INSECTS INJURIOUS TO CORN 149 



Preventive. As the natural food of these insects is grass, it 

 is not surprising that corn planted on sod land should be worst 

 injured; and though the injury done the grass may not have been 

 noticeable, when the available food is so greatly diminished by 

 substituting for grass the comparatively few hills of corn the 

 injury becomes much more serious and apparent. Though the 

 planting of corn on sod land is a most common practice, injury 

 by this and many other insect pests of corn most of whose 

 native food is grass might be avoided by planting any other 

 crop than a grain, such as potatoes. Otherwise plowing late in 

 the fall and harrowing so as to expose the larvae to the weather, 

 or plowing so deeply that they will be buried so that they cannot 

 regain the surface, will do much to prevent injury the next season. 

 Inasmuch as the moth will not lay her eggs upon plowed land 

 if the land be plowed early she will be driven to other fields; 

 but the exact time of oviposition varies for different latitudes. 



Generous fertilization will aid the plants in overcoming 

 injury very considerably. Dr. J. B. Smith advises " the applica- 

 tion of all the necessary potash in the form of kainit, put on as 

 a top-dressing after the field is prepared for planting," and says: 

 "Fall plowing and kainit as a top-dressing in spring will, I feel 

 convinced, destroy by all odds the greater proportion of the web- 

 worms that infest the sod, and would also destroy or lessen many 

 other pests which trouble corn during the early part of its life." 



The Corn-root Aphis * 



Where patches of corn become dwarfed, the leaves becoming 

 yellow and red, with a general lack of vigor, the grower may well 

 be suspicious of the presence of the Corn-root aphis. These 

 little aphids, which cluster on the roots of corn, are a bluish- 

 green color, with a white waxy bloom, and of the form shown in 

 Fig. 127. Two short, slender tubes project from the posterior 

 part of the abdomen which are commonly called honey-tubes, 

 because they were formerly supposed to give out the honey-dew, 

 which is so relished by the ants which tend the aphids to secure 

 it. The winged female has a black head and brownish-black 

 thorax, with pale green abdomen bearing three or four blackish 



* Aphis maidi-radids Forbes. Family Aphididw. 



