INSECT ENEMIES OF WESTERN FORESTS 33 



In addition to breeding under the bark of twigs and branches, 

 adults of the larger species of Phloeosinus have the feeding habit of 

 nipping off the leaflets and of feeding by boring into the small twigs 

 of various cedars and cypresses. This injury is frequently very 

 severe in the case of ornamentals and shade trees. 



JBroad-leaved trees are attacked by various genera of bark beetles, 

 including many species of Micracinae. Oak twig beetles belong 

 to the genus Pseudopityophthorus (p. 132). 



TWIG WEEVILS 



Twig weevils, belonging to the family Curculionidae, are often the- 

 cause of serious damage to the terminals of young coniferous trees. 

 The adult female weevil uses her long, curved beak to excavate a 

 small pocket in the bark of the terminal shoot in which to place 

 her eggs. The young larvae, on hatching, burrow beneath the bark 

 and excavate winding tunnnels between the bark and wood. On 

 leaching full growth each constructs an oval cell, partly in the wood 

 and partly in the bark, in which to pupate. Weevil work is dis- 

 tinguished from that of the twig moths in that there is little exu- 

 dation of resin or pitch, and such as does occur is not mixed with 

 Avebbing or larval castings to indicate the presence of the insects 

 under the bark. The first conspicuous evidence of injury is the 

 dying of the terminal shoot. 



The two most important genera concerned are Pissodes and Mag- 

 dalis. In the East the white pine weevil {Pissodes strohi Peck) is 

 a w^ell known example of the importance of these insects. In the 

 Western States there are several species which do similar damage; 

 though not of economic importance as yet, they are almost sure to 

 be so when second-growth stands and plantations are more widely 

 established. 



Proper silvicultural methods offer the best solution of the weevil 

 problem. Where young trees are grown in dense stands, or under 

 the shade of other trees, weevil injury may be negligible. If in 

 handling young stands subject to weevil injury the shade of older 

 trees can be provided until the young trees reach 25 feet in height, 

 or if the young trees can be grown in dense stands until they have 

 passed the susceptible period, the damage should be lessened. In 

 plantations, where individual care can be given, control can be ob- 

 tained by cutting off the infested stems in May and September and 

 storing these in wire cages of a mesh small enough to hold the beetles 

 but large enough to allow the parasites to escape. If this is done 

 for several seasons almost complete control of the weevils should 

 be obtained. 



The Sitka spruce weevil {Pissodes sitchensis Hopk.) is the insect 

 most injurious to Sitka spruce reproduction in the Northwest. The 

 small weevils attack and kill or seriously injure the terminal shoots 

 of many young trees, causing a crook in the trunk or a forked and 

 worthless tree. Trees from 2 to 8 inches in diameter and 5 to 25 

 feet in height are the most susceptible to attack. The species is 

 distributed throughout the range of Sitka spruce. 



The adults are light to dark brown, oval-shaped beetles, about 

 three-sixteenths of an inch in length, with a prominent curved beak. 



130643°— 39 3 



