HORTICULTURAL DIVISION 695 



type of disease plays a major role in making wood lots unprofitable, often 

 producing a cull or loss from decay amounting to twenty or thirty per cent 

 of the value of the stand at time of cutting. These decay fungi enter the 

 trunks in various ways -- through fire scars, lightning injuries, other wounds, 

 knot holes, old stumps and roots. Fungous organisms sometimes utilize 

 more than one means of entrance. The loss which these fungi produce can 

 often be lessened greatly by the observance of certain general rules of forest 

 sanitation and protection: (i) By preventing forest fires the park manager 

 can eliminate one important mode of entrance for decay fungi -- fire scars. 

 (2) By care in any cutting operations he can lessen the number of wounds 

 on the trees left standing. (3) If he cuts trees so that the stumps are low, 

 decay is less likely to spread from the old stumps to the growing sprouts. 

 (4) By removing the diseased trees in all cutting and thinning operations 

 the owner can largely eliminate the source of infection for healthy trees. 

 It is often difficult to detect decay in trees, but hollows at the base of trees 

 or high up in the trunks, open fire scars, fruiting bodies (conks, punks) 

 of decay fungi on the trunk, and hollow sound produced when the tree 

 is struck with an ax, are the surest indications of it. In such trees the 

 decay is usually progressing faster than new wood is forming. Severely 

 wounded, dead and wind-thrown trees should also be removed. Trees 

 which, because of crowding or some other unfavorable factors, are in danger 

 of dying, should be utilized, since decay and other factors rapidly render a 

 dead tree worthless and dangerous. Trees that are making very slow 

 growth, especially those that have many large dead limbs, are usually 

 more susceptible to decay than vigorously growing trees and should be cut 

 in thinning operations. (5) For forest plantings it is often advisable to use 

 a mixture of species, so that if one species is seriously affected by decay 

 or other diseases a full stand can still be obtained. Diseases develop less 

 abundantly in mixed stands than in pure stands. 



Trees in planted parks or parks which have been extensively cleared 

 are subject to a number of diseases not shared by forest trees. The clearing 

 away of adjacent trees and undergrowth leaves the surviving trees in 

 unnatural conditions to which some species of trees will not adjust. They 

 usually show their lack of adjustment by becoming stag-headed and slowly 

 dying. Changes in the level of the water table are frequently made in 

 clearing park land, with the result that the surviving trees either suffer 

 from lack of water or the roots are drowned. Many trees are injured by 

 changes in the level of the soil or cutting away of the roots in the process 

 of road building. In parks with extensive lawns which are kept carefully 

 cut, the trees in time suffer from lack of humus and show signs of starva- 

 tion. This is probably the most frequent cause of dying trees in parks of 



