Historic, Archive Document
Do not assume content reflects current scientific knowledge, policies, or practices.
V
Book number A423
13750 F762L
u. S. DEPT. OF AGRICULTURE TIONAL AGRICULTURAL LIBRARY
SEP 1 8 1962
c & R- PREP
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THE
PROBLEM
Young ponderosa pine deformed by spruce budw orm.
Insects destroy enough timber in the United States each year to build over a million houses.
Forest owners wage a constant battle to keep the insect population within reasonable bounds. With knowledge gained by experience and research, they can take precautions such as depriving bark beetles and wood borers of breeding places by cutting out susceptible or infested trees or by cleaning out stored logs and the debris left by logging. But despite such care, sometimes insect populations increase suddenly and threaten to lay waste a whole forest. When this happens, emergency measures must be taken.
DIRECT CONTROL
For example, a few years ago the spruce budworm began to take a heavy toll of the for- ests of the Pacific Northwest. On a cost-
Drifting insecticide from this low-flying plane destroys billions of tree-killing insects.
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sharing basis, the U. S. Forest Service, State agencies, and private landowner s joined forces to protect their lands. Airplanes, loaded with DDT insecticide, sprayed millions of acres of infested trees. The dramatic suc- cess of this operation justified the cost in both dollars and slight loss of fish and wildlife.
In I960 another insect, the European pine shoot moth, appeared on ornamental trees and shrubs in the State of Washington. Because control of this insect is so difficult, the North- west Forest Pest Action Council recommended a crash program to eradicate it before it could invade nearby pine forests. Nurserymen and homeowners cooperated, and crews began the monumental task of hunting out and killing ev- ery insect. Using the only known control method, crews fumigated infested trees with the deadly methyl bromide gas. The work is not finished, but the insect has thus far been confined to the cities.
Dead larva of European pine shoot moth lies amid ruin it created.
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Fumigation chamber encloses infested tree. Crew member checks time and temper- ature requirements with control center.
Pacific silver fir gouted by balsam woolly aphid.
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This shipping box brought 10,0
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Balsam woolly aphid infestation on bark of subalpine fir tree.
BIOLOGICAL CONTROL
An important facet of the research prograr proper balance of beneficial and harmful insect ductive.
In 1954, a European insect, the balsam wo age to true fir trees in the Pacific Northwest, but its existence was first recorded in Maine ir San Francisco Bay area, and shortly after 193 Oregon.
Control of the aphids was difficult. Becai on the bottom sides of limbs, in bark crevices, reach them. Hand spraying was effective but v^a ure, logging infested, dead, and dying trees w£
problems because most of the affected trees we:ii
access roads, and mills can presently use only forest products.
Meanwhile, research has concentrated on dii
tigations came the program, initiated in 1957, aphids. From Australia, Czechoslavakia, Swe flies and beetles to reduce the aphid numbers while others were kept in the laboratory for redng atory insects imported since 1957, 4 have becoe
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predatory insects from Europe.
Predatory insects are released on infested subalpine fir.
s to develop ways of helping nature achieve a o that our forests will remain healthy and pro-
y aphid, was found to be causing serious dam- 3w it came to the United States is not known, )08. Twenty years later it was found in the it was discovered in the Willamette Valley of
they live in protected places--under lichens, c. --insecticides spread by airplanes could not a long and costly job. As an emergency meas- recommended. But this, too, presented in high-elevation areas not reached by timber Limited amount of true fir in the manufacture of
ling other means of control. Out of the inves- importing beneficial insects to prey on the 1, India, Pakistan, Japan, and Germany came ome were released directly in the forests, ng and propagation. Of the 18 species of pred- established. One beetle, Laricobius erichsonii,
Laricobius erichsonii adult feeding on bal- sam woolly aphid.
Pacific silver fir gouted by balsam woolly aphid.
This shipping box brought 10,000 predatory insects from Europe.
Balsam woolly aphid infestation on bark of subalpine fir tree.
BIOLOGICAL CONTROL
An important facet of the research program is to develop ways of helping nature achieve a proper balance of beneficial and harmful insects so that our forests will remain healthy and pro- ductive.
In 1954, a European insect, the balsam woolly aphid, was found to be causing serious dam- age to true fir trees in the Pacific Northwest. How it came to the United States is not known, but its existence was first recorded in Maine in 1908. Twenty years later it was found in the San Francisco Bay area, and shortly after 1930, it was discovered in the Willamette Valley of Oregon.
Control of the aphids was difficult. Because they live in protected places--under lichens, on the bottom sides of limbs, in bark crevices, etc. --insecticides spread by airplanes could not reach them. Hand spraying was effective but was a long and costly job. As an emergency meas- ure, logging infested, dead, and dying trees was recommended. But this, too, presented problems because most of the affected trees were in high-elevation areas not reached by timber access roads, and mills can presently use onlyja limited amount of true fir in the manufacture of forest products. j
Meanwhile, research has concentrated on finding other means of control. Out of the inves- tigations came the program, initiated in 1957, of importing beneficial insects to prey on the aphids. From Australia, Czechoslavakia, Sweden, India, Pakistan, Japan', and Germany came flies and beetles to reduce the aphid numbers. Some were released directly in the forests, while others were kept in the laboratory for rearing and propagation. Of the 18 species of pred- atory insects imported since 1957, 4 have become established. One beetle, Laricobius erichsonii,
Laricobius erichsonii adult feeding on bal- sam woolly aphid.
is especially successful. Studies at Wil- lamette Pass, Oregon, reveal that this predator has become so abundant that it is eating as many aphids as are being produced--an encouraging step towards true control.
Also, parasites and insect diseases are allies in the control of damaging in- sects, and they have become the objects of intensive research.
In one study, spruce budworms are being mass-produced and reared in the research laboratory so that their life cycles, habits, and reactions to such factors as parasitism and disease may be analyzed.
Parasites are known to be helpful agents in keeping spruce budworm popu- lations low. But why are their activities less effective on budworms infesting white fir than those on Douglas-fir trees?
While keeping watch on the trend of the spruce budworm population, entomol- ogists noted that some of the larvae were apparently suffering from a disease. Lab- oratory examination at first indicated that it was a granulosis virus, but electron microscope examinations did not verify this diagnosis. The disease is contagious, however, and often fatal; but still many larvae recover and produce normal adults. What is this disease? Could it be a poten- tial weapon? Researchers must find the answ er.
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Larva of parasite in typical feeding position on spruce budworm larva.
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Full-grown parasite larva kills its host.
Adult parasite laying egg in body of spruce budworm larva hidden in twig scar.
THE FUTURE
There are many more harmful in- sects than those mentioned here. Each is destructive in its own -way. Some are foliage eaters, some suck life-giving juices from tender shoots, some feed upon the cambium layer under the bark, some bore holes into the wood or attack the cones and seeds. All must be con- trolled, and all will require special pro- cedures of control. All present challenges for the researcher.
Insects may have a relation to the diseases of trees or vice versa, and there is a possibility that forest genetics re- search can develop strains of trees strong enough to resist the ravages of both.
Research into these problems has been carried on for many years in the Pacific Northwest by State and Federal agencies and by schools and private or- ganizations. As knowledge increases, the needs of researchers increase for adequate equipment and facilities in or- der to maintain the pace set by the demand for more and more information.
For the Pacific Northwest Forest and Range Experiment Station, a long- felt need is being fulfilled by the con- struction of a new research laboratory on the Oregon State University campus.
It is designed not only for solution of problems already mentioned but for others plaguing the forest manager as well, such as those involving improvement of forest stands, protection against forest tree diseases, and watershed management.
Insects being reared at research laboratory are closely watched.
Electron microscope at laboratory allows study of insect virus diseases.
Architect's model of new Forest Service laboratory at Corvallis, Oregon, soon to be ready for occupancy.
TACIFIC NORTHWEST
FOREST AND RANGE EXPERIMENT STATION U.S. DEPT OF AGRICULTURE • FOREST SERVICE
June 1962
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