A look at forest insect research

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.

■

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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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.

il:

M

Larva of parasite in typical feeding position
on spruce budworm larva.

wf

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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