26 PRELIMINARY REPORT OX ALFALFA WEEVIL. 



Cache Junction in 1910. It does, however, occur in the Bear River 

 Valley from Evanston, Alniy, and Lyman, Wyo., northward into 

 Bear Lake County in extreme southeastern Idaho. Previous obser- 

 vations would indicate that by a natural diffusion the insect has 

 spread a distance of about 30 miles each year. As a matter of fact, 

 the beetles are continually being found where least expected, and 

 they have not been found where, judging from their habits, we would 

 feel most confident of their occurrence. 



The most rapid dispersion of the insect during the last two years 

 has been toward the northeast from the original point of infestation 

 in the Salt Lake Valley. Its injury is now noticeable wherever 

 alfalfa is grown in the river valleys east of Ogden to the Wyoming 

 State line and northward to the southern extremity of Bear Lake. 

 It is known to occur, however, as previously stated, as far north as 

 Cokeville, Wyo., and southward to Evanston and Lyman, where 

 specimens were taken during the summer of 1911. This north- 

 eastward trend of diffusion in the weevil must be considered in con- 

 nection with prevailing southwest winds at the time when the beetles 

 are flying, and, in fact, careful search over the newly infested territory 

 seems to render it highly probable that to this cause is due this 

 northeastward diffusion. The finding of individual larva well 

 scattered over Wyoming fields with little or no indications of intro- 

 duction by human agencies, together with the finding of larvae in an 

 irrigated valley isolated from other cultivated crops by 35 miles of 

 dry desert country, are conditions hard to explain in any other way 

 than that the south winds of spring and summer have resulted in 

 carrying flying beetles over low mountain ranges to fertile fields 

 beyond. To just what extent the winds are able to carry the adults 

 into new territory is not known, but at any rate migration in other 

 directions has taken place much less rapidly. 



FIELD EXPERIMENTS IN DESTROYING THE ALFALFA WEEVIL. 



Several extended series of experiments in destroying the alfalfa 

 weevil were carried out at various points in the infested territory 

 in Utah, but only those that have shown the best results will here be 

 mentioned. 



Quite naturally, a measure that will destroy a greater or less 

 number of the insects and at the same time encourage the growth 

 of the plant, and is of practical application, will not only be the most 

 attractive one to the farmer but will result in a double benefit. For 

 this reason disking was looked upon as probably offering the best 

 results. It was thought that by disking and spraying a more rapid 

 growth of the alfalfa plants would be secured, and by following this 

 with the use of a brush drag a great many of the larvae would be 

 crushed and destroyed. Mr. Ainslie's observations made in 1910 



