74 EXPERIMENT STATION. [Jan. 



discovered, and tomatoes gathered the morning after fumiga- 

 tion were eaten with a relish by all who did not know to what 

 the fruit had been subjected. 



The conclusions reached from the exj)eriments are as fol- 

 lows : — 



1. Eumigation during sunlight cannot be practised without 

 resulting in the serious injury or death of the plants. 



2. Fumigation during cloudy days is very unsafe at best 

 and is not advised. 



3. Fumigation on moonlight nights is also unsafe, frequently 

 resulting in considerable injury. 



4. Good results are obtained by fumigation on clear nights, 

 without a moon, or on cloudy nights. 



5. The best results are obtained by fumigation on clear, dark 

 nights, with a house temperature of from 55° to 65° F., fol- 

 lowed by complete ventilation for from fifteen to thirty minutes 

 and a rather low temperature in the house the next day. 



G. Plants fumigated while drops of water remain on them 

 are likely to be injured ; fumigation should therefore be given 

 only to plants not so recently watered as to have leaves or stems 

 still wet. 



7. The moisture in the house (humidity) should not be high, 

 to obtain the best results. 



8. Under the conditions named in NTos. 5 and 7, fumiga- 

 tion for tomatoes, using .01 gram of 98 per cent, potassium 

 cyanide for each cubic foot of space for a period of forty min- 

 utes, should insure satisfactory results, and the time with 

 cucumbers could safelv be extended to an hour and a half with 

 advantac:e. 



In general, the experiments show that with tomatoes the 

 period during which fumigation can safely bo applied to the 

 plants is hardly long enough to more than kill the adult white 

 fly, but a repetition of the treatment three times at intervals of 

 two weeks should be effective. With cucumbers, treatment can 

 be prolonged with safety, but it is doubtful if the eggs can be 

 destroyed, using a safe strength of the cyanide, and for this 

 reason repetition of the treatment as with the tomato is 

 desirable. 



