24 



failure of growers to get satisfactory results in the employment of the 

 recommended measures, that directions had not been properly fol- 

 lowed. Oj^erations against certain pests, to be successful, nnist be 

 done with exactness. The requirements are sometiuies too compli- 

 cated, involving considerable familiarity with entomology, so that the 

 average man is unable to properly carry out directions. For such 

 cases demonstration work has a legitimate field. It is perhaps an 

 open question whether the responsibilities of the economic entouioio- 

 gist go auy further than to study the life and habits of a given pest 

 and to point out the appropriate remedy, leaving the matter of its 

 utilization entirely with those directly concerned; but it has been 

 much to the good of the cause that uiany workers haA^e demonstrated, 

 sometimes over and over again, the l)enefits to be derived from insecti- 

 cidal applications. Indeed, this has been no small part of the work 

 thus far. 



Future jn-obleuis will probably not materially differ in character 

 fiom those of the past, but more and more should methods of preven- 

 tion replace the actual a^jplication of insecticides. If there is any- 

 thing in the idea that varieties differ with respect to their sus(;epti- 

 bility to insect attack, this matter should be thoroughly investigated. 

 Certain facts might be adduced that seem to indicate that this is, in a 

 limited way, true. Certain of our native vines are more resistant to 

 Phylloxera than European varieties descended from Yinifera. The 

 Northern Spy apple is said to be nnich less subject to attack from the 

 woolly aphis than other varieties, and its roots are often used as graft- 

 ing stock on this account. The immunity of the Kieffer pear from 

 the attack of the San Jose scale is a matter familiar to most of you. 

 The different varieties of plums vary much with respect to their sus- 

 ceptibility to the curculio. Other similar instances might be given. 

 The possibility of protecting trees and. plants from insect attack by 

 the use of certain fertilizers or the introduction into the circulation, 

 through the roots or otherwise, of substances objectionable to insects, 

 has often been suggested. Recent investigations abroad indicate suc- 

 cess in this method of preventing insect injury. Doctor Smith, in this 

 country, has been able to reduce the injuries of the pear midge by the 

 use of kainit. and this same fertilizer is considered valuable in protect- 

 ing cabbage, onions, and numerous other plants from certain of their 

 insect enemies. Thorough detailed life-history studies nnist replace 

 the often scant remarks concerning the four principal stages of 

 insects, and this improvement is already well under way. The inter- 

 relations between insects and their environment, e. g., their parasites, 

 and the influence of climate, altitude, and soil, is as yet almost an 

 untrodden field. A more accurate knowledge of the laws governing 

 the distribution and successful existence of insects must furnish much, 

 of practical value. 



