— 109 — 



EXPERIMENTS WITH ROOT KNOT, AND RESULTS. 



By W. Egbert Smith, of Napa. 



In the fall of the year 1890, I discovered that some of my prune 

 trees, then two years old from the planting, were badly affected with 

 root knot. I made inquiry of neighboring orchardists as to what might 

 be done to prevent or cure the disease, for I was a beginner in tree cult- 

 ure, but my neighbors seemed to know as little as I about root knot; 

 and the only advice I could get was to cut off the knots and thoroughly 

 cut away the affected wood. Acting upon this suggestion, I had the 

 soil removed from two rows (about sixty trees) sufficiently to expose the 

 first large branching roots, and providing myself with a chisel and a 

 half inch gouge, I went to work on the exposed knots, carefully cutting 

 them away and gouging out the diseased wood. I learned a thing or 

 two while at this work. I found, as others have, I presume, that the 

 root knot is attached by quite a small foot stalk, or root-of-the-knot, 

 which extends quite deeply into the stock or root of the tree. This root- 

 of-the-knot, or core as it may be called, can be traced by a discoloration 

 and softening of the woody substance. Owing to this fact it is quite 

 difficult to entirely remove the diseased wood. I found it so, especially 

 when clusters of knots were found — some as large as a man's fist — 

 growing under the base of the main roots, as well as around the princi- 

 pal root stem. This kind of work was not only tedious, but, as I found 

 later, was quite discouraging; because young knots rapidly grew again 

 the next year from the same core. Observing the soft and spongy 

 nature of the knot led me to think that the application of some sub- 

 stance in fluid form might penetrate and kill the diseased wood without 

 injuring the healthy wood. I determined to make some experiments in 

 this line at once. 



For these experiments I selected common substances, not with any 

 theory about their particular chemical action, but rather because they 

 would be cheap and easily applied, if successful, and because they were 

 somewhat used by orchardists for other purposes. The chosen list 

 embraced sulphuric acid, carbolic acid, petroleum, coal tar, cupric sul- 

 phate, ferric sulphate, sodium chloride, and potassium carbonate. About 

 a dozen of the worst affected trees were selected for treatment, and 

 wooden tags were prepared with the names of each substance to be 

 applied; also, the date of treatment, October 31, 1890, was written on 

 each tag. The acids were each diluted with water one half. The sul- 

 phates, chloride, and carbonate were dissolved in water to a saturated 

 solution. The application of these fluids was made by boring into 

 the root knots with a carpenter's brace and three-eighths bit. I aimed 

 to bore to the core of the knot. Then, from small bottles, I poured 

 these holes full of the prepared fluids, attaching the tags to branches 

 at the base of each tree, as the work proceeded. The soil was then 

 thrown back to the tree, and no further special attention was given 

 them until the fall of the next year. 



In the fall of 1891 they were examined and some trees found dead — 

 some alive, with the knots alive, also — and some alive with the knots 

 dead. This last named and much desired result had occurred with two 

 trees treated with the saturated solution of cupric sulphate (bluestone) 

 and one tree, the only one, treated with dilute carbolic acid. The result 



