This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
We hear complaint from all over our country about the above disease of the Strawberry plant, asking the cause and remedy of the same. It is the general opinion that it is caused wholly by a fungus attacking the leaf. This may be partly the cause, but is my opinion there are other causes. Having watched it for several years past, I have always found it worst, or of any account only in certain seasons, such as the past, when we have a fine March and April and the plants start off finely, then a cold spell in May with frost, which checks suddenly the growth of the plants. The leaf spots and turns red, and by the time the fruit ought to ripen, the plant has no vitality left in it. Having frequently examined the roots, I have always found them infested with a blueish louse, sometimes so numerous that they cover the leaf-stems. This I think is one great cause of the trouble generally known as the blight. In favorable seasons, when everything conduces to the continued growth of the plants, the louse has no chance to gain any advantage over them; but, as soon as the weather is too cold or too dry with cold, they increase rapidly and suck all the life out of the young rootlets, which weakens the plants, and gives fungus or any other disease a chance to affect the leaf.
Whenever the leaf is perfectly green the roots will be found all right, but when the leaf is spotted or red, early in the season, something is wrong at the root, and I have always found that louse there, at some time in greater or less numbers. I am aware that there is a sun-scald, which some varieties, such as Jucunda, are liable to, but I refer only to the blight that attacks all kinds. Nothing is exempt from it in some seasons. I do not say this is the cause, but as far as my observation goes, I have good reason to believe it is; and think if we can find a remedy to destroy the lice on the roots, we would have little or no blight on such hardy kinds as "Wilson, Monarch of the West, etc. I have been trying liquid tobacco, which I think helped, but was not thoroughly effectual. I think, if those, whose plants get affected next May or June, will give them a thorough examination, they will find the roots affected as well as the foliage.