﻿6 BULLETIN 8, U. S. DEPARTMENT OF AGRICULTURE. 



EFFECTS OF ATTACK OF THE LARViE. 



The initial effect of the work of the larvae in the roots of corn is a 

 shortening of the ears, leaving long tips devoid of kernels. As the 

 infestation and injury increase, plants fail to develop ears, and 

 finally a dwarfing of the stalks occurs. The appearance of the crop 

 is precisely the same as it would be if the land were impoverished. 

 Indeed many farmers, ignorant of the real trouble, claim that their 

 soil has " run out " and is incapable longer of producing corn. One 

 farmer insisted that his corn was damaged by careless cultivation. 

 For this reason much injury may be done by the pest before it is 

 recognized at all. 



NATURAL ENEMIES. 



The Biological Survey has found specimens of Diabrotica longi- 

 cornis in stomachs of the nighthawk {Ghordeiles virginianus) and 

 the wood pewee (Myiochanes virens). 



The natural enemies of this species are exceedingly few, the prin- 

 cipal one being the parasitic fly Celatoria diabroticce Shim., figured in 

 Bulletin 5 of this department as an enemy of the adult of the bud- 

 worm. Mr. George G. Ainslie, however, has found that the beetles 

 are attacked by the so-called chinch-bug fungus, Sporotrichum 

 globidiferum. The larvse of the click-beetle Drasterius elegans Fab. 

 are also frequently found among those of this species and may destroy 

 some of them. 



CROP ROTATION AS A PREVENTIVE MEASURE. 



In all of the history of this, one of the most destructive pests in 

 the cornfield, there is not an instance on record in which corn has 

 been injured when planted on land following a crop of small grain, 

 such as wheat, rye, barley, or oats. Except on grounds subject to 

 overflow, which prevents a rotation of crops so that corn is or must 

 be grown for two or more successive years, this pest is one of the 

 easiest to control. Two instances only need be cited in order to prove 

 this fact. 



In Dekalb County evidence of the protection afforded by the rotation of 

 crops is afforded on a much larger scale. On a farm of 4.600 acres owned by 

 Hon. Lewis Steward, near Piano, rotation of crops has been the regular rule; 

 1,600 acres of this land was planted to corn this year, and 700 acres were care- 

 fully examined by Mr. Webster. In August only 10 acres of this entire tract 

 was found affected by the corn rootworm, and this was where, in the rear- 

 rangement of the fields, a small tract of ground happened to have been .planted 

 to corn the previous year. All about Mr. Steward's place, on farms where 

 rotation was not systematically practiced, the damage done was serious and 

 general. 1 



1 Quotation from 14th Rept. State Ent. 111., p. 29, 1885. 



