394 



Garden and Forest. 



[Number 502. 



Entomological. 



A Willow Pest. 



THE destructive Willow-borer, Cryptorhynchus lapathi, 

 is another insect which has found its way from the 

 Old to the New World, and has now become well estab- 

 lished in its new home. The first published notice of its 

 appearance in this country seems to be that given by 

 William Juelich in Entomologica Americana for 1887 (vol. 

 iii. , page 123), who says in that year he found it infesting 

 a Willow in West Bergen, New Jersey, and that five years 

 previously, in 1S82, he had found his first specimen in 

 another locality. In the same season it was found in the 

 northern part of New York City. During many years it 

 has been known to occur in Cambridge, Boston and in 

 their vicinity, and for several years it has proved destructive 

 to almost all species of Willows growing in the Arnold 

 Arboretum. It has been found boring in stems of all the 

 native Willows with the exception of a few mountain or 

 very slender-stemmed species which are too small to afford 

 the borers sufficient sustenance or give them tissue enough 

 in which to make their borings Of the foreign Willows 

 which become large trees, such species as the White 

 Willow, Crack Willow and Laurel-leafed Willow are more 

 or less attacked, but seem to be less liable to serious 

 damage than the Babylonian Weeping Willow. Besides 

 Willows, this borer has been found to attack all the culti- 

 vated Poplars in the Arboretum, particularly when these 

 trees are young, and this season it has been rarely found 

 in small plants of two species of Birch, the Dwarf 

 Birch, Betula pumila, and the Red or River Birch, B. 

 nigra. In Europe it has been reported as boring 

 in Alders. These instances give a hint of the 

 possible increase in the variety of plants upon 

 which the insect might thrive. So abundant is the 

 pest and so extensive its ravages that it is rarely 

 possible to find a good health)' plant among the 

 shrubby Willows in many localities about Boston. 

 In the shrubby species most of the larvae are 

 found boring in the lower parts of the stems or 

 nearest the ground, but in those which reach the 

 stature of trees the pests are often found in the 

 higher parts of the stem and the higher limbs. 



Cryptorhynchus lapathi is a beetle belonging to 

 the great curculio family, which contains thou- 

 sands of species, and it has been long known in 

 Europe, where it is often mentioned in entomo- 

 logical writings and essays on the culture of 

 Willows. It was described as Curculio lapathi by 

 Linnaeus, and by later authors placed in the genus 

 Cryptorhynchus. Wherever they occur in eastern 

 North America the beetles may be found during 

 July and August on the bark, or sometimes on 

 the foliage of the plants they infest. They are gen- 

 erally not very active in their movements, and 

 when alarmed fold their legs and drop to the 

 ground and remain quiet for a time, in which 

 condition they are not easily seen on account of ■■ 



the fact that their colors and markings harmo- 

 nize with most soils and debris. 



The body varies in different individuals from one-third 

 to three-eighths of an inch, or slightly more, in length. 

 The general color is dull black, with a few very short jet 

 black tufts of bristles or scales upon the wing covers and 

 thorax. Under a magnifying glass the wing covers or 

 elytra are each plainly pitted or indented in ten longitu- 

 dinal rows, and the thorax is also minutely but irregularly 

 punctured. Scattered over the forward half of the wing 

 covers are numerous minute whitish scales, which are 

 mostly so placed as to form a more or less distinct, broad 

 V-shaped mark, and the tips of the wing covers for about 

 one-third of their length are almost white, with a dense 

 covering of these light-colored scales. 



The under side of the abdomen is black or with a few 

 scattered whitish scales upon it, and the sides of the thorax 



are densely covered by white scales. The head and pro- 

 boscis are black, the proboscis usually withdrawn, except 

 when the beetle is active. The legs are black, but marked 

 by numerous white scales disposed either singly or in 

 groups and particularly numerous on the femora, which 

 are usually distinctly whitish on the basal halves of the 

 first pair of legs. 



During the summer the eggs are deposited by the beetles 

 in or upon the bark of the Willow or plant attacked ; they are 

 hatched soon afterward and the young grubs eat their way 

 into the stem. During the summer and autumn they attain 

 only part of their ultimate growth, remain dormant during 

 winter and continue their boring in springand reach full size 

 in June or early July. When fully grown the larvae are be- 

 tween three-eighths and one-half of an inch in length, fleshy, 

 of a dull white color, with brown head and darker mouth 

 parts and an oblong brownish shield on the first segment, 

 back of the head; they are provided with six very short 

 tubercle-like legs on the anterior segments. When fully 

 grown the grubs or borers change to pupae in their burrows 

 in the wood, and in two or three weeks afterward emerge as 

 beetles. Commonly, larvae, pupae and beetles may be 

 found at the same time. Very often the stems of Willows 

 are so riddled by the numerous boring larvae that there is 

 neither fresh tissue nor sapwood left through which the 

 sap can pass, or old tissue or heart wood to support the 

 stem erect, and death or breaking down follows. 



In spring the plants infested are usually indicated 

 by quantities of fine chippings or "sawdust" on the 

 bark or around the base of the stem. Much sap escapes 

 through the holes out of which the sawdust is thrown, and 



Fig. 51. — A Willow Pest— Cryptorhynchus lapathi. 



Section of infested wood. 2. Beetle (enlarged). 3. Larva (enlarged). 



4. Pupa, dorsal view (enlarged). 5 Pupa, side view (enlarged). 



sap-loving beetles and other insects are often plentiful on 

 the bark or among the debris. 



As to a remedy, the cutting out of all infested parts in 

 spring would seem the best, but as any wild Willows, or 

 even plants of other genera, may harbor the pests the idea 

 of extermination cannot be entertained. Where a few 

 choice plants are to be protected heavy soap washings, 

 applied on the bark in July and August, may prevent egg- 

 laying by the beetles. Some parasites have been observed, 

 and these may help to keep this Willow-borer from becom- 

 ing unduly abundant. At least eight or ten species of 

 parasites are said to affect this Cryptorhynchus in Europe. 

 It is recorded as a native of Siberia and other parts of north- 

 ern Asia as well as Europe. 



The above figure has been made by Mr. C. E. Faxon. 



Arnold Arboretum, Jamaica Plain, Mass. ./• Gr._/fiC«. 



