Ant Yee on No eRe pAb ce wt fen Enc? tH thw i tet Wes : od ew tr . fs rari Ms ee eee cad Re siete Mey pote Reve Sirs decane Sutin B- D aiiiatidi Be dedi died i epee 4 Se Fa hah REN. Cootho = ——_- te Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. CIRCULAR No. 32, THIRD REVISE. Issued December 10, 1907. United States Department of Agriculture, BUREAU OF ENTOMOLOGY, THE LARGER APPLE-TREE BORERS. By F. H. Carrrenpen, In Charge of Breeding Experiments. Among the most troublesome of the insect pests with which the fruit growers of the United States have to deal are two species of bor- ing beetles known, from the appearance of their larvee, as the round- headed and flat- Headed apple-tree borers. The first of these belongs to the family Cerambycide and the other to the Buprestide. In ad- dition, there is another species called, after the adult form, the spotted apple-tree borer and to distinguish it from the round-headed borer, which it closely resembles. The two species first mentioned are common and injurious throughout a wide extent of country—the former to seed fruit trees, the latter also to stone fruit as well as to a great variety of forest and ornamental trees. The third is a com- paratively rare insect and rather exceptionally injurious so far as known. THE ROUND-HEADED APPLE-TREE BORER. (Saperda candida Fab.) Fie. 1.—Saperda candida: a, larva, from side; b, from above; c, female beetle; d, pupa—all enlarged one-third (original). INTRODUCTORY REMARKS AND DESCRIPTION. The round-headed apple-tree borer is, next after the codling moth, the worst enemy to apple culture in Ognestian The first intimation that the grower may have of the presence of this borer in his trees, unless he be forew arned, is in their retarded 13806—No. 32—07 2 growth and the sawdust-like castings, consisting of excrementitious matter and gnawings of woody fiber, which the larve extrude from the openings into their burrows. This manifestation is usually accompanied by more or less evident discoloration of the bark and, in early spring particularly, by slight exudation of sap. The parent of this borer is a beautiful beetle, measuring from three- fourths to nearly an inch in length, the male being perceptibly nar- rower than the female. The antenne are long, stout, and many- jointed, being somewhat shorter than the body of the insect itself. ‘These organs and the legs are gray, the undersurface of the body and the head are silvery white, and the upper surface is light yellowish brown with two longitudinal white stripes extending through the thorax and elytra or wing-covers to the tip, as is shown in the accom- panying figure 1, ©. The larva, when mature, measures from three-fourths to a little over an inch in length (22-26™™). It is legless, fleshy, and some- what grub-like in appearance, cylindrical in form, and light yellow in color. The head is darker, particularly about the mandibles, which are nearly black. The first thoracic segment is large and broad and bears on its summit numerous small tubercles, placed closely to- gether. The remaining joints of the body are narrower, the constric- tions between them being deep and conspicuous. The first seven abdominal segments bear on the upper surface of each a peculiar elevated process, as shown at figure Ew The pupa, illustrated at d, is iecily as long as the adult insect, which it resembles in a superficial manner, the head being bent down toward the breast, and the legs and long antennz folded upon the ventral surface. Its color is similar to that of the larva. Saperda candida was given its specific name by Fabricius in the year 1787, and was again described as new by Thomas Say, in 1824, under the name of S. bivittata, the latter remarking at the time that it injured apple trees by boring into the wood. DISTRIBUTION. This species is native to this country and is present in injurious numbers in practically every State of the apple-growing region east of the Rocky Mountains. It inhabits, like so many other injurious in- ‘sects, the upper austral and transition life zones; comprising the better agricultural portion of all except the extreme southern States. It has ‘been reported to occur in one locality, Agricultural College, Miss., ‘which lies in what is considered the lower austral zone. As with many other noxious species, too, it is in the older States, particularly of New England and New York, where orchards have been long estab- lished, that injuries are most pronounced. Until recently this species {Cir. 32] 3 was not known as especially injurious about the District of Columbia, but at the present time it has become very abundant and destructive, whole orchards both of young and mature trees having succumbed to its ravages. | Its known distribution includes Canada, all of the New England States, New York, New Jersey, Pennsylvania, Delaware, Maryland, Virginia, West Virginia, District of Columbia, Ohio, Illinois, Michigan, Iowa, Missouri, Kansas, and restricted localities in Texas, Alabama, and Mississippi. FOOD PLANTS AND NATURE OF INFESTATION. This borer is practically limited in its food to the apple and kindred woody plants. It is most injurious to quince and apple, and some- what less so to pear. It infests also crab apple and thorns of different Species, mountain ash, chokeberry, and juneberry—in short, practi- cally all except one or two kinds of trees and shrubs belonging to genera included in the family Pomacee. The wild plants are its natu- ral food, but certain varieties, at least, although often inhabited by this insect, are for some reason not so susceptible to its injury as are our cultivated trees. This species inhabits more particularly the base of the trunk of trees, often being found below the surface of the earth, especially in young nursery stock. It is to such trees that it is most injurious, for it soon works around the trunk, separating the wood from the bark, interfering with the flow of sap, and producing the effect of girdling, a result which is very apt to be produced even when no more than two or three larve occur on the same tree. Very fre- quently four or five larve dwell together in a single small tree and in a short time injure it quite beyond recovery. In old trees larve occur somewhat higher up the trunk, in exceptional cases at a distance of several feet from the base or even, still more rarely, in the lower limbs. As arule, however, they are seldom found except within a foot or two of the base. Trees of all sizes are frequently killed or weakened to such an extent that they are unable to mature a full crop of fruit. The experience of many years shows that injury follows where grasses, weeds, or other rank vegetable growth are permitted to accu- mulate about the trunks of the trees, since the beetle, like all nocturnal insects, naturally seeks concealment, and the conditions thus afforded are most favorable for its attack on cultivated plants. LIFE HISTORY. The beetles make their first appearance of the season late in May or in June, according to locality. During the night they come forth from the trunks of the trees in which they have bred, and at this time may be seen in flight. During the day they hide away in some secluded [Cir. 32] -. place, under leaves or in similar situations, on the trees which they inhabit. Soon after their first appearance the sexes mate and eggs are dee posited. . The female first makes an incision in the bark—probably by means of her mandibles—causing it to split slightly; then, turning head upward, she places an egg under the bark nearly a quarter of an inch from the incision, accompanying the deposition by the extrusion of ‘‘a gummy fluid which covers and secures it to its place and usually fills up the aperture. In young trees with tender bark the egg is usually thoroughly hidden, while in older trees it is sometimes so shallowly imbedded as to ae readily seen.’ ‘The egg is pale rust-brown in color, one-eighth of an inch long, one-third as wide at the middle, flattened so as to have a depth of about one-third the width.’’* Its shell is fairly tough and resistant, not sculptured, and sufficiently plastic, when laid, to receive impres- sions from the woody fibers between which it is forced. Oviposition has been observed from June to September in a single locality (Law- rence, Kansas), but June is the month in which most of the eggs are Jaid. Fitch and others observed the beetles in the trees, near Albany, N. Y., as early as April. Regarding the duration of the egg stage, Mr. E. W. Junkins ® states that a young borer larva was observed July 7 from eggs that were deposited June 15. This would give a period of twenty-two days, but we have no further data bearing on this point. The larve, soon after hatching, tunnel under the bark and feed on the sap-wood, gradually working their way upward and afterwards downward, usually remaining within a short distance of, or below the surface of, the ground, particularly in young trees. By the beginning of the second year the larve, according to observations conducted by the writer, attain an average length of about five-eighths of an inch. The larval growth will naturally vary according to temperature, mois- ture, quantity of food available for consumption, and other condi- tions. With the approach of cold weather the larvez cease feeding, but with the beginning of warm spring weather—in the District of Columbia as early as the latter days of March—they again commence forcing their excrement and castings, consisting of gnawed particles of wood, out through holes which they make in their burrows. By the end of the second year the larve have increased considerably in size and have now penetrated deeper into the solid heart-wood, their burrows being closely packed behind them with castings. The third year the larve gnaw outward to the bark, form a pupal cell composed a Above quotations from account by Riley in New York Weekly Tribune, Feb. 20, 1878; Kans. Hort. Rept. for 1879, pp. 196-201. b New England Homestead, Jan. 3, 1885. [Cir. 32] 5 partly of their castings and, with their heads pointing toward the bark, transform to pupe. With the approach of May and June they cut their way out by means of their powerful mandibles and issue through a round hole as mature beetles.