124 The Canadian Horticulturist. 



THE BLACK KNOT. 



|HE following letter appeared in a recent issue of the St. Mary's 

 Argus, and was sent to the Canadian Horticulturist for repro- 

 duction by Mr. T. H. Race, believing that it might at least awaken a 

 new interest in the subject, whether the theory advanced be accepted 

 or not. The contribution is from Mr. T. W. Gibbs, of Oshawa, who has evi- 

 dently given considerable study to the subject : — 



On pages 137 and 138, vol. 4, 1881, of the Canadian Horticulturist, Mr. N. Hend- 

 lickz mentions a Belgian writer, the author of '* God, His Providence in His Insects," who 

 describes in that work the insect which is the cause of the black knot. Mr. Hendrickz, 

 unfortunately, gives a very brief description of the little pest. 



I think, Mr. P]ditor, that the scientific professors in our colleges and the entomologists 

 have a good deal to answer for. If the average farmer had been told that the cause of the 

 V)lack knot was a very industrious insect, instead of a fungoid disease, there might have 

 been a united effort made to check its ravages, but having been told that a fungus was the 

 cause, despair has seized the average fruit grower, and the industrious pest has been allowed 

 to multiply at his own sweet will, causing a loss annually in this Canada of ours of hun- 

 dreds of thousands of dollars in fruit, to say nothing of trees. During the past thirty-five 

 years I have been trying to persuade the fruit growers that an insect was the cause of the 

 trouble and the '* black fungus " the effect, but with very partial success. In the past two 

 years I have talked with thousands of fruit growers, and in the county of Brant I have 

 found 75 per cent, of tlie fruit raisers aware of the true cause ; in the town of Goderich the 

 same knowledge exists. 



In the town of Paris I met the only man, l>esides myself, who had ever observed the 

 fully developed insect. In appearance it is very similar to the "Curculio," but a little 

 softer and a little more pleasing to the eye. I liave met with one or two observant men 

 who have geen it in the sheet along with the curculio, when they have jarred the trees for 

 the latter insect, but I have never yet met with a man, besides myself, who has seen the 

 mature female deposit her eggs. On the young branches of the plum and cherry she scores 

 downwards in parallel lines one or two inches. Her cutter is entirely different from the 

 curculio ; the latter makes a crescent -shaped cut in the fruit, and then deposits the egg in 

 the curve. The black knot insect lias a cutter projecting from the proboscis, very similar 

 to a phlegme. After cutting deep enough the outside bark curls oflf on both sides of the 

 cut, then she deposits her egg in the soft succulent inner bark. In warm weather the grub 

 .soon hatches and immediately begins to eat its way into the middle of the limb ; a spongy 

 gall begins to form, and it is weeks, aye months, before the excrescence becomes black — in 

 fact the fungus does not and cannot exist until the excrement of the grub exudes with the 

 gum from the wound, making a suitable soil for the fungus, any more than the edible 

 mushroom can be propagated without horse manure. If any observant man will make a 

 careful examination of his trees in early June, he will see some small tender branches of his 

 cherry and plum trees with the bark curling off" on l)oth sides. Careful examination will 

 disclose the egg. I have many times seen the whole performance, and the egg finally de- 

 posited. Now, I will defy any man to propagate or innoculate plum or cherry with the 

 fungus. 



How is it that the fruit growers have never thought to enquire why, if their theory 

 was correct, the fungus never propagated in the wounds caused by men's boots, ladders, 

 etc. ? It never did and never will unless the egg is laid and the grub ejects its excrement 

 with the gum ; later on the fungus appears. 



Prof. Maynard (vol. xv. fol. 229 Canadian Horticulturist) says: *'The diseased 

 wood should all be cut out or the disease will extend. " I state emphatically it is not a 

 <li8ease, and if you cut the grub the fungus will perish for want of proper nutriment. 



It is impossible for any man to find, either in plum or cherry, any black fungus one 

 ♦luarter of an inch beyond where the grub has eaten its way into the wood, and ejected its 

 excrement. Cut out the grub or grubs (I have frequently found three or four), leave as 

 many mycelium threads (see Prof Panton) as you please, not another fungus spore will 

 strike root ; they all perish for want of nutrition, in other words, want of excrement. 



The grub is creamy white, with a brown head ; when fully grown, about three-quarters 

 of an inch long ; has strong sharp mandibles ; has six feet in front, terminating in sharp 



