September 19 1894. ] 



Garden and Forest. 



373 



The Woodpecker and Bird's-eye Poplar. 



AT the late meeting of the American Association for the 

 _/~\_ Advancement of Science, Professor A. D. Hopkins, 

 Entomologist of the West Virginia Experiment Station, 

 read a paper on certain conditions of wood which result 

 from attacks of birds and insects. The most interesting 

 part of the paper to readers of Garden and Forest is that in 

 which he identifies a bird as the cause of the peculiarly 

 waved or curled quality sometimes found in the grain of 

 Tulip Poplars, and presumably of Sugar Maple. At least, 

 he seems to have established that the rare and beautiful con- 

 dition known as Bird's-eye Poplar is caused by a succes- 

 sion of elevations and depressions in the annual layers of 

 wood due to punctures in the bark made by woodpeckers. 

 Referring to his investigations, Professor Hopkins says : 



It was found that the depressions occurring in the wood be- 

 neath the bark corresponded with the punctures made by the 

 birds in the outer bark. The portion of the living bark affected 

 by the puncture becomes dead and dry, causing a calloused 

 condition at the sides and at the bottom of the wound. This 

 calloused condition pressing upon the cambium during the 

 process of the first annual growth of wood after the wound is 

 made causes it to be less, or, in other words, thinner, at that 

 point than beneath the unaffected bark. This depression is 

 followed by subsequent annual layers until sufficient new bark' 

 forms beneath the wound to insure normal condition. Thus, 

 seventy-five or more annual layers may be sufficiently affected 

 in this manner to show the wavy or curled condition in the 

 surface of the wood in which they occur. It will readily be 

 seen how a tree subjected to the attack of woodpeckers from 

 the time it is a few inches in diameter until it has reached ma- 

 turity would show this condition throughout the wood. 



The economic importance of a knowledge of this fact is also 

 apparent. If the lumber manufacturer should desire a quan- 

 tity of Bird's-eye Poplar he has only to select the trees and 

 logs, the bark of which shows the work of the woodpeckers in 

 the greatest profusion, being reasonably certain that they will 

 yield a greater or less quantity of lumber showing the desired 

 condition. Whether or not every tree so affected will show 

 the desired condition, or whether Bird's-eye Maple is caused 

 in the same manner, I cannot say positively, but I see no rea- 

 son why it should not be so. I do know that a species which 

 appears to me to be the downy woodpecker, Dryobates (Picus) 

 pubescens, is extremely fond of the sap of the Sugar Maple 

 (from which Bird's-eye Maple is obtained), and that this bird 

 often perforates the bark of this tree with innumerable holes 

 to obtain the sap. 



Entomological. 

 The Flat-head Pear-borer. 



UP to quite a recent date the Pear-tree was that one of 

 all our fruits which was least troubled by insect at- 

 tack, its few enemies being rarely abundant and easily 

 controlled when they did increase abnormally. In this re- 

 spect it differed sharply from its ally, the Apple, which has, 

 without exception, the greatest number of insects infesting 

 it of all our cultivated plants. 



Within the last decade the Pear has been gradually losing 

 • its exemption from insect attack, and the crop in some lo- 

 calities is now more endangered than any other. Of our 

 native insects the Pear-blister mite is increasing, but may 

 be easily controlled, and it is to foreigners that we owe 

 most of the danger. The Pear-tree Psylla was introduced 

 many years ago, but has, up to recent times, been con- 

 fined to a few northern localities — most troublesome, per- 

 haps, in central New York and in Connecticut. Nurseries 

 from central New York have sent out stock containing 

 some forms of the insect, and as a result several orchards 

 in New Jersey, and at least one in Maryland, have been 

 seriously injured. The probability is that at many other 

 points the insects have been introduced, without noticea- 

 ble increase as yet. 



More recently the Pear-midge has been imported, and 

 this is spreading slowly, but steadily, ruining every locality 

 over which it extends. 



During the spring of 1894 there was brought to my at- 

 tention an injury to Pear-trees in Essex County, New 



Jersey, which is yet more serious than any of those above 

 mentioned, since it strikes the tree itself instead of the 

 crop, and kills it in a few years. The culprit in this in- 

 stance is a native, a species of Agrilus, which has been 

 rare heretofore, and had never been taken in New Jersey 

 even by collectors. The injury is done by the larva, which 

 burrows between the bark and sap-wood, always in living 

 tissue, and makes immensely long, irregular galleries, under 

 which the wood dies, and over which the bark cracks. 

 When a number of these insects are working in the same 

 tree the galleries cross or join, and the tree is girdled and 

 dies. When a few larvae only infest it each year the tree 

 dies more gradually, the area available for the supply of 

 sap being reduced from year to year. In vigorous varie- 

 ties, like the Keiffer, the trees will repair damages for some 

 time, but even these succumb at last, repairs being omitted 



Fig. 60. — Pear-tree, showing galleries made by borers. 



first in the widest parts of the borings, and as the dead 

 patches extend, reconstruction is less and less complete. 



The illustration given herewith shows a Seckel Pear- 

 tree at the point of branching, the bark being removed 

 from the trunk and one of the branches to show the gal- 

 leries. The tree was between five and six inches in diame- 

 ter, and had been healthy and a prolific bearer until these 

 insects attacked it. The irregularly cracked appearance of 

 the bark, which indicates the presence of the larva, is well 

 shown in the picture. Not only the trunks, but the branches, 

 are attacked, even those not exceeding half an inch in 

 diameter, and sometimes the trees die from the top, some 

 branches going each year until all are dead. Even young 

 trees just from the nursery become infested, and I have a 

 small tree set out one fall, infested next summer, and dead 

 the spring following. 



