88 HcjHHi OH (I Tn<d of Turred Felt '' Discs" 



the same number of unprotected ones. A net gain of 57-9 per cent, 

 was thus effected by using the protective discs. 



The results obtained with the cabbages were even more striking as 

 only one plant was lost out of 408 protected by the discs. The infesta- 

 tion, however, was not nearly so severe in the cabbages as in the cauli- 

 flowers. Only 13-2 per cent, of the unprotected cabbages were lost as 

 against 63-0 per cent, of the cauliflowers. 



Market-gardeners, and gardeners generally, hold the opinion that 

 cauliflowers are much more liable to be destroyed by maggot attack than 

 cabbages, and the results obtained in these trials give strong support to 

 this view. Whether it is a fact that cabbage-root flies are more strongly 

 attracted to cauliflowers than they are to cabbages, or whether the 

 former plants succumb more readily to maggot attack than do cabbages, 

 remains a subject for further enquiry. The above results clearly show 

 that, on similar land, cauliflowers suffered much more severely from 

 root-maggot infestation than cabbages. The only factor that differed 

 in the two cases, was that the cabbages were planted out a month 

 earlier than the cauliflowers, and consequently were well established, 

 and growing vigorously, before the maggot attack became severe. 



Gibson and Treherne, who discuss very fully this question of the 

 relative susceptibility of cauliflowers and cabbages to maggot attack, 

 make the following statement: 



"We consider that the supposed susceptibility of cauliflowers over 

 cabbages is probably due to the lesser vitality of the former plants." 



During a period of seventeen days between June 25th and July 11th, 

 1915, at Agassiz, B.C., 1418 eggs were deposited on six cabbage plants, 

 while only 1038 were laid on six cauliflower plants ; these results lead 

 them to believe that no special choice exists on the part of the fly to 

 deposit on cauliflowers over cabbages. On the other hand, in the table 

 given on p. 26 of their bulletin, they state that 6602 eggs were laid on 

 twelve cabbage plants during 133 days, an average of 550-1 per plant, 

 equal to four eggs per plant per day. On six cauliflowers 5515 eggs 

 were laid during 117 days, an average of 919-1 eggs per plant, equal to 

 seven eggs per plant per day; i.e. nearly twice as many eggs were laid 

 on cauliflowers as on cabbages. Although the periods of time were 

 not coincident — the countings of the eggs on the cauliflowers being made 

 later in the year than in the case of the cabbages — the results would 

 appear to indicate that the flies were more strongly attracted to the 

 cauliflowers than to the cabbages. 



i 



