THE EELATION OF INSECTS TO SLASH DISPOSAL Q 



Nevertheless, a felled tree is rarely attacked. Here, again, it is obvi- 

 ous that slash disposal does not reduce the number of beetles, and the 

 concentration caused by the slash appears to be unavoidable. 



Another lodgepole pine insect {Dendroctonus murrayanae Hopk.) has 

 habits similar to those of D. valens Lee, discussed under yellow pine. 

 Evenden has found this species of economic importance in crosstie 

 operations in Wyoming. Breeding readily in the stumps, it subse- 

 quently attacks the bases of the larger standing trees not included in 

 the sales. Kepeated attacks of this kind weaken the tree to such an 

 extent that it succumbs to the attack of other bark beetles on the bole. 



MONTEREY PINE IN CALIFORNIA 



Several serious outbreaks of Ips on the Monterey pine {Pinus radiata) 

 near Monterey, Calif., have been accounted for as caused by wood cut- 

 ting and clearing, where the wood has been left piled in the forest. 

 Other factors, however, enter into this problem, since similar cutting 

 in other years has produced no epidemics. The turpentine beetle 

 (Dendroctonus valens Lee), which breeds usually in stumps, often 

 becomes primary in its attack upon standing trees of this species. 



Because of the value of the Monterey pine as an ornamental and 

 shade tree, special precautions in slash disposal may well be taken to 

 help minimize insect damage to it, which occasionally becomes serious. 



THE SOUTHERN PINES 



The southern pine beetle (Dendroctonus frontalis Zimm.) and three 

 species of Ips (/. calligraplius Germ., /. avulsus Eichh., and /. grandi- 

 collis Eichh.) are the most important pine insects of the South. The 

 first species mentioned rarely attacks anything but living trees, whereas 

 the three species of Ips are mxore commonly found in tops, cull logs, 

 and stumps than in standing pines. All these species are so intimately 

 associated in the destruction of living trees that it is impossible to 

 consider them separately. On the other hand, the infrequency with 

 which the southern pine beetle attacks slash, cuU logs, or wind-blown 

 trees immediately eliminates it as an argument for the disposal of 

 such material. 



Very few reports of dying pine timber in the South that can be 

 associated with slash as a factor have been called to the writers' 

 attention, and extensive observations by several entomologists have 

 not revealed any striking examples. In fact, experimental cuttings 

 of timber, conducted throughout the year with the express purpose 

 of furnishing the breeding material for these insects, have utterly 

 failed to produce attacks in the surrounding standing trees. Never- 

 theless, there are many examples which show that these species are 

 all strongly attracted to areas where cutting is being carried on in the 

 summer. If sufficient material is on the ground they invariably 

 attack it, and occasionally small quantities of neighboring living tim- 

 ber are killed. For example, a freshly sawn pile of lumber, brought 

 to a home site for building purposes, attracted to that vicinity a suffi- 

 cient number of these insects to kill a number of trees adjacent to the 

 pile. 



It is therefore reasonable to conclude that slash serving as breeding 

 material for these insects is not a menace, but that because of the 

 attraction which it exerts on them local logging or clearing opera- 

 tions in the summer should be avoided. 



