ENTOMOLOGY 25 



RESULTS OF CONTROL OP INSECTS. 



Enormous as is the annual loss which may now be fairly 

 charged to insects, it would undoubtedly be vastly greater if such 

 pests were left absolutely unchecked and no efforts were made to 

 limit their operations. Were it not for the methods of controlling 

 insect pests, resulting from the studies of the Bureau of Entomol- 

 ogy and of the official entomologists of the various .States, and the 

 practice of these measures by progressive farmers and fruit-growers, 

 the losses from insects would be greatly increased. Familiar illus- 

 trations of savings from insect losses will occur to anyone familiar 

 with the work in economic or applied entomology in this country. 

 The cotton worm, before it was studied and the method of con- 

 trolling it by the use of arsenicals was made common knowledge, 

 levied in bad years a tax of $30,000,000 on the cotton crop. The 

 prevention of loss from the Hessian fly, due to the knowledge of 

 proper seasons for planting wheat, and other direct and cultural 

 methods, results in the saving of wheat to the farm value of from 

 $100,000,000 to $200,000,000 annually. Careful statistics show that 

 the damage from the codling moth to the apple is limited two-thirds 

 by the adoption of the arsenical sprays, banding, and other methods 

 of control, representing a saving of from $15,000,000 to $20,000^ 

 000 in the value of this fruit product alone. The existence and 

 progress of the citrus industry of California were made possible by 

 the introduction from Australia of a natural enemy of the white 

 scale, an insect pest which was rapidly destroying the orange and 

 lemon orchards, this introduction representing a saving to the peo- 

 ple of that State of many million dollars every year. The rota- 

 tion of corn with oats or other crops saves the corn crop from the 

 attacks of the root worm to the extent of perhaps $100,000,000 an- 

 nually in the chief corn-producing regions of the Mississippi Val- 

 ley. The cultural system of controlling the boll weevil is already 

 saving the farmers of Texas many millions of dollars, and, in fact, 

 making the continuance of cotton growing possible; and scores of 

 similar illustrations could be cited. 



The losses occasioned by insects to farm products exhibit a 

 wide range in different years, due, as a rule, to favorable or un- 

 favorable climatic conditions, and also to the abundance, from time 

 to time, of natural enemies. The result is more or less periodicity 

 in the occurrence of bad insect years. In other words, periods of 

 unusual abundance of particular insect pests are, as a rule, followed 

 by a number of years of comparative scarcity. Furthermore, sea- 

 sons which may be favorable to one insect may prove unfavorable to 

 others, hence there may be not only periodicity in the occurrence 

 of the same insect, but more or less of a rotation of the different 

 insect pests of particular crops. 



CONCLUSIONS. 



A general analysis of the insect losses for this country has 

 been given in the introductory paragraphs. In concluding it is 

 only necessary to emphasize again the fact that these losses, enor- 

 mous as they are estimated to be, could be legitimately .swelled by 



