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(Cryptorhynchus lapathi Linnæus) Order, Coleoptera

Family, Curculionide ROBERT MATHESON

Ever since its introduction from Europe, in 1882, the poplar and willow borer or weevil has been a serious pest, not only in nurseries in the eastern part of the United States but also to the basket willow industry and to poplar and willow trees used for landscape planting. During the past ten to twenty years the weevil has become so abundant in many eastern nurseries that in many cases the nurserymen have almost abandoned the raising of carolina and other species of poplars to supply the demand for a rapidly growing shade tree. Also many young groves of poplars have been seriously injured, while large shade trees have been rendered unsightly by the breaking off of branches that have been so riddled by the boring of the larvæ as to be unable to resist high winds.

As this beetle is largely distributed through infested nursery stock, it would seem that the most efficient means of reducing the injury that it causes would be by controlling its work in the nurseries. If nurserymen could furnish trees known to be absolutely free from the pest, its further distribution would be restricted, and means could then be adopted to control its activities where it is at present causing serious injury. During the past three seasons the writer has conducted experiments which have proved very successful in controlling this pest under nursery conditions. These experiments are discussed in the present bulletin, which also gives a biological account of the insect.

HISTORY OF THE SPECIES

In Europe The poplar, willow, or alder snout beetle, the Erlenrüssler of German writers, is a European insect. For centuries it has been a pest to alders and willows in Europe, and it has been the subject of many entomological papers.

Linné (1758) described the adult in his Systema Nature, giving as its host plant Rumex lapathi. Curtis (1791) published the first account of the natural history of the beetle. He found the larvæ injuring ornamental willows in his garden. He first observed the work of the beetle on Salix viminalis in 1780, and after a few years of study succeeded in finding all its stages except the egg, which he supposed was laid under the bark or

in crevices resulting from injury. His figures of the various stages of the insect are the first ever published. Paykull (1792) records the beetle as injuring Salix species, and also refers to Linné's statement that dock (Rumex lapathi) is one of its host plants. Bechstein and Scharfenberg (1804) quote from Curtis's work, and also refer to the injuriousness of the beetle in Germany.

The insect is recorded in all the early systematic works dealing with the snout beetles (Rhynchophora), but no biological data are added. Ratzeburg (1839) records alder as one of its host plants, stating that in Silesia the beetle is known as the alder destroyer (Erlenwürger). Nördlinger (1856) records the insect as doing serious damage to young birches from five to eight feet high, their tops breaking off after having been seriously injured by the numerous larval galleries.

Westwood (1863) describes a serious outbreak of the beetle in ornamental willows in Essex County, England. Ratzeburg (1868) gives a much more extended account of the beetle and its injuriousness throughout the forests of Germany. His account of its life history is incomplete, though he gives many details as to its food plants and habits. Altum (1881) records the beetle as doing serious injury to stands of white and of black alder in various parts of Germany, as well as attacking several species of willows. He does not clear up any of the various disputed points not well understood regarding the habits and life history of the insect. Judeich and Nitsche (1889), though they discuss the insect in some detail and list all its known food plants, leave the question of its biology in the same condition as they found it.

The beetle is discussed more or less in detail also in many recent European works on forest and shade tree insects, but no attempt has been made to clear up the many obscure points in its bionomics. Scheidter (1913) gives an extended account of its life history in various parts of Germany, and seems to have added considerable new biological data, much of it differing widely from that found in America.

In America This European insect was first recorded in America by Juelich (1887), who collected a single beetle at Williamsbridge, New York City, in 1882. In 1887 he found willows infested by the insect at West Bergen, New Jersey. In the previous year Ottomar Dietz had collected a single specimen on Staten Island, so that at this early date the insect was established in the extreme southeastern part of New York and the northeastern corner of New Jersey. Smith (1891) reported its spread in New Jersey and the destruction by it of nearly all the clumps of willows, as well as many fancy ornamental trees, at Newark and Arlington.

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Howard (1895) states that E. V. Wilcox sent him specimens of the beetle and the larva from Cambridge, Massachusetts, reporting that willows in that section were severely infested. Jack (1897) records the beetle as being very abundant about Boston and Cambridge, it having been present in the Arnold Arboretum for many years and at that time proving very injurious to many species of willows and poplars and to two species of birches. Up to that time it had been supposed that the insect was restricted to the eastern Atlantic border, but in 1896 Ottomar Reincke collected it near Buffalo.

The beetle has now become well established in the Eastern States but its westward and northward spread has not been very rapid. Burgess (1903) records it from Ashtabula, Ohio, in 1901; Bues (Bues and Sandsten, 1904), from two nurseries in Wisconsin in 1903; and Washburn (1904) reports receiving specimens from the extreme northwestern corner of North Dakota, where the insect had been introduced on nursery stock from New York. This stock had been first shipped to a Minnesota nurseryman, who in turn had distributed it, some of it reaching northwestern North Dakota. It is clear that the beetle was thus, in all probability, widel distributed in the Northwest.

Patch (1908) first observed the insect at Orono, Maine, in 1907, and in 1911 it was found also at Augusta and at Presque Isle. Forbes (1911 a) records the beetle from Chicago in 1908, where it was abundant and destructive throughout the city. He reports that it has not been found elsew here in the State.

FOOD PLANTS The poplar and willow borer has a fairly wide range of food plants. European writers record it as attacking the following species: alders Alnus viridis DC., A. incana Willd., A. glutinosa Willd.; willows Salix caprea L., S. viminalis L., S. purpurea L., S. triandra L.; poplars – Populus alba L.; birches — Betula species. Jack (1897) states that in America all the native willows except the slender-stemmed species are subject to attack. This is confirmed by C. S. Sargent, Director of the Arnold Arboretum at Cambridge, Massachusetts. Of the imported willows the following have been observed injured in the Arnold Arboretum: Salix alba L., S. fragilis L., S. babylonica Tourn., S. pentandra Linn. Ti ne following species of poplars are also recorded as host plants: Pop

balsamifera L., P. deltoides Marsh., P. alba L. Schoene (1907 a)

ds the following species of willows as host plants: Salix lucida Muhl., S. cca prea L., S. cordata Muhl., S. sericea Marsh., S. alba L., S. amygdaloide s Anders. In addition two species of birch are known to have been injured-Betula pumila L. and B. nigra L. These, however, are rarely attacked.

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FIG. III.

TRUNKS OF SEVERELY INJURED CAROLINA POPLAR TREES, FIVE YEARS OLD

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FIG 112.

INJURED AND UNINJURED POPLARS At 1 3ght and left, five-year-old trees, severely injured: an uninjured four-year-old tree in the center.

All were grown under identical conditions in the experimental plot

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