68 ENTOMOLOGICAL SOCIETY OF ONTARIO. 



FARM PRACTICE AND FERTILIZERS AS INSECTICIDES. 



By John B. Smith, Sc.D., New Brunswick, N. J. 



It is safe, I think, to assume that every economic entomologist has been at times 

 woefully disappointed at the outcome of what seemed the most promising experiments. 

 Most of us have learned by sad experience that because a poison, or one used as such, 

 acts well in one instance we can not be at all certain that it will act equally well in an- 

 other. Many of us have run across insects that seem to eat all our usual insecticides with 

 perfect impunity, or upon whom they act so slowly that they are practically 

 of no effect I have in mind at present, from my own experience, the 

 Rose chafer, Macrodactylus subspinusus (Fig. 34) of which many farmers 

 claim, from experiment, that the arsenites do not injure it. I am not quite 

 ready to agree to this, but I am certain that they act so slowly as to be 

 useless. 



Yi(. 34 Frequently we find insects whose life habits are such that we cannot 



reach them with insecticides, even if we have such as would readily kill 

 them. Of such a nature is the " Boll " oc " Corn worm," the larva of Heliothis armiger, 

 which in tomatoes lives in the fruit, and in corn lives in the ear ; in both cases safe from 

 any application we can make. We have next a series of forms which in their injurious 

 stage live in the soil itself and feed upon the roots of our crops. In cases such as I have 

 mentioned our battery of poison is of little or no avail, because there is no proper 

 opportnity to make use of it. We must adopt other tactics and, if possible, use preventive 

 measures. These may be either positive, as where we cover a tree trunk with a substance 

 mechanically protecting it from injury ; or they may be more indirect, as when we change 

 a crop, or plant late, or early, to avoid the period at which injury is done. This latter 

 means of prevention is one which, in my opinion, is worthy of the closest attention and 

 consideration on the part of entomologists. Not the mere planting early or late, but the 

 question of so arranging farm practice as to avoid insect injury to the important cro;). 

 Insects have a life history which in the vast majority of cases is practically invariable. 

 There is, usually, a fairly well-marked date of appearance, a tolerably defined period of 

 adult life, and a normal period of development. The first and most important problem 

 to be solved is the exact life history of the injurious species. That done, before the matter 

 of insecticides is to he considered at all, the question should be : Can we avoid trouble or 

 injury by modifying our practice without impairing quantity, quality, or price of crop 'i 

 In many more cases then is usually believed a mere change of time will avoid injury. I 

 do not claim any originality in this suggestion, and need only instance the fact that by 

 a proper attention to the date of sowing, damage from the Hessian fly may be avoided. 

 Rotation of crops, if intelligently practised, will frequently prevent trouble when 

 insecticides are out of the question. Our fellow member, iMr. Webster, applied this principle 

 in dealing with the Diabroiica longicornis, ensily controlling what threatened at one time to 

 become a very serious pest. Trap crops, planted principally to save the more important 

 staple, are often available. For irstance a full crop of late squashes may be obtained, free 

 from the borer, Melittia ceto, if summer squashes are first planted and the Hubbards and 

 Marrowfats somewhat delayed. The summer squashes will attract the vastly greatest 

 percentage of moths to oviposition, and these may be removed after getting an early 

 crop, filled with the larvae that would otherwise have attacked the later vines. The pro- 

 position to use corn as a trap crop to prevent injury from the Boll worm to cotton has been 

 forcibly urged by Mr. Mally in a recent bulletin from Dr. Riley's office. Methods of 

 cultivation are frequently of use — as for instances in squashes again, where borers attack 

 the vines near the roots. In fertile soil the joints may be covered at intervals and roots 

 will be formed at every such joint sufficient to mature the fruit, even if entirely cut off 

 from the original base of supplies. I have mentioned only a few instances to illustrate 

 the suggestions made, and make no claim to originality so far as the principles involved 

 are concerned. All have been applied by no means as often as they might have been, but 



