REPORT OF THE SOCIETY 55 



There is perhaps one other thought that might be dealt with and that relates 

 to the economic control of insects affecting vegetable crops in general. The 

 work of the entomologist has developed certain recognized control operations 

 which in the majority of cases are proving satisfactory and economical. One 

 must always bear in mind, however, that the control of vegetable insect 

 pests has to be cheap enough to be brought within the economics of crop 

 production. This is not always possible. I think it would be no harm to 

 draw attention to that aspect of insect control which has to do with the improve- 

 ment of vegetable strains. A sound healthy plant growing from a sound 

 healthy seed is better able to produce economic commercial returns than a 

 plant growing from poor seeds low in vitality. For instance, in a field of 

 turnips being grown for cattle feed the treatment of sach a field with mercury 

 bichloride would probably cost more than the plants were worth and in the 

 majority of cases it would not be practicable to pursue control measures with 

 insecticides. As the result of some practical experience in this very connection 

 which I had once in a dairy section in the Lower Fraser Valley of B. C, it 

 was found that the degree of seeding obviated the danger of severe attack by 

 the cabbage root maggot. With plants which germinated at the rate of bet- 

 ween fifty and seventy to the linear foot of row, the degree of injury was not 

 as great as when the young seedlings appeared at the rate of between twenty 

 and thirty. The larvae of the cabbage root maggot as you doubtless are 

 aware, move to some extent along the row attacking plants as they go. How- 

 ever, such larvae do not leave the plants until they have exhausted practically 

 all available plant food. This period of migration which, of course, coincides 

 with the period of spring oviposition, take place previous to the time of thinning 

 the crop and the period of thinning usually coincides with the termination of 

 the spring oviposition period. Hence the thinning operations leave the sound 

 plants intact. If, therefore, L^urnip seed shows a high percentage of germination 

 it is natural that the quality of seed bears very closely upon the economic 

 control of the cabbage root maggot in field turnips. Exactly the same line of 

 thought might be pursued with onions, where with heavy seeding followed 

 by thinning good strong healthy plants obviate or outgrow the spring attack 

 of the onion maggot. 



The weight of heads and roots bears a close relationship to the strength 

 of the seed and it is this point that I would refer to as it bears directly upon 

 this question of plant pollination. There is no reason in the world whj' we 

 should not develop our own home-grown seed industry. Usually such 

 seeds are stronger when grown locally. They are suited to their environment 

 and if we can guarantee their purity the resulting plants are obviously better 

 and more worth growing. It is usually claimed, of course, that our costs of 

 production for seed crops are too high to compete with Europeans. You are 



