Circular No. 109. ■ United States Department oi Agriculture, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. THE LEOPARD MOTH. :> rn pyrina Fab. I a By I.. 0. Howabd and 1' 11. • 'mittkm>i.s LNTBOD1 < rOBT. Deciduous trees of many kinds, grown for shade and for ornament in northern New Jersey and eastern NCw York, arc subject to severe injury by the larval stage of the European leopard moth (Zeuzera pyrina Fab.). Among the shade trees, elms and maples suffer the tot damage, but as this species is a very general feeder it attacks practically all descriptions of trees and shrubs with the except ion of the evergreens. In the region mentioned this species is. everything con- sidered, the most serious menace to the growth of shade trees, since, unlike the majority of lepidopterous insects, the larva 1 of the leopard moth do not feed upon the foliage, hut bore into the branches of the plants which they infest and feed upon the living wood. The larva- usually begin operations in twigs and small branches and with their larger growth bore and tunnel into the larger branches and trunks. This work has the effect of girdling, the injured portion- being blown down by heavy wind storm-, while in the case of severe attack the u th of the tree is checked, frequently causing it- death. Attack is not confined solely to shade and ornamental plant-, but orchard- are n injured. DX84 i: i !• i i \ i Injury by this species i> accomplished solely by the larva, which is a fleshy, grublike caterpillar, pale yellowish in color, frequently with pinkish tinge. The head, thorax, and anal plates are brownish- black and the surface of the body i> very Bparsely hairy hut covered 1 Family < -\ nonym- 09 with large and prominent tubercles arranged as shown in the illustration (fig. 1, c). When fully mature the larva attains a total length of about 2 inches. A lateral view of the larva in its burrow is shown in figure 1 at c. This species derives its name from the spotted appearance of the moth, illustrated at figure 1, a, b. There is great diversity in the size of the two sexes, the female (a), which is a heavy-bodied moth and a very feeble flyer, being much the larger. It will be noticed that the smaller male (b) has a more slender body, which permits a more ready flight, and is also distinguished from the female by the pos- Brail" 'II: MINI wV v BBS ! I \ sn i* t DISTRIB1 I i"\. The leopard moth, like bo man] other dangerous pests, is a European species which has been introduced into the United States in com- paratively recent years. Its old world distribution is credited central and southern Europe, southern Sweden, southwestern Africa, Algeria, and northern Morocco, and tin- western portion of Asia Minor. This Bpecies was introduced into the United States Borne time prior to 1879, in which year, on the authority of Mr. Jacob Dull, a living moth was captured in a spider's web al Hoboken, N. -I." In lsM Dr. E, B. Southwick, then entomologist of the public park- of Nrw York City, recognized the destructive work of this species in Centra] Park.* In 1887 it was Been al Newark, N. J., but was nol actually recorded as occurring in this country until the following \ ear. In 1890 the junior author observed the moths at electric lights at ( Grange, X. J. Fortunately the spread of this insect, part icularly in the immediate vicinity of New York City, has been very slow, a fact which may be attributed to several causes, (1) the slowness of the flight of the female, (2) the dominance of sparrows in large cities, causing our native bird-, such as woodpeckers, to be driven to the country, where the\ destroy the moths, and (3) the bowl-shaped electric-light globes, hollow at the top and closed at the bottom, which were formerly in general use in our large cities. The males are Btrongly attracted to brilliant lights and many were captured and perished in these globes in earlier years. Other cities in New Jersey where this species has been troublesome are Elizabeth, [rvington, Montclair, Arlington, Asbury Park, Ocean Grove, and New Brunswick. Mr. II. M. Russell of this Bureau collected specimens at Bridgeport, Conn., in 1901. The species is now an inhabitant also of Staten Island and has spread on Long Island well beyond the confines of greater New Y'ork. South- ward it was reported a pest, in 1901, at Ocean (dove. N. .1.. and by 1905 it was recorded by Kelt as occurring at rlensico, N. Y.. 25 miles north of New York City. By 1907 it was captured at New Haven, Conn., by Prof. II. W. Foote. It i- now stated to he injurious in the vicinity of Boston, Ma—. i ood i'i a\ re. In it- original home the leopard moth is recorded a- living on a considerable number of common tree-, including elm. lime or linden, ash, beech, birch, walnut, oak. chestnut, poplar, alder, and, rarely, horse-chestnut. Among orchard tree- it is reported to do injury to pear, apple, and plum. In the United State- it attacks all of these nc of which would have been able to destroy the tree if no! re- moved. Mi. A. Iliit'ii.il wrote that in maple trees which this spe* was infesting at Ocean Grove, N J., there was an average of from -ix to eight borers to a tree and thai he had found from ten t<» 1 i f t • •« -i i . and in one instance as high as thirty four, in a single tree. I>> the time tlic larvae within have attained full growth infested limbs of a certain size arc likely to break off, especially during or after a Bevere atorm, for the full-grown larva in man] girdles the branch. The manner of girdling is shown at the top of the Bection of wood illustrated in figure _'. In 1893, after everj Btorm in Central Park greal quantities of limbs were Been, some entirely broken off and others still hanging to the, trees. 'The larva, when fully mature, transforms to pupa within the burrow, the change beginning to occur during the second May after the hatching of the eggs, the larva thus requiring nearly two years to complete its growth. The pupa. I>\ means of a sharp protuber- ance on it- head, i- enabled to force it- way partly OUl of the burrow . after which the skin splits open and the moth emerges. Theemptj pupal skin remains for some time projecting From the orifice. The presence of this borer in a branch is manifested by little accumulation- of chip-, matted excrement, or fra--. which indicate the entrance to the burrow-. After a time these orifice- are closed from within b) a silken web, which i- doubtless to protect the con- tained insect from it- natural enemies. Smaller twigs wilt and break oil' and often it is onl\ when the severed twigs or branches have been broughl down in number- by high winds that the work of the insect is first recognized. Where the larger larvae have worked just under the bark this -plit- open the next season, leaving an uglj -car a- a reminder of it- pernicious operations. \ \ 11 i: vi. i nil k-. \" specific natural enemies of the leopard moth appear to have been recorded in this country, although in Europe E. A. Fitch has reared an indeterminate chalcidid of the .-uhfamih EncyrtUMB. In the explanation of the cause of the -low spread of the moth from cities and large town- to the country, allusion ha- been made to the fact that native bird- probably assist in holding this insect in check in the suburbs. Actual observations on this head appear to be wanting, but there are the best of reasons for believing that birds, like the woodpeckers, which naturally look over the bark and collect all kinds of borer.-, prey on this species, while it i- believed o Entom. Mo. Mag., Vol. XVIII. p. 116 Perha] Dalm., mentioned by Dalla Torre (not M - Bymenoptei >rum, p. .'it;. [Cir. 109] that sparrows sometimes destroy the eggs or young larvae in such places. Smith has expressed the belief that when the insect suc- ceeds in getting away from the outskirts of cities its enemies increase in number, many insectivorous birds aiding in holding it down. During the da}" the moths must be fed upon by birds and later by bats and night-flying birds. The habit of the larvae of desert- ing one twig and migrating to a larger one undoubtedly leaves them exposed to the same natural enemies, as this has been observed to happen in the daytime as well as after nightfall. It follows that the protection of native birds, especially the woodpeckers and related species, will greatly assist in restraining the undue increase of this borer. METHODS OF CONTROL. The protected and concealed manner of life of this species, as shown by the life history, which will apply in the main to other borers also, renders it very difficult of treatment by means of insect- icides or other direct measures. The most efficacious remedial meas- ure consists in cutting off and destroying affected branches and in the injection of bisulphid of carbon into the holes or burrows where the larva? are at work. Pruning and cutting back. — Twigs or branches which, by their wilting or by the frass which accumulates at the entrance to their burrows, indicate the presence of this borer, should be carefully searched out, the smaller ones pruned away and the larger ones cut back, the amputated portions being promptly burned. After windstorms, the affected branches which have fallen to the ground and those which remain attached to the tree should be collected and burned. Wherever trees show that they are past recovery it is best to take them out and promptly destroy them. The word promptly is used advisedly, for this insect, as has been shown previously, fre- quently migrates from one twig or branch to another. Bisulphid of carbon. — In the case of young and rare trees and others which show only a few larval burrows in the bark, bisulphid of carbon is the best remedy and one which has been in general use against the present species in the public parks of New York City. It is injected into the openings of the burrows, and the openings are afterwards closed with various substances. For this injection a mechanic's long-spouted oil can of small size may be used on large trees, but against a related species the writers have made very good use of a small glass syringe, such as may be purchased at any drug store for ten cents. These glass svringes are most serviceable, be- cause the exact amount of bisulphid may be seen when drawn into the syringe and because the reagent does not injure the thread pack- [Cir. 109] ing.° Metal syringes may also be used, but it is inure difficult to measure the exact amount and the bisulphid acts on the leather packing. Rubber syringes can not be used because of rapid corrosion. A I >■ >u i a teaspoonfuJ of the liquid bisulphid is sufficient for each Imiit"\\ . For stopping the holes after injecting the liquid, putty and moist clay, advised l>\ some, have oot been found bo serviceable as grafting wax. Coal tar may be substituted For the latter, or the holes maj be closed l>\ inserting a wooden plug and breaking '>r sawing it off level with the trunk. In anj case the stopper should l>e tight, to exclude water from rains, which might tend to produce decomposition of the surrounding wood or in\ ite other insects, like black ants and second- ary borers, of which there are manj species, and injurious fungi. Carbon bisulphid should be handled with the usual precautions against fire, which means that the operator should not smoke while at work. Although a deadl) poison, it will Dot injure ordinarj tree- when applied as described. Killing with wires. It is possible t<> reach and destroy some larve by forcing a copper or other pliable w ire into the channels. This is a well-known borer remedy. It is impossible, however, 1>\ this means to kill the insects in all cases, owing t<» the length or crookedness "t the harrows. Bisulphid of carbon should then he used. Electric lights. 'To what extent electric lights arc serviceable a- an agency in the destruction of the moths of this borer has not been definitely determined. Col. Nicholas Pike and Dr. J. B. Smith, however, have advised placing shallow pans around electric-light poles in and around parks to attract the moths. The pans are par- tially filled with water and a few drops of kerosene are poured into them. The moths flying against the e> drop into the pans and are promptly killed when they come into contact with the oil. In this way many males can he destroyed. Inspection. -In large parks the destruction wrought by this l><>rcr annually is an important item, and it will he found a source of profit to establish a system of inspection consisting in the employment of parkkeepers and hoys, and others who may he engaged at lower » During the la-t years >i the nineteenth century a long row of beautiful red oaks bordering the streel between the grounds of the Depart meat of Agriculture and those of the Smithsonian Institution were badly infested by the related carpenter worm {Prionoxythu robinia Pont. |. Nearly every tree was infested and frequently two or three burrows showed near the (ops of the trunks. Bisulphid of carbon was applied, as described above, and the hobs closed with grafting wax A year later no in- could be found at work, but wherever this remedy had been applied a small remained. Two years later these had entirely disappeared and the trees looked as if they had never been infested. [Clr. 109] UNIVERSITY OF FLORIDA 8 3 1262 09216 5439 wages, to keep a constant lookout for evidences of borer attack on valuable trees. On this head Southwick has reported that in 1893 he spent two months in fighting this insect alone in the city parks of New York, collecting wagon loads of limbs and branches and destro) 7 - ing the larvae or pupae. Maintaining trees in thrifty condition. — If valuable trees are to be protected, the insect should not be allowed to breed in useless growth. The borers in such trees should be destroyed or the trees promptly felled and burned. Care should be exercised in transplanting new trees, and fertilizers should be used in order that the trees may be always thrifty, the better to withstand attack. This means protect- ing them from the attack of aphides, scales, and defoliators, such as tussock moths and the fall webworm, and keeping them free from disease. Finally, in the control of this species promptness and thoroughness can not be too strongly emphasized. The bisulphid of carbon remedy should always be used where applicable, and the inspection system advised should be instituted in all public parks and on city streets infested by this pest. Individual owners of valuable trees should become acquainted with the pernicious nature of this borer, and united action should be secured with neighbors who also suffer from the ravages of the pest. Note. — After this publication was in type we received information that trees in the college yard of Harvard University, Cambridge, Mass., are being severely injured, the large elms being the most seriously attacked. Approved : James Wilson, Secretary of Agriculture. Washington, D. C, May 27, 1909. [CIr. 109] o