b THE TOBACCO THKIPS. 



summer of 1904, with inquiries concerning an injury to shade-grown 

 tobacco in Florida. The insect causing this injury was variously 

 described as " a little parasite," " a flea," " an unknown insect," etc. 

 Not until the winter of 1904 could anything definite be learned. At 

 that time a report was received from Mr. T\ T . W. Cobey. tobacco- 

 breeding expert, of the Bureau of Plant Industry, describing the 

 nature of the injury. 



It seems that on tobacco grown in the South, and under shade espe- 

 cially, insect enemies of the crop are found at their worst. Of the 

 many insects with which the planter has had to deal in the past, the 

 budworm, requiring two and three applications a week of arsenicals, 

 has been far in the lead in the amount of damage done. It often 

 happens, when a crop is introduced into a new locality, that insects 

 previously unknown, finding in it a desirable food, leave their 

 natural food plant, multiply rapidly through new and more favor- 

 able conditions, and thus become serious pests. This is what has 

 happened to shade-grown tobacco in the South. The suckfly {Dicy- 

 plnis minimus Uhl.), which first appeared on tobacco in 1888, has 

 made the raising of a second crop of shade-grown tobacco in Florida 

 unprofitable. The leaf miner or splitworm (Fhtlwrimtea operculella 

 Zell., formerly known as Gelechia solanella Boisd.) also has at- 

 tacked and become injurious to tobacco. And now comes a new pest 

 in this new tobacco thrips, which has threatened to surpass the 

 destructive budworm in actual injury. 



Injury by the tobacco thrips was first observed in 1902, on tobacco 

 grown in the field on which the first shade was erected in 1896. 

 Since that time the insect seems to have increased rapidly, until, 

 during the summer of 1905, the thrips was found in all shade tobacco 

 fields examined, and the opinion is expressed by several planters 

 that, if allowed to continue its ravages, it is on a fair road to com- 

 pletely check the production of the shade crop. 



The history of shade-grown tobacco in this country dates back to 

 the year 1896, when one-fourth of an acre of slat shade was put up at 

 Quincy, Fla. It was found that Sumatra wrapper tobacco grown in 

 this way nearly, if not altogether, equals the quality of the imported 

 article. So successful has been the raising of this tobacco that to-day 

 over 3,000 acres are grown under shade in Florida and the adjoining 

 counties of Georgia, while Texas has a smaller acreage. 



NATURE AND EXTENT OF INJURY. 



The injury occasioned by the tobacco thrips is known as " white 

 vein," which, as the term indicates, is due to a white appearance of 

 the veins (see PL I, fig. 2). These veins show in the wrapper when 

 manufactured into cigars. The injury is brought about by the re- 

 moval of the sap by the adult thrips in feeding on the upper surface of 

 the leaf. The thrips feed on the space between the veins as well as 





