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 pupe 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. 
