226 SECOND THOUSAND QUESTIONS IN AGRICULTURE 



with much favor, perhaps because in many cases the burrows are open 

 only after the damage has already been done and the insects escaped. 



For Ants' and Wasps' Nests. A small amount of carbon bisulfid 

 poured into the underground nests of ants, wasps, yellow jackets and other 

 insects of like habits will usually exterminate the colony. This method, 

 however, is of little avail against the Argentine ant, because of the many 

 small nests. 



Tobacco Fumes. 



For very tender house and greenhouse plants infested with plant 

 lice, thrips and other small insects or mites, it is sometimes advisable to 

 fumigate them with slowly burning tobacco, to avoid injury to the foliage, 

 but even in such cases hydrocyanic acid gas, if properly handled, is much 

 better and is gradually replacing the tobacco punk and other commercial 

 fumigants of a similar nature. 



Hydrocyanic Acid Gas. 



Hydrocyanic acid gas is usually generated by the addition of cyanide 

 to diluted sulphuric acid. The generation is made in an earthenware jar, 

 or in a special fumigating machine, the gas being confined in a fumigating 

 house, or, as is more often the case in California, in a tent thrown over a 

 tree. Any one desiring to use this form of fumigation should apply to 

 C. W. Woodworth, Professor of Entomology, Berkeley, for detailed 

 publications. 



FUNGOUS DISEASES AND FUNGICIDES.* 



Professor R. E. Smith of the University of California points the 

 purposes of fungicides in this way : "It should be clearly understood that 

 all control of plant diseases by spraying, dipping, disinfecting, etc., must 

 be accomplished entirely by prevention rather than cure. In other words, 

 these fungicides, to be effective, must be applied for the purpose of poison- 

 ing and killing the spores or germs of the parasites and thus preventing 

 their further spread and development." 



Bordeaux Mixture. 



Bordeaux mixture continues to be the most generally used of all 

 fungicides. Its effectiveness and harmlessness to plants depends upon care 

 used in its manufacture, on condition of atmosphere and of plant. The 

 formula ordinarily used, the 5-5-50, is entirely harmless when the plant is 

 dormant. It may also be used on some growing plants ; others it will kill 

 or greatly injure. It may be used even stronger than the formula given 

 when the plant is dormant, but these proportions are effective with most 

 fungous troubles. By the 5-5-50 formula is meant : 



*Chiefly as stated by W. H. Volck, horticultural commissioner of Santa Cruz 

 County. 



