6 BULLETIlSr 778, U. S. DEPAETMENT OF AGEICULTUEE. 



All of the foregoing experiments were conducted in a commercial 

 greenhouse, and each test represents a 50-foot bed of roses. For the 

 most part the killing results of all six experiments were satisfactory. 

 Unfortunately, however, the molasses served as a medium for the 

 development of sooty mold, and, moreover, where lead arsenate was 

 used an objectionable white deposit developed. The presence of 

 either on cut flowers necessarily would reduce their value and in 

 some instances would eliminate them from the market. As the rose 

 midge usually is present at a season when the grower can ill afford 

 to have objectionable deposits on his cut flowers, it is evident that 

 any of the foregoing combinations will be unsatisfactory, unless some 

 method of counteracting these objectionable features is developed. 

 In addition to the foregoing, 1 part of nicotine sulphate (40 per 

 cent nicotine) to 400 parts of water, with the addition of enough soap 

 to produce suds, was tested. The results of this experiment were very 

 unsatisfactory, fully 95 per cent of the larv^se being uninjured. 



To determine the value of tobacco dust in preventing the full- 

 grown larvae, or grubs, from entering the soil, the following cage 

 experiments were conducted: (1) S'oil around caged plants covered 

 with dry tobacco dust; (2) same as former except that the dust was 

 wet. Full-grown larvse which were placed in the cage containing 

 dry dust were active for 24 hours, but did not go below the surface, 

 whereas the larvae similarly placed in cage 2 were exceedingly active 

 upon coming in contact with the wet dust, acting as if they were 

 burned, and after from 5 to 8 hours they were all dead. All larvae 

 used in the check immediately entered the soil. 



Having determined a satisfactory method of preventing the 

 entrance of the full-grown larvae into the soil, all of the rose beds 

 in the infested houses at Colgate, Md., were covered on October 12, 

 1916, with tobacco dust averaging from one-fourth to one-half inch 

 deep. To prevent the larvae from entering the dirt walks of the 

 houses, all walks were sprayed with 5 per cent kerosene emulsion. 

 Simultaneously nightly fumigation with tobacco stems was inaugu- 

 rated and continued until October 30, inclusive, and from that date 

 until November 8 the houses were fumigated every other night. The 

 object of this fumigation was to kill all adults before eggs were 

 deposited. 



Although this control work was not undertaken until October 12, 

 its effectiveness was soon apparent, and by the latter part of October 

 it was very difficult to locate an infested bud. Not onl}'^ was the 

 midge under control, but the owner was enabled to bring on his fall 

 crop earlier than was the case in 1915. On May 7, 1917, these houses 

 were carefully examined, and only 6 larvae were located, 2 in the 

 buds of the Haclley and 4 in the buds of the Eadiance. All plants 

 at this -time were in excellent condition and gave promise of pro- 



