CHAPTER VI 

 ARTIFICIAL METHODS OF CONTROL 



It has been indicated that Nature has methods for the control of any- 

 continued undue abundance of insects, by a resulting scarcity of food; 

 by weather conditions; by insectivorous birds, and other animals; by 

 parasites and diseases; and probably in other ways also. But it seldom 

 pays to wait for the results so obtained, as they generally require a num- 

 ber of years for completion, and measures which may be termed artificial, 

 inasmuch as they are used by man, also have their value. 



These measures may be divided into two groups, viz., those which 

 aim to establish conditions unusually favorable to the plants or un- 

 favorable to the insects; and those which attempt either to poison or 

 otherwise directly kill the insects. In some cases perhaps, a given treat- 

 ment might seem to belong as properly in ona of these groups as in the 

 other, but in general the line of separation is quite distinct. 



Whatever the method and its effectiveness may be, there is always 

 the cost of using it to bear in mind. When this cost is greater than the 

 loss would otherwise probably amount to, it is evident that little will be 

 gained by treatment, except that in such cases possibly, omitting it for 

 this reason one year may result in such an increase of the pest as to pro- 

 duce serious results the following season. In other words, treatment 

 costing more than the probable loss may sometimes pay as a sort of in- 

 surance. In general, though, in every case where insect attack occurs, 

 the estimated cost of the treatment should be weighed against the 

 probable loss without it, in deciding whether to treat or not. 



GENERAL FARM PRACTICES 



These are chiefly methods for raising crops which distinctly increase 

 their vigor and growth or remove conditions favorable to insects. 

 Healthy crops, clean culture, the rotation of crops, late or early plowing, 

 and the time of planting are the chief farm practices which belong here. 

 Special methods for particular cases, directed more with reference to the 

 insects than to the handling of the plants, such as hand picking, the use 

 of repellents, burning insects, heat, trap lanterns, etc., may also be in- 

 cluded here, leaving the measures dealing with insects by the use of poisons 

 and by fumigation for later consideration. 



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