CONTEOL OF WHITE GEUBS. 



18 



Summary of Results. 



HACIENDA SANTA RITA, GUANICA CENTRALE. APPLIED MARCH 13, 1917; 



COUNTS MADE APRIL 3, 1917. 



Average grubs i>er stool 



Cyanamid ^ lb. per stool 

 No. application (check) .. 



4.1 

 3.6 

 3.8 



HACIENDA PULIDO, CENTRAL ROCHELAISE, MAYAGuEZ, P. R., APPLIED OCTO- 

 BER 8 TO SIX-MONTHS-PLANT CANE; COUNTS MADE NOVEMBER 23, 1917. 



Cyanamid and acid phosphate 1 lb. per stool.. 

 Cyanamid and acid phosphate 21bs. per stool . . 

 No. application ( check) 



Number of stools Average grubs per stool 



3.2 

 3.3 

 5.1 



In this experiment there was so inueh variation in soil conditions, 

 a ledge of tosea coming out near the surface over much of the field, 

 that not nmeh reliance can be placed on the figures obtained. 



At Central Aguirre applications were made in the absence of 

 sufficient grubs to obtain any reliable figures. In one field it was 

 noted that first-instar grubs were present in treated stools, indicating 

 that the eggs are not killed by applications of one pound of cyanamid 

 per stool. 



The applications made at Corsica Central were not disturbed. 

 Applications of one pound of cyanamid and one pound of cyanamid 

 and acid phosphate caused no injury at all to young ratoon cane. 



Cyanamid alone and cyanamid mixed with an equal weight of 

 acid phosphate are of no practical value against white grubs wiien 

 applied in amounts up to two pounds to the stool, either when ap- 

 {)lied as a surface dressing or when worked into the top four inches 

 of soil. 



Poison sprays. 



Numerous attempts have Ikmmi made from time to time to kill 

 the beetles by spraying their food plants witii arsenical poisons. 

 Since the beetles have biting inouthparts, are hearty feeders and 

 do not fly far, but confine their feeding activities to the immediate 

 vicinity of the cane fields, it seemed highly proliable that such 

 methods of eoutrol would meet with some success. The arsenicals 

 used in these experiments were arsenate of lead and Paris green. 

 Of the numerous experiments conducted the following four have 

 been selected as lieing indicative of the results obtained. 



