CONTROL OF WHITE GRUBS. 



17 



Experiment XXII. — Use of Light Against the Beetles. 



No. 



of 



light 



Where located 



In cane field. 



On roof of bldg. 

 near cane tieltf 



Kind of light 



Arc light. 



500 c. p. Pitner 

 gasoline lamp 



Time when run 



No. [Average 

 ofbeetles ^<5- 

 caught 



Niglitly from April 20 to May 31. 



Run for 23' evenings in July, j 

 Aug., Oct . and November 



250 

 65 

 24 



caught 

 per night 



6 



1.5 



1 



' On ciiil.x 7 iiiirlits \x-crc Mu.\' l)(.'(.'tles taken. 



The results ot* these trials clearly show that little success can be 

 expected with light as a means of attracting the beetles. Since these 

 experiments were conducted it has been found that PJiyllopJtaga 

 beetles of the Island are ordinarily attracted to light only during 

 their flight to their food plants in the early part of the evening. 

 The flight only lasts about an hour, and once they have started 

 feeding the beetles are no longer attracted by light. Hence it would 

 be useless to run the lights for more than an hour each night. 



Collection of the grubs and beetles. 



The most successful method of controlling the white grub tliat 

 has yet been found is that of collecting the grubs and ])eetles. The 

 method is rather expensive but it is the only sure way of keeping 

 the pest from increasing. 



Some idea of the expense may be obtained from the following 

 figures supplied by Guanica Central, where this method is practiced. 

 During seven months in 1914, a total of 2,255,000 beetles and 1,662.000 

 grubs were collected at a cost of $2,710.60. The following year 

 2,46S,000 l)eetles and 2,425,000 grubs were collected at a cost of 

 .t:j,448.77. ^lore of the grubs and beetles are being collected each 

 year by this central in an endeavor to reduce the numbers of this 

 pest, but unfortunately the method is not very generally practiced 

 by the cane growers of the Island, and in fact the majority of the 

 growers use no method of control whatsoever. 



Collections of the grubs should be made when the land is being 

 plowed, fjarge numbers of the grubs are tuimed up at this time and 

 should be collected by boys and women following the plows. Where 

 tui-keys, chickens, and hogs are available they .should be turned into 

 the fields at plowing time, as they w^ill And and devour those grubs 

 that the pickei's fail to see. 



The beetles feed at night on the foliage of the cane and the trees 

 in the vicinity of the cane fields. They are rather sluggish in their 



