THE PRACTICAL ENTOMOLOGIST. 



63 



, BLACKKNOT. 



In the first volume of the Practical Entomolo- 

 gist, pp. 48 — 51, I showed that Black-knot is 

 nothing but an assemblage of minute funguses, 

 which perfect their seed, or "spores" as Botanists 

 term it, the latter end of July; aud that conse- 

 quently, as this fungus is an annual plant, by cutting 

 off and destroying the Black-knot early iu July its 

 further propagation may be effectually stopped. 



My observations and experiments referred exclu- 

 sively to the Black-knot on the Wild Plum, (Pru- 

 nus americana.) But from the eyidence which 

 will be adduced below, it appears to follow as a 

 necessary consequence, that the Black-knot on the 

 Cherry is caused by a distinct species of fungus 

 from that on the Plum. It is possible therefore, 

 that the period at which the Cherry fungus ma- 

 tures its seed, may differ somewhat from that at 

 which the Plum fungus matures its seed; and in 

 that event the proper period for cutting off and 

 destroying it, must also differ more or less. 



The following appeared in the iV! Y. Scm. Tri- 

 bune of Feb. 2, 18G(J, from the oen of Mr. Jas. H. 

 Parsons, of Franklin, N. Y. 



" Are the black-knots which infest the plum and the 

 cherry-trees the same in kind? Thirty years ago we hail 

 a number of large and thrifty plum-trees, which bore an 

 abundance of fruit every year. When the black-knot 

 appeared, the plum-trees rapidly disappeared. We then 

 set out cherry-trees which thrived for a dozen years or 

 more, when the black-knot attacked them also, and this 

 year, for the iirst time, they yielded no fruit, and may 

 be considered dead, as the black-knots upon the few that 

 yet remain are more numerous than the leaves were the 

 last summer. In the meantime several plum-trees have 

 started up, and more are appearing every year, and all 

 of them are apparently healthy; scarcely a black-knot 

 is to be found upon any of them, and upon some, none nt 

 all. And yet all of these trees stand less than two rods 

 from infected cherry-trees. 



Dr. Trimble in his work on Fruit Insects, re- 

 marks to the same effect as follows : — 



In the outskirts of Buffalo and Black Rook, N. Y. * * 

 there were Black-knots un the Plum-trees, but I saw none 

 on the Cherry-trees, as iu New Jersey and many other 

 places, (p. 90.) 



So far as- regards the Wild Plum (Prunus ame- 

 ricana,) and the Wild Black Cherry (Cerasus sero 

 tiua,) I can state the same thing from my own ob- 

 servations in the neighborhood of Rock Island, 111. 

 Both trees are very common there; and I have 

 been familiar with both for many years. Yet, 

 although on the former Black-knot is very com- 

 mon, I never saw a single specimen on the latter. 

 Neither, so far as I am aware, have we any Black- 

 knot on the cultivated Cherry. 



But from the following observations of Mr. Isaac 

 Hicks, of North Hempstead, N. Y., it would rather 

 seem as if there must be more than one kind of 

 fungus growing on the Cherry — one kind probably 

 originating from the Wild Red Cherry, (Cerasus 

 pBnnsylvanica,) which is closely allied to the culti- 

 vated Cherry, and thence spreading on to the latter, 

 and the other growing on the Choke Cherry, (Cer- 

 asus virginiana,)* which, as well as the Wild Black 



* The wild Choke Cherry in some places is nearl}^ dis- 

 patched by the ravages of' the Black-knot." {Gardeners' 

 Mcmthly, June 1866, p. 170.) 



Cherry (C. serotina), differs remarkably from the 

 tame Cherry in the fruit growing like currants 

 in "racemes." Clearly Black-knots of all kinds must 

 have originated in Native American trees, and 

 spread thence to our cultivated trees; for Black- 

 kuot is utterly unknown in Europe, whence both 

 our cultivated Plums and our cultivated Cherries 

 were originally imported. It will be remarked that 

 Mr. Hicts, in the course of his very acute and 

 valuable observations, confirms the above state- 

 ments, as to the Plum Black-knot not extending 

 on to Cherry or the reverse. 



It is evident there are several of the fungus that attack 

 fruit-trees. There is one peculiar to the Wild Cherry, 

 one to the common Cherry, such as the Morello and Duke 

 class, and one that belongs to the Plum. Each variety 

 of trees mentioned has its peculiar style of fungus, as 

 much as different species of animals and insects have 

 peculiar parasites which prey on them. About forty 

 years ago the Black-knot swept off all of a kind of bitter- 

 sweet Cherry that was quite common here, the name I do 

 not know. About seven years ago the fungus attacked 

 the Cherry-trees to the west of this place, in King's county. 

 Long Island, especially the Kentish and Early Richmond, 

 and nearly killed them all. It gradually spread to thia 

 place, moving eastward, and attacked the trees on the 

 west side of the orchard first. All efforts by burning 

 and cutting, proved unavailing, for being propagated by 

 minute spores, they spread from my neighbor's trees, 

 and hence our single efforts were unavailing. They now 

 appear to be clear from this pest such as were not killed, 

 and perhaps this generation will not be tioubled again. 



The Plum fungus has its periods of increasing, in cer- 

 tain places, to a great extent, and again being nearly 

 c^ctinet. We may state that the Plum knot did not pre- 

 vail here at the time of the Cherry-tree disaster, nor did 

 the Wild Cherry knot show any thing of an increased 

 abundance. The spores of the Cherry-tree fungus find 

 more resistance, or rather the bark of certain kinds does 

 not allow them to lodge and grow on those varieties as 

 well as on others, as the Morello class were sadly knotted, 

 while the Mazzard was entirel}' free, and Elton, Dow- 

 ner's Late, Honey, Ac, were nearly or quite free. 



Now we believe and argue, that the kind of fungus that 

 destroyed the bitter Cherry forty years ago, could not be 

 the same as the present fungus on the Cherry, or else it 

 would have also attacked the Kentish and others then. 

 And if the Plum knot is not caused by a different fungus 

 from the Wild Cherry, why does one prevail on one kind 

 of tree at a certain period while the other is free from it? 

 (Gardeners' Monthly, November, 1800, p. 335.) 



The practical inference to be drawn from the 

 above theory is, that plum-growers need not be 

 alarmed when their neighbors' cherry-trees are 

 swarming with Black-knot, and cherry-growers 

 need not be alarmed when their neighbors' plum- 

 trees are infested in the same manner. For the 

 disease can only spread from plum-tree to plum- 

 tree, and from cherry-tree to cherry-tree; just as 

 the Mildew and the Hot on grape-vines can never 

 spread on to apple-trees or currant-bushes. It would 

 further seem to follow, that Black-knot growing 

 upon the wild Choke Cherry cannot spread upon 

 our cultivated Cherry, and still less upon our cul- 

 tivated Plum-trees ; but Black-knot undoubtedly 

 can and dues spread from the wild Plum-tree on 

 to the tame Plum-tree, and probably from the wild 

 Red Cherry on to our tame Cherry-trees. 



Strictly speaking, this Black-knot question be- 

 longs to the Botanists rather than to the Ento- 

 mologists. But as the saying ils, I have already 

 " put my foot into it," and according to another old 

 saying, " One may as well be hung for a sheep as 

 for a lamb." B. D. W- 



