This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
For two years I have put sulphur in a few of my plum trees, and have got some fruit from those trees alone. I think as sulphur is usually put into the trees, it can be of no possible use. A hole is bored, a little sulphur thrown in, perhaps half filling the hole, and stopped with a loose plug. Of course the air soon dries up the pores about the hole, and no part of the sulphur is absorbed and carried up with the sap. I have tried this mode several times without the least success. For two years past, suspecting what might be the cause of failure, I have proceeded more cautiously, and all I can say is, on those trees I had some fruit, on others none at all. I first bored a smooth half-inch hole, with a sharp center-bit, almost through the sap wood. I then took fine sulphur, in a half-inch gouge, and with a round stick crowded the hole as full of this substance as it could be pressed, up to the point I wished my plug to reach. I then fitted the plug with entire accuracy, so as not to split the bark, while it still pressed hard upon the sulphur, and excluded all air from the hole. I then sealed the outside fast with grafting wax, so as to exclude air from without.
Of course, if the sulphur is pushed into the heart-wood, or if the air come into the hole it can do little or no good, as it cannot be absorbed.
I suspect also, that after the sulphur is pretty well absorbed, so as to leave the hole in part vacant, the effect must cease, and as I did not repeat the process, it may be that was the reason why many of my plums were at last stung by the curculio. Still, hero again I consider nothing proved, only let us "keep trying." But as this process would naturally be ordinarily performed, it is evident it must utterly fail, even if good in itself. Let it be performed on both sides of the tree with great care, and repeated once in two weeks, or so - or once a week - and then it would be fairly tested. Let us also try with care, some more soluble minerals, or salt of iron, copperas, etc. - finely pulverised - and carefully inserted. Probably none of these would reach the fruit without injuring the tree. But that is not certain until it is tried; for even a noxious exhalation from the bark and leaves, might repel the intruder.