268 ANNUAL REPOETS OF DEPARTMENT OF AGRICULTURE. 



tlie boll weevil in check by this method have been improved and 

 thoroughly tested on a large scale. Cotton planters all over the 

 weevil-infested portion of the cotton belt are taking up this method, 

 and hundreds of individual inquiries in regard to it have been 

 answered. The bureau is certain, however, that the exact methods 

 which have been successful under conditions that exist in the Mis- 

 sissippi Delta will not be perfectly applicable to all portions of the 

 cotton belt. Therefore, circulars have been issued regarding the 

 general application and making it plain to planters that methods 

 should be varied according to conditions. The weevil has been more 

 numerous during the summer of 1919 than it was during the previous 

 summer, and planters have therefore been more than ever desirous 

 of trying this remedy. The bureau, therefore, has been especially 

 anxious to guard them from mistakes. 



An enlargement of this investigation seems necessary to bring 

 about the best results. Experimental farms should be established 

 in a dozen or more cotton-growing regions, and the very best method 

 for each region must be worked out before planters can apply the 

 remedy with confidence. The commercial results that have been 

 reached alread}', however, in the delta region assure ultimate results 

 of probably equal value in the other parts of the cotton belt after 

 these comparative studies shall have been made. 



Other cotton insects. — At the laboratory at Madison, Fla., a 

 study of the Hemiptera attacking cotton east of the jSlississippi River 

 has been completed. At this station also a thorough study has been 

 made of the varieties of sea-island cotton with especial reference 

 to earliness of growth under boll-weevil conditions. Thirty-two 

 varieties have been tested in this Avork. The importance of early 

 fruiting of sea-island cotton under weevil conditions can not be over- 

 estimated. Careful studies at this point have also been made on the 

 relation of the immature stages of the weevil to temperatures. The 

 dry period in Florida, usually commencing about the SOth of May 

 and extending to the 20th of June, seems to retard the weevil to such 

 an extent that the problem of growing upland cotton under weevil 

 conditions is very encouraging. 



Insects affectxng sugar cane. — The best hope for control of the 

 moth borer of sugar cane now seems to be the importation and estab- 

 lishment of parasites which exist in Cuba. Experts were sent to Cuba 

 in the beginning of the fiscal year and again in April, 1919. Para- 

 sites have been imported, and every effort is being made to propagate 

 them in the Louisiana cane fields. 



Tobacco insects. — In Florida, promising control of the tobacco 

 flea -beetle has been obtained with certain insecticides — an important 

 result, as in 1918 one grower claimed a loss from this insect of $650 

 per acre. Dusting methods in the shade-grown tobacco region have 

 been revolutionized by the introduction of power machines which 

 are capable of dusting from 10 to 20 acres per day more than can be 

 done with hand dusters. For the tobacco thrips it has been found 

 that nicotine sulphate, 14 ounces, and soap, 3 pounds, to 50 gallons 

 of water, gives satisfactory control if applied properly once a week 

 during the emergence period. A very important point is the time ot' 

 application. Much valuable work has been done on other tobacco 

 insects. 



