fiEiViEblAL MEASURES. 



68 



B 



where they could find shoUcr or to remain where they were, exposed 

 to the attacks of their predaceous enemies, the birds. In the instance 

 cited probably many were eaten by birds, as these were quite abund- 

 ant at the time, and the fields were bare. 



In the observations dealing with the dispersal of the beetles 

 throus^hout the fields it was determined that for the greater part the 

 beetles remain and lay eggs near the place where they have been 

 feeding. From this it is easy to see that in the fields which contain 

 the greatest number of old beets and beet tops the largest number of 

 beetles wiU deposit their eggs. As the wireworms can not travel 

 very far from where the eggs are laid it is readily seen that large 

 numbers of beetles in a field are the forerunners of large numbers 

 of wireworms in that field later, with their resulting injuries to the 

 crop. 



A condition leading to the successful hibernation and dispersal of 

 wireworms is illustrated in Plate XXIII, figures 1 and 2. In these 

 instances the immediate proximity of alfalfa fields to those containing 

 beets affords effective shelter for 

 the hibernating beetles, and, as 

 alfalfa is only second as a host to 

 beets, provides abundant food for 

 a continual supply of larvae and 

 adults. Reinfestation under such 

 conditions is naturally very likely 

 to occur through the migration of 

 the beetles from the alfalfa to the 

 beets, and both crops may thus 

 ])e injured. 



The main drawback to clean cul- 

 ture is that even where it is prac- 

 ticed faithfully several years must pass before positive results mU 

 be apparent. As has been stated, the same thing is true with regard 

 to fall plowing for the destruction of the pupse. This would be 

 advantageous in one way, however, in that the benefits would be felt 

 for two years after the treatment had been discontinued. The main 

 difficulty is that a grower, after practicing this remedy for two years, 

 might suffer heavily from wireworm injury, become discouraged, 

 and stop the treatment. The only way to give this remedy a fair 

 trial would be to practice it faithfully and wait until the third or, 

 better, the fourth year before drawing conclusions. 



The greatest advantage of this remedy is that it is entirely feasible 

 and, being cultural in character, is also entirely practical, regardless 

 of the crop grown. For the best results it should be practiced in 

 conjunction with faU plowing, and to reduce the injury from the 

 wireworms already in the soil early planting should be employed. 



/ALFALFA 

 F/ELO 



Fig. 9.— Diagram of beet fields, to illustrate the 

 effect of clean culture in reducing, injury by the 

 sugar-beet wireworm. (Original.) 



