6 Farmers’ Bulletin 1185. 
In warm seasons the plants get an early start, which tends to post- 
pone the turning point, but since this is more than offset by the rapid 
development. of the weevils the damage is likely to come early. An 
extreme case of this occurs when the season is dry as well as warm; 
then the drought retards only the alfalfa, while the weevils develop 
without hindrance, and check the growth while it is still too small 
for profitable handling. It is in such circumstances that spraying 
yields its greatest returns. 
In cold, backward seasons the situation is the opposite of that just 
described. The growth of the plants is hindered by the weather, but 
not so much as the weevil’s egg laying, hatching, and feeding, and 
I'ic, 3.—First crop ready to cut, ten days after spraying. The white area is an un- 
sprayed strip. 
the crop becomes nearly mature before its growth is halted. In the 
abnormally late season of 1917, when in Utah March temperatures 
were delayed 30 days, and April and May temperatures 15 days be- 
hind the normal schedule, the first crop was fully mature before any 
injury had taken place, and the result was the only good first crop 
since the introduction of the alfalfa weevil. At such times the effect 
of spraying upon the first crop is least pronounced, and its effect 
upon the second crop becomes the principal consideration. 
A heavy frost during the growing season has but little effect upon 
the insect, merely delaying the egg laying, hatching, and feeding for 
a few hours, but it may seriously stunt the alfalfa plants and thus 
a — 
