388 Pomona College Journal of Entomology 



Tents are mended every day with a sewing machine. The patches are 

 sewed on the underside so as not to cover up the numbers. And the seam 

 is not so liable to catch on a limb as the torn canvas under the patch, which 

 is not always sewed down. A full 1 hour or 45 minute exposure should 

 be used, as is the common practice with potassium cyanide. 



OBSERVATIONS 



Temperature. — In using potassium cyanide we were always very careful 

 not to fumigate when it was between 36° or 40° F. above zero (or lower) 

 because we were always sure to receive severe burnings. Even as high as 

 42° F. with moisture might prove disastrous. The fruit of the Valencia 

 orange trees has been a source of considerable trouble with us on account 

 of burnings. When it was decreed that we must use sodium cyanide, I 

 was afraid of fumigating a Valencia orchard, so managed to get enough 

 of the potassium to do the work. Every precaution was taken to observe 

 all the rules regarding temperature and moisture, but in spite of everything 

 we burned considerable of the fruit. The same was true in regard to 

 cold and damp nights in our work on lemons. It was a practice with us to 

 quit at 40° F. above zero or when the leaves of the trees became damp 

 enough to strike them and feel the spray hit the hand. In this county 

 there are many fogg>' and damp nights, which are excellent for the crops, but 

 bad for fumigation. If the bulk of the work was not done during the 

 months of September and October it was found difficult to do it afterwards. 



In using the sodium cyanide we found out that the matter of moisture 

 and moderate cold 40° F. did not make any difference at all. In fact many 

 tests were made when the trees were very damp and the thermometer was as 

 low as 37° without a sign of burning. In these tests the regular black scale 

 dosage, as shown, was used. This information zve consider to be ver\ valuable. 

 because it zvill mean that more work can be done while the crew is in the 

 field a)id in operation. Many nights we have been able to w(^rk but 2 or 

 3 hours, and under such conditions it was very difficult to keep a crew in the 

 field at all. This may not have been the experience with all other parties, 

 but was certainly so with all who used it in this vicinity. 



Killing Power. — In the matter of efficiency against black scale, I am satisfied 

 that the work done will equal that done by the use of the potassium cyanide. 

 Some five or six hundred acres were fumigated and all results are splendid. 

 There was no guess-work, nothing but intelligent and up-to-date fumigation 

 with marked tents and chemical charts. 



Costs. — Last fall potassium cyanide, 98 to 99 per cent pure, cost our 

 growers 25i/2 cents a pound delivered. Sodium cyanide cost 29 cents a 

 pound delivered. The cost per ounce of potassium was approximately 1.593c; 

 that of sodium, 1.801c; or about $.016 for potassium and $.018 for the sodium. 

 The following tal)!c will give some idea of the diiYercnce in costs : 



