118 



IOWA ACADEMY OF SCIENCE 



Vol. XXV, 1918 



Sometimes, it is true, the situation is so difficult that there is 

 really not much that can be done. More often, however, the case 

 is far from hopeless, and even if great damage has been done, 

 specific recommendations may be given so that further damage 

 may be avoided in the future. 



ArecJ Where Wh'de-^rub Dama<^e Is Expected 



Figure 7. 



Severe damage by white grubs in Iowa has occurred in 1912 

 and 1915. Injury to corn and grass lands (timothy and blue- 

 grass) in extreme northeast Iowa has been especially severe. The 

 area affected is shown in fig. 7. In 1912 the loss to the corn 

 crop alone in the five counties of Allamakee, Clayton, Dubuque. 

 Delaware and Jackson, amounted to more than three million 

 bushels. At 39 cents a bushel, the value of corn at that time, 

 this loss amounted to more than a million dollars. 



Since loss to meadows and pasture was not taken into con- 

 sideration, and since the damage by the grubs extended into 

 adjoining counties, this figure falls cons:dera])ly short of the 

 whole amcmiit. Again, in 1915, at least an equivalent loss oc- 

 curred, although less noticed because of heavy precipitation 

 which kept vegetation green above the surface although the grubs 

 kept busy at their work all summer on the roots below ground. 



Severe damage by white grubs is usually periodical in occur- 

 rence. In the Iowa outbreak, which also extends into Illinois 

 and well into Wisconsin, it was early determined that every 

 three years would bring about a recurrence of the trouble. This 



