Chapter IV: Peach-Growing in New York (3)

In the final stage of the disease the trees assume the yellowish leaves which give name to the trouble, though sometimes the yellow is tinged with red. Yellows is an unfortunate name since so many other troubles of the peach cause the foliage to take on the jaundiced appearance of this disease. The third stage marks the beginning of the end--sometimes three years, sometimes five or six, but always death sooner or later, there being no instance on record of a diseased tree having been cured.

This, in brief, is the usual course of yellows, but it follows no invariable rule in its development. Yellows is known to be spread as a contagion by affected buds in nursery stock, by nursery-trees, by orchard-trees, and may even be communicated by pits from affected trees. That it must be caused or transmitted in still other ways is apparent to all who have had experience with the disease. It seems not, however, to linger in the soil, for trees may be set in the very spots from whence diseased plants have been removed without danger to the newcomer. "War to the knife and the knife to the hilt"--absolute extermination, root and branch, by ax and fire, is the only known method of subduing yellows.

Little-peach is possibly a variant of peach-yellows or, at least, is very similar in nature. It seems to have been described first in Michigan in the early nineties of the last century but had attacked orchards in New York before that time so that it is now impossible to say where it first appeared. Be that as it may, the disease is not now the exclusive possession of either state but in the twenty years of its history has become as widely distributed as yellows, covering about the same territory, and seems now to be equally destructive. Outwardly the disease differs from yellows chiefly: (1) In delayed rather than premature ripening of the under-sized fruits of little-peach; (2) the leaves usually show more green than in yellows and show a decided tendency to droop or roll; (3) little-peach, as a rule, appears later in the season than yellows; (4) the characteristic, sickly, wiry shoots of yellows are seldom present in little-peach. Little-peach is kept at bay, as in yellows, by extermination of affected trees.

Rosette, though distinct in most of its symptoms from yellows and little-peach, is clearly similar in nature, is just as virulent and contagious, is communicated in the same ways and requires the same treatment. On trees affected with rosette the fruits shrivel and drop and tufts or rosettes of leaves develop freely. Rosette is not found in New York nor north of the Potomac and hence is of but passing interest to peach-growers in this State.

Brown-rot (_Sclerotinia fructigena_ (Persoon) Schroeter), known also as fruit-mold and ripe-rot, attacks flowers and shoots of the peach, but is most conspicuous on the ripe or ripening fruits. Here its presence is quickly detected by a dark discoloration of the skin which is afterwards partly or wholly covered with pustule-like aggregations of gray spores. The decayed fruits fall to the ground or more often hang to the tree, becoming shriveled mummies, each mummy being a storehouse of fungus threads and spores from which infestation spreads to the next crop. The rot spreads with surprising rapidity on the fruits in warm, damp weather either before the fruit is picked or in baskets while being shipped or stored. Preventive remedies have so far met with but indifferent success; probably the best method of control is to destroy the mummy-like fruits and all other sources of infection either by picking them from the trees, or much better by plowing them under deeply. Even so it is impossible to exterminate all of the countless myriads of brown-rot spores. Spraying with the self-boiled lime-sulphur mixture three times at intervals of three weeks, beginning as the calyxes drop, is the appointed preventive but the results are uncertain, as this is one of the diseases in which it is difficult to touch the spot in spraying. Varieties of peaches show various degrees of susceptibility to brown-rot.

Peach leaf-curl (_Exoascus deformans_ (Berk.) Fuckel) is the best-known and probably the most prevalent fungus disease of the peach in New York. The disease appears in early spring as the leaves unfold and continues until warm, dry, summer weather prevails. The name describes the disease so that all may know it--the leaves curl, then become puckered, distorted and much thickened, turn from normal green to yellow, tinged with red, and finally fall. In severe cases the trees may be defoliated, though a second covering of leaves almost always comes out. Leaf-curl is most prevalent and most virulent in cool, moist weather. The disease is easily controlled by spraying with lime-sulphur, bordeaux mixture or any other good fungicide applied while the trees are dormant.

In common with other species of Prunus the foliage of peaches is attacked by several fungi which produce diseased spots on the leaves, the dead areas usually dropping out leaving holes as if punctured by shot, giving the names "shot-hole fungus," "leaf-spot" and "leaf-blight." Two fungi are in the main responsible for these leaf-troubles, _Cylindrosporium padi_ Karsten and _Cercospora circumscissa_ Saccardo. The ravages of these fungi are prevented by the use of the self-boiled lime-sulphur mixture. With these, as with other fungi, cultivation has a salutary effect as it destroys diseased leaves which harbor the fungi during their resting period and keeps the trees vigorous enough to resist the fungi.

Peach-scab (_Cladosporium carpophilum_ Thüm.) is a common and destructive fungus in peach-growing districts on the Atlantic seaboard and is found rather frequently in New York but seldom does much injury in the State. It appears in sooty, black spots and blotches on the surface of the peach, causing atrophy and hardening of the parts affected which, in severe cases, crack badly. Twigs and leaves may be affected. White-fleshed sorts suffer most and are ruined for the market even in mild attacks. Self-boiled lime and sulphur, if it does not wholly prevent infections, at least alleviates the trouble.

Peach-growers in New York are much plagued by a mildew yet suffer small loss from it, though the disease greatly injures peach-foliage in some regions. The delicate, white or grayish powder, giving the name "powdery mildew," consists of the spores and mycelium of a fungus (_Sphærotheca pannosa_ (Wallroth) Léveillé) which attacks the leaves of several species of Prunus causing them to curl and crinkle and sometimes to drop. It occurs most often when there are sudden changes in temperature. When treatment is necessary, the self-boiled lime-sulphur mixture is used.

In common with all tree-fruits, the peach is attacked by crown-gall (_Bacterium tumefaciens_ Smith and Townsend). In New York crown-gall seldom greatly injures old trees but nursery plants are sometimes girdled by the galls, seriously injuring them. Badly diseased young plants, therefore, should not be planted. The galls are tumor-like structures, usually at the juncture of top and root, which vary from the size of a pea to that of a large egg, forming at maturity rough, knotty, dark-colored masses. Neither preventive nor cure is known. Planting diseased trees is not a safe practice, nor should the peach be set in ground known to have recently had trees badly infected. The raspberry is a common carrier of crown-gall and should not be planted as an inter-crop in a peach-orchard.

The peach suffers more or less from an excessive flow of gum. This gumming is usually a secondary effect of injuries caused by fungi, bacteria, insects, frost, sunscald, and mechanical agencies. There is a good deal of difference in the susceptibilities of varieties to this trouble, sorts having hard wood suffering less than those having soft wood. There is less gumming, too, on trees in soils favoring the maturity of wood, under conditions where sun and frost are not injurious, and, obviously, in orchards where by good care the primary causes of the diseases are kept out.

INSECTS ATTACKING THE PEACH

The peach has its full share of troublesome insects, entomologists listing about forty species, at least half of which are either destructive or annoying in New York. The peach cannot undergo hardships and once it is beset by parasites, it does not prosper. No small part of the peach-grower's time, therefore, is spent in combating the insect-pests of his trees. The several pestiferous species vary greatly in importance, the peach-borer probably holding first place in destructiveness.

The peach-borer (_Sanninoidea exitiosa_ Say) is probably the commonest and is certainly the most ancient enemy of the peach in America. It is found everywhere east of the Rocky Mountains and, since it is a native, its natural host being the wild species of Prunus, it has been a parasite on the peach from the earliest introduction of this fruit. All in all, it is the most destructive insect-pest of the peach, its presence always endangering the life of the tree. All peach-growers know the peach-borer. It is a white, grub-like caterpillar with a yellowish, shield-like head, which lives and feeds in the trunk of the peach just below the surface of the ground, eating out irregular chambers and galleries underneath the bark, sometimes girdling the trees. The pest is easily discovered through the exudation from the infested part of gum mixed with borings and excreta. The borers are found at all times in the summer, usually very small in late summer and autumn but an inch or more in length in early summer. The borer is a larva of a wasp-like moth which lays its eggs in early summer; these hatch in from seven to ten days and the minute borers work their way into the tree. The moth may be deterred somewhat from depositing her eggs by thorough cultivation, mounding the trees and, according to some, by the use of obnoxious coverings or poisonous washes on the trunk. Preventive measures are seldom sufficiently effective, however, and the borers must be destroyed. This is best done by digging them out with a knife or wire--"worming" in the parlance of the peach-grower.

The lesser peach-borer (_Sesia pictipes_ Grote & Robinson) is rather infrequently found infesting the peach in New York. It usually attacks only old trees or those showing injury from freezing or other causes. The borer is much like the common peach-borer, described in the foregoing paragraph, but is smaller, seldom reaching the length of four-fifths of an inch. Unlike the true borer, it infests the trunks as well as the crowns of peach-trees, feeding in much the same way. Fortunately the pest is not common in the State, for it is rather difficult to control, since not only the crown but the trunk must be reached in worming for the pest.

The plum-curculio (_Conotrachelus nenuphar_ Herbst) is sometimes a troublesome pest of the peach. It is a rough, grayish, hump-backed snout-beetle somewhat less than a quarter of an inch in length, an insect so familiar to fruit-growers as hardly to need description. The female beetle pierces the skin of the young peaches and places an egg in the puncture. About this cavity she gouges out a crescent-shaped trench, the puncture and trench making the star and crescent of the Ottoman Empire, hence the common name, "Little Turk." The egg-laying process may be repeated in a number of fruits and from each egg a larva hatches within a week and burrows to the stone, making a wormy fruit. Most of the infested fruits drop. Poisoning with an arsenate is the chief means of combating the pest. Rubbish and vegetation offer hiding places and hibernating quarters for the insects and hence cultivated orchards are most free from curculio. The thin-skinned nectarines are damaged most by the insect but peaches are attacked rather freely. Early peaches suffer much more than late ones from curculio; thus, of standard sorts in New York, Greensboro and Carman are usually injured more or less while Salwey and Chili seldom show a puncture. The plum-orchard is usually the source of supply of curculio and early peaches ought not, therefore, be set with or near plums.

San Jose scale (_Aspidiotus perniciosus_ Comstock) is as harmful to peaches as to any other tree-fruit. The insect is now so well known in all fruit-growing regions as scarcely to need description. It is usually first recognized by its work, evidence of its presence being dead or dying twigs--oftentimes the whole tree is moribund. Examination shows the twigs or trees to be covered with myriads of minute scales, the size of a small pin-head, which give the infested bark a scurfy, ashy look. If the bark be cut or scraped, a reddish discoloration is found. Leaves and fruit as well as bark are infested, the insidious pest, however, usually first gaining a foothold on the trunk or a large branch. Reproduction is continuous throughout the summer in this climate so that the insects multiply by leaps and bounds. The peach, possibly, succumbs more quickly than any other fruit, three years sufficing for the destruction of a young orchard if the pest be brought in on nursery stock. The rougher-barked, older trees resist longer and suffer less injury. Still, old orchards are irretrievably ruined in one or two seasons of unrestricted breeding. Peach-growers, in common with all fruit-growers, find the lime-sulphur solution applied in the dormant season the most effective spray in combating this insect. There are several insect-enemies of the scale that are valuable allies and entomologists say that the insects seem more susceptible to the climatic condition of the country than formerly but still natural checks are far from sufficient and the peach-grower should quickly attack with the spray-nozzle at the first appearance of scale.

Besides the San Jose there are several other scales more or less abundant in New York orchards, two of which make the peach their favorite host. These are the West Indian peach-scale (_Aulacaspis pentagona_ Targioni) and the Peach-Lecanium (_Eulecanium nigrofasciatum_ Pergande). Neither, however, is very troublesome as far north as New York and both are kept well under control by the treatment for the more common San Jose. The Lecanium is responsible for the discolored, sooty peaches occasionally found in parts of the State; for, though the discoloration is caused by a soot-fungus, the fungus lives in the honey-dew of the scale.

The black peach-aphis (_Aphis persicæ-niger_ E. F. Smith) is sometimes a serious pest in light peach-soils in New York but is not nearly as troublesome here as it is in states having a larger proportion of sandy land since it seems to find life easiest in light, warm soils. The insect is an intensely black, shining louse with brownish legs. It lives underground more than above ground, maintaining itself for most part on the tender roots of newly set or nursery trees, being found only occasionally on shoots and foliage. An expert eye detects the presence of the lice by the sparse and jaundiced foliage of young trees which an untrained eye would say were down with incipient yellows--indeed countless numbers of young trees have been sacrificed to the yellow's pyre when they suffered only from lice on the roots. The pest is easily detected on stock received from nurseries--the chief source of infestation--and the trees may be dipped or fumigated as for San Jose scale, thus completely exterminating the aphids. Good culture and a dressing of some fertilizer will help to carry young orchards through an infestation though treatment to a dose of a pound of ground tobacco stems worked in the soil about the roots may be necessary.

There is, too, a green plant-louse (_Myzus persicae_ Sulzer) more or less common on peaches in the State every season. It is very similar in appearance to the green aphis of the apple and other plants and makes its presence known by much the same effect on the leaves. It works on the underside of the leaves along the veins, causing the leaves to pucker, curl and crinkle much as with leaf-curl. This green louse, however, is seldom numerous or harmful enough on peaches to require treatment. Should treatment be required, no doubt nicotine, now the standard remedy for aphids on foliage, would keep the pest under.

The fruit-tree bark-beetle (_Eccoptogaster rugulosus_ Ratzeburg), known in New York as the shot-hole borer, is often a serious menace to old or decrepit peach-trees. The beetle is a small, cylindrical insect an eighth of an inch long, one-third as wide, the body uniformly black and the surface closely and deeply pitted and punctured, the punctures on the wing-covers arranged in rows. Injury to the peach by this insect is first indicated by exudation of gum from trunk and branches and later by numerous small, round holes as if the tree had been struck by shot. Healthy, vigorous trees are seldom attacked and if so the larvae do not develop, but a peach-tree suffering a decline from any cause whatsoever is open to immediate attack and once the pest gains foothold the plant is doomed. Here, indeed, an ounce of prevention is worth a pound of cure, for keeping the orchard constantly in healthy, vigorous condition to avoid accidental introduction, and prompt removal and destruction of infested trees, both preventive measures, constitute the only satisfactory treatment.

The peach twig-borer (_Anarsia lineatella_ Zell.) imported from Europe, has at times been a troublesome pest of the peach in parts of the United States but causes little injury in New York. Still, it can be found every year in nearly every peach-district in the State and needs, therefore, to be guarded against since it may some time appear in sufficient numbers to become formidable. The adult is a moth the larva of which is about one-half inch long, pinkish in color. This larva is the borer and in early spring attacks tender shoots boring down into the pith. It passes from one succulent shoot to another so that often many wilted shoots may be examined before the borer is found. Fortunately peach-trees send out shoots about as rapidly as this pest can destroy them so that in New York, at least, unless the tree is much weakened in vitality, not much harm is done. The twig-borer has small chance in a well-kept orchard, but, should it attain headway, prompt treatment with arsenate of lead will at once cut short its career.

Occasionally complaints come that the common rose-bug or rose-chafer (_Macrodactylus subspinosus_ Fabricius) is at work on the peach. Leaves, flowers and fruits are eaten. The fuzz on the epidermis of the fruit is a deterrent but once a beetle gets through into the flesh, a dozen more join in the banquet and the peach is quickly ruined. Now and then one hears of a crop destroyed by the beetle. Insecticides seldom avail, for the insects are very resistant to poisons. The insects breed only in waste places and hence they may be looked for in the orchards of the sloven or where slovenly kept fields adjoin. Cultivation and sanitation are, then, the preventives. In New York rose-bugs are abundant only in warm, sandy soils.