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Vol. L. LONDON, AUGUST, 1918 No. 8 



POPULAR AND PRACTICAL ENTOMOLOGY. 



The Relation of Agronomy to Entomology: A Practical 



Illustration. 



by john j. davis, west lafayette, indiana. 



Numerous instances are on record where the occurrence of a 

 noxious insect has resulted in recommendations which are not only 

 effective in controlling the pest, but at the same time a benefit to 

 agriculture. It is here sufficient to illustrate with such common 

 examples as the northern corn root-worm {Diabrotica longicornis) 

 and the corn root-aphis {Aphis maidi-radicis) which are controllable 

 by proper rotations, and the alfa,lfa weevil {Phytonomiis posticus) 

 which is checked by the use of methods beneficial to the plant and 

 disastrous to the insect. Recommendations for Hessian fly control 

 may likewise be considered beneficial from the point of view of the 

 agronomist, since it has been learned that the time of seeding to 

 avoid the fly attack in the fall is coincident with the proper seed- 

 ing date regardless of insect prevalence, and further that the 

 supplementary recommendation, namely that of destroying the 

 summer brood of fly by plowing under the stubble, is a good 

 agronomic practice according to certain authorities, and especially 

 in those sections where the fly is so frequently abundant. 



In the past we have been largely dependent on two practices 

 for the control of the common white grub (Lachnoslerna spp.), 

 namely that of pasturing hogs in infested fields and a rotation 

 whereby corn, the most important field crop injured by grubs, is 

 planted the year of grub abundance on ground which was con- 

 tinually cultivated during the flight of May-beetles the preceding 

 spring. In other words, the control is practically a recommenda- 

 tion to plant corn on corn ground, that is, corn on ground likely 

 to contain fewer grubs, in order to avoid injury. This can hardly 

 be considered a remedy since it avoids rather than destroys the 

 insect, and the practice of planting corn on corn ground is not good 



