FOREST PROTECTION 



205 



— 30,000 



— SOUTH — NORTH WEST CONTINENTAL UNITED STATES 



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1940 



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Figure 77 



Some diseases, such as chestnut blight, have 

 caused catastrophic losses. Some, such as blister 

 rust, are being held in check in most areas through 

 rigorous control efforts; others, such as littleleaf, 

 are being combated through adjusted manage- 

 ment practices, and still others are at present 

 mainly in the status of threats, such as oak wUt 

 and sweetgum blight, or of no great importance 

 to our timber resource, such as persimmon wilt. 

 During the past half century, the incidence of 

 "new" diseases presents no clear trend. For the 

 5 decades included, the number of serious new 

 forest diseases reported varied from 2 to 4 per 

 decade, with a peak in the 1930's. 



In addition to the diseases reported above as 

 new since 1900, there have been buildups of major 

 consequence, often associated with abnormal 

 weather or changes in forest conditions, on the 

 part of several diseases native with us, or natural- 

 ized many years ago. Diseases of this type that 

 have risen in importance at one time or another 

 since 1900 include Elytroderma needle cast on 

 ponderosa pine and fusiform rust of southern pines. 



In the tables in this report dealing with growth 

 impact from destructive agents, the losses from 

 all types of events are included, whether endemic 



or epidemic, introduced or native. The only ex- 

 ceptions are the losses from those individual cat- 

 astrophic events that are listed in table 133, p. 217. 



Diseases Reduce Our Timber Supply 



Earlier, it was shown that diseases cause 22 per- 

 cent of the growing-stock mortality and 56 percent 

 of the growth loss, representing 45 percent of the 

 impact on total national growth. While this 

 tremendous volume loss is composed of major 

 damage by many diseases, 3.4 of the 5.0 billion 

 cubic feet is ascribable to the heart rots alone. 

 The bulk of the growth impact from diseases is 

 growth loss rather than mortality (table 127 and 

 fig. 72). Such diseases as the heart rots, leaf 

 diseases, and killers of seedlings and saplings cause 

 little mortality loss of measurable volume, yet 

 account for the larger share of the ultimate effect 

 of disease on wood production. 



The damage is not localized in any particular 

 section of the country (table 128). Thus, 40 per- 

 cent of the Nation's 1952 growth impact from 

 disease on sawtimber is in the North, largely the 

 Northeast and Lake States, 35 percent is in the 

 South, 22 percent in the West, and 3 percent in 

 Coastal Alaska. 



