304 



JOURNAL OF econo:mic ento^^iology 



[Vol. 8 



be difficult and is decidedly easier than the process of adding the two 

 figures which is now done in obtaining the distance over. 



A few examples will help in understanding the process. A tent 20 

 X 30 gives a relative size of 22 (difference 10 giving 2 to add to the 20) 

 and the dose given on the table under 22 is 3 oz. 25 x 37 gives a dose 

 a little over 27 and the dose of 28 which is 4 J oz. would be correct. 



Where the leakage is not .25 per cent or other factors enter into the 

 calculation, the process is still very simple and easy. Thus mth a 

 .30 per cent, 23 x 28 tree, the dose would be 4 oz. instead of the 3J 

 shown in the table based on a .25 per cent leakage. 



Taking about the most complicated case — a 20x26, 15 per cent tent, 

 with rents amounting to 10 sq. in., determine the weakest dose for 

 black scale. The size would indicate 3 oz. and the dose would have 

 dropped to 2 oz. because of the tight tent-^but for the holes which 

 moves the number to 2| and finally the weak dose for black scale 

 drops it down two intervals to If which is correct under these condi- 

 tions. 



If one had in this case a .30 per cent leakage the tent should not be 

 used because the relative size is less than 30 and efficient fumigation 

 is not to be expected. 



There can be no doubt that all these factors should be taken into 

 consideration in fumigation if the best work is to be done and this 

 dosage table may help to remove the difficulties which have hitherto 

 seemed to the fumigators to be insurmountable. 



THE USE OF WATER UNDER PRESSURE FOR THE CONTROL 



OF MEALY BUGi 



By W. W. YoTHERS, Bureau of Entomology, Orlando, Florida 



Owing to the ineffectiveness of spraying with insecticides for the 

 control of mealy bugs in Florida it is interesting to know how a citrus 

 grower controlled this pest successfully. These results were obtained 

 by Mr. A. H. Brown, manager of the Atwood Grapefruit Company, 

 Mana vista, Florida. 



This grove of more than 200 acres is fitted with a high pressure ir- 

 rigation system throughout and hydrants are placed at intervals so 

 that hose 100 feet long when attached will reach all the trees. The 

 system furnishes about 60 pounds pressure. When used to control 

 the mealy bugs a nozzle made out of three-fourth inch pipe three feet 

 long is used. The end is flattened so that the aperture is about 1 inch 

 wide and one-eighth of an inch opening. Since the mealy bug con- 



1 Published by permission of the Chief of the Bureau. 



