262 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1934 



INCREASE DUE TO IMPORTATION 



A glance at the extensive list of injurious insects in North America 

 which have been introduced, impresses one with the importance of 

 this heading.^*' Thirty-seven out of 73 of our most injurious pests 

 have been imported from other countries. More recent introductions 

 include the Japanese beetle, European corn borer, pink boll worm, 

 oriental fruit moth, European elm scale, and the lesser corn stalk 

 borer. All of these are in the stage of dispersion at the present time. 

 Many others, kept out by determined vigilance, are intercepted every 

 year by quarantine inspectors at ports of entry. 



THE INTRODUCTION OR DEVELOPMENT OF NEW CROPS 



The introduction of new crops to North America has resulted in 

 the pests of the crop following close behind. The semitropical crop 

 of cotton, fed upon by the Mexican cotton-boll weevil, is now attacked 

 by this insect over nearly the whole of the cotton belt, even when 

 grown well northward in the temperate region. Citrus pests fol- 

 lowed the introduction and extensive development of citrus fruits in 

 Florida, Texas, and California. Each of the three districts has a 

 somewhat different coterie of pests with which to contend. 



The areas for growing Sudan grass have been limited largely by 

 the chinch bug. Sweet corn is attacked too severely in the sub- 

 tropical regions by the corn-ear worm, the armyworm, and other pests 

 to be a commercial possibility. 



There has been a marked increase in the number and destructive- 

 ness of pests of pecans attacking the trees or nuts of this relatively 

 new crop. Many of the pests have transferred from other trees, es- 

 pecially hickory, black walnut, oak, and similar nut-bearing trees. 

 Some of the worst enemies have not spread as yet throughout all 

 the pecan-growing regions. 



The changing status of the insect pests of farm legumes and the 

 shift to the new hosts as they increased in acreage is a situation 

 sufficiently recent for present-day entomologists to have observed. 

 Crimson clover was the first legume to be used extensively as a hay 

 and soil-building crop. Then, about 60 years ago, alfalfa was intro- 

 duced. This crop was relatively free of insect damage until about 20 

 years ago when the clover insects had so thoroughly adopted it that 

 insect damage became a grower's problem. Then came winter vetch 

 and sweet clover, which the alfalfa insects rather promptly adopted. 

 Cow peas and soy beans are also attacked by some of the old clover 

 insects. Lespedeza shows no insect damage in Kansas so far, but the 

 clover or alfalfa insects Avill no doubt in time adopt it as a food 



" Herrick, Glenn W. Manual of injurious insects, pp. 16-17. Henry Holt, 1925, 



