99 



commenced on August 15, using a kerosene emulsion made with 1 

 part of kerosene, 1 part of whale-oil soap, and S parts of water. This 

 was applied to a few plants to note the elfect of the emulsion upon the 

 plants, A few applications showed practically no effect, but repeated 

 aj^plications showed the burning of small spots, and also the burning 

 of the tips of the leaves. However, the injury is not sufficient to be of 

 any great importance. 



An experiment to demonstrate the effect of the emulsion upon the 

 pupa? was conducted as follows: Two lots of leaves were selected on 

 which were a large number of pupa\ One lot was treated with the 

 emulsion and the other not treated, and both lots put into breeding- 

 cages. From the leaves not treated a large number of insects were 

 hatched, while from those treated only two emerged. 



Accordingly, on August 18, experiments were commenced upon the 

 coffee on the Experiment Station farm. The coffee field contained 

 231 plants, ranging from 6 inches to 6 feet in height and well shaded 

 by bananas. All the plants were badly affected at this time. At 

 first the plants were sprayed on Mondaj^s and Thursdays. This was 

 continued until October 3. After that date they were sprayed on Oc- 

 tober 13, 17, 21, 26, and 31, and on November 5. The trees were num- 

 bered, and a careful record was kept of the number of affected leaves 

 on each tree. From time to time the injured leaves were picked from 

 such trees as were entirely free from recent attacks. Care was taken 

 not to pick the leaves from a tree until it was evident that the leaves 

 had been deserted by the larv.ie. These leaA^es were placed in breeding 

 cages and careful records were kept of the number of adults which 

 came from them ; thus we Ivuow that only a very few insects were 

 removed in this manner. 



The picking of these deserted leaves facilitated the work in two 

 ways: (1) The absence of the old leaves made it very much easier 

 to look for newly affected leaA'es; and (2) trees that were not affected 

 were not sprayed. 



For the first six weeks the trees yielded to the treatment very 

 slowly, and September 26 only about one-third of the trees were unaf- 

 fected. After that date the trees jdelded to the treatment more 

 rapidly, and on Xovember 5 they were absoluteW fiee from the 

 insects and were in excellent condition. The small trees responded 

 to the treatment much more rapidlj" than the large ones. 



The writer is reasonably sure that the treatment above described 

 is a good one, but it is impossible at this time to say how effective it 

 Avill prove, owing to the fact that at this season of the year the insect 

 enters a quiescent period which prevents our continuing the experi- 

 ments or determining to what extent the reduction was due to natural 

 causes and to what extent to our treatment. 



