THE SUGAR-BEET WIREWORM. 



(Limonius californicus Mannh.) 



HISTORICAL. 



The sugar-beet wireworm (Limonius californicus IMannli.) has been 

 known in the coast lowlands of southern California for many years, 

 having been more or less destructive to sugar beets during the time 

 they have been grown here, and prior to that time was known as an 

 alfalfa and corn pest. In many locaHties the alfalfa had to be 

 plowed up and replanted every few years, as the ravages of this larva 

 so tlunned it out tliat only a partial crop could be harvested unless 

 replanting was resorted to at intervals. Owing to the fact that the 

 ground in the alfalfa fields is nearly always damp to the surface, the 

 wireworms seldom worked deep, and while they tunnelled through 

 the crown of the plant, it was only a chance injury or a heavy infesta- 

 tion that could make itself felt, so that its destructive powers in the 

 alfalfa fields is proof enough of its abundance. 



The wireworm has also been noted as a corn pest for years, many 

 growers reporting that on occasions it has been impossible to secure 

 an average crop even Avith several plantings. Mr. Nelson Ward, of 

 Compton, reports that on puUing up cornstalks he has discovered 

 from 17 to 30 wireworms burrowing through the roots and into the 

 crown of a single plant. 



LOSSES DUE TO THE SUGAR-BEET WIREWORM. 



There is great variation in the estimates of losses ascribed to tliis 

 insect, and very probably the correct estimate would run far above 

 the others. The reason for this is that unless the injury is excep- 

 tional it is likely to go entirely unnoticed. When the mreworms 

 work scatteringly, their injury is apparent only to the observer who 

 is looking especially for it, and at the right time. The writer bases 

 tliis assertion on observations made during the early spring of 1912. 

 At tliis time the adults were being collected, and as several hundred 

 acres of beet fields were carefully gone over several times, it was 

 possible, by close observation, to get a good estimate of the progress 

 of the injury and the total damage done. 



The sugar beets were quite small, having just been tliinned, and 

 were consequently at just the right age to receive the greatest injury. 

 The roots were simple, not having swelled, and wherever a beet plant 

 was attacked it was generally killed, as the roots were almost invari- 

 ably severed by the feeding of the wireworms. All the plants which 

 were noted wilting down were examined, and always with the same 



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