6 BULLETIN 426^ U. S. DEPARTMENT OF AGRICULTURE. 



been found on mature green trees. Polyporus volvatus is common on 

 dead trees. The damage done by the former is minor, and that 

 wrought by the latter is of no importance. 



INSECTS. 1 



Insects are responsible for the destruction of large quantities of 

 merchantable sugar pine timber. In the northern portion of the 

 tree's range bark beetles of the genus Dendroctonus are very destruc- 

 tive ; in the southern portions their work is supplemented by that of 

 the flat-head beetles of the family Buprestidse. The annual loss of 

 sugar-pine timber from beetles is roughly estimated at not less than 

 one-half of 1 per cent of the merchantable stand. In certain localities 

 epidemics of insects have resulted in the loss of from 5 to 10 per cent. 



While the roots, limbs, twigs, fohage, cones, and seed of this tree 

 all have insect enemies a tree is never known to have been destroyed 

 except by those which attack the trunk. The mountain pine beetle 

 (Dendroctonus monticolse, Hopk.) is by far the most serious enemy. 

 The adult beetles bore through the cork bark and deposit their eggs 

 in the hving inner bark, which is an important part of the circulatory 

 system of the tree. Upon hatching, the larvse or grubs completely 

 girdle the tree by consuming the tissues in narrow channels or galleries 

 extending around its circumference. The presence of these beetles in 

 a tree is denoted first by reddish " pitch-tubes " or deposits of resin and 

 wood dust caused by the beetles' entrance and later by the yellowing 

 of the crown when the tree begins to feel the effect of the girdling. 



The red turpentine beetle (Dendroctonus valens Le Conte) attacks 

 the base and roots of the tree. Generally its work is of a secondary 

 nature, but occasionally, when very numerous, it is the primary cause 

 of death. According to the Bureau of Entomology it is also one of 

 the primary causes of basal fire wounds.^ 



From the Kern River southward a species of flat-head borer ( Melan- 

 o'phila gentilis Le Conte) causes a considerable loss. The five-spined 

 engraver beetle (Ips confusus Le Conte) is occasionally responsible 

 for the killing outright of young sugar pines in the sapling or pole 

 stage of growth and for the dead tops of many more mature trees. 

 Other less important insects do minor damage to various parts of the 

 tree. Among these are a weevil (Pissodes yosemifei Hopk.), which 

 injures the bark and young saphngs; a saw-fly (LopTiyrus sp.), which 

 damages the fohage, and the sugar pine cone beetle (ConopJiihorus 

 lambertianse Hopk.), which attacks the stems of the young cones as 

 well as the cones themselves and causes the latter to fall before 

 maturity, thus preventing the maturing of the seed. 



1 Inquiries in regard to insects afleeting forest trees should be addressed to the Branch of Forest Insects, 

 Bureau of Entomology, U. S. Department of Agriculture. 



2 See pages 153-165 of Bureau of Entomology Bulletin 83, Part I, "Practical information on the scolytid 

 beetles of North American forests. Barkbeetles of the genus Dendroctonus," by A. D. Hopkins. 



