532 ANNUAL REPORT OF THE Off. Doc. 



jibaudoncd silo or ice-liouse may produce an exceptionally heavy 

 crop, while the mushroom house, built after the most approved pat- 

 tern, ma}^ prove a complete failure. Indeed, there is so much un- 

 certainty, that old growers are cautious about giving advice, and 

 will say they know nothing about the growing of mushrooms. If 

 anyone is fond of uncertainty, and wishes to engage in a tirst-class 

 lottery, let him go into mushroom growing. 



It is a general opinion that the cause of many failures is in the 

 spawn. It may be, that in its manufacture, it has been overheated, 

 or, on shipboard it has possibly been too close to the boiler, and 

 the moisture and heat have started it to grow, either of which would 

 damage it seriously. Perhaps we sometimes get old spawn, which 

 is considered very objectionable. It is very difficult to tell good 

 spawn — spawn that will produce desirable results with any- degree 

 of certainty, and but few of the men who grow mushrooms are 

 able to separate the good from the bad. It seems that this should 

 centainly be a part of the business that every grower might under- 

 stand. The manure, spawn and labor are all expensive, and there 

 should be some security that the spawn is fresh and strong, and that 

 it only needs the warmth, moisture and plant food properly applied, 

 to reward the grower for his vigilance and labor. 



ARGUMENTS FOR AND AGAINST THE FUMIGATION OF ALL 

 KINDS OF NURSERY STOCK LIABLE TO INFESTATION BY 

 SAN JOSE SCALE. 



By Prof. H. A. Surface, Economic Zoologist of Pennsylvania. 



By fumigation we mean subjecting an object to exposure to 

 deadly fumes when confined within a closed space. The vital range 

 between a tree and an insect attacking the same is so wide that 

 the fumes may be made strong enough to kill the pest without in- 

 juring the tree or plant. It is found by many experiments that 

 fumigation is the only effective means of killing the San Jos6 Scale 

 and certain other destructive pests when found upon nursery stock, 

 and thus preventing their spread to orchards in which this stock is 

 to be planted. 



One may fumigate with carbon-bisulphide or any other material 

 that will produce deadly fumes, but the best material that is now 

 known is hydrocyanic acid gas, generated by dropping cyanide of 

 potassium into sulphuric acid diluted with water. The requirements 

 in the State of Pennsylvania, and in fact in most states of the 

 Union, are that the cyanide must be 98 per cent, pure, the sulphuric 

 acid must be 1.83 per cent, specific gravity, and the following amount 

 must be used for each one hundred cubic feet of enclosed space: 



One oz. (by weight) of cyanide of potassium. 



Two oz. (by measure) of sulphuric acid. 



Four oz. of water. 



The sulphuric acid is to be poured into the water in an earthen 

 or wooden vessel, and the cyanide is to be dropped in suddenly. Then 

 the operator must escape from the room just as quickly as possible. 

 It is best to have the proper amounts computed according to the size 



