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Yearbook^ of Agriculture 1949 



The heart rots that develop through 

 naturally suppressed branches and 

 branch stubs are the most prevalent in 

 western conifers. Some fungi enter al- 

 most entirely through dead branches 

 that contain heartwood and that are 

 nearly always an inch or more in diam- 

 eter. Others enter through branch 

 stubs that contain heartwood. Man- 

 agement of forests to maintain a high 

 density in the young stands, so that 

 branches do not form heartwood be- 

 fore being shaded out, and artificial 

 pruning in more open young stands 

 will reduce the incidence of such de- 

 cay. Ground fires, insect epidemics, 

 and heavy partial cuts that heavily thin 

 stands and thereby stimulate the for- 

 mation of large branches on the sur- 

 viving trees are important factors in 

 providing favorable places of entrance 

 for these fungi. 



A stand of timber badly burned or 

 damaged by wind or ice should be 

 salvaged promptly or heavy losses from 

 decay may ruin the merchantability 

 of a high proportion of the volume. 

 Prompt salvage cuts of this type require 

 knowledge on the part of timber man- 

 agers of the high toll that decays can 

 take in badly broken or heavily fire- 

 scarred stands. 



Many timber stands have been re- 

 peatedly burned by ground fires so that 

 practically all old trees have scars at 

 their butts. Fungi entering through 

 these scars account for a large propor- 

 tion of the heart rot in older stands. 

 The so-called butt rots are usually con- 

 fined to the roots, stump, and basal 16- 

 foot log, but occasionally extend much 

 farther. Other rots known as trunk rots, 

 which may enter through butt scars or 

 any wound or dead stub on the trunk, 

 usually are more extensive and often 

 cause entire trees to be culled. The 

 resinous pines are not so subject to butt 

 rot following injury as the nonresinous 

 conifers and hardwoods. 



The dwarf mistletoes of western 

 conifers cause enlarged branches and 

 burls on the trunk that provide points 

 of entrance for heart rot fungi in old 

 trees. Dead areas on these burls, stubs 



of swollen branches, holes in the stem 

 where enlarged branches have been 

 pulled out, and broken tops offer major 

 rot hazards from mistletoe infections. 

 In western hemlock in the Northwest, 

 heart rots established through mistle- 

 toed knots and burls account for more 

 decay than from any other cause. Silvi- 

 cultural methods to prevent serious 

 mistletoe infections in future timber 

 stands are now being developed. 



In the East, oak stump sprouts that 

 arise more than a couple of inches high 

 on the parent stumps are very likely to 

 become butt-rotted from the old stump. 

 Ground-level sprouts seldom contract 

 rot from a parent stump. One cleaning 

 operation made in a sprout stand at 

 about 15 years of age can eliminate the 

 decay-susceptible high-origin sprouts 

 and provide single-stemmed crop trees 

 rather than sprout clumps. Two defects 

 can thus be minimized by a timely 

 cleaning. In the case of scarlet oak, a 

 pruning at 15 to 20 years will elimi- 

 nate many of the future rot pockets and 

 holes at the bases of dead branches, so 

 common in this poorly self-pruning 

 species. 



Decay reduction and silviculture are 

 also linked in pruning, through de- 

 creasing decay where small branches 

 are pruned or possibly increasing it 

 where large branches are cut. The re- 

 moval of trees with spore-shedding 

 conks, where practicable, is good silvi- 

 culture. A number of common heart 

 rot fungi may enter the trunk through 

 the roots, either through root wounds, 

 root grafts, or contact with decayed 

 roots of other trees. These rots are 

 controllable mainly through the knowl- 

 edge of the age at which they become 

 important and arrangement of the 

 cutting schedules accordingly. 



MAJOR LOSSES from heart rot can 

 definitely be prevented. A certain 

 amount of decay is bound to occur in 

 any timber stand, but we already have 

 the means of keeping such losses to 

 low levels. For many species that can 

 be achieved by adjusting downward 

 the cutting age when necessary, by 



