CHRYSANTHEMUM MIDGE. 21 



fish-oil soap will kill the adult almost immediately after emergence, 

 if the spray is applied not more than three or four days previously. 



A separate sash house was erected closely adjoining the greenhouse 

 in which the spraying was done. Here 100 plants were fumigated 

 nightly for approximately eight weeks, tobacco paper at the rate of 1 

 sheet to every 650 cubic feet of space being used. While some burning 

 resulted, the midge was held in check. From these two experiments 

 it is evident that either practice would be efficient. 



A large commercial grower in Indiana reports that following in- 

 structions of this bureau he entirely eliminated the midge from his 

 houses by fumigating with tobacco papers every night from December 

 20, 1917, to March 20, 1918. 



Experiments conducted in several greenhouses in the District of 

 Columbia in 1919 have indicated that consistent nightly fumigation 

 is very effective in keeping down this insect. In several places where 

 this was not advisable an effective spray was applied, consisting of 

 nicotine sulphate (1-800) plus soap (one-half ounce to 1 ounce to 

 each gallon of solution). 



SUMMARY OF CONTROL AND RECOMMENDATIONS. 



From the life history, as well as from the experimental data thus 

 far submitted, it is clear that certain points must be kept in mind 

 if the best practical results are to be secured. First, several genera- 

 tions are always present in greenhouses during the spring and fall 

 occurrences ; second, the adults emerge and mate during the very early 

 morning hours, and egg laying quickly follows; third, preliminary 

 control experiments show that the egg stage may be controlled by 

 means of spraying or dipping the cuttings or plants; fourth, it has 

 been demonstrated that the adult can be killed easily at the time of 

 emergence by consistent spraying; fifth, fumigation experiments 

 in a commercial house proved that the adult is easily killed by fumi- 

 gation either with nicotine papers or hydrocyanic-acid gas; sixth, 

 experiments applicable to general propagation practices show con- 

 clusively that such measures offer a reasonable safeguard and pro- 

 tection against doubtful stock and infested material without injury 

 to the plants. 



By adherence to a definite control program, involving any of the 

 above cited measures, either singly or in combination, the insect 

 can be readily controlled. 



In case of a very light infestation daily picking of gall-infested 

 leaves will hold the pest in check. Should this practice prove ineffec- 

 tive, nightly fumigation for a period of two or three weeks may be 

 resorted to. 



