LEAF BLIGHT OF THE PEAR. 



THE LEAF BLIGHT OF THE PEAR 



BY JOHN TOWNLEY, MOUNDVILLE, WIS. 



On reading the communication on leaf-blight, by Mr. Hooker, I was reminded of a 

 paper on a similar subject by the late Andrew Knight. On referring to it, I find Mr. 

 Knight's observations so nearly coincide with those recorded by Mr. Hooker, that it is 

 probable the diseases observed by them are identical. The attack of a parasitic fungus 

 (and as will probabl}^ hereafter be found of the same species,) seems to have been the im- 

 mediate cause of disease in both cases. As so little seems to have been M'ritten hitherto 

 by horticulturists on this important subject, I send you extracts from Mr. Knight's pa- 

 per, considering that a statement of the facts observed by him, and of the experiments he 

 made with a view to determine how the disease is communicated from one plant to anoth- 

 er, and whether by any expedient it could be prevented or cured, might possibly prove in- 

 teresting to Mr. Hooker and to the growers of pears generally. I may mention that 

 Mr. Knight's paper was read before the Horticultural Society in 1815, and that the fun- 

 gus which attacked his pear trees was known to botanists at that time by the name of 

 Lycopcrdon cancellatum. 



"I observed, about seven years ago, a disease upon a few of the leaves of one of the 

 pear trees in my garden at Downton. Bright yellow spots, from which a small quantity 

 of liquid exuded, appeared upon the upper surface of the leaves in June; and subsequent- 

 ly, several conic processes, about one.third of an inch in length, were protruded from the 

 same parts, but from the opposite surface of each leaf; and from these a large quantity of 

 brown impalpable powder, consisting of very minute globular bodies, was discharged in 

 August and September. These minute globular bodies I concluded to be seeds of a species 

 of fungus; but as a few only of the leaves of my trees were affected, and no very injurious 

 effects were visible, I did not take anj^ measures to prevent their dispersion over my gar- 

 den. 



" I did not, however, long remain ignorant of the formidable nature of my new enemy: 

 for within two years, every pear tree in my garden became in some degree diseased. The 

 leaves onl}', at first, api)eared to be injured; but the disease soon extended itself to 

 the annual branches in many protuberant yellow spots, beneath which the bark was found 

 to have acquired a bright yellow color; and as far as this color extended, the bark and 

 the wood beneath it invariably perished, either in the same or following season, leaving 

 wounds similar to those inflicted by canker, but less curable. The fruit also became dis- 

 eased and worthless, and almost all the young shoots, when once attacked, perished in the 

 following winter. These effects were not confined to my garden, but extended to the 

 pear trees in an orchard which was two hundred yards distant, and I cannot entertain a 

 doubt, but that the disease was communicated to these by seeds which had been conveyed 

 by the prevalent west winds. I endeavored during the summer of 1813 and 1814, to 

 check its progress in my garden, by picking off every diseased leaf; but I found all my 

 efforts nearly abortive, and I have been obliged to destroy the greater part of my pear 

 trees: those which remain have become annually more diseased, and I fear never can be 

 ultimately preserved, unless a remedy for the disease can be discovered." 



Mr. Knight tried the effect of sprinkling the leaves with quick-lime and fresh wood 

 ashes, but he had not an opportunity of observing the ultimate effect of these substances, 

 most all the leaves fell off prematurely, 

 hose of a single small standard pear-tree, on which flour of sulphur had 



