64 THE SUGAR-BEET WIREWORM. 



Considering that all the growers have idle horses during the late fall, 

 the plowing would not appear to be a large item of expense, espe- 

 cially when its value to the soil is taken into consideration. 



In conclusion it may be safely stated that the clean-culture remedy, 

 especially when reenforced ])y fall plowing and early planting, is easily 

 the most promising remedy which has thus far come under observa- 

 tion during the sugar-beet wire worm investigations. 



SUMMARY. 



(1) The sugar-beet wireworm kills the beet plant by injuring the 

 root. It is most injurious while the })eets are young and is destructive 

 only in the wireworm or larval stage. 



(2) The life cycle probably covers four years. About one month 

 each is required for the egg and pupal stages; seven to nine montiis 

 for the adult stage, during the greater part of which the beetle is in 

 hibernation; and about three years, or the rest of the time, for the 

 larval stage. 



(3) Thus far it seems to be impractical to employ remedies against 

 the larvte. As these Hve underground and are protected by a thick 

 integument it is difficult to injure them. They also seem able to eat 

 a certain quantity of many poisons and deterrent substances with 

 safety. 



(4) Plowing in the fall is a fair remedy against the pupae, but at 

 that time of the year the soil is dry in southern California and is 

 turned up in large clods; consequently many pupae escape destruction. 



(5) Much of the injury to the beets may be avoided by early 

 planting, thus giving the roots a good start before the wireworms 

 are doing their most extensive feeding. 



(6) Clean culture against the adults, by compelhng them to seek 

 shelter elsewhere and exposing them to the attacks of their bird 

 enemies, seems to be the most practical remedy found thus far for 

 this insect. The efficiency of this remedy would be increased if fall 

 plowing and early planting were used with it. 



BIBLIOGRAPHY. 



1843. Mannerheim, G. G. von.— Bull. Soc. Imp. Nat. Moscoii, vol. 16, p. 283, 1843. 



Original description of Limonius calif OTtiicus under the name 

 Cardiophorus californicus. 



1912. Vaile, K. S. -Ann. Kept. Hort. Coram. V^entura County, 1912. 



Brief account of damages, and remedies proposed for experiment. 



