112 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



gipsy moth larvae can feed and maintain themselves until they reach 

 a considerable size is very limited. 



THE ALFALFA WEEVIL. 



The situation regarding the alfalfa weevil, an insect obviously 

 imported from Europe, and which became established in the vicinity 

 of Salt Lake City, Utah, is continuing to become more serious and 

 alarming. The last Congress made immediately available $10,000 

 for an investigation of the pest. Experts of the Bureau of Ento- 

 mology, working in cooperation with the Utah Agricultural Experi- 

 ment Station, have traced the spread of the insect from Salt Lake 

 City south to Springville and north to Ogden. west to beyond 

 Tooele and east to Wyoming. Judging from what has been observed 

 between Salt Lake City and Ogden, and between Ogden and Brig- 

 ham, the uniform normal spread of the pest is about 30 miles a year, 

 though circumstances may greatly change this. Many experiments 

 have been carried out with mechanical devices for destroying the 

 pest in infested alfalfa fields and thereby protecting the second and 

 third crops. An investigation was made of the parasites of this 

 weevil in Italy, and during March and April last large lots of the 

 stems of alfalfa containing eggs parasitized by a minute parasite 

 were sent to Salt Lake City, arriving there in good condition and 

 the parasites emerging in numbers. Three other parasites were sent 

 over later, and an attempt is now being made by agents of the bureau 

 to establish them in the Utah alfalfa fields. 



WORK IN THE ORANGE AND LEMON GRONTIS OF CALIFORNIA AND FLORIDA. 



In my last report I mentioned the completion of the study of the 

 problem of hydrocyanic-acid gas fumigation in California, directed 

 against certain scale insects on citrus trees, and stated that the care- 

 ful experimental work carried on had resulted in a great reduction 

 in the cost of fumigating, since one treatment under the new meth- 

 ods was as lasting in its effects as three or four distinct treatments 

 under old commercial methods. Observations during the past year 

 have shown that this was an underestimate, and that an orchard 

 once fumigated will remain clean for three years before it is neces- 

 sary to repeat the operation. Thus the cost of keeping an orchard 

 free from scale is now only one-sixth of what it used to be in the 

 days of commercial and unscientific treatment. 



The work in Florida against the white fly having demonstrated 

 that in most cases the gas treatment is too expensive, attention has 

 been directed to the determination of the most practical and effective 

 spray application. Tests have been made on a large scale, often 

 over entire orchards, with a variety of insecticides, and it now seems 



