FOREST PROTECTION 



207 



Blister rust losses are being held to a low level in 

 most of the East by the control program. On 

 private lands in the Lake States, the rust is 

 materially damaging young stands, which repre- 

 sent the predominant age class of the region. In 

 the Northern Rocky Mountain Region, the rust 

 has become established throughout the range of 

 white pine. In the Inland Empire, losses are 

 already heavy, but the rust's full effect has not 

 yet been felt. In California the rust has spread 

 south to the central Sierra Nevada and is causing 

 considerable damage in the northern end of the 

 State. The effectiveness of control progi"ams in 

 the West has been demonstrated, however. 



The dwarfmistletoes lead the diseases in amount 

 of damage caused in the Southern Rocky Moun- 

 tain Region, and also cause considerable damage 

 to ponderosa pine, lodgepole pine, and Douglas-fir 

 elsewhere in the West, and to black spruce in the 

 Lake States. Trees of all sizes are attacked. 

 Some are killed before they reach merchantable 

 size, and others are stunted for long periods. 



Birch dieback, since 1930, has destroyed much 

 of the yellow and paper birch in New England 

 and adjacent Canada. It is New England's most 

 devastating disease since the chestnut blight. 

 Damage from this disease in 1952 resulted in a 

 growth impact of 494 million board-feet. Its 

 exact nature and cause are not completely under- 

 stood, but there can be little doubt that reduced 

 rainfall and abnormally high temperatures are im- 

 plicated. The bronze birch borer has added to 

 the destruction by killing many trees weakened 

 by dieback. 



Root rot caused by Poria weirii damages many 

 western conifers, but is particularly serious on 

 Douglas-fir in the Pacific Northwest, where it 

 severely attacks stands as young as 20 to 60 years 

 of age. There is no question but that this dis- 

 ease, with a current annual growth impact of 454 

 million board-feet, has become a major silvicul- 

 tural problem in the Northwest. 



Fusijorm rust is the most important disease of 

 loblolly and slash pines. The alternate hosts for 

 this southern rust are the oaks. Although trees 

 of all ages are susceptible, the stem cankers that 

 kUl seedlings and saplings are the most damaging. 

 The disease continues to increase as fire protection 

 favors the increase in oak over pine and also 

 increases the proportion of loblolly and slash pines 

 at the expense of the more rust-resistant longleaf. 



The hardwood canker diseases attack a wide 

 range of species, expose the trunks to decay, and 

 lead to cull, wind breakage, and reduced wood 

 quality. They are important primarily in New 

 England, and the Middle Atlantic, Central, and 

 Lake States. Hypoxylon canker of aspen causes 

 by far the most serious disease mortality loss in 

 the Lake States. 



Littleleaf, a fungus root disease associated with 

 poor internal soil drainage and soil deterioration. 



attacks shortleaf and to a lesser extent loblolly 

 pine. It is the most important silvicultural prob- 

 lem in shortleaf management in much of the 

 Piedmont and in the upper Coastal Plain of 

 Alabama. It reaches important proportions on 

 6 million acres from Virginia to Mississippi, and 

 occurs in scattered stands over a wider acreage, 

 with a total current annual growth impact of 146 

 million board-feet. 



Pole blight is a disease of undetermined cause, 

 characterized by dieback and gradual decline of 

 the entire crowns, leading to the complete breakup 

 of large areas of pole-sized western white pine. 

 This blight caused a growth impact of 61 million 

 board-feet, almost all in trees 8 to 20 inches in 

 diameter. Blighted stands now occupy 92,000 

 acres in northern Idaho and adjacent Washington 

 and Montana. 



Brown spot is a fungus disease of the needles 

 and one of the main reasons that longleaf pine 

 remains in the "grass" stage for many years before 

 starting height growth. Where brown spot has 

 been controlled by either prescribed burning or by 

 foliage sprays, early height gi-owth has been initi- 

 ated and the time required to gi'ow a crop of 

 longleaf pine reduced as much as 20 percent. 



Oak wilt is currently the most highly publicized 

 tree disease in the Nation. Since it is a virulent 

 killing disease to which all oak species tested are 

 susceptible, it deserves the attention it is receiving. 

 There is strong evidence that it has been in Wis- 

 consin and Iowa for 40 years or more. More 

 recently, it has been found scattered over a wide 

 area in the Lake and Central States, from Penn- 

 sylvania to North Carolina, and westward through 

 Tennessee and northern Arkansas to eastern 

 Kansas and Nebraska. Oak wilt has destroyed 

 great numbers of oaks in the Middle West; in 

 Wisconsin and Iowa, many oak areas from a few 

 to about 100 acres in extent have been practically 

 denuded. The wUt has been slowly but definitely 

 spreading in the Appalachians and Pennsylvania. 

 In terms of current impact on our Nation's oak 

 supply, oak wilt has not had a great effect (table 

 128), and its importance lies in the threat that, 

 if left uncontrolled, it could gradually build up to 

 serious proportions over much of our oak timber- 

 land. 



Sweetgum blight is a newly recognized disorder 

 of unknown cause, characterized by dieback of 

 the crown and more or less rapid death of entire 

 trees. It occurs in varying degrees in all States 

 where sweetgum grows. A particularly spectac- 

 ular dying of sweetgum that has been taking 

 place in recent years in Maryland and Delaware 

 may be an aggravated stage of the blight that 

 occurs elsewhere in the South or may prove to 

 be a separate disease. The 42 million board-feet 

 of damage from sweetgum blight is made up of 

 the two types combined. 



Elytroderma needle cast is a serious disease of 





