INSECTICIDES, PREVENTIVES, AND MACHINERY. 427 



white grubs. Badly infested fields may even be ploughed more 

 than once, and in different directions, just to give the chickens 

 an opportunity of picking up the insects. I have seen flocks so 

 well trained that whenever the plough harness was put upon the 

 horse they gathered together, waiting until he was taken to the 

 field. 



Turkeys are exceedingly useful where grasshoppers are to be 

 dealt with, because they are especially fond of these insects ; and 

 for the same purpose Guinea-fowls are also advisable. Here 

 again the practical farmer will find, with a little observation, just 

 about the range of usefulness of the various fowls, and will be 

 able to adapt his cultivation somewhat to their peculiarities. 



In the matter of the fertilizers to be used we have also an oppor- 

 tunity for careful selection. We may say generally, that manure 

 and all vegetable matter in a decaying state favors the develop- 

 ment of insects. It affords both food and lodgement to many 

 species, and when it is put on in the fall or winter in a coarse 

 condition, it is a direct benefit to insects that hibernate, even 

 when ploughed under. On the other hand, the mineral fertil- 

 izers, especially those containing a considerable percentage of 

 salt, are unfavorable to insects of all descriptions, and to some 

 they are deadly. Experience has shown that plant-lice are sus- 

 ceptible to the action af the salty fertilizers, and that cut-worms 

 and wire-worms are affected by them to a considerable extent. 

 Among corn insects, injury from the root web- worms may be 

 entirely avoided by using the mineral fertilizers instead of barn- 

 yard manure, if fall or very early spring ploughing is not feasible. 

 So the time of application is important, as is the amount to be 

 applied. For instance, in land infested by wire-worms and to be 

 put into corn, the best tmie for the application is just after it has 

 been prepared and after the seed has been planted. Then all 

 the potash should be put on, in the form of kainit, in one appli- 

 cation, while as much as is desirable of the nitrogen should be 

 put on in the form of nitrate of soda. In this way the soil 

 becomes impregnated with a rather concentrated salty mixture 

 which is fatal to many of the insects. The same amount of fer- 

 tilizer distributed in several applications, or put on the ground in 

 fall, or when vegetation covers it, would be entirely ineffective. 

 Mineral fertilizers are advisable wherever their use is otherwise 



