68 



THE EEPOET OF THE 



No. 36 



Table Showing Results of Experiments on Cabbage Maggot at Guelph, 1918 



Method used. 



No. 

 plants. 



No. dead 

 from all 

 causes. 



No. alive. 



No. 

 dwarfed. 



alive. 



vigourous. 



Corrosive sublimate 



Tarred felt paper discs 

 round and hexagonal 

 kept clean 



Tarred felt paper discs 

 round and hexagonal 

 not cleaned 



Check 



100 



100 



86.6 

 40.4 



Note. — The better results obtained from the tarred felt paper discs at Guelph 

 than at Burlington were apparently due to the plants at Burlington being set 

 deeper in the soil and to the soil being sand, whereas the Guelph soil was clay. 

 The greater amount of shade and the greater difficulty in keeping soil off the plants 

 at Burlington gave the insects a better chance to cause injury. The corrosive 

 sublimate in both cases was used at the strength of 1' part to 1,000 parts of 

 water, or one ounce to 50 pints of water, and was applied with a watering can 

 with a spout in which was inserted a small piece of wood to conduct the liquid 

 directly *to the roots without waste. Four applications were given in each case, 

 the first, four days after the plants were set out and the remaining three at intervals 

 of seven days. At each application sufficient liquid was used to wet thoroughly 

 the roots. At Guelph more than was necessary was applied and at first a slight 

 yellowing of the plants occurred, but they soon outgrew this and became just as 

 vigourous as any plants in the plot. At Burlington no yellowing was observed 

 and the plants were very vigourous throughout. 



Corrosive sublimate has shown itself to be a very valuable substance in com- 

 bating this pest, but a great deal of work is yet necessary to determine the best 

 strengths to use, the number of applications necessary, and the best time to make 

 each of these. Tests will also have to be made to determine whether this substance 

 can safely be used with radishes and if so in what way. There is very little doubt 

 that the growers would much more readily use corrosive sublimate than apply 

 the tarred felt paper discs. They seem to have a decided objection to using the 

 latter, though they have been recommended for so many years. 



Prof. Jones : In the treatment of cabbage plants for Eoot Maggot was there 

 any difference observed iri the fertility of the soil to which corrosive sublimate 

 had been added as compared with that to which it was not added? 



Mr. Huckett: No observable difference. 



Prof. Jones: Corrosive sublimate is one of the strongest of our disinfectants, 

 and in addition to destroying the egg or the larva of the Cabbage Maggot it would 

 have a marked influence on the bacterial content of the soil. It would destroy 

 the nitrogen fixer and the nitrifiers and also the decomposing species of bacteria; 

 and providing there was not plenty of available food material in the soil ready 

 for the plants to use, then on account of the corrosive sublimate I should imagine 

 that synthetic action of the bacteria in the soil as well as decomposition action 

 would be materially interfered with. That would depend upon how long the 

 mercuric chloride was active in the soil after it had killed the maggots. Of course 



