REMEDIAL MEASURES 49 



those few found in tlie house at this time of the year are adults 

 that escaped the summer treatment. 



The time required for this insect to complete all its life 

 histor}' stages is not more than five weeks, allowing one week's 

 time for oviposition. It follows that an indefinite number of 

 broods are possible, and if left unchecked their numbers may 

 easily become most seriously destructive. 



Although this species of white-fly is a serious pest on to- 

 matoes and cucumbers it is not confined to these plants, nor is 

 it confined to forcing houses alone. On July 18, an immense 

 swarm was discovered in the gardens out of doors. A careful 

 investigation was made to discover nymphs on as many plants 

 as possible. They were found on a stray potato plant and 

 strawberry leaves. On July 26, some were found on 

 currant leaves, also on the leaves of a species of Erigeron. 

 On July 29, some were found on goldenrod, and a little later 

 a nymph was found on a chrysanthemum leaf. Of course, 

 these were very few and in all cases on the under surface of 

 the leaf. Unfortunately it has not been determined whether or 

 not these nymphs complete their life history successfully. 



Mr. W. E. Britton of the Connecticut station gives a list of 

 58 plants upon which he found the nymphs. It follows that 

 this pest has a wide range of adaptation in food plants. In 

 our studies we have no evidence of its establishing itself in the 

 open in a serious way. 



REMEDIAL MEASURES 



Kerowater Sprays. Our experiments during the summer of 

 1901 showed that the adult white-flies are very easily killed by 

 spraying with a mechanical mixture of kerosene and water, 

 with 5 per cent, of kerosene. We used for this purpose a knap- 

 sack kerowater sprayer. When the plant on which they are 

 resting is disturbed these adults fly into the air, making a 

 miniature cloud. If those thus in the air are hit by the kero- 

 water spray they drop down and die. In spraying it is desir- 

 able to begin at the top of the plants and work down. 



We used this method to advantage out of doors, the adults 

 being very easily destroyed even on badly infested plants. 



The extent to which the kerowater spray can be employed 

 to destroy the nymphs will depend largely on the plant attacked. 

 Some greenhouse plants are very easily injured by kerosene. 



