure, and as a rule the sprays were applied with great thorough- 

 ness. 



The following year the first applications were delayed until a 

 reasonable amount of infection had taken place throughout the nurs- 

 ery, and were made at intervals of 14 days. The same power outfit, 

 pressure, etc., were employed, and the spraying was done as thor- 

 oughly as could be expected under commercial conditions. Table 

 10 shows the results of spraying experiments for the control of citrus 

 scab in a sour-orange and rough-lemon nursery at Orlando, Fla., 

 during 1919 and 1920. 



Table 10. — Scab control in the citncs nursery in 1919 and 1920. 



Formula. 



Year. 



Spray materials used. 



Spray injury on 

 foliage or twigs. 



Control of scab. 



No. 1.. 



1919 

 1919 



1919 



1919 



1919 



1920 

 1920 



1920 



1920 



1920 



1920 

 1920 

 1919 



1920 



Plain Bordeaux mixture, 3-3-50 



Bordeaux mixture, 3-3-50, plus 0.5 per 

 cent oil as emulsion. 



None.. 



Absolute. 



No.2 



do 



Do. 



No. 7 



Russeting of leaves 



moderate. 

 DefoUation serious. 



. .do 



Do. 



No. 9- 



T.iiTnp,-siiIphiir solutinn 



Moderate, about 



No. 10 



Lime-sulphur solution plus 0.5 per 



cent oilas emulsion. 



Plain Bordeaux mixture, 3-3-50 



Bordeaux nuxture, 3-3-50, plus 0.5 per 



cent oil as emulsion. 

 Bordeaux mixture, 2-2-50, plus 0.5 per 



cent oilas emulsion. 

 Bordeaux mixture, 1-1-50, plus 0.5 per 



cent oil emulsion. 

 Commercial Bordeaux paste plus 0.5 



per cent oil as emulsion. 



50 per cent. 

 Do. 



No. 1 



None 



Absolute. 



No.2 . . .. 



do 



Do. 



No. .'^ 



do 



Do. 



No. 4 



do.. 



Do. 



No.o 



do 



Do. 



No. 6 '. 



do 



Do. 



No. 8 



Copper soap 



do 



Do. 



Check 









Check.... 







fection, 90 per 

 cent. 

 Serious infec- 









tion,somewhat 

 less than 1919, 

 72 per cent. 



At the end of each year 1,000 or more leaves were selected at 

 random and counted for each plat and the presence or absence of 

 citrus scab recorded. 



The beneficial results associated with citrus-scab control were 

 very evident during the progress of the work. It was especially 

 noticeable during the spring and early summer of 1919. On June 

 30, 1919, measurements of growth in height were made over the 

 various plats. At that time and throughout the rainy season of 

 June and July the stunting effect of citrus scab was conspicuous. 

 When the rains stopped and dry weather set in, thereby largely 

 preventing citrus-scab infection, the check plat made a surprisingly 

 rapid growth until checked by cold weather. 



