4° 



mature leaves of all the plants. The unusual spread of the Mildew 

 on this occasion was accomplished by bees which seemed to be espe- 

 cially attracted by it, as shown by the fact that they were continually 

 lighting upon the infected leaves. The prevention of this Mildew 

 consists in growing the plants under normal conditions as regards 

 ventilation, light, heat, moisture, etc. In case infection should occur 

 to a large extent from some mishap in the management of the crop, 

 recourse could be had to some spraying mixture such as Ivory soap 

 applied warm. It is prepared by dissolving one ten-cent bar of 

 soap in 15 gallons or more of hot water, and should be applied warm. 



Troubles Caused by Animal Parasites. 



Some other troubles with which growers of greenhouse cucumbers 

 have to contend are caused by organisms belonging to the animal 

 kingdom such as aphis, thrips, nematode or gall-forming worms, etc. 

 See figs. 14 and 15. Freezing or sterilizing the soil constitutes an 

 efficient remedy for the extermination of nematode worms. 



General Treatment of Cucumber Houses. 



Since pests of various kinds are likely to increase with the age of 

 the house, it is good practice to follow some systematic treatment of 

 the house each year as a means of prevention. As cucumber houses 

 are usually empty for a portion of the year it is possible to apply 

 stringent remedies. We have made a practice each year of thoroughly 

 fumigating our houses with either burnt sulphur or hydrocyanic gas 

 or both before putting in the crop. We have burned sulphur at the 

 rate of 200 grams (about 6 oz.) to 1000 cubic feet of space and 

 hydrocyanic gas at the rate of 



25 grams cyanide (nearly i oz.) 

 i more by weight of sulphuric acid. 

 |- more by weight of water than acid. 

 This amount is sufficient for 100 cubic feet. 



The sulphur treatment is not as expensive as the cyanide, and 

 while the sulphur is desirable for some things the cyanide is better 

 adapted for others. Either of these treatments will effectually 

 remove certain pests common to greenhouses, and we believe it desir- 

 able for growers to practice fumigation methods. 



