20 JAMESTOWN CONGRESS OF HORTICULTURE 



peaches, and in some seasons is slightly injurious to apples. The 

 apparatus for spraying is as a rule poorly constructed, clumsy, and in 

 great need of general improvement and adaptation to particular condi- 

 tions. Demand good machinery and pay for it. It is essential to suc- 

 cess. Those who know these things must teach, by demonstration, 

 those who know imperfectly or do not know at all. Literature is 

 valuable as an aid to demonstration teaching but can never take the 

 place of it. Too much dependence on literature is one of our great 

 educational mistakes. Send out fewer bulletins and more men. 



Briefly, then, we shall improve on the pathology of the last century 

 if we take time to be careful and thorough. Study the causes of failure 

 and profit by the results. Demand better-trained minds and improved 

 apparatus, and depend in our teaching more upon men and less upon 

 books. 



INSECT ENEMIES. 



A. L. QUAINTANCE, WASHINGTON, D. C. 



The protection of crops from insect injuries is one of the impor- 

 tant cultural problems. There is scarcely a wild or cultivated plant 

 but which furnishes food for a score or more of insects, and the num- 

 ber of species which may attack a given crop in many instances runs 

 up into the hundreds. Thus in the United States the apple furnishes 

 food directly or indirectly to some 280 different kinds of insects; the 

 grape upwards of 200, and about the same number has been recorded 

 as attacking the peach. Corn is fed upon by at least 50 fairly important 

 destructive insects, and wheat and oats together by perhaps twice that 

 number. Clover furnishes food for somewhat more than 80 species, 

 while so new a crop as the sugar beet is attacked by at least 70 different 

 insect pests. 



Not all of these insects are injurious every year, but any one of the 

 species which at present may be comparatively unimportant is liable at 

 any time, under changed con'ditions of environment, to become seriously 

 destructive ; as witness the outbreak the past spring in the grain fields 

 of the middle west of the so-called "green bug," a species of plant 

 louse; that of the pea louse a few years ago in Maryland and Dela- 

 ware; and the pear thrips, which at the present time is doing great 

 injury to the deciduous fruit interests in portions of California. These 

 two latter species were quite unknown to science previous to their 

 appearance in such destructive numbers. There are, however, a con- 

 siderable number of species that vary comparatively little from year 

 to year, chronic pests, so to speak, that may confidently be counted 

 on to put in appearance at their stated times, and these are responsible 

 for our principal insect losses. 



LOSSES FROM INJURIOUS INSECTS IN THE UNITED STATES. 



The actual damage inflicted by insects to crops is very difficult to 

 estimate, but attempts have been made from time to time to express in 



