242 ANNUAL EEPORTS OF DEPARTMENT OF AGRICULTURE. 



tific and practical standpoints, as indicating the probable origin 

 and control of disease infection, have been made with reference to 

 early food plants. A large collection of cucurbits was maintained, 

 upon which observations were made throughout the season, the pref- 

 erence of the beetles for each as a food plant being noted. 



In cooperation with plant pathologists of the Bureau of Plant 

 Industry, an attempt was made to overwinter a large number of 

 cucumber beetles by feeding them on diseased and healthy vines, 

 the object being to ascertain whether they would transmit the mosaic 

 disease in the spring when placed on healthy plants. This point 

 remains yet to be established, since the beetles failed to hibernate 

 successfully. The conclusions reached at the Madison, Wis., station 

 were that lead arsenate at the rate of 4 pounds to 50 gallons of water 

 is the most efficient poison. Arsenate of lead sweetened was more 

 than twice as efficient as plain arsenate of lead. 



The tarnished plant-bug, melon aphis, common squash bug, and 

 onion thrips, were studied as possible carriers of disease. 



The spinach aphis has been under observation in tidewater Vir- 

 ginia for several years, and results are available for publication. 

 Experiments show that this species transmits the spinach blight or 

 mosaic. It is held in check to a large extent by introduced pre- 

 dacious enemies and climatic factors, although during exceptional 

 outbreaks areas must be sprayed to effect control. 



Sugar-beet insects. — In California the beet leafhopper was the 

 principal subject of investigation, and a preliminary report has been 

 prepared in which this insect as the disseminator of the " curly top " 

 of sugar beets is discussed. Additional wild plants that harbor the 

 virulent factor of this disease have been discovered and shipments 

 of parasites from Hawaii have been made. At the California field 

 station also the bean aphis and salt-marsh caterpillar are being in- 

 vestigated. 



Studies of the development, seasonal history, and control of the 

 western flea-beetle in Colorado have been practicall}'^ completed. 

 This species is implicated in injuries to the sugar beet. 



In addition to the work conducted at Pasadena, Cal., agents have 

 been engaged in work on sugar-beet wireworms. The beetles, or 

 adults, were killed by poisoned baits, but additional experiments are 

 necessary to determine the value of these. For killing the larvse, or 

 wireworms, poisoned baits were unsuccessful. 



An important insect enemy to sugar-beet seed production, the false 

 chinch bug, has been the subject of observation throughout the year, 

 and measures for its control on seed beets have been devised in 

 cooperation with the Bureau of Plant Industry. Careful study is 

 being made to determine to what extent the nymphs can be controlled 

 on their natural wild food plant. 



Investigations of the sugar-beet webworm have been completed. 

 The insect is readily controlled in its larval form with arsenicals. 



Bean and pea insects. — The pea aphis has been under observation 

 during the past year in Virginia, Michigan, and California, and 

 additional food plants have been recorded. Studies of the life his- 

 tory of the bean ladybird have been completed. Additional work 

 remains to be done in securing satisfactory arsenicals for use on very 

 young beans. 



