MUSHROOM PESTS AND THEIR CONTROL U 



operator is usually well outside the door before the first charge 

 begins to generate gas. 



As the floor is always the coolest part of a house that is heating 

 or at peak heat, it is here that insects and mites are most likely to 

 survive the heat. With any method of fumigation it is there- 

 fore desirable that as much of the gas as possible be kept in the 

 lower part of the house. Unless fans are kept running in the house 

 at the time of fumigation, the gas, being hot as well as lighter 

 than air, will rise to the top of the house. The best results have been 

 obtained by raising the fans to the level of the fourth or fifth beds, 

 about 5 or 6 feet or more from the floor. In the case of the pot method 

 the air blast from the fans should be directed straight down over 

 each generator. This causes the gas to blow along the floor and 

 between the lower beds. After 20 or 25 minutes the concentration 

 becomes nearly uniform throughout the house, but for the first 20 

 minutes most of the gas is along the floor where it is most needed. 

 Unless fans are of the fully enclosed type, it is better to wait for 

 about 10 minutes before turning them on, as there is a remote possi- 

 bility of gas and air forming an explosive mixture which might be 

 set off by a spark. In experimental fumigation of commercial mush- 

 room houses it was demonstrated, by using chemically equivalent, 

 dosages of calcium cyanide and sodium cyanide with acid (1 : 1% : 2) , 

 that sodium cyanide and acid was much superior to calcium cyanide 

 in the concentration of gas obtained and was about half as expensive 

 per fumigation. 



Sodium cyanide is extremely poisonous, and great care should be 

 exercised in handling it. It should be stored under loch and hey 

 where it is not accessible to children or careless persons. The same 

 precautionary measures should be tahen ivith the acid. 



The same rules as to procedure and safety apply to fumigation at 

 peak heat in cellars or other small spaces as apply during prepara- 

 tion for the crop. Hydrocyanic acid gas should not be used in or 

 adjacent to dwellings at all, and sulphur only when there is no pos- 

 sibility of the fumes escaping. In these places it is better to depend 

 upon heat for mushroom-pest control at any time when the beds do 

 not contain spawn. 



GENERAL SANITARY MEASURES 



After the house has been through the "heat" and has been prop- 

 erly fumigated, precaution should be taken to prevent reinfestation 

 by insects and the other closely related pests mentioned previously. 

 Doors and ventilators may be made fly-tight with cheesecloth, or, 

 better, 30-mesh copper screen, if it is found possible to do so with- 

 out interfering too much with ventilation. This prevents the en- 

 trance of flies and also of any mushroom mites that they may be 

 carrying. 



Control of individual species of pests is discussed under separate 

 headings. 



In passing from a house infested with mushroom pests to one not 

 so infested, great care should be taken that no insects are carried on 

 the person or clothing. 



