23 



BULLETIN OF 

 MASSACHUSETTS BOARD OF AGRICULTURE. 



INSECTICIDES. 



Br A. H. KiRKLAKD, Assistant Entomologist. 



Insect attacks of various kinds are chief among the causes which 

 hinder the successful development of crops, and, if neglected, too 

 often set at naught the labors of the farmer or gardener. Thanks 

 to the discoveries of modern science we are now able in nearly all 

 eases to find a means of checking these ravages by simple remedies 

 if employed at the right time. A brief digest of our present knowl- 

 edge of insecticides is given herewith in the hope that, while it 

 presents but little that is new, it may prove in some measure 

 helpful. 



The feeding habits of insects attacking the exterior parts of 

 plants afford us a ready means of separating them into two general 

 groups, biting insects (various caterpillars, beetles, etc.) and suck- 

 ing insects (plant lice, scale insects, etc.). The members of the 

 first group devour the substance of the plant by means of their 

 jaws, while those of the second group secure their nourishment 

 by the aid of a slender beak inserted into the plant tissues. The 

 substances to be used in the destruction of insects are determined 

 in great measure by these feeding habits and may in like manner 

 be separated into two classes : first, internal poisons used against 

 biting insects ; and second, external irritants or contact insecti- 

 cides employed in destroying insects of the second group. The 

 desirable qualities of an insecticide of either class are : — 



1. That it should kill quickly. 



2. That it should not burn the foliage or otherwise injure the 

 plant. 



3. That it should be cheap enough to be of practical value. 



In addition to these requisites an insecticide of the first class 

 should be capable of remaining upon the foliage in an effective 

 condition for a considerable period of time. 



