. Fruit-Tree Bark-Beetle (Scolytus rugulosus Ratz.) . gh by fine bird shot. These are the exit holes of beetlesthat have in their larval stage mined and developed under the are also made by the mature insects, probably chiefly males, inthe latter days of a season after midsummer, evidently for no otherpurpose than for food. A piece of twig, showing exit holes in the barkand the galleries of the insects beneath it, is reproduced in figure 2. The insect which causes this injury is a member of the Scolytidge, afamily of cylindrical bark-and-wood-boring beetles. The adult or beetleis sh
. Fruit-Tree Bark-Beetle (Scolytus rugulosus Ratz.) . gh by fine bird shot. These are the exit holes of beetlesthat have in their larval stage mined and developed under the are also made by the mature insects, probably chiefly males, inthe latter days of a season after midsummer, evidently for no otherpurpose than for food. A piece of twig, showing exit holes in the barkand the galleries of the insects beneath it, is reproduced in figure 2. The insect which causes this injury is a member of the Scolytidge, afamily of cylindrical bark-and-wood-boring beetles. The adult or beetleis shown at figure 1, a. It is about one-tenth of an inch in length andthree times as long as wide; uniform black in color, except the tips ofthe elytra or wing-covers and a portion of the legs, which are dull punctuation of the thorax and of the elytra is also illustrated andat b the peculiar form of the short abdomen is shown. This insect isa European introduction and is sometimes known as the shot-borer,orchard scolytus, and fruit Fig. 2.—Work of ScoU/-tus rugulosus in twig ofapple—natural size (au-thors illustration). In Europe the species first attracted attention by its occurrence onyoung apple trees in 1834; in the United States it was noticed for thefirst time in 1877 through its injury to peach. Available data indicatethat plum is more susceptible to attack than othertrees, while peach, cherry, and apple are attackedabout equally. Pear is also quite subject to infesta-tion, and apricot, nectarine, quince, mountain ash,and Juneberry trees also harbor this species. InEurope mountain ash has been recorded by Dobner,and hawthorn and elm by EichhofT. Two important factors that have operated in thepast have had a marked effect in increasing thenumbers and consequent injury by this as well asother fruit-tree borers: (1) The introduction of otherdestructive insects and diseases into many of thedistricts which this insect inhabits, which has un-doubtedly, b
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectfruitdiseasesandpest
