THIRTY-FOURTH FRUIT-GROWERS^ CON\TENTION. 



109 



difference in strength of killing dosage between these three experiments, 

 we would be able to determine the effect of length of exposure on the 

 results secured. 



To obviate as much as possible the factor of leakage of tents which 

 would vary in covering trees of different sizes, trees of as uniform size 

 as we could obtain were used. For the first two experiments the con- 

 tents of the trees were of no great variation, the tree running between 

 11 and 14 feet in height. Our first two experiments, however, consumed 

 most of the larger trees, so that for the third experiment we were com- 

 pelled to utilize what remained. The trees of this _ third experiment 

 were consequently somewhat variable in size, and noticeably smaller 

 for the most part than those of the first two experiments. The infesta- 

 tion of scale was severe on many of the trees. 



During the latter part of January, an examination of the results of 

 these experiments was made. Fully two weeks were devoted to this 

 examination during which thousands of purple scales were examined. 

 The method was a very careful one. In all cases the scales were over- 

 turned and examined Avith a powerful hand lens. In those instances in 

 which the entire contents of the scale were not at once revealed, the 

 delicate ventral scale was ruptured, and the contents scraped out. 

 Through this way not a single egg could escape observation. Examin- 

 ing the results of the experiment of 30 minutes' exposure we found 

 live adult females on the branches, leaves, and fruit at the dosage of 

 % of an ounce per hundred cubic feet. Above that dosage all insects 

 were killed on the leaves and the branches. On the fruit, however, some 

 still survived at 1 ounce per hundred cubic feet, but were killed at all 

 strengths above. The immature insects were all destroyed by the 

 smallest dosage used. Healthy eggs were found on the leaves, and on 

 the branches up to the rate of 1% ounces, but were destroyed by all 

 heavier dosages. On the fruit, however, only the dosage rate of 2^ 

 ounces proved a complete success. This experiment would lead to the 

 conclusion that for normal shaped orange trees from 11 to 14 feet high 

 and above, exposed to gasing for 30 minutes, a dosage at the rate of 

 2 ounces per hundred cubic feet will destroy the purple scale in all its 

 stages on the leaves and on the branches. If the tree contain fruit 

 infested with scale, it is necessary to increase the dosage rate to 2i/2 

 ounces to accomplish the same result. 



The second experiment, which had an exposure of 60 minutes, 

 showed that all insects on the leaves and the branches were destroyed 

 by the dosage rate of % of an ounce. No live insects were found on 

 the fruit examined, but inasmuch as a very small amount of scaly fruit 

 was available throughout this experiment, we are inclined to leave the 

 effect on the fruit incomplete until further experimentation has been 

 done. A dosage of IV^ ounces and above destroyed all eggs on the 

 leaves and the branches." In the small amount of fruit examined, many 

 instances of healthy eggs were found in the % and 1-ounce tests. In 

 the IV2 ^iid 1^4-oi-^i^c^ tests a single case of healthy eggs was observed 

 in each instance. In the 2-ounce test all eggs were destroyed on the 

 fruit. This experiment would lead to the conclusion that for normal 

 shaped orange trees, from 11 to 14 feet in height and above, exposed 

 tu gasing for one hour, a dosage at the rate of II/2 ounces per hundred 



