I inclose you a few leaves of the white pine, covered more or less, as you will perceive, with eggs of what I take to be the uAmerican Blight," as they call it in England. If not this, it is an insect very much resembling it, and attacking in its perfect state principally the axils of the limbs and branches, though being more or less scattered over the tree. I have observed for several years, that our larches and pines, and particularly the Scotch fir, are apt to be very much infested with these troublesome insects early in June, confining themselves principally to the trunks and branches on the pines and firs, but upon the larches scattered indiscriminately over the foliage, and more especially attacking the young wood. By August the insects upon the larch generally disappear, probably wafted by the wind and the pendulous motion of the branches, and disseminated like the seeds of the dandelion and thistle. Those upon the pines and firs, however, seem to remain the year through, resting quietly upon the trunk, and principally at the axils of the limbs.

The difference in the action of the insect upon the pine and larch, is that when they disappear upon the latter, there is no trace of them (beyond the enfeebled growth of the tree) until they suddenly make their re-appearance in June; whereas, upon the pines they seem to hang about all winter in a listless, indifferent state, while the leaves of badly affected trees are more or less covered with their eggs, as is the case with the leaves I enclose.

I should be glad to know, in the first place, what becomes of the insect from August to June, when it re-appears upon the larch. As it has but little or no power of locomotion, as it appears, beyond the wafting about by the wind, one can hardly account for its sudden re-appearance. Secondly, I should be glad to know if there is any feasible method of controlling an enemy which, if he goes on progressing in numbers and force, will soon destroy many of our valuable evergreens. In Scotland, I understand, the disease has proved so formidable as to have entirely destroyed several thousand acres of larch and fir plantation, upon the estate of the Duke of Athol; and I find that I have already lost several pines and Scotch firs from this most perplexing enemy.

You may imagine how impossible it is to attack this disease in the shape in which I send it to you - each leaf upon a large pine surrounded by several nests of eggs. When in the spring they assume the shape of the woolly aphis, or American blight, it is possible to subdue it by a preparation of sulphuric acid, in the proportion of 3/4 oz. acid to 7 1/2 oz. water, scattered through a garden engine over the foliage: but this is not very effectual, unless when thoroughly done; and then when thoroughly done, is very apt to destroy, or very much deface the tree, especially if young.

Perhaps some of your readers more fortunate than myself, may have discovered some method less dangerous, and more effectual, for subduing this enemy. If not, I very much fear, (at least in our part of the country,) that in a few years we shall know the white pine and scotch larch only by name and recollection. More than this, I do not see why all the new pines will not be similarly affected. The Piceas and Abies seem exempt so far, though I am sorry to find the Deodar cedar is apt to lose its leader every summer, from the attacks of the pine weevil. At Messrs. Parsons' Nursery, Flushing, that fine avenue of Deodars just commenced, had their leaders all more or less cut up by this destructive insect My Deodars are also more or less attacked every year in June, by another enemy - a beetle - which gnaws patches the size of a sixpence on the trunk and principal limbs. I have found dusting the tree with sulphur, though not particularly becoming to an evergreen, efficacious in repelling the attacks of this beetle.

I have examined carefully the pines and larches of my neighbors upon the river, and find them more or less affected - those places the worst where the Scotch larch abounds, which would confirm what my lamented friend Mr. Downing used to say, that it was a disease that made its appearance in this country within the last ten or twelve years, and is now being scattered through it, from the large importations of Scotch firs and larches, and from these has been communicated to that fine evergreen, our white pine. If it proves fatal in Scotland, why should it not here! In fact it has, in my own case, in several instances. I should be very glad if some one interested in this most important branch of ornamental planting, the evergreen family, would take the subject in hand, and devise some ways and means of protection.