CONTROL OF WHITE GBUBS. 



15 



In this experiment the death rate of the beetk^s was not greater 

 than would be normal with healtliy beetles kept 'without food. It 

 seems probable in this case that the beetles were eaptured l)eforv' 

 tbey had consumed any considerable ({uantity of the poisoned foliage. 



As a result of these experiments it would appeal- that the spray- 

 ing of tlie food plants of the beetles would undoubtedly cause the 

 death of a portion of the beetles: that the working of the poison 

 is slow and that the beetles would probably crawl to their burrows 

 in the soil before dying-; and that arsenate of lead is more effective 

 as a poison for the beetles than Paris green. Unfortunately the 

 practice of spraying large fields of cane and the trees in the vicinity 

 of the fields is too expensive to be practical. 



MKCIIANICAL METHODS. 



Use of dynamite against the white grubs. 



To test the value of dynamite as an agent with wiiich to destroy 

 the white grubs in infested land an (Experiment was carried out, in 

 which various charges of dynamite were exploded at different depths 

 in the soil and at distances of five feet apart. Previous to the blast- 

 ing a careful estimate was made of the number of gru1)s present 

 in the field. Three areas of eight scpmre feet were seiei-ted in dif- 

 ferent parts of the field and a count made of all the grubs found 

 within those areas. By this method it was estimated that there were 

 one hundred and ninety-six thousand and twent}^ grubs per aei-e. 



Experiment XX. — Experiments with Dynamite Against the White Grub. 



As may be seen from the chart, best results were obtained hy 

 using a charge of one-half stick of dynamite. However, even tluit 

 amount exploded at distances of five feet apart left one-hall' the 

 surface of the ground undistur))ed. and in the art^a that was thrown 

 up by the exi)losi()n only seventy-two per cent of the grubs were 

 killed. ^lany of the grubs wei-e thrown out on the surface of tiie 

 soil without injury. With charges at five feet apart it would have 

 required one thousand seven hundred and forty-two charges pei- acre, 

 which would have made the cost per acre. excliisi\-c of fuses, caps. 



