12 THE SUGAR-BEET WIRE WORM. 



result, viz, the tender taproot was cut and blackened and a search 

 generally revealed the offender, a wireworm, in the soil near by. A 

 great amount of just such work was noted, but it differed from that 

 of 1911 in that it was more scattered. 



In 1911 the wireworms seemed to be working in groups, and many 

 spots of varying size were completely cleared of beets. In 1912, 

 however, the fields were almost entirely free from this type of work. 

 Places were observed where from three to six beet plants had been 

 killed in one group, but by the time the beets are mature tlieir foliage 

 so covers the ground that all trace of the injury is lost to the casual 

 observer. One incident will illustrate this point. A small beet field 

 of 10 acres located near the laboratory was carefully watched that 

 some idea might be gained of the progress and time of injury. Every 

 day many of the plants were found dead, but seldom were more than 

 three or four plants killed in a place. While this inji ry was con- 

 siderable it was kept well scattered. At the time of the last examina- 

 tion the beets, then nearly ripe, so covered the ground with their 

 foliage that even where several adjoining plants had been killed it 

 was difficult to find any signs of the injury. This shows that it is 

 an easy matter to overlook the .destructive power of this wireworm. 



The sugar-beet wireworm may be considered the worst insect 

 enemy of the sugar beet in southern Cahfornia at the present time. 

 It has tliis distinction for two reasons: First, it is constant, appearing 

 every year to a greater or less extent; and, second, its injury occurs 

 in such a manner that replanting is generally impracticable, or at 

 least of Httle value. Wliile beets and alfalfa appear to be the favorite 

 food plants, the sugar-beet wireworm is also very injurious to corn 

 (fig. 3, p. 18) and beans (Pis. VI, VII). 



It would be a difficult matter to figure the loss due to the wire- 

 worm, either in percentage of the crop, tons, or doUars, but an 

 approximation will show its importance economically. Mr. R. S. 

 Vaile, horticultural commissioner of Ventura County, in his annual 

 report for 1912, places the loss to lima beans alone in his county at 

 $10,000. For 1913 he estimates the loss at $25,000 or more. If 

 the other counties where this wireworm is destructive are taken 

 into consideration it will be seen that probably the lima-bean growers 

 alone lose at least $50,000 a year by this insect. Add to this the loss 

 to sugar beets, wliich is })robably even greater, and it is readily seen 

 that this wireworm presents no small problem in southern CaUfornia. 



INSECTS FOUND WITH THE SUGAR-BEET WIREWORM. 



Collections of wireworms in the beet fields of southern Cahfornia 

 show at a glance that they are made up of several s})ecies. These 

 differ widely in appearance, hence there is little cliance of their being 

 mistaken for one another. Two of them, Limonius californicus Mannh. 

 and Drasterius livens Lee, are of the waxy color usually found in 



