218 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



In this paper the discussion relates to nursery stock that has been 

 exposed to San Jose scale attack. This condition is necessarily a very 

 uncertain one, as it depends on so many points upon which we have 

 no definite data, such as the distance which birds, insects, squirrels 

 and other animals that frequent trees will travel from one tree to 

 another, and the distance which the young insects may be blown by 

 the wind, and on other conditions which vary so much, that they are 

 never just the same in any two cases, such as the number and degree 

 of infestation of the trees or shrubs which constitute the origin of 

 infestation. It is the general supposition that nursery stock standing 

 through the growing season within a half mile of infested trees is 

 exposed to infestation. If the origin of infestation should be only a 

 few trees or a single small tree, and the degree of infestation slight 

 and not of long standing, the distance within which stock is considered 

 as exposed to attack is correspondingly less. However, this does not 

 concern us now. The inspector must determine in each case whether 

 or not stock is exposed to infestation after taking into consideration 

 all the circumstances. Our discussion relates to the kinds of stock, or 

 rather species of trees and shrubs, that should be fumigated on account 

 of exposure to San Jose scale attack, and species that may safely be 

 exempt from fumigation. 



In those states which have any regulations, all, with three possible 

 exceptions, require that all stock known to be infested be destroyed. 

 In a little more than half of them the practice is to require the 

 fumigation with hydrocyanic acid gas of all the remaining deciduous 

 stock which may be safely fumigated; in a smaller number the prac- 

 tice is to exempt stock not subject to attack, and in one state at least, 

 the exemption extends to all stock except certain fruit trees. 



The question as to what stock should be fumigated, and what may 

 safely be exempt ought not to be difficult to determine. Our experi- 

 ence with the San Jose scale has been extensive enough to indicate 

 to us what stock is subject to attack and what is not. Doctor Brit- 

 ton's lists, which represent the results of the experience of those whose 

 observations have been the most extensive, with a slight revision, 

 which can be made as the results of observations made since their 

 first publication, will serve as our best guide in determining this point. 



To require the fumigation of species of trees and shrubs that have 

 never been known to be infested with the scale, though exposed to 

 attack, is going to extremes. It places a burden upon the nursery- 

 men that is, so far as we are able to demonstrate, useless. It is not 

 a matter of so much importance to the nurserymeii who grow mostly 

 or entirely fruit stock, and little or no ornamental stock not susceptible 

 to attack. The fumigation of their small amount of nonsusceptible 



