22 THE TOBACCO THRIPS. 



ADDENDA. 

 THE TOBACCO THRIPS IN 1905-6. 



Although the writer was unable to continue the work in Florida 

 the past year (1900), as planned, he took advantage, in November, of 

 the opportunity offered to visit Quincy. An interview with several 

 planters was sufficient to further convince him of the practicability 

 of spraying with the kerosene emulsion and the efficiency of this spray 

 when carefully applied. 



The injury produced by the thrips the past year has been only 

 about 60 per cent of that of 1905. This is undoubtedly due to the 

 variation in the period and the amount of precipitation, as before 

 stated by the writer. 



EFFECT OF THE SPRAY. 



As previously stated, the writer was associated during the work on 

 this insect with Mr. W. W. Cobey, tobacco-breeding expert of the 

 Bureau of Plant Industry. During the past two years Mr. Cobey 

 has had opportunity to observe the results obtained from the use 

 of the kerosene-emulsion spray and at the request of the writer has 

 prepared the following statement in relation to its effect on the 

 character of the tobacco and the desirability of its use : 



It is the opinion of the writer, after a careful comparative study of the 

 treated and untreated tobacco, that the use of kerosene emulsion on tobacco, 

 when carefully prepared and applied at the proper time under favorable con- 

 ditions, is in every way practicable and can be profitably employed by tobacco 

 growers in preventing almost wholly the ravages of this insect. There was 

 considerable apprehension among the tobacco growers at first regarding the 

 probable injurious effects of the kerosene emulsion on the character of the 

 tobacco. However, a careful study of the cured and fermented tobacco from 

 the sprayed plants showed that the spraying with kerosene emulsion had not 

 injured the quality or reduced the value of the crop. It has been impossible 

 to discover any difference in the color, elasticity, or aroma of the treated and 

 untreated tobacco after curing and fermenting. On the other hand, the pre- 

 vention of injury to the tobacco by the thrips, by means of the kerosene-emul- 

 sion spray, prevented a serious loss to the grower. 



The injured tobacco may be fermented sufficiently to even up the color of 

 the leaves and darken the white or discolored veins so that the injury will not 

 be noticeable, but this severe sweating will darken the leaves to such an 

 extent that they can only be classed as dark wrapper. 



The use of the spray was quite general during the season of 1906, and seri- 

 ous injury to the tobacco from the thrips was thus prevented. It was found 

 by those who commenced to apply the spray early in the season and were 

 forced to discontinue it after the tobacco was about 2 feet high, that there was 

 but very little injury by the thrips, while those who did not use it suffered a loss 

 to an extent of about one-fourth of that of 1904. During the year the injury 

 under slat shade was very slight. 



For those who may apprehend injury to the quality of the tobacco it may 

 be said that the experiments conducted during the last two seasons indicate 

 that when spraying is begun very early in the season it will not be necessary 

 to continue it after the crop is about half grown. 



