SPECIAL FARM TOPICS 215 



tained from the state experiment stations or from the Department 

 of Agriculture. (Y. B. 1908.) 



However efficient, in general, rotation of crops may be in the 

 suppression of insect pests, the measure may easily be so applied as 

 not only to prove ineffective, but actually disastrous. This is espe- 

 cially true in the change from a g;rass to a grain crop, and also in the 

 process of breaking up and bringing under cultivation swamp lands, 

 notably in the Middle West. The farmer who destroys the grass 

 plants in his fields and in their stead attempts to grow Indian corn, 

 by so adjusting his plowing and planting that the grasses are killed 

 out, leaving the insects that feed upon them on the verge of starva- 

 tion at the time his corn is pushing above ground, will find that he 

 has made a serious mistake. A certain period of time must elapse 

 between the destruction of the old and the starting of the new vege- 

 tation, in order to starve or drive out the insect enemies. (Y. B. 

 1908.) 



How Danger May Be Avoided. In many portions of the Mid- 

 dle West a very large percentage of the annual loss to the corn crop 

 by reason of insect attack is occasioned by this sort of a change from 

 grass to a corn crop. 



In the case of reclaimed swamp lands it is always best to plow 

 during the summer, in the fall, and again in the spring before plant- 

 ing to corn. It is sometimes best to crop once with rye before at- 

 tempting to grow corn at all. The reason for this is that the enemies 

 of grasses and rushes growing in these lands before their reclamation 

 will remain as long as this sort of vegetation exists, even to a limited 

 extent, and if planted at once to corn they will attack this precisely 

 as they do their native food plants, and destroy it. Very many se- 

 rious losses have proven this to be true. On the other hand, where 

 the reclamation has been completed before any attempt is made to 

 grow corn on these lands, no such trouble has been experienced. 



A precisely similar trouble is sometimes experienced with tim- 

 othy meadows of long standing. An insect, commonly known as 

 the bill bug, breeds in the bulbous root of this grass, sometimes in 

 sufficient numbers to kill out the larger portion of it. The pest 

 develops in the fall and remains in the field over winter to begin 

 operations as usual the following spring. Now, if the infested field 

 were to be plowed late in summer or early in fall the insect would 

 probably abandon it, or, if not then, certainly in spring, as it could 

 neither feed nor breed there ; but if, as is frequently the case, plow- 

 ing is left until spring and corn is planted soon afterwards, the in- 

 sects transfer their attention to the corn, frequently killing the 

 plants outright, and in other cases causing what is generally known 

 as "frenching." This trouble is due to injury to the Tower part of the 

 stem, causing the plant to dwarf and throw up numbers of lateral 

 shoots or suckers from the same root, no ears being produced. In 

 the two cases just cited it is essential that the existing vegetation be 

 entirely destroyed, thus either starving the insects or forcing them 

 to abandon the field before the ground is planted to corn in spring. 



