- 19 - 
In 1923, 30 days elapsed after the first spray was applied until 
the irarfoers of worms began to drop off naturally, hut a corres- 
ponding period of tine in 192-1 was hut 5 days. A spray is effect- 
ive for approximately 10 days after application when plants are 
growing normally. This explains why, in southwestern Idaho, a 
second application was necessary in 1923, hut was of little extra 
benefit in 1924. 
In 1923 eggs hatched during the months of May and June, and were 
present in the field even after the first crop had been cut. In 
1924 eggs had practically all hatched oy the 25th of May. June, 
1923, was so wet and cold that alfalfa grew slowly and weevil 
larvae also matured slowly. A condition existed, therefore, such 
that a fewer number of worms, by feeding over a longer period of 
time, caused more injury than a larger number feeding for a com- 
paratively short time. In 1924 weevil injury was nearly all done 
by May 25; worms began to cease feeding, and many fields made a 
certain amount of recovery naturally. Tho lack of moisture and 
irrigation water and the intense heat of early May had the effect 
of hastening the development and feeding of the weevil, of reducing 
its feeding period and of retarding the growth of the alfalfa. 
Most of the growth of the alfalfa was made then after feeding 
abated and after irrigation water was applied more generously, so 
that plants virtually took a nerc start. 
The years 1921, 1922, and 1923 were quite similar in regard to 
development of alfalfa weevil and injury caused ^y it, so they may 
be taken to represent more nearly a normal condition than 1924. 
It is safe to ass->ime that conditions in 1925 will more nearly ap- 
proximate those of the three years first named than those of 1924 
and that we may reasonably expect injury from the alfalfa weevil 
again this season. The entomologist has made examinations in the 
field since last summer and has found an abundance of live beetles 
surviving. There are those who believe that the parasitic enemies 
of the weevil have them under control. Others maintain that the 
extreme drouth and heat of last summer killed them. The weevil 
parasite common in Idaho kills the worms before they can transform 
to beetles, so that either of these suppositions is untenable in 
the face of evidence that there were an abundance of beetles that 
entered the winter alive after they were supposed to have been 
killed by parasites or weather. 
The only safe conclusion is that tho weevil will be a limiting 
factor in the production of alfalfa hay in 192 5 if weather condi- 
tions are favorable for the pest. The only assurance of raising 
a full crop of hay is to be prepared to control the pest if necess- 
ity arises. If one is not already prepared to combat the weevil 
and plans to fight it this season he must arrange for the early 
purchase of machinery and supplies, for they cannot often be pro- 
cured at the time needed. The saving on one crop will pay for 
labor, equipment and supplies for several years. If control 
should prove not to be necessary, equipment and supplies do not 
deteriorate, and can be considered in the form of crop insurance 
that may not be drawn upon until another season. 
Conditions mentioned above are for southwestern Idaho. It is 
recognized that conditions in tho south-central or eastern parts 
of the State are different. 
