320 FoRTY-srxTH Report on the State Museum 



trees wliich had been set the year before. Tliese trees, in the autumn 

 after they Avere planted, wore an unliealthy aspect, and had patches of 

 a blackish rust upon their branches. During the second summer, the 

 trees died; and other trees on which this same rusty matter was found, 

 proved to be infested with the same insects." 



Whether the insect had appeared in the United States prior to this 

 is not definitely known, yet there is reason to believe that it may have 

 been operatino- in the State of New York as early as in 1824, if not in 

 the preceding century. 



In an article on " Pear-Tree Blight " by Dr. J, J, Thomas, in the 

 Cultivator for June, 1850, vii, p. 204, it is stated that Mr. E. J. Genet 

 had written expressing his belief that the disorder was caused by an 

 insect observed by him, and operating in the following manner: At a 

 little before midsummer, in the absence of dew for several nights, liquid 

 drops could be seen falling from a pear tree, which was subsequently 

 found to proceed from minute aphides thickly covering the shoots or 

 branches, and which had at first escaped notice from the indentity of 

 their color with that of the pear bark. They continued for about ten 

 days, and then disappeared. The varnish which these insects exuded was 

 legarded as poisonous to the tree. 



Mr. Genet states that the same disorder had appeared on the banks 

 of the Hudson in 1780-1793, and in 1802-1807. As these attacks may 

 not have been seen by the writer, it is not improbable that the}' were 

 the true "pear blight." " In 1824," Mr. Genet writes (probably from 

 personal observation), "the same disorder prevailed, and lasted four 

 years. In 1846 we were once more suffering from the same cause, and 

 our pear trees are still ])rostrated by its fatal attacks. This disease has 

 been called by some 'fire-blight.' One writer says it is produced by 

 the Ap/ns lunata, a small insect covered by fine, white wool, but the 

 insect whicli came under my observation is very different in every char- 

 acteristic — so small as to escape observation in the first stage, and so 

 similar to a fly at maturity as to mislead an inattentive observer." 



As the insect, from characters given, could not have been the common 

 and well-known apple-tree aphis, there can hardly be a doubt of its 

 having been the pear-tree Psylla. Its introduction may easily have 

 occurred as early as 1824, as pear-trees had been imported by nursery- 

 men for thirty j^ears prior to that date.* 



Dr. Harris' attention Avas first drawn to the Psylla in 1848 by Dr. 

 Plumb, through a communication published in the American Agricul- 



* See article on " Early Pear Importations" in the Couniry Gentlemnn for December ], 1892 

 page 907, where importation of pear-trees as early as in 1794 is recorded, and of other fruit-trees 

 in the first decade of tlie present centui-y, which, doubtless, " would easily be the means of 

 mporting such'noxious insects as infested them." 



