UBRARY ^>fe. STATE PLANT BOARD ^_^ u^-^^ Issued March 7, 1911. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— CIRCULAR No. 134. L. O. HOWARD. Entomologist and Chief of Bureau. DAMAGE TO TELEPHONE AND TELEGRAPH POLES BY WOOD-BORLNG LNSECTS. T. E. SNYDER, Agent and Expert. r5;j8°— u WASHINGTON : GOVERNMENT PRINTING OFFICE : 1911 S5 BVREA r OF ENTOMOLOGY. L. O. HowAKD, Entomologist and Chief of Bureau. C. L. Marlatt, Entomologifit and Acting Chief in Absence of Chief. R. S. Cliftox, Executive Assistant. W. F. Tastet, Chief Clerk. F. H. Chittenden, in charge of truck crop and stored product insect investigations. A. D. Hopkins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect investigations. F. M. Webster, in charge of cereal and forage insect investigations. A. L. Quaintance, in charge of deciduous fruit insect investigations. E. F. Phillips, in charge of bee culture. D. M. Rogers, in charge of preventing spread of moths, feld work. RoLLA P. Currie, in charge of editorial irork. Mabel Colcord, librarian. Forest Insect Investigations. A. D. Hopkins, in charge. H. E. Burke, J. L. Webb, Josef Brunner, S. A. Rohwer, T. E. Snyder. \\'. 1). Edmonston, W. B. Turner, agents and experts. Mary E. Faunce, preparator. William Middleton, Mary C. Johnson, student assistants. Circular No. 134. iss"t-.i March 7. rjii. United States Department of Agriculture, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. DAMAGE TO TELEPHONE AND TELEGRAPH POLES BY WOOD-BORING INSECTS.^ By T. E. Snyder, Agent and Expert. It has recently been determined tlirougb special nivestigations con- ducted by the Bureau of Entomology, in cooperation with telephone and telegraph companies, that serious and extensive damage is being done in certain localities to standing poles by wood-boring insects. The object of this circular is to give information on the principal as well as other types of insect injury to poles, so that line inspectors may distinguish the various types and determine and report on the character and extent of the damage. CHARACTER OF THE INJURY. The principal injury to the poles consists in large mines in the wood near the line of contact with the ground, necessitating the frequent resetting or even the replacement of the damaged poles. These irregular mines (fig. 1) run both transversely and longitudinally throughout the heartwood, and are sometimes 7 inches long, but vary in length. This injury is usually in the outer layers of the wood for a distance of from 2 to 3 feet below and sometimes from 1 to 2 feet above the line of contact of the pole with the surface of the ground. The greatest damage is to that area just below and just above the surface of the ground; here the conditions of air and moisture are most favorable. The mines, often very close together, completely honeycomb the wood in a zone from 3 to 4 inches in from the exterior of the poles (fig. 3); this so weakens the poles that they break off close to the surface of the ground. The basal 2 feet is ' Revised extracts from Bulletin 94, Part I, Bureau of Entomology, U. S. Department of Agriculture, 1910. 77538°— Cir. 134—11 1 UBRARY OTATE PLANT BOARD, INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES. ^m' Fin. 1.— Work of the pole borer (J'urandra brunnia Fab.) in in untreated eliestniit pole: a, (lallery of the jMjle borer, showing; jiiipal chamber witli the etitranee phijjged with eNcclsior-like \voo«l fibers; work near \):\s(? of iK)le, below jjround. b, Mines of the pole borer near surface of ground. Natural size. (Author's ilhistration.) INSECT DAMAGE TO TELEPHOXE AND TELEGRAPH POLES. 3 usualh' sound. Even if the damage is not serious enough to cause the poles to break off under strain, they are hkely to go down during any storm, and thus put the wire service out of commission; such damaged poles are a serious menace along the right of way of rail- roads. Poles that appear sound on the exterior may have the entire basal interior riddled, and the damage is not noticed until the poles break off. If merely isolated poles are injured so as to cause them to break off, they simply lean over, but if several adjacent poles are affected, especially where there is any unusual strain, that por- tion of the line is very hkely to go down. THE PRIXCIPAL INJURIOUS SPECIES. The principal injurious species is the chestnut telephone-pole borer, or pole borer/ which is an elongate, creamy-white, wrinkled, Fig. 2. — /, Tho pole borer: Male and female beetles. .\ The pole borer: Young larva?. /, Slightly enlarged; ?, twice natural size. (Author's illu.stration.) round-headed grub or larva (fig. '2,2). It hatches from an egg depos- ited by an elongate, mahogany -brown, shiny, flattened, winged beetle, from two-flfths to four-flfths of an inch in length (fig. 2, 1). It appears tliat the eggs are. deposited from August to October in the outer layers of tlie wood of the pole near the surface of the ground. The young borers, upon hatching, excavate shallow gal- leries in the sapwood, then enter the heartwood, tlie mines being gradually enlarged as tliey develop. As they proceed they closely pack tlie fine boring dust behind them. Tliis peculiar semidigested boring dust, which is characteristic of their work, is reddish to dun- ' Parandra hrunnca Fab. Since the publication of Bulletin 94, Part I, of this Bureau, this borer, first found to be injurious to chestnut telephone poles, has been found injurious to arborvitae poles, and as it also injures telegraph poles, the name "pole borer" is more appropriate and comprehensive. 4 IXSECT DAMAGE TO TELEPHONE AXD TELEGRAPH POLES. nisli yellow in color and has a claylike consistency. The burrows eventually end in a broad chamber, the entrance to which is plugged \Wth excelsiorlike fibers of wood. Here is formed the restino: staoje, or pupa, which transforms to the adult beetle. Often all stages, from very young grubs only about one-fourth inch long to full-grown grubs over 1 inch long, pup?e, and adults in all stages to maturity are present in the same pole. Adidts have been found living from July to September. The insect attacks poles that are perfectly sound, but will work where the wood is decayed; it will not, however, work in wood that is ''sobby" (wet rot), or in very ''doty" (punky) wood. It has not yet been determined just how soon the borers enter the poles after they have been set in tlie groinid. However, p( les tliat had been Fin. 3.— Damage to an untreated chestnut telegraph pole near surfai-o of ground by the pole borer. (Author's illustration.) stanchng only four or five years contained larvte and aihilts of this borer in the heartwood, and poles that liad been set in the ground for only two years contained young larva^ in the outer layer's of the wood. The ])resence of the borers in injurious numlxM's can l)e (h'ter- mined only by removing the earth from about the base of the i)ole; the large holes iiuide when the a(hdts come out are found near the hue of contact with the soil. Often large, coarse borings of wood hber project from these exit holes. Sometinu^s the old dead parent a(hdts are found on the extcM'ior of the poh's uiKhM-ground. During August the young achihs iiiny he found in shallow depressions on the exterior of j)ol('s below the gi-onnd surface. INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES. 5 INJURY BY OTHER INSECTS. It is not to be concluded that injury by the pole borer is the only type of insect damage to poles. Indeed, a very common injury is by white ants, or termites. In lines from 10 to 12 years old serious damage by these insects occurred in as high as 15 per cent of the poles, and their work is often present, at least superficially, in as high as 75 per cent of the poles under all conditions of site. The damage, however, is usually to the outer layers of the wood, where it is moist or there is incipient decay, and is more superficial and local- ized than that of the pole borer. Xevertheless, the sound heartwood of poles is often completely honeycombed, especially at the base. The work of white ants is found both in sound wood, ''doty" wood, and ''sobby " wood. Sometimes a large channel runs up through the core of the heart and the sides are plastered with clay, forming a hollow tube w4th several longitudinal interior galleries. Their work often extends from 2 to 4 feet above the surface of the ground. They leave the outer shell of the wood intact and work up through the longitudinal weathering checks, covering the exterior of the pole with earth to exclude the light. AYliite ants will damage poles that have been set in the ground only two years. Evidently they enter the pole from below the surface of the ground. Injury by a giant round-headed borer is sometimes found in chest- nut poles. The large mines of this borer are found in the sound and decayed wood of poles. Often where there is rot present the heartwood near the surface of the ground is completely honey- combed by this borer. Longitudinal weathering checks in chestnut poles are often widened, and other defects enlarged by large, black carpenter ants and other smaller black ants, which thus hasten decay. KNOWN EXTENT OF THE DAMAGE. The pole borer has seriously damaged as high as 10 to 15 per cent of the chestnut poles which have been set in the ground for from 10 to 12 years in lines in North Carolina, Virginia, West Virginia, Mary- land, and the District of Columbia. It has only recently been deter- mined that it has also seriously damaged a considerable proportion of the arborvitse^ telephone poles in part of a line in Illinois. It is evident, then, that this insect is an important factor in decreasing the normal length of service of chestnut and arborvitae poles. POSSIBILITIES OF PREVENTING DAMAGE TO POLES. Methods of treating poles superficially by brushing with various preservatives have proved to be temporarily efficient in keeping out wood-boring insects, if the work is thoroughly done and not I Thuja occidentalis. 6 INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES. onlv the butt, but also the basal area, is treated. If the pole is not thoroucrhlv brushed, the pole borer and other insects enter through the untreated or imperfectly treated portions, especially through weath- erino- checks and knots. Where the base is left untreated, insects, espedallv white ants or termites, enter the pole from below ground and avoiding the treated portions, come right up through the pole. Imprecrnating the poles with creosote by some standard process (either bv the open-tank or bv a cyhnder-pressure process) will keep out wood-boring insects. In the open-tank method only the area most subject to the attacks of wood-boring insects (i. e., the basal 8 feet) is treated, while by the cylinder-pressure processes the entire pole is impregnated. „ Therefore to efTectuallv protect poles from the depredations ot wood-borin- insects it is recommended that they be impregnated with creosote by either the "open-tank" process or by a cylinder-pressure process. \T^tArr^v