THE ROSE MIDGE. 7 



ducing a full crop of flowers. These houses were again carefully 

 examined on June 19, and no injury was to be found on any of the 

 plants which had been infested so severely during the fall of 1916. 

 Moreover, the owner reported that up to June 19 more than twice as 

 many blooms had been cut as during the entire previous year. 



The rapid elimination of this pest was due no doubt to two causes, 

 (1) nightly fumigation, which killed off the adults before egg-laying 

 took place, and (2) the application of tobacco dust, which prevented 

 the larvse from entering the soil. Moreover, the tobacco dust served 

 a dual purpose, since it prevented the larvae from entering hibernat- 

 ing quarters and at the same time fertilized the soil. 



METHODS OF CONTROL. 



It is evident from the experiment described above that a severe 

 infestation of the rose midge can be controlled, if not entirely elimi- 

 nated, in a comparatively brief period by the careful application of 

 tobacco dust on the soil and by persistent nightly fumigation with 

 tobacco, in the form of stems, nicotine papers, or one of the volatile 

 nicotine preparations.^ 



Where earth walks are present, it is advisable to spray the walks 

 also with a 5 or 10 per cent kerosene emulsion.^ 



In the case of light infestations, the midge can be controlled by 

 systematic nightly fumigations with tobacco fumes, wliich should 

 be continued until all adults disappear ; or by a careful application, 

 at the proper season, of tobacco dust. Inasmuch as the broods prob- 

 ably overlap during the summer, there is a possibility that frequent 

 syringing of the plants would cause much of the dust to wash down 

 into the soil before all larvae matured; hence there is a chance that 

 some would fall on and enter earth where the dust had lost its 

 effectiveness. It would seem, therefore, that the most opportune time 

 to apply the dust, if not accompanied with nightly fumigation, is 



1 Although tobacco stems have been used in greenhouses from time immemorial they are 

 being replaced rapidly by nicotine paper and the volatile nicotine extract, owing to the 

 fact that the nicotine content of the stems is so variable. Tobacco stems in the proper 

 condition (those which have not been allowed to become wet and dry out) will yield good 

 results. As there is no satisfactory and easy method by which the florist can determine 

 accurately the nicotine content of tobacco stems, however, it will probably be a saving 

 of time and money to use the nicotine papers or the volatile nicotine extracts, in which 

 case the dir-ections on the label of the container should be followed. 



- Kerosene emulsion (stock solution, 66 per cent oil) is made after the following 

 formula : 



Kerosene (coal oil, lamp oil) gallons 2 



Soap (flsh-oil or laundry) (or 1 quart soft soap) pound J 



Water (soft) gallon 1 



First dissolve the soap in boiling water, then remove the vessel from the flre and 

 immediately add the lierosene, thoroughly agitating the mixture until a creamy solution 

 results. The stock solution may be more conveniently made by pouring the mixture into 

 the tank of a spray pump and pumping the liquid through the nozzle back into the tank 

 for five minutes. A 10 per cent solution can be made by adding to each gallon of the 

 stock solution about 5S gallons of water. In some regions the water is " hard," and in 

 such eases it should be broken with a lit.tle lye, or rain water should be used. 



