Effects of bifenox, DCPA, and napropamide on ectomycorrhizal development of conifer seedlings in central and northern Rocky Mountain nurseries

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Researc h Paper
INT-341

May 1985

Effects of Bifenox,
DCPA, and
Napropamide on
Ectomycorrhizal
Development of
Conifer Seedlings in
Central and Northern
Rocky Mountain
Nurseries

Alan E. Harvey
Russell A. Ryker
Martin F. Jurgensen

Mie Resbe hale
sGNN9 tree -t¢ [MMs

THE AUTHORS

ALAN E. HARVEY, principal plant pathologist, is Pro-
ject Leader of the Silviculture of Cedar, Hemlock,
Grand Fir, and Douglas-fir Ecosystems and Forest Tree
Diseases of the Northern Rocky Mountains research
work unit at the Forestry Sciences Laboratory,
Moscow, ID. Dr. Harvey received a B.S. degree in biol-
ogy (1960), anM.S. degree in plant pathology (1962), a
Ph.D. degree in plant pathology (1968), and an aca-
demic year of postgraduate work in plant pathology
(1972). He joined the Intermountain Station in 1965.

RUSSELL A. RYKER, principal silviculturist, is Project
Leader of the Ecology and Silviculture of Rocky Moun-
tain Douglas-fir and Ponderosa Pine Ecosystems
research work unit at the Forestry Sciences Labora-
tory, Boise, ID. He received B.S. and M.S. degrees in
forestry from the University of Missouri and conducted
research in the silviculture of hardwoods for the North
Central Experiment Station prior to joining the Inter-
mountain Station in 1963.

MARTIN F. JURGENSEN, professor of forest soils,
teaches and conducts research in forest soils-soils
microbiology. He earned a B.S. degree in forestry
(1961), an M.S. degree in silviculture (1965), and a Ph.D.
degree in soil science (1967). He has held positions of
research associate and assistant professor at North
Carolina State University. He is currently with the
Department of Forestry, Michigan Technological
University, Houghton, MI.

RESEARCH SUMMARY

Postseeding and postgermination treatments with
three weed control herbicides (Bifenox, DCPA,
Napropamide) at two rates of application caused little
reduction of ectomycorrhizal development on 1- and
2-year-old conifer seedlings in Central or Northern
Rocky Mountain nurseries. In many cases, herbicide
treatment increased ectomycorrhizal development,
particularly with DCPA. In general, herbicide treatment
effects on ectomycorrhizal development were species
and nursery specific.

The use of trade, firm, or corporation names in this
publication is for the information and convenience of
the reader. Such use does not constitute an official
endorsement or approval by the U.S. Department of
Agriculture of any product or service to the exclusion
of others which may be Suitable.

Effects of Bifenox, DCPA, and
Napropamide on
Ectomycorrhizal Development
of Conifer Seedlings in Central
and Northern Rocky Mountain

Nurseries

Alan E. Harvey
Russell A. Ryker
Martin F. Jurgensen

INTRODUCTION

Herbaceous weeds are a major problem in Central and
Northern Rocky Mountain forest tree nurseries. Weed
competition, when uncontrolled, seriously reduces
survival and growth of tree seedlings. Weed control
practices most often used are fumigation and costly
hand or mechanical removal. Hand or mechanical weed-
ing is slow, often unsatisfactory, and increasingly expen-
sive. Soil fumigation is highly effective in reducing the
number of viable seeds in the soil but does not prevent
reinvasion from nearby areas. Thus, herbicides are
attractive as an economical means of reducing weed
competition.

Several years of testing pregermination and early post-
germination herbicides have shown that several may be
useful for weed control in Central and Northern Rocky
Mountain nurseries (Ryker 1981). Among these, the
herbicides Bifenox (Mobil trade name Modown) [methyl
5-(2,4-dichlorophenoxy) -2-nitrobenzoate], DCPA (Diamond
Shamrock trade name Dacthal) [dimethyltetrachloro-
terepthalate], and Napropamide (Stauffer trade name
Devrinol) [2-(a-naphthoxyl)-N, N-diethylpropionamide]
have the potential to reduce hand weeding time by 75 to
95 percent, depending on weed density (Ryker 1981).

Good ectomycorrhizal development is closely related to
the ability of conifer seedlings to grow in nursery soils
(Trappe and Strand 1969), to survive on harsh sites
(Marx 1976), and to successfully afforest or reforest soils
lacking in ectomycorrhizal inoculum (Meyer 1973). Some
herbicides are reported to reduce growth or development
of ectomycorrhizal fungi (Iloba 1974, 1976; Dasilva and
others 1977) and to reduce populations of other soil
microorganisms (Greaves and others 1976; Ogawa and
Yambe 1980). It is possible that herbicides may reduce
ectomycorrhizal development on seedlings in treated
nurseries, thereby reducing seedling quality. Information
on the effects of the above-named three herbicides on

ectomycorrhizal development of seedlings in nurseries is
lacking and is needed before the herbicides can be
approved. This report documents these effects in major
forest nurseries of the Central and Northern Rocky
Mountains.

MATERIALS AND METHODS
Nursery Locations

The nursery locations represented major conifer-
producing nurseries in the Central and Northern Rocky
Mountains. These included the U.S. Forest Service nurs-
eries at Coeur d’Alene, ID; Boise, ID (Lucky Peak);
Albuquerque, NM; Carbondale, CO (Mt. Sopris); the
Montana State Nursery at Missoula, MT; and the pri-
vately owned Mountain Home Nursery at DeBorgia, MT.

Experimental Design

The basic experimental design was a randomized block
that included the herbicide treatments listed in table 1,
and the following seedling species: Austrian pine (Pinus
nigra Arnold) (AP), blue spruce (Picea pungens Engelm.)
(BS), Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco)
(DF), Engelmann spruce (Picea engelmannii Parry ex
Engelm.) (ES), grand fir (Abies grandis [Doug]. ex D.
Don] Lindl.) (GF), lodgepole pine (Pinus contorta Dougl.
ex Loud.) (LPP), ponderosa pine (Pinus ponderosa Dougl.
ex Laws.) (PP), and western larch (Larix occidentalis
Nutt.) (WL). Not all species were tested in all locations,
but only those normally produced at the respective nurs-
ery. The herbicide treatment/species combinations tested
at the respective nurseries are shown in tables 3, 4, and
5 in the results section. Each combination, including the
untreated control, was represented by three replicate
plots. Statistical analysis included ANOVA and
Duncan’s Multiple Range tests, considering treatment
effects and interactions only.

Table 1.—Description of herbicide treatments tested for effects on ectomycorrhizal
development of conifer seedlings at major forest nurseries in the Central

and Northern Rocky Mountains

Formulation

Herbicide (trade name) Rate of active ingredient
Lb/acre (kg/ha)
Bifenox Modown 80% WP! 3 and 6 (3.4 and 6.7)
3 and 6 (3.4 and 6.7)
3 + 3 (3.4 + 3.4)
DCPA Dacthal, 75% WP 10.5 and 21 (11.8 and 23.5)

10.5 and 21 (11.8 and 23.5)

10.5 + 10.5 (11.8 + 11.8)

Napropamide Devrinol, 50% WP 3 and 6 (3.4 and 6.7)
3 and 6 (3.4 and 6.7)
3 + 3(3.4 + 3.4)

Control No treatment 0

Timing

Postseeding
Postgermination
Postseeding plus
postgermination
Postseeding
Postgermination
Postseeding plus
postgermination
Postseeding
Postgermination
Postseeding plus
posigermination

‘WP is wettable powder formulation; total active ingredient is based on the manufacturer's

recommendation.

Field Procedures

Each plot was bed-wide 4 ft by 3 ft (1.2 m by 0.9 m)
along the bed. Each herbicide was applied at two rates
(1X, at recommended rate and 2X, at twice the recom-
mended rate), and at two times (postseeding, postgermi-
nation of tree seed). In addition, we tested the multiple
applications of a 1X postseeding spray followed by a 1X
postgermination spray. Herbicides were applied with a
pressurized sprayer in a water carrier at a volume
equivalent to 85 gal/acre (100 mL/plot). Postsowing
treatments were applied within 2 days after sowing;
postgermination sprays were applied 28 to 35 days after
seedling emergence. Emergence is defined as the time
when most seedlings had shed their seed coats. Five
herbicide treatments plus a control were represented for
each herbicide. A total of 155 treatment combinations
(465 plots) were evaluated for ectomycorrhizal develop-
ment. Other details on the herbicide treatments are
available in Ryker (1981).

Sampling Procedures

Thirteen to 15 adjacent seedlings representing each
plot were lifted in June 1979 (planted April-May 1978,
except at Montana where beds were sown in fall 1977).
Seedlings were lifted carefully with a digging fork to
avoid root loss and damage. In all cases sample seed-
lings were adjacent, located two rows from the edge, and
well away from the end of the plot. Use of adjacent seed-
lings (seedling groups) minimized damage to the plots,
which were also used for phytotoxicity and weed-control
evaluations and standardized general sample location to
avoid border effects. Within these confines, the exact
positioning of the seedling group was random. Seedling
rows were uniform except for occasional missing
individuals. All seedlings were placed directly into a
plastic bag, with no attempt to separate or clean roots

on the site. Plastic bags were put on ice or refrigerated
at 34 °F (1 °C) for transport to and storage at the
laboratory location. All evaluations were completed
within 90 days.

Ectomycorrhizal evaluation procedures.— All ectomycor-
rhizal evaluations were done with no foreknowledge of
plot treatments by three examiners working at least two
at a time. Root systems from each of 10 seedlings ran-
domly selected from each plot sample were carefully
separated and washed in running water prior to exami-
nation. Spot checks on loss of small roots caused by
washing indicated such losses were small. Three types of
root evaluations were made for each seedling: (1) The
total root system was scanned and percentage of
ectomycorrhizal roots was estimated to the nearest 10
percent. (2) Excised from each seedling were 10-cm seg-
ments of major lateral roots (accumulative if necessary)
from the uppermost root system and from the lowermost
part of the root system. In each case, the 10-cm seg-
ments were cut to include just the first short root
nearest the originating major root and to just exclude
the last short root. Total number of ectomycorrhizal
short roots were counted and recorded separately for the
upper and lower 10-cm lengths. (3) Each ectomycorrhizal
short root was categorized into an arbitrary morphologi-
cal type based on external appearance (color, branching
habit, etc.). In cases of doubt, thin sections of short
roots were examined microscopically to determine if a
Hartig net and mantle were present.

Soil Properties

Because of the wide variation in the soils at some of
-the nurseries, basic properties (soil type, physical
makeup, pH, CEC, and organic matter content) were
determined for the study site at each nursery (Ryker
1981).

RESULTS

Initial results comparing numbers of ectomycorrhizal
short roots on shallow, as opposed to deep, lateral roots
indicated no significant differences between treatments.
Significantly more short roots occurred on the shallow
laterals than on the deep. We therefore discontinued use
of deep lateral roots in the evaluation process and pres-
ent only results using surface lateral roots.

Differences between treatments were small, usually
sporadic, and nearly balanced—there were almost as
many cases where ectomycorrhizal short roots were more
numerous on treated seedlings than on untreated seed-
lings as there were cases where they were fewer (tables
2, 3, 4). Across the various nurseries no consistent
patterns of effects emerged between specific herbicides,

significant interactions within a nursery occurred
between all three variables at one location or another
(table 5).

Although differences were small, the most consistent
related changes were slight reductions in numbers of
ectomycorrhizal short roots on Douglas-fir seedlings
treated with all three herbicides at the Montana State
Nursery, Douglas-fir seedlings treated with Bifenox at
the Forest Service nursery at Coeur d’Alene, and slight
increases in ectomycorrhizal short roots on lodgepole
pine seedlings treated with Bifenox and DCPA at the
Forest Service, Lucky Peak nursery (tables 3, 4, 5).
Statistical comparisons based on differences in percent-
age of ectomycorrhizal short roots were almost identical
to those based on actual numbers as seen in tables 2, 3,

species, or treatments. Considering all nurseries, cases of and 4. Therefore, these data have not been presented.

Table 2.—Comparisons of herbicide treatments by mean numbers of ectomycorrhizal short roots (cm) on 10-cm segments of main lateral
seedling root, based on 30 samples for each treatment

Nursery

Coeur d’Alene Albuquerque

Ponderosa pine Engelmann spruce Douglas-fir Grand fir Western larch Ponderosa pine
Treatment x 0 x 0 x a x 0 x 0 x 0
Control (no herbicide) 38.0 9.0 40.6 12.6 30.9 7.4 24.2 ALS 22.0 4.5 42.6 14.6
Bifenox
Bif. 1x1, PS2 + PG$ 37.3a4 9.8 —5 — 23.9a**& 5.8 28.4a 8.2 — — 38.1a 13.7
Bit >4-PS 46.8b* * 11.6 — — 24.6a** 6.6 26.5a 7.5 — _ 45.2a 10.7
Bif. 1x, PG 40.7a 11.6 — _ 26.6b ** 6.4 29.3a 9,9 —_ _ 46.9b 16.1
Bif. 2x, PS 42.9a 11.4 a — 22.6a** 4.9 32.1a 8.5 = — 43.5a 8.8
Bif. 2x, PG 45.5b** 9.6 os = 30.0b 6.4 27.7a LA — = 40.6a 13.6
DCPA
DCPA 1x, PS + PG _— — 36.2a 9.8 _ — — — 23.6a 12.8 45.1a 10.0
DCPA 1x, PS = — 47.6b** 8.9 _ - = — 21.4a 12.1 44.6a 1541
DCPA 1x, PG — — 37.4a 11.0 — _ _ — 24.1a 13:1 47.1a 8.9
DCPA 2x, PS a _ 44.8b 11.6 _ _ aoa —_— 18.5a 5:3 49.6b** 12.4
DCPA 2x, PG — 41.9a 8.4 — _ o _— 21.1a 3.8 41.8a 13.8
Napropamide
Nap. 1x, PS + PG 3i:2a** 8.9 37.8a 9.5 25.0a** Gif 27.2a 9.9 — _ 47.9a 9.1
Nap. 1x, PS 36.0a 11.7 38.8a 15.4 26.9a 7.8 25.1a 7.6 _ — 42.8a 15:7
Nap. 1x, PG 42.0b 9.1 36.3a 12.9 27.9a 8.7 26.6a 14.4 -- _- 34.1b** 11.1
Nap. 2x, PS 32.9a 9.6 32:3a** 112.1 27.9a 7.3 32.2a 16.7 = _— 38.6b 15:4
Nap. 2x, PG 32.5a Cal 34.1a 9.8 30.4b 5.1 27.0a 8.9 a — 45.3a 10.4

‘1x = applied concentration according to manufacturer’s recommendation, 2x = double concentration, for actual concentration of active ingredient (see
table 1).

2PS = immediately postseeding.

3PG = postgermination, usually 4 to 5 weeks after seedling emergence.

“Treatments within a single herbicide group and species (down column) that do not share a common subscript letter are significantly different to at least
a = 0.05 level, Duncan’s multiple range test.

‘Dash indicates this combination not tested.

Gast treatment differs from appropriate control (head of column) to at least a = 0.01 level, Duncan’s multiple range test.

Table 3.—Comparisons of herbicide treatments by mean numbers of ectomycorrhizal short roots (cm) on 10-cm
segments of main lateral seedling root, based on 30 samples for each treatment ;

Nursery

Mount Sopris Lucky Peak
Ponderosa pine Lodgepole pine Engelmann spruce _ Ponderosa pine Lodgepole pine

Treatment x to x to x o x o x G
Control (no herbicide) 37.6 (al 35.7 6.5 48.7 8.9 35.5 6.3 36.1 7.1

Bifenox
BifsiscPS2?= PG? 3 70a! 9.8 34.9a 6.5 —s = 38.6a 5.8 43.1a""& 8.4
Bif. 1x, PS 31.4a 13 33.0a 6.8 _ — 38.6a 8.6 39.6a 7.0
Bif. 1x, PG 35.2a 9.9 36.3a 59 — — 39.0a 48 41.6a"~* 8.9
Bif. 2x, PS 38.0a 7.7 35.1a 7.0 — — 33.5a 6.7 41.2a7* 7.4
Bif. 2x, PG 33.9a 9.9 31.2b;% 355 _ — 37.6a 6.9 45.9a"" 9.

DCPA
DGPA 1x,PS + PG — — = — — — 35.6a 6.3 43.8a"* Wee:
DCPA 1x, PS — — — — = = 37.7a 6.5 38.2b 5.8
DCPA 1x, PG — — — — — — 38.2a 6.1 38.3b 7.8
DCPA 2x, PS — = = = — = 38.8a 9.1 41.0b**— 9:7
DCPA 2x, PG = — _ — — = 37.6a 8.1 44 8a" 8.5

Napropamide
Nap. 1x, PS + PG 35.2a 9.9 35.4a 15 43.3a 6.9 = _ =
Nap. 1x, PS 33.7a 8.1 37.4a 9.3 43.6a 9.0 — _ — =
Nap. 1x, PG 37.0a 7.6 35.7a 7.2 45.6a 11.4 — — — _
Nap. 2x, PS 37.5a 12.4 33.1b 7.3 45.2a 8.2 = — — =
Nap. 2x, PG 34.2a 6.5 34.3a 6.4 46.1a 9.4 = _ — =

11x = applied concentration according to manufacturer's recommendation, 2x = double concentration, for actual concentration of
active ingredient (see table 1).

2PS = immediately postseeding.

3PG = posigermination, usually 4 to 5 weeks after seedling emergence.

“Treatments within a single herbicide group and species (down column) that do not share a common subscript letter are signifi-
cantly different to at least 2 = 0.05 level, Duncan’s multiple range test.

5Dash indicates this combination not tested.

6-- — treatment differs from appropriate control (head of column) to at least a = 0.01 level, Duncan’s multiple range test.

7 — treatment differs from appropriate control (head of column) to at least a2 = 0.05 level, Duncan’s multiple range test.

Table 4.—Comparison of herbicide treatments by mean numbers of ectomycorrhizal short roots (cm) on 10-cm
segments of main lateral roots, based on 30 samples for each treatment

Nursery
Mountain Home Montana State
Lodgepole pine Blue spruce Austrian pine Ponderosa pine Douglas-fir

Treatment x 0 x 0 x oO x oO x Oo
Control (no herbicide) 45.1 8.5 55.1 11.4 59.9 fal 34.3 6.8 28.3 7.7

Bifenox
Bif. 1x1, PS2 + PG$ 41.6a4 7.9 57.9a 11.0 58.1a 7.9 37.1a 10.1 19.0a**® 3.6
Bif.. 1x,.PS 40.3a 6.4 58.0a 11.7 61.5a 8.1 38.4a 8.8 18.8a** 3.7
Bif. 1x, PG 42.3a het 58.9a 14.5 61.9a 9.0 38.9a 10.0 21.4a** 3.8
Bif. 2x, PS 35:8b*" 11.6 55.9a 11.8 61.0a 9.8 33.6a 7.1 23.8b** 5.4
Bif. 2x, PG 41.2a 6.5 64.4b** 11.6 60.8a 9.7 36.0a 8.1 16.36%" 18:5

DCPA
DCPA 1x, PS + PG 47.5a 7.3 52.2a 11.3 56.5a 7.6 33.0a 13.6 21.8a** 6.2
DCPA ix, PS 42.1b 8.3 57.3a 10.9 62.9a 9.3 35.2b 7.8 21.9a** 6.4
DCPA 1x, PG 36.6c ** 12.4 52.1a 12.9 59.4a 9.9 35.2b 6.9 21.0a** 5.3
DCPA 2x, PS 46.0a 8.3 57.6a 12.2 60.5a 8.1 41.3c*/ 125 19.1b** 4.7
DCPA 2x, PG 43.6b 8.7 55.7a 11.6 63.3a 12.1 38.6b 7.8 19.5b** 3.2

Napropamide :
Nap.1x, PS + PG —5 — — — — — 37.8a 9.0 20.5a** 3.6
Nap. 1x, PS —_— - — — a — 38.3a 8.9 24.1b** 4.5
Nap. 1x, PG _ = — = — — 34.1a el 23.4a** 7.0
Nap. 2x, PS _ a — a _ — 36.4a CT 20.7a** 5.3
Nap. 2x, PG — — _ — a — 35.1a 8.0 20.6a** 4.4

11x = applied concentration according to manufacturer's recommendation, 2x = double concentration, for actual concentra-
tion of active ingredient (see table 1).

2PS = immediately postseeding.

3PG = postgermination, usually 4 to 5 weeks after seedling emergence.

‘Treatments within a single herbicide group and species (down column) that do not share a common subscript letter are signifi-
cantly different to at least a = 0.05 level, Duncan’s multiple range test.

5Dash indicates this combination not tested.

6** — treatment differs from appropriate control (head of column) to at least a = 0.01 level, Duncan's multiple range test.

7* — treatment differs from appropriate control (head of column) to at least a = 0.05 level, Duncan’s multiple range test.

Table 5.—Overall interactions between sources of variation and numbers of ectomycorrhizal short roots (cm)

Nursery
Mount Lucky Mountain Montana
Source of variation Coeur d’Alene Albuquerque Sopris Peak Home State
Within individual source
Species alia <2 +3 rn
Herbicide ae ‘ NS4 NS NS NS
Rate - : NS NS * NS NS
Two-way interactions
Species x herbicide - — _— NS “ NS
Species x rate _ ‘ oo . . NS
Herbicide x rate — a — NS ao NS
Three-way interactions
Species x herbicide x rate -— _ _ NS NS

'**Interaction significant, a = 0.01, ANOVA.

*Dash indicates combination not tested in experimental design.
3*Interaction significant, a = 0.05, ANOVA.

4NS interaction not significant.

Table 6.—Properties of soils at respective nurseries

Cation

Particle size distribution exchange Organic
Nursery Soil Type Sand Silt Clay ph capacity matter

—-=---- Percent ------- meq/100g__—s*wPercent
Montana State Sandy loam 57 30 13 6.9 11.76 2.7
Mountain Home Loam 40 50 10 5.6 13.67 4.5
Coeur d’Alene Sandy loam 71 21 8 6.1 6.17 Sal
Lucky Peak Sandy loam 61 26 13 5.8 7.44 sts
Mt. Sopris Sandy loam 55 29 16 6.0 9.87 3.3
Albuquerque Sandy loam 73 20 7 7.4 5.98 4

Color and morphology of ectomycorrhizal short roots
and other aspects of root structure were similar on the
species examined at the respective locations within the
limits of variation of sample seedlings. As would be
expected, differences occurred in root structure and num-
bers of ectomycorrhizal short roots on seedlings from
different nurseries. Since these differences were not
related to the treatments of interest, they were not con-
sidered in the analysis. Table 6 documents general soil
characteristics at each nursery.

DISCUSSION AND CONCLUSIONS

The lack of strong, consistent relationships between
herbicide treatment and numbers of ectomycorrhizal
short roots indicate a relatively unpredictable risk factor
associated with these herbicides and ectomycorrhizal de-
velopment. The strong relationships within nurseries,
both positive and negative, between herbicide-treated
seedlings of particular species and numbers of
ectomycorrhizal short roots clearly demonstrate highly
individualistic responses. Soil differences between nurser-
ies may contribute to individualistic responses and were
likely responsible, at least in part, for between-nursery
differences in mycorrhization. However, with regard to
mycorrhizae and herbicides, the soil characteristics we
measured showed no unusual differences at nurseries
where stronger relationships were observed. Accordingly,

each combination of herbicide, seedling species, and
nursery should be evaluated for possible negative effects.

With the three herbicides investigated here, the most
dramatic reductions were from herbicide treatments on
Douglas-fir at the Montana State Nursery, which aver-
aged 32 percent. This reduction is probably not enough
to cause substantial losses in seedling quality. It does
suggest that Douglas-fir may be a sensitive species. The
bases for such individualistic responses at a particular
nursery are not clear. Because of the lack of explanation,
due caution should be exercised with all herbicides.

The lack of strong herbicide-induced reductions and
frequent increases in ectomycorrhizal development agree
with other experiences (Trappe 1979, 1983; South and
Kelley 1972; Ogawa and Yambe 1980; Palmer and others
1980; Greaves and others 1976; Iloba 1974, 1976, 1977;
Uhlig 1966). Thus, use of these herbicides for nursery
weed control in Central and Northern Rocky Mountain
nurseries does not appear to pose high risks to
ectomycorrhizal development. The combinations and timing
of application tested here could be used in all cases, but
with reservations on Douglas-fir. All herbicides and ap-
plication procedures should be used on this species only
with great caution, particularly at the Montana State
and Coeur d’Alene nurseries. Even in relatively risky
combinations, herbicide use should not be precluded if
growth or outplanting performance of seedlings do not
suffer.

REFERENCES

Dasilva, E. J.; Henriksson, L. E.; Udris, M. Growth
responses of mycorrhizal Boletus and Rhizopogon spe-
cies to pesticides. Trans. Brit. Mycol. Soc. 68: 434-437;
1977.

Greaves, M. P.; Davies, H. G.; Marsh, K. G. P.;
Wingfield, G. I. Herbicides and soil microorganisms.
C.R.C. Crit. Rev. Microbiol. 5: 1-38; 1976.

Iloba, C. Aspect of herbicidal effects on the ectosymbi-
otic microorganism of forest plants. European J. For.
Pathol. 5: 339-343; 1974.

Iloba, C. The effects of some herbicides on the develop-
ment of ectotrophic mycorrhiza of Pinus sylvestris L.
European J. For. Pathol. 6: 312-318; 1976.

lloba, C. The effect of trifluralin on the formation of
ectotrophic mycorrhizae in some pine species. I. Toxic-
ity to mycorrhiza forming fungi. European J. For.
Pathol. 7: 47-51; 1977.

Marx, D. H. Use of specific mycorrhizal fungi on tree
roots for forestation on disturbed lands. In: Utz, Keith
A., ed. Proceedings, conference on forestation of dis-
turbed surface areas; 1976 April 14-15; Birmingham,
AL. Atlanta, GA: U.S. Department of Agriculture,
Forest Service, State and Private Forestry, Southeast-
ern Area; 1976: 47-65.

Meyer, F. H. Distribution of ectomycorrhizae in native
and man-made forests. In: Marks, G. C.; Kozlowski, T.
T., eds. Ectomycorrhizae—their ecology and physiol-
ogy. New York: Academic Press; 1973: 79-105.

Ogawa, M.; Yambe, Y. Effects of herbicides on mycorrhi-

zae of Pinus densiflora and soil microorganisms. Bulle-
tin No. 311. Ibaraki, Japan: Forestry and Forest
Products Research Institute; 1980. 102 p.

7

*U.S. GOVERNMENT PRINTING OFFICE:

Palmer, J. G., Sr.; Kuntz, J. E.; Palmer, J. G., Jr.;
Camp, R. F. Mycorrhizal development on red pine in
nursery beds treated with an herbicide. Forestry
Research Note No. 240. Madison, WI: University of
Wisconsin; 1980. 5 p.

Ryker, R. A. Evaluation of herbicides for weed control in
Rocky Mountain-Great Basin nurseries. In: Proceed-
ings of Intermountain Nurseryman’s Association and
Western Forest Nursery Association combined meet-
ing; 1980 August 12-14; Boise, ID. General Technical
Report INT-109. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain Forest and
Range Experiment Station; 1981: 22-28.

South, D. B.; Kelley, W. D. The effect of selected pesti-
cides on short root development of greenhouse-grown
Pinus taeda seedlings. Can. J. For. Res. 12: 29-35;
1982.

Trappe, J. M. Effects of three herbicides on mycorrhizal
development of Douglas-fir and ponderosa pine seed-
lings in western nurseries. Corvallis, OR: U.S. Depart-
ment of Agriculture, Forest Service, Pacific Northwest
Forest and Range Experiment Station; 1979. Unpub-
lished progress report.

Trappe, J. M. Effects of herbicide Bifenox, DCPA, and
Napropamide on mycorrhiza development of ponderosa
pine and Douglas-fir seedlings in six western nurseries.
For. Sci. 29: 464-468; 1983.

Trappe, J. M.; Strand, R. F. Mycorrhizal deficiency in a
Douglas-fir region nursery. For. Sci. 15: 381-389; 1969.

Uhlig, S. K. Untersuchungen uber die Wechsclwirkung
zwischen Chlor-bis-"athyl-amino-s-triazin (Simazin) und
mycorrhizabildenden pilzen. Wiss. Z. Techn. University
Dresden. 15: 639-61; 1966.

1985-0-576-040/10539

oe
zs

Harvey, Alan E.; Ryker, Russell A.; Jurgensen, Martin F. Effects of Bifenox,
DCPA, and Napropamide on ectomycorrhizal development of conifer seedlings
in Central and Northern Rocky Mountain Nurseries. Research Paper INT-341.
Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Re-
search Station; 1985. 7 p.

Postseeding and postgermination treatments with three weed control herbi-
cides (Bifenox, DCPA, Napropamide) at two rates of application caused little
reduction of ectomycorrhizal development on 1- and 2-year-old conifer seedlings
in Central or Northern Rocky Mountain nurseries. In many cases, herbicide
treatment increased ectomycorrhizal development, particularly with DCPA. In
general, herbicide treatment effects on ectomycorrhizal development were spe-
cies and nursery specific.

KEYWORDS: weed control, herbicide, ectomycorrhizae, Modown, Dacthal,
Devrinol, toxicity, nursery practice

LATE IL ET EET EI EY
PESTICIDE PRECAUTIONARY STATEMENT

This publication reports research involving pesticides. It
does not contain recommendations for their use, nor
does it imply that the uses discussed here have been
registered. All uses of pesticides must be registered by
appropriate State and/or Federal agencies before they
can be recommended.

CAUTION: Pesticides can be injurious to humans,
domestic animals, desirable plants, and fish or other
wildlife—if they are not handled or applied properly.
Use all pesticides selectively and carefully. Follow
recommended practices for the disposal of surplus
pesticides and pesticide containers.

he Pubes fell

U.S. DEPARTMENT OF AGRICULTURE

The Intermountain Station, headquartered in Ogden, Utah, is one
of eight regional experiment stations charged with providing scien-
tific knowledge to help resource managers meet human needs and.
protect forest and range ecosystems.

The Intermountain Station includes the States of Montana,
Idaho, Utah, Nevada, and western Wyoming. About 231 million
acres, or 85 percent, of the land area in the Station territory are
classified as forest and rangeland. These lands include grass-
lands, deserts, shrublands, alpine areas, and well-stocked forests.
They supply fiber for forest industries; minerals for energy and in-
dustrial development; and water for domestic and industrial con-
sumption. They also provide recreation opportunities for millions
of visitors each year.

Field programs and research work units of the Station are main-
tained in:

Boise, Idaho

Bozeman, Montana (in cooperation with Montana State
University)

Logan, Utah (in cooperation with Utah State University)

Missoula, Montana (in cooperation with the University
of Montana)

Moscow, Idaho (in cooperation with the University of
Idaho)

Provo, Utah (in cooperation with Brigham Young Univer-
sity)

Reno, Nevada (in cooperation with the University of
Nevada)