A Study of the Factors of Control. 



As has been suggested in a previous section, man himself is 

 luidoubtedly responsible for much of the damage that has resulted from 

 the attacks of these pests upon his crops. In his clearing and cultivation 

 of the land he has seriously interfered "svith most of the natural agents 

 Avhieh normally have a retarding influence upon the grubs, preventing 

 them from assuming the proportions of a pest. ]Most important, perhaps, 

 is the effect upon the native bird life of clearing large areas ; not only 

 are their nesting places destroyed, but worse, many of the most valuable 

 species are themselves frequently killed by thoughtless individuals. To 

 be sure, excellent laws for the protection of these feathered friends are 

 now on the statute-books, but unfortunately these laws are seldom 

 enforced, especially in the newer districts. Therefore it is the duty of 

 every citizen to become as familiar as possible with the habits of the 

 commoner birds of his locality, so that he can lend his support to the 

 protection of those that defend his crops. Indeed it is only when public 

 opinion is so educated that we can hope that our bird laws will serve 

 their true purpose. 



Again, cultivation has had a retarding influence upon parasitic 

 insects. i\Iost of these feed upon nectar in the adult stage ; hence the 

 removal of all native floAvering plants, due to the clearing of the land, 

 has pushed them far back into the wilds, leaving the pests in our fields 

 to multiply without these restrictions. Obviousl.v. the thing that we 

 can do is to again attract these friendl.v insects by planting more nectar- 

 bearing flowers, especially in the waste places and along the headlands. 



And, further, the clearing of the land is a hardship to numerous 

 other predators which normally live upon the grubs and beetles; yet it 

 is possible to do much to encourage these. 



Finally, our destructive methods of agriculture require a word of 

 warning. The gi'ubs or larva^ of these pests normally feed upon decaying 

 organic matter in the soil, hence, naturally, do little damage to growing 

 plants in rich soils. Ordinarily, however, fields near timber soon become 

 grubby, probably because all the waste organic matter is continually 

 removed by burning, for the grnbs are then compelled to seek their suj^ply 

 of organic matter from the living roots. Commonly such conditions 

 prevail in soils that will not scour well, and hence stick to the ploughs -, 

 consequently it is almost impossilile to i>lougli in the trash, and the 

 farmer usually follows the custom of burning everything, until his land 

 soon becomes too poor to work. Therefore it is most important that we 

 change our methods on such soils. Some suggestions on this point will 

 be given later on in the section where I deal with the subject of conserving 

 humus. 



NATURAL CHECKS. 



These include climate, organic diseases, predatory mammals, lizards. 

 frogs, birds, insects, &c., also parasitic insects and poisonous plants. 



Meteorological conditions undoubtedly have an important relation 

 to control of these pests ; we now know that both excessive heat and 



