78 



equator on white paper. A mark was left at two places on the sheet 

 denoting the fruit's circumfrence. The volume of the fruit was taken 

 in laboratory by placing the fruit into a 1000 ml graduate cylinder 

 and recording water displacement. Samples were multiplied by factors 

 derived from diameter, circumference and volume to give total popula- 

 tion estimate over the entire fruit. 



Alcohol emersion method . At the completion of each set of lens 

 counts, the orange, while still on the tree, was placed into a clear 

 plastic bag 8 x 3 x 15 x .0015 in. containing 50 ml of 95% isopropanol. 

 The bag over the fruit was sealed by twisting it several times around 

 the branch bearing the fruit. The alcohol was vigorously shaken over 

 the orange for ten seconds to remove citrus rust mites. The bag was 

 removed from the fruit and sealed. The fruit was removed from the 

 tree marked for later identification. 



In the laboratory the alcohol was agitated in the bag, and three 

 2 ml samples were pipetted into separate watch glasses. An Olympus 

 binocular microscope at 25X was used to count the number of mites per 

 sample. The three 2 ml samples were averaged and multiplied by the 

 percent of the sample they represented to give total number of mites 

 from each fruit. 

 Results and Discussion 



The average number of citrus rust mites on the equatorial belt 

 of ten fruit (Y) are shown in Table 11. These values were multiplied 

 by the estimated surface area calculated from fruit volume (Sv), fruit 

 diameter (Sd), and fruit circumference (Sc), which yielded estimates 

 of 51.25, 48.56, and 55.93 mites per orange, respectively. The alcohol 

 emersion method gave an average of 53.23 mites per orange (Table 12). 



