This section is from the book "The Gardener's Monthly And Horticulturist V22", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
I notice you frequently write about the Peach Yellows. We know but little about the yellows here: in fact I do not know that I can say I could certainly point out one single case of the yellows.
I will relate the following, thinking it may be of some interest to your numerous readers. Some six or eight years ago the Peach Aphis visited us in unprecedented numbers, destroying most of the young trees one year planted, and severely injuring some two year and older trees. The effects on the trees visited by them was plainly visible, the leaves turning yellow and not having anything like their usual size; many trees dying outright, others so weakened as to be entirely worthless. That season, at the time that Hale's Early Peach was beginning to ripen, the Milford, Del. Fruit Growers' Society invited a number of the Farmers' Club of New York and some Pennsylvania Profs, on Insects; also the late David Petitt of N. J. (said to be the best farmer of N. J.). My memory fails to give the names of the prominent doctors who met at Milford. I was invited to meet with these gentlemen and the Fruit Society, so I prepared myself as best I could. Taking a spade and grubbing hoe I marched off first and dug up two or three of the two year peach trees, root and branch, that had been covered literally black with the Peach Aphis in the spring, but had disappeared on approach of hot weather, letting some of the branches be on with the leaves, and the roots as left by the Aphis. Taking the peach tree branches with me, when I was called upon to give my store of information, I presented the tree aforenamed, asking the doctors what was the matter with those trees.
When to my surprise David Petitt of N. J., pronounced them genuine cases of yellows.
I can tell you it caused no little merriment in the crowded room of Del. Fruit Growers. Not one ever hearing, much less seeing a case of genuine yellows, as we have learned of it through books and papers in other sections.
I explained how the trees I exhibited did come in that condition, and further all I knew about the Aphis from careful observation. I have read all the information T can get on this insect. I must say that even Prof. Riley does not say much about its habits, etc. Of all insects I ever saw, it is the most wonderful.
I have dug up peach roots that were six to twelve inches deep in quite wet red soil, when the surface of the ground was cold, almost frosted. Thousands, yes millions, almost, in some cases were on the roots, the smallest so small as to be hardly seen with the naked eye, yet brought under a microscope, even the small ones were awful looking sap suckers. I have placed roots covered with these insects in bottles of cold water almost to freezing, leaving them in it for thirty-six hours, removed them, placed in warm sunny place, and in half an hour many would creep off; but after exposing them forty-eight hours all appeared dead. I should like to ask some of you doctors how they propagate so rapidly so deep in the soil; appear to do so down even six to nine inches deep, and when weather moderates, come right up, suck out the starting buds, hundreds and thousands on a single bud. I once used tar to save a lot of young valuable stock, the enemy came so strong out of the ground as to cover the tar and bridge over, and make the stocks appear all black. One week finished up the most vigorous stocks. Mild winters and followed by wet, cold springs, suit this great enemy of the peach. Mr. Aphis appears to glory in slight frosts; even a freeze don't budge him: down toward zero fixes him.
If soil is frozen deep for a long time in winter they are not apt to do much damage the following spring.
Repeated doses of the foul stuff tobacco gives them enough, but then you have to wait until they appear on the surface, while many more are sucking the life out of the roots that you can't reach.
Aphis can't stand clear, hot sunshiny days; in June and July they usually all disappear, but ah ! what a mark they leave in their track.