Oregon white oak in 

 completely stripped 

 looper. 



Oregon White Oak 



Oregon white oak is 

 threatened by develop- 

 ment and fire exclu- 

 sion — Oregon white oaks 

 are one of the hallmarks 

 of the Willamette Valley. 

 They are ecologically im- 

 portant as food for many 

 wildlife species, espe- 

 cially acorn woodpeckers 

 and wild turkeys. In ad- 

 dition to threats from ag- 

 riculture, urbanization, 

 and exclusion of fire, 

 white oak is host to a 

 plethora of insects and 

 diseases; fortunately, few 

 threaten its survival. 



The most visible and periodically damaging 

 insect is the western oak looper, which defoli- 

 ates trees over large areas. The present out- 

 break has persisted for at least the last 5 years. 

 Populations of this insect near the Dallas area 

 have been so high during the past 4 years that 

 the loopers have defoliated the tops of other 

 hardwoods and Douglas-fir growing in asso- 

 ciation with the oak. 



Armillaria root disease attacks Oregon white 

 oak and is often associated with tree uproot- 

 ing in urban areas. White oak is adapted to 

 droughty summers, and summer irrigation in 

 urban areas and parks seems to contribute to 

 the development of armillaria root disease. 



Ponderosa Pine 



Native pine is disappearing from the 

 Willamette Valley — ^Ponderosa pine was once 

 abundant in the southern part of the 

 Willamette Valley, but urbanization, logging, 

 and fire exclusion have diminished its popu- 

 lation to small scattered patches of trees, es- 

 pecially in the northern part of the Valley. 

 Natural regeneration has decreased, primarily 

 because fire no longer creates seedbeds and 

 removes competing understory vegetation. 



Genetically different from eastern Oregon 

 ponderosa pine, Willamette Valley ponderosa 



late sun}mer can be 

 of foliage by t/ie oak 



pine has few major pests 

 when grown in the Valley. 

 The ponderosa pine cone 

 beetle attacks young 

 cones and compromises 

 natural regeneration. In 

 larger trees, pine bark 

 beetles can attack and 

 kill moisture-stressed 

 pines, particularly in 

 drought years and in 

 overstocked stands. Fo- 

 liage diseases periodi- 

 cally plague eastern Or- 

 egon ponderosa pine 

 planted west of the Cas- 

 cade Range, especially in 

 areas with persistent fog. 



Grand Fir 

 Exotic insect damages grand Jir — The 



balsam woolly adelgid is a minute aphid-like 

 insect that sucks sap from true fir trees and 

 excretes a waxy "wool" that gives it its name. 

 Introduced to the west coast early this century, 

 this often overlooked pest has tremendous ef- 

 fect on the growth and seed production of 

 grand fir and likely is responsible for decreases 

 in grand fir populations at low elevations in the 

 Willamette Valley. 



Hybrid Poplar 

 Poplar is host to a recently introduced 

 foliage disease — Since 1980, commercial hy- 

 brid poplar plantations have rapidly expanded 

 in the northern Willamette Valley and along the 

 Columbia River in Oregon and Washington. In 

 1 99 1 , two new species of melampsora leaf rust 

 were reported from plantations near 

 Scappoose, Oregon, and Woodland, Washing- 

 ton. These particular rusts are considered the 

 most economically important poplar leaf rusts 

 in the world. As of 1995, one of these rusts 

 has become established in the Pacific North- 

 west, and the other (Eurasian poplar leaf rust) 

 has not. Hybrid poplar clones resistant to 

 these and other diseases are being developed 

 continually. 



Oregon — 32 



