64 THE REPOKT OF THE No. 36 



Changing the Soil Annually. The value of changing the soil annually 

 as a method of controlling rose midge, supplemented by the pinching off of all in- 

 fected buds, has been proved by the experience of the Bedford Park Floral Co., 

 Toronto. According to the foreman, the midge has been present in these green- 

 houses for the past four years, and although at times it has been fairly abundant on 

 Ophelia roses, it has never increased to such an extent as to cause any serious 

 loss. The soil in these houses is removed and replaced annually during the period 

 early May to the first of July. Infested buds have always been destroyed as soon 

 as they were noticed. 



Liquid Baits. Several experiments were conducted at Grimsby in 1919, in 

 order to determine if it were possible to trap the adult midges by means of liquid 

 baits. Pans containing various mixtures with the following substances used as 

 lures — molasses, oil of citronella, oil of lemon, oil of rhodium, oil of cloves, kerosene, 

 cresol — were suspended among the rose bushes, and were left for two or three weeks. 

 A considerable number of Diptera were caught in the pans, but not one of the 

 " catch " proved to be a rose midge — most of the insects were fungus-gnats. 



Deying Off. Although this method has not been tested, it seems certain that 

 the rose midge could be exterminated in a greenhouse by drying off all the rose 

 plants at the same time during the summer. As there would be no tender shoots 

 on the plants for at least four weeks, the midge would die of starvation. 



Tobacco Fumigation and Destruction of Infested Buds. Since 1916 

 Messrs. Miller & Sons, Toronto, have been combating the midge by means of tobacco 

 fumigation, and pinching off and destruction of all infested buds. At first 

 they made a practice of fumigating for a period of three or four weeks in spring, 

 and again whenever the midge became troublesome, but as this method did not 

 wholly eliminate serious midge injury, they changed the system this past year, and 

 fumigated every other night from early April to the last of October. This kept the 

 insect down to insignificant proportions all season, and as a result no damage worth 

 mentioning was effected. 



The disadvantages of this remedial measure are (1) that in places where 

 tobacco stems are not easily procured and where commercial nicotine preparations 

 would have to be used, it is very costly: (2) that it does not wholly eradicate the 

 pest: and (3) that according to some florists frequent fumigations stunt the growth 

 of the plants. 



Nicotine Fumigation and Tobacco Dust Treatment. In 1916 Messrs. 

 Sasscer and Borden * of the United States Bureau of Entomology, having deter- 

 mined by cage experiments that a covering of tobacco dust on the rose beds would 

 prevent the full-grown larva? from entering the soil, conducted the following ex- 

 periment in a midge infested house in Maryland. All the rose beds were covered 

 on October 12th, 1916. with tobacco dust averaging from one foiiTth to one half 

 inch deep. To prevent the larva? from entering the dirt walks of the houses, all 

 walks were sprayed with kerosene emulsion. Simultaneously nightly fumigation 

 with tobacco stems was inaugurated and continued until October 30th, inclusive, 

 and from that date until November 8th the houses were fumigated every other 

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

 deposited. 



The results secured from this experiment were excellent — the midge was prac- 

 tically eradicated. 



* The Rose Midge — Bulletin No. 778 of the United States Department of Agriculture. 



