77 



existed on the roots of certain forest-trees in this whole region of 

 country; and when apple-orchards began to be planted, it emigrated 

 on to the apple-trees. 



This rotting away of the roots, which, as it appears, had been 

 noticed as long ago as 1858 by Mr. Dnnlap, and attributed to its true 

 cause, is popularly known in South Illinois as "rotten-root," and was, 

 at one time, considered as a mere natural decay, superinduced by the 

 system of root-grafting now so very generally adopted in the West; 

 while, as we have seen, Dr. Long, of Alton, attributed it to the oper- 

 ation of stagnant water on the roots.* The "Early Harvest" apple 

 is said to be peculiarly subject to this mortal malady. Similar cases, 

 where insects give the preference to one particular varietv, or avoid one 

 particular variety of a cultivated plant, are common in Economic 

 Entomology. For example, the Colorado Potato-bug (Doryphora 

 lO-lineata, Say) is known to avoid the Peach-blow Potato, and, as 

 has been already shown, (above, page 28), the Eose-bug prefers the 

 Clinton to all other grape-vines. 



But although the more southern parts of Illinois are far worse 

 afflicted by this insect than the northern counties, yet it exists and does 

 considerable damage even in North Illinois. Mr. Kinney, the Eock 

 Island nurseryman, informs me that he has often noticed a woolly 

 louse, which can be nothing else but this species, on the roots of his 

 young apple-trees, along with just such knots and swellings as it 

 usually produces elsewhere, and he has himself lost four or five bear- 

 ing apple-trees, and knows of 20 or 25 others that have been lost by 

 his neighbors, through what, from his description, must be the same 

 "rotten-root" that prevails so extensively in South Illinois. Mr. L. 

 Woodard, nurseryman, of McHenry Co., North Illinois, also told me, 

 that he had occasionally noticed a few woolly lice on the roots of his 



*Mi\ Kiley informs me that apple-trees, and more especially those that 

 are young, -sometimes die in South Illinois "with their roots entire and dis- 

 colored throughout from tlie surfar-e-mark downwards," but with "no trace 

 of any insect whatever;"' and that this very distinct disease is "known in the 

 West and by Warder, Flagg and others as 'Rotten-root.' " I am quite con- 

 fident that the dead trees, with their roots almost entirely rotten, in Mr. 

 Wright's orchard were killed by the Root-louse; and the peculiar appearance 

 which they presented has been already described, so that it can be recognized 

 with facility. But T by no means wish to be understood as asserting, that 

 every apple-tree that dies in South Illinois dies of the Root-louse. Perhaps, 

 under the popular name of "Rotten-root," two very distinct affections of the 

 roots of the Apple-tree have been confounded together, the one caused by the 

 Root-louse and the other arising from unknown causes. I hope to investigate 

 this question more fully during the coming season. 



