44 



ADDITIONAL OBSERVATIONS ON THE TOBACCO STALK WEEVIL. 



The trouble experienced through the ravages of the tobacco stalk 

 weevil {TricKobaris mucorea Lee), at the experiment station of the 

 Bureau of Soils located at Willis, Tex., and in charge of Mr. Lawson 

 H. Shelfer during 190^, as reported by Mr. Chittenden in Bulletin 38 

 (pp. 66-70), was such as to raise grave doubts as to the possibilhry of the 

 soils station being able to continue their tobacco experiments during the 

 following year. Accordingly by request of Prof. Milton Whitney, 

 Chief of the Bureau of Soils, Mr. G. H. Harris, of this Division, was 

 detailed to Willis to make observations on this insect during Januaiy 

 and February, after which another field agent, Mr. J. C. Bridwell, 

 was appointed for the purpose and detailed by the Bureau of Soils, 

 under the direction of the Entomologist. The work, therefore, con- 

 tinued from January until September, when Mr. Bridwell finished his 

 report, which follows. It should be added that, according to Mr. 

 Bridwell's observations, the acreage under cultivation to tobacco was 

 not entirely sufficient for the thorough study of the life history of 

 the stalk weevil and that the insects were not present in such abun- 

 dance as to make it possible to make perfectly satisfactoiy tests with 

 insecticides. Nevertheless, it is to be regretted that an under-spray 

 of an arsenical solution was not made on insects isolated on leaves for 

 the purpose, that we might learn whether the beetles would devour a 

 sufficiency of the poisoned leaves to destroy them. It seems probable 

 that arsenate of lead might be so used, in spite of the woolly texture 

 of the under surface of tobacco; at least we suggest, if a good oppor- 

 tunity should offer, that it be tried. From the observations of Messrs. 

 Shelfer, Harris, and Bridwell there can be no doubt that this is one of 

 many species of insects which are what we term periodical, or, in 

 other words, irregular as regards injuriousness; and it may be some 

 time before injury is reported similar to that which happened in 1902, 

 while again the insect might appear in great numbers a }^ear or two 

 hence. Some additional facts were learned in regard to the insect's 

 life history, and it is to be especially noted that it feeds on potato, 

 which has suggested the use of potato and jimson weed as trap crops. 



Washington, I). C, September 5, 1903. 



Sir: I have the honor to submit the following report upon the tobacco stalk weevil 

 {Trichobaris mucorea Lee.) , based upon work done at Willis, Tex., by Mr. G. H. 

 Harris in January and February, and by myself from March until July, of the pres- 

 ent year. The principal work undertaken was field observations of the habits of the 

 weevil, and endeavor was made to determine its life history and particularly the 

 place and manner of hibernation, its food plants, and if possible its original food 

 plant, and whether the species is single or double brooded. 



The remedies suggested by the habits of Trichobaris were studied, though the 

 acreage of the tobacco and the degree of its infestation 'by this species at Willis were 

 too small to make satisfactory experiments in some lines. This was particularly true 



