102 PROTECTION OF PLANTS, 1915-16 



more watchful for the first appearance of insect outbreak than after a series 

 of unusually wet years." 



General Methods of Control. 



The various methods of control of injurious insects may be grouped 

 into two general classes: A. Cultural or Preventive Methods — those practices 

 of culture or of handling the crop that prevent, or interfere with, the 

 development of injurious insects; and B. Artificial or Remedial Methods — 

 those which deal with injurious insects when they appear by the use of 

 poisonous or contact substances, or other artificial means. 



Cultural or Preventive Methods. 



For most farm crops Cultural Methods are the only practicable me- 

 thods. They are essentially Preventives. The most important cultural 

 methods are the following : 



1. Rotation of Crops. — The growing of crops year after year on the same 

 land permits many insects which feed on the roots to develop and multiply. 

 On the other hand, a good crop rotation makes it impossible, or very diffi- 

 cult, for an insect to pass through its life stages without being seriously 

 disturbed and its food supply destroyed. 



(a) Some rotations are preferable to others when wireworms and white 

 grubs are abundant. For exam.ple, where corn is the chief crop a rotation 

 of clover, corn, oats is better than forage grasses, corn, oats. Professor 

 Forbes, of Illinois, advises plowing the grass in early fall, and sowing clover 

 either with barley, wheat, or rye. The clover is allowed to stand two years 

 and is followed by corn or roots. Certain crops such as clover, barley, wheat 

 and rye, are not so liable to attack as are corn, potatoes, mangels, oats; 

 they are better adapted to follow sod. 



(b) Moreover, if sod infested with white grubs is broken up early, 

 sown to turnips or rape, and pastured with hogs in late summer and autumn 

 most of the white grubs will be destroyed by the hogs. As the grubs burrow 

 deeply at the approach of cold weather it is not advisable to pasture hogs 

 late in the season. Clover is seldom attacked by white grubs, and hence, 

 is useful as a "starvation" crop before planting to corn, potatoes or mangels. 



(c) Where the Clover- Root Borer is injurious in second year clover 

 fields, plow up the sod after the first season. 



2. Good Cultivation. — This involves careful treatment of the soil, the 

 crop, and its products, (a.) It means careful attention to the waste pro- 



