462 



HEART ROT 



GEORGE H. HEPTING, JAMES W. KIMMEY 



Heart rots, which are caused by 

 fungi that attack the wood of living 

 trees, are to blame for an estimated an- 

 nual loss of 1 .5 billion board feet in our 

 commercial forests. In money, the loss 

 lies somewhere between the approxi- 

 mately 10 million dollar value given 

 the cull as stumpage and the 47 million 

 dollar value given it as logs. 



Every timber species in the United 

 States is subject to attack by one or 

 more species of the fungi, but fortu- 

 nately a large part of the losses can be 

 prevented by proper management. 



In trees that have a clearly defined 

 heartwood oak, ash, and most coni- 

 fers, for example the heart rots are 

 usually confined to the true heartwood. 

 In many other hardwoods, normal 

 heartwood forms irregularly, and de- 

 cay of the inner sapwood is also called 

 heart rot. The term "sap rot" is used 

 for the decay of dead or dying sapwood. 



When a fungus that is decaying the 

 heartwood of a tree has developed for 

 a number of years, it often produces a 

 spore-bearing structure like a mush- 

 room or a bracket-shaped conk. Each 

 year one such structure can produce 

 millions of tiny spores, which are car- 

 ried about by air currents. When a 

 spore comes to rest upon exposed wood 

 and conditions are suitable, it germi- 

 nates and sends fungus filaments into 

 the wood. By means of these threads 

 the fungus spreads through the tree, 

 feeding upon and rotting the heart- 

 wood as it goes. Some fungi, which 

 cause some of our common root and 

 butt decays, rarely produce spores, but 

 spread largely by growth through the 

 soil. 



Entrance points for rot fungi are 

 usually provided by the exposure of 

 heartwood when the trunk, top, limbs, 

 or roots are wounded by fire, logging, 

 or storms. Butt rot in sprout hardwoods 

 usually is transmitted from the rotting 

 stump to the attached sprout. Some of 



the most important heartwood destroy- 

 ers gain entrance through branch stubs 

 or branches killed by natural sup- 

 pression. 



THE HIGH DECAY GULL in many 

 eastern hardwoods reflects mostly fire- 

 scarring, ice damage, and abandon- 

 ment of defective trees in past logging. 

 Decay cull in most eastern softwoods 

 and in the southern pines now has 

 reached a small percentage because 

 their cutting ages have been reduced. 

 Improved timber management prob- 

 ably will keep the losses from decay at 

 a low figure for those species. 



The basic problem of timber man- 

 agement in the West now is to bring 

 hitherto unmanaged forest land into 

 maximum production. The two prin- 

 cipal problem types are forest lands 

 that have been cut-over or burned (on 

 them new growth is inadequate) and 

 stagnated virgin stands of overmature 

 old-growth timber. Heart rots are in- 

 volved in the management of both 

 types. Through good forest practices, 

 heart rots in future timber stands of 

 the West may be kept at a minimum if 

 the factors leading to heart rot are 

 fully understood. 



Decay factors affect silvicultural 

 practices throughout the country in 

 seven important ways: In the deter- 

 mination of the cutting age; in the 

 system of harvest cutting; in the choice 

 of trees to be cut in partial-cutting 

 systems; in requiring special salvage 

 cuts in timber burned or otherwise 

 damaged ; in managing mistletoe-dam- 

 aged stands; in requiring the early 

 treatment of hardwood stump sprouts ; 

 and in pruning and similar operations. 

 Each is discussed here. 



In most of our eastern and southern 

 species, the age at which the trees will 

 be cut (based upon the rate of return 

 from the land) will be lower than the 

 age at which decay ordinarily becomes 



