﻿46 BULLETIN 1357, U. S. DEPARTMENT OF AGRICULTTJKE 



period of the plants consistently produced an average mortality of at 

 least 95 per cent of all beetles above ground. Fumigation with 

 vaporized nicotine did not kill the adults. 



The effectiA^eness of hand picking the beetles, as practiced by many 

 florists, may be counteracted by the overlapping of generations of 

 this insect. It is therefore evident that to be successful hand picking 

 must be done very thoroughly and persistently. 



A modification of hand picking, wherein kerosene nicotine oleate 

 was used to film the surface of the pools and puddles in heavily 

 watered beds, killed any beetles which came in contact with the in- 

 secticide while struggling in the water. 



Cleanliness was practiced persistently in one greenhouse and was 

 of material assistance in reducing a heavy infestation. Immediately 

 after cutting back the plants many adults in the soil and debris 

 were destroyed by scraping and removing a layer of surface soil to 

 a depth of about 2 inches, and then treating it to kill them. 



Treatments of the soil with the following insecticides either failed 

 to kill the larvae and pupse or were detrimental to the plants : 



Acid phosphate. ' Lye (sodium hydroxide). 



Borax. Nicotine sulphate solution. 



Carbon disulphide. Orthodichlorobenzene. 



Hydrated lime. Paradichlorobenzene. 



Kerosene nicotine oleate. Sodium cyanide solution. 



Contact with tobacco dust, which was placed on the soil surface, 

 killed newly hatched larvse, and the leaching of tobacco dust and 

 wood ashes also killed some larvse and pupse in the soil. 



RECOMMENDATIONS FOR CONTROL 



A successful control program entails a combination of several 

 ■measures, since no single practice will suffice. In order to be effective 

 such measures must be persistently followed and applied in such a 

 manner that they will not conflict with the normal cultural program 

 and conditions under which roses are grown. 



During the summer months the protection of the plants from im- 

 mediate as well as future injury is the paramount consideration. 

 This may be accomplished by fumigating with hydrocyanic-acid gas 

 during the drying-off period to kill as many adults as possible, and 

 by scraping the surface soil from the beds when the plants are cut 

 back, and then spraying them with lead arsenate or calcium arsenate, 

 using 4 pounds to 50 gallons of water, to protect the swelling buds 

 from the further depredations of the beetles. 



From September to December eradipaiion of the beetles should 

 be the florists' aim, because they are still emerging and continue to 

 feed voraciously for some time. Every effort should therefore 

 be directed toward ridding the houses of as many of the over- 

 wintering beetles as possible in order to prevent a recurrence of an 

 infestation the following spring. During this period dusting must 

 be very thorough and continuous, in order that the foliage may be 

 kept coated with the poison. Hydrocyanic-acid gas, however, can 

 not be used at this time at a killing strength without causing severe 

 injury to the plants. Two or more treatments by filming the sur- 

 face water of the bed with kerosene nicotine oleate may then be most 

 effectively used to kill many adults. Beginning about the middle of 



