The Apple-Tree / The Open Country Books—No. 1

by L. H. Bailey

There is no question about the efficacy of spraying. Its value has been demonstrated time and again. The methods and the materials may be learned from the experiment station publications in any State, wherein the advice is kept up-to-date.

In the days before the perfecting of the spraying processes, the codlin-moth was controlled by catching the pupating larvæ. Taking advantage of the habit of the worm to find lodgment under the bark on the trunk, it was the practice to scrape the loose bark from bole and large branches to destroy the hiding-places and then to tie a band of cloth around the trunk. Under this band the worms were taken, as they spun themselves up in the cocoons. This is a lesson taken from the industrious woodpeckers, who, in the winter, search the trees for the pupæ and make holes through the flakes of bark to get them. The scraping of apple-trees is not much recommended now for the reason that this special necessity is passed, and because the better tillage and care together with the soaking of the branches and trunk in the spraying operation, tend to keep the tree vigorous and the bark properly exfoliated.

So the worm in the apple has a delicate and interesting history. From egg to imago the transformations proceed with regularity, and they are marvelous. Had we not traced the sequence, no man could tell by appearances that the larva, the pupa and the moth are one and the same animal. They seem to have nothing in common. So is the egg stage as different as the other three, but we are measurably prepared for this epoch, since we know seeds so well; the egg and the seed are analogous. That a moth in the air should come from a crawling worm in an apple is indeed one of the miracles of nature. The worm leaves the apple ere it falls; how the worm knows the time is again a mystery. By some instinct, it is able to cognize a dying apple. The later worms, either the lastlings from the early brood or the product of subsequent broods, may remain in the apple when it is harvested, particularly in an apple picked before it is quite mature and from which the worm has not escaped.

The apple-worm ruins the crop by killing many of the fruits and by blemishing the remainder. Seldom are there two worms in an apple. They seem to respect each other's hunting-ground. From the worm's point of view and from man's, one is enough.

If man has dominion and if he needs apples, then is he within his rights if he joins issue with the insects. Yet is the insect as interesting for all that. I think we should miss many of the satisfactions of life, and certainly some of the disciplines, if there were no insects. My apple-tree is a great place for a naturalist. Van Bruyssel wrote a book on "The Population of an Old Pear-Tree." "When certain blue spirits begin to flit about me," he writes, "I depart from my study to go and read, in what I am allowed, even by my clerical uncle, to call my book of devotions. The devotions I mean are not in my book-case. No publisher, if he ever thought of such a thing, could bring them out. They are a page of the book of Nature, opened in the country, under blue sky, displayed at all season." What a marvelous company Van Bruyssel found on his old pear tree; and what inexhaustible worlds did Fabre discover in the lives of the spider, the fly, the caterpillar, the wasps, the mason-bees and others!

Therefore we need not pause with the other four hundred and more insect citizens of the apple-tree. Some of them, as the San José scale, are not peculiarly apple-tree insects. My tree has another crew of inhabitants, and to this company we may now have introduction.

The spots on the leaves and fruits are not deposits of dirt nor are they caused by mysterious conditions in the atmosphere, as once supposed, nor is it in the nature of leaves to be spotted and of fruits to be scabby; nor are the one-sided dwarfed fruits merely accidents. The organism responsible for these blemishes is less evident than the codlin-moth; yet what fruit-grower knows the eggs of the codlin-moth? But the organisms are as definite as are the insects; no longer are the fungi things without form and without positive cycles.

On the ground are apple leaves, shed in the autumn. On the leaves are spots or lesions,—injured or "diseased"—infected with the apple-scab fungus. Under a good microscope the investigator finds immature fruiting bodies in these areas. In the early days of Spring, these bodies or winter-spores mature. A rain discharges them in astonishing numbers. Rising in the air (for they are incredibly light), these spores lodge on the unfolding leaves and flowers of the apple, and there begin to germinate, invading the tissue. The tissue is penetrated and killed so rapidly that the practiced eye soon discovers a "spot." The leaf, if badly infected, may not reach full size; it may curl; it may die and fall; the tree thereby is injured.

From the fungus in the active diseased areas, another kind of spore develops rapidly. It is the summer-spore, which may be produced in prodigious numbers, and being discharged carries the disease elsewhere.

All summer the process of spore-formation and distribution keeps up. If conditions are favorable, the tree is invaded in foliage and fruit. The flower-stems in the unfolding buds are attacked by the winter-spores and the flower falls. The apples become spotted from the invasion of the summer-spores, perhaps misshapen. Late infections may not show at picking time, but develop on the fruit in storage. The affected leaves are cast in the autumn, the winter-spores begin to form, the snows come and hide the processes, in spring the spores mature; and so does the round of life go on and on.