NINETEENTH ANNUAL YEAR BOOK— PART IX 487 



CROPS INJURED. 



These grubs, under natural conditions, are found only in grass sod. They 

 live three years in the ground, but never travel from one field to another. 

 When sod that is infested with them is plowed up and put into other 

 crops, the grubs are compelled to feed upon whatever they find there. The 

 crops that suffer worst are corn and potatoes. Small grains are seldom 

 injured severely because of their abundant root system and early maturity. 

 Buckwheat and the leguminous crops, such as clover, alfalfa and the va- 

 rious forms of beans and peas are not natural food plants for the grubs and 

 are seldom damaged. 



THE LIFE CYCLE. 



The life cycle of the white grub can be readily seen by referring to figure 

 2. This insect should not be confused with the large grub so often found 

 in manure piles and stack bottoms. The two differ in both life history 

 and feeding habits. 



The clumsy brown May beetle or "June bug" so often seen about the 

 lights in the spring, is the parent of the common white grub. These 

 beetles emerge from the ground in the evening during May and early June, 

 as shown in figure 2, to feed on the foliage of many species of trees and 

 shrubs. They return to the soil in the early morning to hide during the 

 day and to deposit their eggs. The eggs are deposited in rather compact 

 soil, preferably grass sod or a good stand of small grain. Eggs are sel- 

 dom deposited in loose cultivated ground or in a heavy stand of pure clover 

 or alfalfa. 



The eggs hatch in three or four weeks and the young grubs feed that 

 summer on the grass roots and decaying vegetable matter in the soil, do- 

 ing little damage. About the middle of October, as shown by figure 2, they 

 begin to burrow deeper into the soil. The winter is passed below the 

 frost line, from four to six feet below the surface. They reappear at the 

 surface in May of the second year and by the end of the season have attained 

 nearly their full growth. It is during this year that the greatest amount 

 of damage is done. 



The second winter is also passed deep in the soil. The grubs feed only 

 a short time during May and early June of the third year, then they go down 

 to a depth of about five or six inches and construct an oval earthen cell 

 within which they transform to a pupa and, in August, to the adult beetle. 

 They remain in this cell until the following spring, when they come out 

 to fly to the trees and later to lay eggs for the next generation. 



"When the grubs are in the field there is no practical method by which 

 we can get rid of them without injury to the crops. They can probably be 

 best controlled by proper crop rotation. Fields that are intended for corn 

 or potatoes in 1921 should have a good stand of one of the clovers or alfalfa 

 or be in some cultivated crop in 1920. Fields known to be badly infested 

 with small grubs in the fall of 1920 should be left in grass or sown to 

 some small grain that will stand up well on that kind of soil. 



