56 FARM PRACTICE IN RELATION TO INSECTS 



jurious species attack not simply a single variety of plant, but any that 

 comes within the same group, — for example, the striped cucumber 

 beetle, which will feed impartially on melons, squashes, and cucumbers. 

 It should be noted in passing that the plan that is good practice 

 from the standpoint of avoiding insect attack is likewise the procedure 

 recognized as wisest in maintaining the fertility of the soil and avoiding 

 difficulties on other scores. 



Special Questions in Crop Rotations 



Even where unlike crops follow one another, it may be wise to alter 

 the program because of threatening insects left by one crop for the next 

 in the rotation. To illustrate: when a field has been in sod for a 

 number of years, it is apt to harbor large numbers of wireworms. This 

 is due to the fact that sod ground forms the natural breeding place of 

 this insect. The presence of the wireworms might not be suspected, 

 for the grass roots on which they feed are so numerous in the soil that 

 no appreciable damage would be done to the sod. But, break up this 

 sod, so that the grass roots are killed, and plant the field to potatoes. 

 The wireworms will still be there in considerable numbers, since they 

 normally spend two or three years in the larval stage. In the whole 

 field there will be left for them to feed on nothing but the seed potatoes 

 that the owner has placed in the ground. The result, if the field was 

 well infested, will be a wholsesale destruction of the seed potatoes, 

 and if the owner replants, a repetition of the same performance. Had 

 the field been planted to clover, or some other similar crop in the 

 family of legumes, there would have been little or no injury. 



Fall Plowing 



Deep fall plowing is of value in destroying many forms of soil- 

 inhabiting insects — as well as helping to form a good seed bed and 

 conserve soil moisture. It is the habit of several pests of field and 

 garden crops to spend the winter as pupae or adults in the soil, some- 

 times in little earthen cells. Deep plowing, late in the fall, dis- 

 turbs these and throws many of them up to the surface of the ground. 



