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UNIVERSE OF .LLINO.. LIBRARY AT URBANA-CHAMPAIGN

L161— 0-1096

AUG 1 2 1992

flBWCULTURE LIWABY

Giant Foxtai 1

Setaria Faberi Herrm.

Bulletin 803
University of Illinois at Urbana-Champaign

College of Agriculture
Agricultural Experiment Station

ontents

Early History and Introduction into the United States 1

Rapid Spread 2

Growth Habits and Characteristics 3

Identification of Giant Foxtail 6

Seed Production, Viability, and Longevity 8

Competition 9

Control 14

Summary 17

References... ..18

AGRICULTURE LIBRARY
JAN 3 0 1991

UNIVERSITY OF ILLINOIS

arly History and Introduction into the United States

The exact origin of giant foxtail [Setaria
faberi Herrm.]* is not known. Li, Pao, and
Li (70) have suggested that perhaps this
tetraploid originated from an ancient cross
of green foxtail [Setaria viridis (L.) Beauv.]
with an unknown diploid species. Wolfgang
Herrmann, a German botanist, provided the
first known botanical description of this
species in 1910 (46). His description was
based on a plant collected from the Szech-
wan province of China sometime between
1885 and 1891 by Reverend Ernst Faber,
a missionary.

Chase (18) reports that seed of giant
foxtail was found by seed analysts in 1932
in millet imported from China. Although it
has been suggested that millet imported
from China during our drought years of the
1930s may have been the primary source
of giant foxtail introduced into the United
States, the species was actually present
earlier (30,32). One collection was made
on September 19, 1925, on Long Island,
New York, and another near Philadelphia
on September 9, 1931 (94).

The introduction of the plant may have
occurred earlier still. Plant explorers
brought the seed of many plants, including
millet, from the Orient in the early 1900s,
and several varieties of millet were raised at
Arlington Farm, Virginia, between 1909
and 1925 (90). It may be coincidence, but
giant foxtail was subsequently reported
growing near a greenhouse at Arlington
Farm in 1936 (1).

A translation of Herrmann's Latin de-
scription of the plant collected by Faber
does not appear to indicate fine pubescence
on the upper leaf surface as usually associ-
ated with giant foxtail in the United States.
Actual inspection of Faber's plant in an her-
barium in Vienna, Austria, in 1985, failed
to reveal the fine pubescence. Reports from
several U.S. weed scientists visiting China
suggest difficulty in finding plants with the
characteristic leaf pubescence.

A letter dated July 9, 1989, from Profes-
sor Yang-han Li of the Weed Research
Laboratory of Nanjing Agricultural Univer-
sity indicates that giant foxtail does occur in
several parts of China as a common but not
serious annual weed. Professor Y.L. Keng,
a well-known taxonomist of grass in China,
indicates that some plants referred to as
Setaria faberi in China have the character-
istic pubescence on the upper leaf surface
while others do not. It is not unusual to
have some variation within a species.

It is difficult to be certain that giant foxtail
was introduced into the United States from
China. The majority of evidence thus far,
however, suggests this probability.

The original species designation for giant foxtail was Selario faberii Herrm. However, the
Terminology Committee of the Weed Science Society of America changed the spelling to Setaria
faberi Herrm. The latter is the current official designation.

apid Spread

Regardless of the exact source or reason for
introduction, giant foxtail soon became well
established in the United States. Giant
foxtail's rapid adaptation may have been
partly because the land elevation, soils, and
climate in this plant's native China resem-
bled those features in some of the agricul-
tural areas in the United States where the
plant eventually became established (53).
Some reports suggest giant foxtail's spread
along railroads in the United States (32,94).
The seed also serves as a food for wild
birds, which may have contributed to the
plant's spread.

During the 1940s, giant foxtail continued
to spread and became established as a
weed. By the 1950s, the plant was quite
prevalent in the Midwest (29,48,49,91). In
Illinois, for example, the first collection re-
ported was in 1938; by 1955, giant foxtail

Figure 1. The distribution of Setaria faberi Herrm. is indicated on the shaded
portion of the map. The map is based on communication with weed scientists
and taxonomists during 1988-1989.

had spread to most counties of the state
(48). Nationwide, also in the 1950s, the
plant was present from Connecticut to
South Dakota and from Minnesota to Mis-
souri, Kentucky, and North Carolina (29,32,
49,91,126). Giant foxtail was soon consid-
ered to be the most serious annual grass
weed in many agricultural production areas.

The advent of 2,4-D as a herbicide for
com in the late 1940s, and the broadleaf
weed control it provided, may have afforded
more opportunity for giant foxtail to be-
come established (59). The trend from
check-planted com to hill-dropped com
and drilled com, along with the subsequent
reduction in cross-cultivation, may also have
contributed to the spread of giant foxtail
(53). The increasing and extensive acreage
of com and soybeans with life cycles similar
to that of giant foxtail may have also fa-
vored giant foxtail.

Fortunately, the introduction of
selective, soil-applied preemer-
gence herbicides in the late 1950s
offered control of giant foxtail,
which resulted in the rapid adop-
tion of their use. In some areas,
use of soil-applied herbicides in-
creased dramatically from treat-
ment of 5 percent of the row crop
acreage in 1960 to treatment of
nearly all acreage by 1980.

Today, giant foxtail is found in
the United States primarily in the
Midwest, the East, and portions of
the South. The plant's range ex-
tends from New England to the
Great Plains, from Minnesota to
Louisiana, to Georgia and the
Carolinas (Figure 1).

rowth Habits and Characteristics

In the Midwest, giant foxtail usually begins
to emerge about mid- April (45,53). The
seed is relatively small (2 to 3 mm). Emer-
gence has been reported from seed at a
depth of 4 or 5 inches (51,53). But most
problems are caused by seed located in the
top 2 inches of the soil (53). When mean
daily soil temperature reaches about 50°F to

Figure 2. The Achilles' heel stage of growth for giant foxtail (left). At
this stage the seedling depends on the thin threadlike mesocotyl between
the seed and the crown for support. The mesocotyl can be easily broken
at this stage by disturbing the soil with a rotary hoe. After the crown
roots form (right), control is more difficult.

60°F, plants may emerge within a week to
10 days after the soil is disturbed or the
seed is planted. Morre and Fletchall (74)
found germination to be comparable at vari-
ous temperatures between 59°F and 86°F.
When seeded 1 inch deep on May 8 at Ur-
bana, Illinois, seedlings emerged in 8 to 10
days. At 2 weeks, seedlings were 1/2 to 1
inch tall with two leaves. At 3 weeks, plants
had three to four leaves, and at 4 weeks,
they had five to six leaves. At 5 weeks,
plants were tillering and crown roots were
becoming established (53).

As a young giant foxtail seedling grows,
the crown of the plant at the base of the
stem becomes established near the soil sur-
face. The fine subcrown internode or meso-
cotyl is found between the crown and the
seed (51,75) (Figure 2). Although the meso-
cotyl supplies nutrients from the seed to the
emerging plant, it is not sturdy enough to
provide mechanical support. Within 1 or 2
weeks after emergence, roots appear from
the crown of the plant and become estab-
lished in the soil to provide mechanical sup-
port and nutrients and water from the soil
(53,61).

Thus, these first few weeks are very criti-
cal in the life of the plant. Farmers wishing
to control giant foxtail should consider this
very vulnerable stage as the giant foxtail's
Achilles' heel. If the top 1/4 to 1/2 inch of
soil is disturbed before the crown roots be-
come established, the thin threadlike meso-
cotyl cannot support the plant, causing it to
fall over. The action of an implement such
as a rotary hoe can easily break the meso-
cotyl, thus killing the plant. Once the crown
roots become well established, however,
control is much more difficult (61,63).

Giant foxtail usually begins heading in

Figure 3. A single giant foxtail seedhead can produce over 1,000 seeds.

30 60 70

Shade (percent)

80

Figure 4. The effect of shade intensity on the mean per plant dry weight of seed, stems and

leaves, and roots of giant foxtail.

Source: Knake, E.L. 1972. Effect of shade on giant foxtail. Weed Sci. 20:588.

late June to mid-July. Flowering starts near
the tip of the panicle 4 to 5 days after it
emerges. The base of the panicle flowers
last. Although there has been controversy
about classification of giant foxtail as a
short-day plant, short days do tend to favor
flowering. Under short-day greenhouse
conditions, viable seed have been produced
3 weeks after emergence (45,51,106,107).
Some observers consider the head of

giant foxtail to be a spike, but it is techni-
cally classified as a restricted panicle. Fully
developed, mature heads may be 5 to 7
inches long. It is common to have 500 to
1,000 seeds per head, and as many as
1,400 seeds per head have been counted
(Figure 3) (54,58). A plant that has been
clipped earlier or has started growing late in
the season may produce relatively few seeds
on a single head.

Giant foxtail starts tillering a few weeks
after emergence. A large plant may pro-
duce 20 to 30 basal tillers. In addition, the
nodes of the main culm and basal tillers may
produce 10 to 20 stem tillers (54).

In a study at Urbana, Illinois, vigorous
plants growing in full sunlight each averaged
nearly four new leaves per day from mid-
June to late July. At maturity, plants aver-
aged 188 leaves per plant (54).

Although shading can decrease the rate
of growth of giant foxtail (Figure 4), more
than 95 percent shade is required for all
growth to cease (54,98). This high degree
of shading is attainable under the canopy of
a crop such as soybeans or com. Relatively
high populations of about 23,000 or more
com plants per acre can provide 97 percent
shade or more (Table 1) (54).

The use of directed spray application of
herbicides for control of giant foxtail in com
has sometimes been proposed. In order for
herbicides with only moderate selectivity to
effectively control giant foxtail while mini-
mizing com injury, a height differential be-

tween giant foxtail and corn is desirable (Fig-
ure 5). However, an appropriate height
differential may occur for only a short pe-
riod, necessitating a very timely application.
For example, if the herbicide directions
specify application of the treatment only
after com is 15 inches tall and giant foxtail
is less than 8 inches tall, this height differ-
ence may exist for only a few days (61).

Table 1. Mean Percent Shade Provided
by Various Corn Plant Populations

Population

Shade

plants per acre

percent

22,800

97.3

18,600

96.2

17,100

95.9

15,200

95.8

13,400

92.4

Source: Knake, E.L. 1972. Effect of shade on giant
foxtail. WeedSci. 20:588.

70-i

Figure 5. The growth rate and height differential for com and giant foxtail based on the
three-year mean of observations during 1963, 1964, and 1965 in 20 fields each year in
Champaign County, Illinois.

Source: Knake, E.L., and F.W. Slife. 1967. Height differential of com and giant foxtail in
relation to postemergence weed control. Weeds 15:24.

dentification of Giant Foxtail

Giant foxtail is an annual grass with erect
stems. The stems and leaf sheaths are hair-
less except for a fringe of white hairs along
the margins of the leaf sheaths. Stiff hairs
about 2 mm long compose the ligule. The
leaf blades are 1 to 2 cm wide, 15 to 30 cm
long, and pubescent on the upper surface.
The spikelike, densely flowered panicles, 10
to 15 cm long, droop to form an arch. The
mature plant is 4 to 5 feet tall, with some
reaching 6 to 8 feet (94).

Although the vestiture or covering of the
leaf surface is considered important in iden-
tification of giant foxtail, the terminology
used has varied. Herrmann (46) mentions
the scabrous condition of the upper surface
of the leaf of the plant collected by Faber,

and Rominger (94) indicates that both upper
and lower surfaces are scabrous. These
very short, harsh projections to give the
scabrous condition might be distinguished
more easily by feel than with the naked eye.

In addition to the scabrous condition,
very fine, relatively straight hairs about 0.5
to 1.0 mm long are commonly found on the
upper leaf surface (Figure 6). Although
translation of Herrmann's Latin description
(46) does not appear to mention this fine
pubescence, Rominger does include it in the
description he based primarily on plants col-
lected in the United States.

Various terms are used to describe pubes-
cence, and the terminology is often not very
precise. Considering Lawrence's definitions

Figure 6. The very fine hairs (pubescence) on the upper leaf surface of giant foxtail are a major identifying
characteristic.

(68) and the key he presents from Wiegand,
we would tend to agree with Schreiber's use
of "pilose" (103). However, "villous," "ve-
lutinous," or "puberulous" may also be pos-
sibilities, depending on how one interprets
length, density, and erectness of the hairs.

In contrast to the pubescence on the
upper leaf surface of giant foxtail, yellow
foxtail has only a few long hairs at the base
of the leaf; green foxtail has none. The pu-
bescence of giant foxtail may be readily
observed by bending a leaf over to expose
the upper leaf surface to the gleam of the
sun (Figure 6) (32).

Other plants that have some similarity to
giant foxtail have been observed in the Mid-
west. Schreiber (103) has helped to clarify
the distinction. In addition to Setaria viridis
var. major (Gaud.) (giant green foxtail),
Schreiber has described Setaria uiridis var.
robusta purpurea Schreiber (robust purple
foxtail) and Setaria viridis var. robusta-alba
Schreiber (robust white foxtail). While these
three plants may be of similar size to giant
foxtail, the drooping head of giant foxtail is
a major distinguishing characteristic.

Schreiber (102) reports that the giant
green, robust purple, and robust white fox-
tails do not have the degree of seed dor-
mancy that giant foxtail does. He noted
that these other species do not seem to

compete well with giant foxtail and are not
as persistent. However, Oliver and
Schreiber (79) note that these other three
species were not as susceptible to some
herbicides as was giant foxtail.

Another species of Setaria found occa-
sionally is Setaria verticillata (L.) Beauv.
(bristly foxtail). This species is rather
unique, with the retrorsely barbed bristles
of the head causing it to attach to clothing
rather easily.

eed Production, Viability, and Longevity

With more than 1,000 seeds on some
heads and more than 20 heads on some
plants, giant foxtail is a prolific seed pro-
ducer (54). Heltsley (45) explored the possi-
bility of producing giant foxtail as a crop in
Illinois. Although the seed contains about
22 percent protein and has been experi-
mentally fed to chickens, it shatters readily
at maturity. One test yield averaged only
350 pounds of seed per acre (45).

Seed counts have indicated 554 giant
foxtail seeds per gram or 251,516 seeds
per pound (53). Weight of 1,000 seeds is
reported as 1.8 (53) to 1.9 grams (113).

New heads form over a relatively long
period and can be observed in various
stages of maturity at one time. Some heads
may produce immature seed (51,54). One
test by King (51) indicated that 20 percent
of the seeds were imperfect or unfilled. For
some seed lots, germination was in the
range of 35 to 60 percent. Such factors as
temperature, moisture, light or dark, and in-
hibitory substances may affect germination.
Work by King (51) and by Heltsley (45)
indicate that seed exposure to outdoor win-
ter conditions or alternate warm and cold
temperatures enhance germination. A
study by King (51) indicated 10 percent
better germination in light than in dark.

Observations by King (51) and our own
observations suggest that germinating seed
on moist filter paper produces one or more
substances that inhibit germination of other
seeds of the same species. The presence
of soil or charcoal, however, appears to
absorb the inhibiting substances and negate
their allelopathic effects. Alternate wetting
and drying of the soil has been suggested

as a possible way to remove inhibitory
substances. The seed coat does not appear
to inhibit germination, and scarification has
reduced germination (51).

The seeds of a closely related species,
Setaria uiridis (green foxtail) were reported
by Chepil (19) as generally not germinating
in the fall of the year that they are pro-
duced. After overwintering, the seeds ger-
minated readily the next spring. Several
hundred giant foxtail seeds may germinate
per square foot in the field. Heltsley (45) re-
ported 300 to 700 seedlings per square
foot. In our studies, we found an average of
410 seedlings per square foot in cultivated
areas and 704 seedlings per square foot in a
fencerow (53).

The results of long-term studies to indi-
cate longevity of giant foxtail in the soil are
not available as for yellow foxtail. Because
the seeds appear to be quite similar, the 30-
year period cited in the W.J. Beal burial
studies for yellow foxtail (6) may also apply
to giant foxtail. Under actual field condi-
tions, however, many seeds in the upper
soil profile either germinate or decompose
within a few years. Work by Dawson and
Bruns (25) with green and yellow foxtail
under field conditions suggests maximum
longevity of less than 15 years.

Interest in the longevity of giant foxtail is
primarily academic. Because the plant is so
widespread and well established, it is not
likely that this weed will be eradicated soon
from infested areas. Conscientious control,
however, can reduce seed production, the
number of seeds in the soil reservoir, and
the degree of infestation in individual fields.

pmpetition

The herbicide 2,4-D was discovered and in-
troduced in the 1940s primarily for the
control of broadleaf weeds. The cost was
quite low. In the mid- to late 1950s, a new
generation of soil-applied herbicides was
introduced. Some of these provided control
of grass weeds such as giant foxtail; how-
ever, their cost was significantly more than
the cost of 2,4-D. Thus, farmers began ask-
ing if weeds such as giant foxtail decreased
yields sufficiently to justify the cost of those
new herbicides at $2 to $5 per acre for a
14-inch band applied over the crop row.

It seemed reasonable to assume that
degree of yield reduction would depend on
intensity of the infestation. But to help
answer the farmers' question, studies to de-
termine "thresholds" were initiated at the
University of Illinois Agronomy South Farm
at Urbana in the late 1950s (53,59).

During the 1960s, additional competi-
tion studies were conducted at Urbana to
determine the best time to control foxtail
(62). The results of this research became
increasingly meaningful as postemergence
herbicides were introduced and offered an
alternative to the earlier preemergence
treatments. Studies to determine the effect
of time that giant foxtail began growing
would provide a basis for decisions about
how long control was needed from a herbi-
cide or how many treatments might be
needed (60).

The studies indicating the effect of shade
on giant foxtail would have important impli-
cations as farmers increased com plant
populations per acre, changed to narrower
rows, and increased the amount of "solid-
seeded" drilled soybeans. Observations
made to better understand the life cycle of
giant foxtail and the morphological charac-

teristics provided additional leads for design-
ing chemical and nonchemical control
measures.

Effect of various intensities of giant
foxtail. The studies of the late 1950s and
1960s, conducted at Urbana, Illinois, aided
in developing a better understanding of the
nature of competition or interference be-
tween weeds and crop plants (53,59,60,
62). Several studies by others have also
helped in the developing and testing of con-
cepts and theories relating to such competi-
tion or interference (27,73,77,86,108,
109,112).

Each unit area of land has a certain
amount of available energy in the form of
nutrients, moisture, and light for which
weeds and crops compete. The farmer's
primary responsibility is to convert this en-
ergy into a form useful to human beings — a
form that can be conveniently stored, trans-
ported, and processed.

The total amount of energy units that can
be harvested from a unit area of land ap-
pears to be relatively constant in a given
situation. Crop yields are generally reduced
in proportion to the amount of weeds pres-
ent. A very general rule of thumb is that
one pound dry weight of weeds means one
pound dry weight less of crop. Figure 7
illustrates the effect of giant foxtail on the
dry weight of com, and Figure 8 illustrates
the effect of giant foxtail on the dry weight
of soybeans. Note that the total dry weight
of crop plus weeds remained about the
same as the total dry weight of crop pro-
duced without weeds present (53). Table 2
shows the effect of giant foxtail on com and
soybean yields (53). As expected, an in-
crease in weeds means a corresponding

50

I
DC

o 12
1

H

X

o

co

b

10 20 30 40 50 60 70

Dry Weight (Hundred Pounds per Acre)

80

90

Figure 7. The effect of giant foxtail on dry matter produced by corn.

H = stalks and cobs, Q = shelled corn, and O = weeds.

10 15 20 25 30 35

Dry Weight (Hundred Pounds per Acre)

40

45

Figure 8. The effect of giant foxtail on dry matter produced by soybeans:
| = straw, O = beans, and | U = weeds.

10

Table 2. Effect of Giant Foxtail on Corn and Soybean Yields
(Three- Year Means)*

Giant foxtail

Corn yield

Soybean yield

plants per foot of row

50

12

6

3

1

0.5"
Weed-free check

bushels per acre

70.6" 27.6a

78.4b 31 .9b

82.1b'c 34.6C

85.0c'd 36.2"

86.4d'e 36.8d

90.48'' 37.1 d6

93.5' 38.5"

"Statistical analyses according to Duncan's multiple range test were at the 0.05
probability level. Any two means followed by the same letter do not differ significantly.
"One weed every 2 feet.

Source: Knake, E.L., and F.W. Slife. 1962. Competition of Setaria faberii with corn
and soybeans. Weeds 10:26.

Table 3. The Percent Reduction in Corn and Soybean Yields from the
Presence of Giant Foxtail (Three- Year Means)

Giant foxtail

Corn yield

Soybean yield

plants per foot of row
50
12
6
3
1
0.5*

percent reduction

25 28

16 17

12 10

9 6

7.5 4.5

3 3.5

"One weed every 2 feet.

Source: Knake, E.L., and F.W. Slife. 1962. Competition of Setaria faberii with com

and soybeans. Weeds 10:26.

decrease in crop yield. Table 3 presents
similar information as the "percent reduc-
tion" in yield.

In competition studies with soybeans
(53,59), one of the main effects from com-
petition was a reduction in the number of
pods per plant and a concomitant reduction
in yield. There was little or no effect on the

size of the beans or the number of beans
per pod (53,59).

Phytotoxic substances from one species
may also inhibit the growth of another spe-
cies. This is referred to as allelopathy. A
combination of competition and allelopathic
effects is termed interference. In the green-
house, Bell and Koeppe have demonstrated

11

significant allelopathic effects from giant
foxtail on corn, but effects were not as evi-
dent on soybeans (8,65).

The concept of economic thresholds,
the degree of infestation at which control
becomes economically advantageous, has
been used for insect infestations. The infor-
mation in Table 3 could similarly be used to
determine the level of weed infestation at
which it is economically feasible to control
the weeds. But as well as considering the
direct loss from even a few weeds and the
cost of their control in a given season, con-
sideration also needs to be given to the
weed seeds produced and their subsequent
effects in future years.

In addition to the effect of various intensi-
ties of giant foxtail on crop yields, studies
were conducted to determine the effect of
time that giant foxtail starts growing and the
effect of time of removal or control.

Effect of when foxtail starts growing.

In studies at Urbana, Illinois, from 1961
through 1963 (60), giant foxtail was seeded
in some plots at the same time as the crop.
In other plots, the giant foxtail was seeded

3, 6, 9, or 12 weeks after the com was
planted. The results reported in Table 4
indicate that the soybeans soon had the
competitive advantage over the giant foxtail
when they were given a 3-week head start,
and the giant foxtail was not able to make
significant growth (Figure 9).

As reported in Table 4, the results with
com were similar. Giant foxtail exhibited
more growth in com than in soybeans
(Figure 9), but the final yield of com was
not significantly affected if the com had a
3-week or more head start.

Although weed species and geographic
locations may affect the results, these data
from the Midwest suggest the critical impor-
tance of control of giant foxtail during the
first few weeks that the crop is becoming
established. A good crop canopy of soy-
beans or considerable shading from com
plants can then provide the competition
required to control the giant foxtail. A two-
step process can be considered as a relay
control strategy: (1) early control with
herbicides or by mechanical means and (2)
later control provided by the crop itself.

2,500

In Corn
In Soybeans

6 9

Weeks Weed-Free

All season

Figure 9. The pounds of dry matter per acre produced by giant foxtail as affected by the
number of weeks that com and soybeans were weed-free.

Source: Knake, E.L., and F.W. Slife. 1965. Giant foxtail seeded at various times in corn
and soybeans. Weeds 13:331.

12

Effect of when foxtail is removed. In

another study conducted at Urbana, Illinois,
from 1963 through 1965 (62), giant foxtail
was seeded at the same time as the crop in
all plots except the weed-free check plots.
The giant foxtail was then removed at ap-
proximately six-day intervals at heights of 3,
6, 9, or 12 inches. The results of these
studies indicate that the giant foxtail was not
sufficiently competitive with soybeans or
com to cause significant yield reduction if
removed before reaching a height of about
6 to 9 inches (Table 5).

This study suggests that the competition
from giant foxtail during the early vegetative
growth stage of soybeans is not nearly as
critical as later when soybeans are in the
reproductive stage of growth — flowering,
setting pods, and when beans are filling.

These studies (61-63) support the feasi-
bility of using postemergence herbicides or
other control measures early in the season
to control giant foxtail in corn and soy-
beans. The treatment should provide good
control and be adequately selective to avoid
any adverse effects on the crop.

Table 4. The Effect of Time of Seeding Giant Foxtail on Corn and
Soybean Yields (Three- Year Means)

Giant foxtail seeded
after crop

Corn

Soybeans

Same day
3 weeks
6 weeks
9 weeks
1 2 weeks
Weed-free check

bushels per acre

114.9* 27.9*

130.6 37.7

131.7 38.8

130.1 38.9
132.3 38.4

132.2 38.3

The yield was significantly lower than the weed-free check according to Dunnett s test
for comparison of all treatment means with a control at 0.05 probability level.
Source: Knake, E.L.. and F.W. Slife. 1965. Giant foxtail seeded at various times in
com and soybeans. Weeds 13:331.

Table 5. The Effect of Time of Removing Giant Foxtail on Yields
of Corn and Soybeans*

Giant foxtail height
when removed

Corn

Soybeans

inches

bushels per acre

Weed-free check
3
6

144
143
142

30
30
30

9

139

29

12

137**

28

Foxtail left all season

126**

12"

The means are three-year means for corn and two-year means for soybeans.
"The yields were significantly lower than the weed-free check according to Dunnett's
test for comparison of all treatment means with a control at 0.05 probability level.
Source: Knake, E.L.. and F.W. Slife. 1969. Effect of time of giant foxtail removal
from com and soybeans. Weed Sci. 17:281.

13

ontrol

Although giant foxtail is one of the most sig-
nificant weed problems for farmers, control
can be readily achieved through cultural,
mechanical, and chemical methods.

Cultural Control

Noncrop areas. In noncrop areas, such
as roadsides, ditchbanks, and fencerows, a
desirable perennial species such as smooth
bromegrass, tall fescue, or crown vetch can
provide very effective and economical con-
trol of giant foxtail. Because giant foxtail
simply cannot compete with such vigorous,
well-established perennials, it is essentially
nonexistent in these areas. Even a peren-
nial weed such as quackgrass precludes
growth of giant foxtail. The seeds of giant
foxtail may still be present in such areas,
however, and giant foxtail can quickly rein-
vade if the perennial is controlled.

Several soil sterilants and postemergence
treatments such as glyphosate (Roundup)
are available if needed for bare-ground areas
such as parking lots, storage areas, and
driveways.

Cropland. Winter wheat is also very com-
petitive with giant foxtail and provides good
control. But soon after harvest, giant foxtail
can grow rapidly in small-grain stubble and
produce considerable seed. Control can be
achieved through tillage or by spraying with
a suitable herbicide.

Spring-seeded small grain such as oats is
much less competitive with giant foxtail than
winter wheat. However, a good stand of
oats can suppress foxtail. After the small-
grain harvest, foxtail can resume prolific
growth and produce considerable seed.

A good, dense stand of a forage crop
such as alfalfa or clover is also quite com-
petitive with giant foxtail once the forage is
well established. Giant foxtail can, however,
present a problem for new seedings and
thin stands of forage crops (45,100).

In addition to the competitive effect of
crops such as wheat and alfalfa, allelopathic
effects may also be involved in suppressing
growth of giant foxtail (65,74,84).

Mechanical Control

Mowing. Mowing of giant foxtail in small-
grain stubble does not provide effective
control. Clipped plants produce new
growth quickly, and heads, though small,
produce seed quickly (101).

Rotary hoc. The timely use of the rotary
hoe (63,72,89) can provide effective control
of giant foxtail in com and soybeans. The
rotary hoe can be used after seed germina-
tion, before emergence while seedlings are
"in the white," or soon after emergence. It
is important to use the rotary hoe before the
crown roots of giant foxtail help the plant to
become more firmly established.

Row cultivation. Row cultivation is effec-
tive and can provide control when giant
foxtail plants are small enough to smother
from soil thrown into the row. Band appli-
cation of herbicides over the row makes
cultivation easier, but this is not as popular
as it formerly was (58).

14

Biological Control

Giant foxtail may not be immune to attack
by insects and diseases. Thus far, however,
there have been very few reports or obser-
vations of significant effect from natural
enemies with the possible exception of
chinch bugs.

Chemical Control

Many herbicides provide control of giant
foxtail (10,57,58,63,64,89). Some herbi-
cides can be applied and incorporated prior
to planting. Other herbicides can be applied
preemergence to the soil surface at planting
time. Some herbicides can be applied either
way. Herbicides are also available for post-
emergence control after the foxtail is up and
growing (7,12,13,33,36,123).

For most of the soil-applied herbicides,
optimum placement is in approximately the
top 2 inches of the soil (57,64,88). The

moisture in the shoot zone, the most critical
site of uptake for some herbicides (Table 6),
enhances uptake by the emerging shoot
(4,22,34,39,57,64,88, 114,118). Surface
applications are effective if followed by ade-
quate rainfall to provide sufficient moisture
for absorption of the herbicide by the
emerging weed seedlings. Incorporation of
the herbicide allows less dependence on
rainfall if the soil is sufficiently moist to mo-
bilize the herbicide so it can be absorbed by
the weed seedlings.

Corn. Control of giant foxtail in com is
possible with the use of thiocarbamates such
as butylate (Sutan) and EPTC (Eradicane)
and chloroacetamides such as alachlor
(Lasso) and metolachlor (Dual). These
herbicides are used in combination with
other herbicides, such as atrazine and cyan-
azine (Bladex), which improve control of
broadleaf weeds.

Table 6. The Effect of Herbicide in Shoot, Root, and Seed Zones on the Dry Weight of Giant
Foxtail Tops

Herbicide in

Herbicide

Concentration

Root
zone

Shoot
zone"

Shoot and
root zones0

Seed
zone

parts per million

dry

weight of tops as percent of check

Atrazine

6

99.4

36.6

30.8

41.9

Propachlor

3

93.7

25.8

25.2

23.3

EPTC

1.5

101.0

67.7

53.9

74.5

Trifluralin

0.5

91.5

43.0

40.6

52.1

Alachlor

1

104.4

52.7

57.1

89.0d

Chloramben

1.5

49.7a

83.4

23.7

13.09

Note: A sublethal concentration was used to allow observation of additive effects should they occur. The
experiment was designed as a factorial, and analyses of data were performed at the 0.05 probability level for all tests
of significance.

"In the root zone, only chloramben caused a significant reduction in the dry weight of tops.

bln the shoot zone, all herbicides caused a significant reduction in the dry weight of tops.

'The interaction effects were not significant, indicating that effects were not synergistic but additive.

dAlachlor was less effective in the seed zone than in the shoot zone.

'Chloramben was more effective in the seed zone than in the shoot zone.

Source: Knake, E.L., and L.M. Wax. 1968. The importance of the shoot of giant foxtail for uptake of

preemergence herbicides. Weeds 16:393.

15

For postemergence control of giant fox-
tail in corn, some triazines are effective if
applied when giant foxtail is about 1 1/2
inches tall or less. The use of tridiphane
(Tandem) with some triazines has given
improved control. Certain sulfonylurea
herbicides are a more recent development
for postemergence control of grass weeds
in com.

Soybeans. Dinitroaniline herbicides, such
as trifluralin (Treflan) and pendimethalin
(Prowl), provide control of giant foxtail in
soybeans. Chloroacetamides such as
alachlor and metolachlor are also quite ef-
fective. A herbicide for broadleaf weed
control is frequently used in conjunction
with these herbicides. Chloramben
(Amiben) and clomazone (Command) have
provided good control of giant foxtail and
some broadleaf weeds.

Several postemergence herbicides have
been introduced to control grass weeds such
as giant foxtail in soybeans. These herbi-
cides include sethoxydim (Poast), fluazifop-P
(Fusilade), quizalofop (Assure), and fenoxa-
prop (Option).

Forage crops. For establishing alfalfa and
some clovers, soil-applied EPTC (Eptam) or
benefin (Balan) are quite effective for control
of giant foxtail. Some of the relatively new
postemergence herbicides for soybeans,

such as sethoxydim (Poast), fluazifop-P (Fu-
silade), and quizalofop (Assure), also have
potential for some broadleaf forage crops if
registered for this use. Poast has been reg-
istered for use in alfalfa.

Set-aside acres. Once they are well es-
tablished, legumes such as alfalfa and clover
compete well with giant foxtail and provide
effective control. Thus, on cropland set
aside from production as a result of govern-
ment programs, legumes can provide good
cover and effective control in short-term
programs. Perennial grass or a grass-
legume mixture is generally more appropri-
ate for long-term programs; eventually, the
grass will dominate. Some of the herbicides
indicated for forage crops can also control
giant foxtail in set-aside acres.

Noncrop areas. In some stubble fields
and in noncrop areas, glyphosate (Roundup)
can effectively control giant foxtail. Glypho-
sate is applied as a postemergence spray
when giant foxtail is small. Early application
at relatively low rates of the herbicide makes
treatment economical. Glyphosate does not
provide long-term control, and treatment
may need to be repeated. But because
glyphosate can kill existing giant foxtail
plants and prevent regrowth and heading of
the treated plants, it is usually much more
effective than mowing.

16

lummary

Giant foxtail is the most significant annual
grass weed species in Illinois and much of
the Midwest. Recent reports from the
People's Republic of China suggest that
giant foxtail may be even more widespread
and intense in the Midwest than in China
where it may have originated.

Thresholds have been established to indi-
cate the degree of com and soybean yield
reductions caused by various intensities of
giant foxtail. These thresholds can be used
to determine the relative economic advan-
tage for use of various control measures in
individual fields with different intensities of
the weed.

Studies of the time of giant foxtail re-
moval indicate some flexibility in timing of
control measures during the first few weeks
of giant foxtail growth. But control should
be achieved sometime during these first few
weeks to avoid yield reductions.

Studies in which giant foxtail was seeded
at various times also suggest emphasis on
early control in the first few weeks of
growth. With adequate crop plant popula-
tions to provide shade and other competi-
tive effects, giant foxtail that emerges in
mid- to late season is not likely to make
sufficient growth to significantly affect
yields.

For most effective control of giant foxtail,
a system should be planned to provide con-
trol on all areas of the farm — in corn, soy-
beans, small grain, forages, set-aside acres,
fencerows, and other noncrop areas.

Chemical and nonchemical controls can
be quite effective when used in a comple-
mentary manner. Effective control can be

provided by using clean seed, narrow rows,
and relatively high plant populations to pro-
vide shade and good competition; early
rotary hoeing before crown roots form;
early row cultivation so that soil can be
moved into the row to smother foxtail; soil-
applied herbicides; and postemergence
herbicides. There is little evidence thus far
of much natural control from insects or
diseases for this introduced species.

Most farmers are doing a relatively good
job of controlling giant foxtail in corn and
soybeans. Soil-applied herbicides for con-
trol of grass weeds are currently used on
nearly all com and soybean acreage. Sev-
eral postemergence herbicides are now
available for effective control of grass weeds
in soybeans. Additional herbicides are being
introduced for selective postemergence
control of grass weeds in com.

There is a need for more emphasis on
giant foxtail control in small-grain stubble,
forages (particularly when establishing leg-
umes), set-aside acres, fencerows, and other
noncrop areas.

Infestations of giant foxtail can be con-
trolled well enough to avoid yield reductions.
With good control practices on all areas of a
farm, the intensity of infestations can be
reduced gradually. However, some seed
may remain viable in the soil for many
years, and there is little hope of eliminating
the species completely.

17

eferences

1. Allard, H.A. 1941. Some plants found in
Virginia and West Virginia. Virginia J. Sci.

2:119.

2. Anderson, R.N., R. Behrens, and A.J. Linck.
1962a. Effects of dalapon on some chemical
constituents in sugar beets and yellow foxtail.
Weeds 10:4.

3. Anderson, R.N., A.J. Linck, and R. Behrens.
1962b. Absorption, translocation, and fate of
dalapon in sugar beets and yellow foxtail. Weeds
10:1.

4. Appleby, A.P., W.R. Furtick, and S.C. Fang.
1965. Soil placement studies with EPTC and
other carbamate herbicides on Auena sativa.
Weed Res. 5:115.

5. Ashton, P.M., and K. Dunster. 1961. The
herbicidal effect of EPTC, CDEC, and CDAA on
Echinochloa crusgalli with various depths of soil
incorporation. Weeds 9:312.

6. Beal, W.J. 1941. Sixty-year period for Dr.
Beal's seed viability experiment. (H.T. Darling-
ton) Am. J. Bot. 28:271.

7. Biniak, B.M., and R.J. Aldrich. 1986. Reducing
velvetleaf and giant foxtail seed production with
simulated-roller herbicide applications. Weed Sci.
34:256.

8. Bell, D.T., and D.E. Koeppe. 1972. Noncom-
petitive effects of giant foxtail on growth of com.
Agron. J. 64:321.

9. Blackshaw, R.E., E.H. Stobbe, and A.R.W.
Sturko. 1981. Effect of seeding dates and densi-
ties of green foxtail on the growth and productiv-
ity of spring wheat. Weed Sci. 29:212.

10. Blanchard, K.L., and R.S. Dunham. 1965.
Comparison of various herbicides for control of
giant foxtail growing in com. NC Weed Control
Conf. Res. Rept. 13:87.

11. Bloomberg, J.R., and L.M. Wax. 1978.
Absorption and translocation of mefluidide by
soybean, common cocklebur, and giant foxtail.
Weed Sci. 26:434.

12. Boydston, R.A., and F.W. Slife. 1986. Altera-
tion of atrazine uptake and metabolism by
tridiphane in giant foxtail and corn. Weed Sci.
34:850.

13. . 1987. Postemergence control of giant

foxtail in corn with tridiphane and triazine combi-
nations. Weed Sci. 35:103.

14. Bubar, C.J., and I.N. Morrison. 1984. Growth
responses of green and yellow foxtail to shade.
Weed Sci. 32:774.

15. Buhler, D.D. and T.C. Daniel. 1988. Influence
of tillage systems on giant foxtail, Setaria faberi,
and velvetleaf, Abutilon theophrasti, density and
control in com, Zea mays. Weed Sci. 36:642.

16. Bunting, E.S., and J.W. Ludwig. 1964. Plant
competition and weed control in maize. Proc. 7th
British Weed Control Conf. (Brighton, England)

1:385.

17. Burnside, O.C., and G.A. Wicks. 1967. The
effect of weed removal treatments on sorghum
growth. Weeds 15:204.

18. Chase, A. 1948. The meek that inherit the
earth. U.S. Dept. of Agric. Yearbook (Grass).

19. Chepil, W.S. 1946. Germination of weed seeds.
II. The influence of tillage treatments on germina-
tion. Sci. Agr. 26:347-357.

20. Chow, P.N.P., and R.D. Dryden. 1973. Wheat
tolerance to TCA for green foxtail control. Weed
Sci. 21:238.

21. Clements, F.E., J.E. Weaver, and H.C. Hanson.
1929. Plant competition — an analysis of
community function. Carnegie Institute.
Washington, D.C.

18

22. Dawson, J.H. 1963. Development of bam-
yardgrass seedlings and their response to EPTC.
Weeds 11:60.

37. Gleason, L.S. 1956. Weed control in com in the
wet tropics. Proc. NC Weed Control Conf.

13:54.

23. . 1964. Competition between irrigated

field beans and annual weeds. Weeds 12:206.

24. Dawson, J.H., and V.F. Bruns. 1962. Emer-
gence of barnyardgrass, green foxtail, and yellow
foxtail seedlings from various soil depths. Weeds
10:136.

38. Grafstrom, L.D., Jr., and J. D. Nalewaja. 1988.
Uptake and translocation of fluazifop in green
foxtail (Setaria viridis). Weed Sci. 36:153.

39. Grover, R. 1966. Influence of organic matter,
texture, and available water on the toxicity of
simazine in soil. Weeds 14:148.

25. . 1975. Longevity of barnyardgrass,

green foxtail, and yellow foxtail seeds in soil.
Weed Sci. 23:437.

40. Hamner, K.C. 1940. Interrelation of light and
darkness in photoperiodic induction. Bot. Gaz.
101:658.

26. Dawson, J.H., and E. Dell'Agostino. 1978.
Control of foxtail millet (Setaria italical in new
seedings of alfalfa (Medicago satiua) with EPTC
applied in subsurface lines. Weed Sci. 26:637.

27. Dunham, R.S. 1964. Losses from weeds. Univ.
Minnesota Special Rept. No. 13.

28. Eberlein, C.V., and R. Behrens. 1984. Propanil
selectivity for green foxtail in wheat. Weed Sci.
32:13.

41. Harris, T.C., and R.L. Ritter. 1987. Giant green
foxtail and fall panicum competition in soybeans.
Weed Sci. 35:663.

42. Harrison, S.K., C.S. Williams, and L.M. Wax.
1985. Interference and control of giant foxtail in
soybeans. Weed Sci. 33:203.

43. Hawton, D., and E.H. Stobbe. 1971a. The fate
of nitrogen in rape, redroot pigweed, and green
foxtail. Weed Sci. 19:555.

29. Evers, R.A. 1949. Setaria faberii in Illinois.
Rhodora 51:391.

30. Fairbrothers, D. K. 1959. Morphological
variation of Setaria faberii and Setaria uiridis.
Brittonia 11:44.

31. Feltner, K.C., H.R. Hurst, and L.E. Anderson.
1969. Yellow foxtail competition in grain sor-
ghum. Weed Sci. 17:211.

32. Femald, M.L. 1944. Setaria faberii in Eastern
America. Rhodora 46:57.

33. Fletchall, O.H. 1964. Control of weeds in com
with directed postemergence sprays. NC Weed
Control Conf. Res. Rept. 21:120.

34. Friesen, H.A., J.D. Banting, and D.R. Walker.

1962. The effect of placement and concentration
of 2,3-DCDT on the selective control of wild oats
in wheat. Can. J. Plant Sci. 42:91.

35. Funderburk, H.H., Jr., and J.M. Lawrence.

1963. Absorption and translocation of radioac-
tive herbicides in submersed and emersed aquatic
weeds. Weed Res. 3:304.

36. Centner, W.A. 1964. Herbicidal activity of
several s-triazines as postemergence sprays.
Weeds 12:115.

44. . 1971b. Selectivity of nitrogen among

rape, redroot pigweed, and green foxtail. Weed
Sci. 19:42.

45. Heltsley, R.G. 1953. Distinguishing characteris-
tics, distribution, life history, and control of
Setaria faberii Herrm. M.S. thesis, Univ. Illinois.

46. Herrmann, W. 1911. Uber das phylogenetische
alter das mechanischen Gewebesystems bei
Setaria. Beitr. Biol. Pflanzen 10:1-69.

47. Hitchcock, A.S. 1950. Manual of Grasses of the
United States (2nd ed.). USDA Misc. Publ. 200.

48. Jones, G.N., and G.D. Fuller. 1955. Vascular
Plants of Illinois. Urbana: Univ. Illinois Press.

49. Kenny, R., J.R. Hansen, and J.F. Freeman.
1952. Giant foxtail. Univ. Kentucky Agric. Ext.
Leaflet 132:1.

50. Kern, A.D., W.F. Meggitt, and D. Penner. 1975.
Uptake, movement, and metabolism of cyanazine
in fall panicum, green foxtail, and com. Weed
Sci. 23:277.

51. King, L.J. 1952. Germination and chemical
control of giant foxtail grass. Contrib. Boyce
Thompson Inst. 16:469.

19

52. Kishimoto, E. 1938. Chromosomenzahlen in 67.
den Gattungen Panicum und Setaria. Cytologia

9:23.

53. Knake, E.L. 1960. The effects of competition

from various intensities of Setaria faberii Herrm. 68.

growing with com and soybeans. Ph.D. thesis,
Univ. Illinois.

Kurtz, T, S.W. Melsted, and R.H. Bray. 1952.
The importance of nitrogen and water in reducing
competition between intercrops and com. Agron.
J. 44:13.

Lawrence, G.H. 1955. An Introduction to Plant
Taxonomy. The Macmillan Company, New
York.

54.

-. 1972. Effect of shade on giant foxtail.

Weed Sci. 20:588.

55.

— . 1977. Giant foxtail. The most serious
annual grass weed in the Midwest. Weeds Today

56.

— . 1987. Foxtail — of questionable
parentage. Crops and Soils 39:7.

57. Knake, E.L., A.P. Appleby, and W.R. Furtick.
1967. Soil incorporation and site of uptake of
preemergence herbicides. Weeds 15:228.

58. Knake, E.L, and F.W. Slife. 1961. Controlling
giant foxtail in Illinois. Circular 828, Univ. Illinois
College of Agric., Urbana.

59. - — . 1962. Competition of Sefaria faberii
with com and soybeans. Weeds 10:26.

60. . 1965. Giant foxtail seeded at various

times in com and soybeans. Weeds 13:331.

61. . 1967. Height differential of com and

giant foxtail in relation to postemergence weed
control. Weeds 15:24.

62. . 1969. Effect of time of giant foxtail

removal from com and soybeans. Weed Sci.

17:281.

63. Knake, E.L., F.W. Slife, and R.D. Seif. 1965.
The effect of rotary hoeing on performance of
preemergence herbicides. Weeds 13:72.

64. Knake, E.L., and L.M. Wax. 1968. The
importance of the shoot of giant foxtail for uptake
of preemergence herbicides. Weeds 16:393.

65. Koeppe, D.E., and D.T. Bell. 1973. Chemical
warfare between weeds and corn. Weeds Today

4(2):16.

66. Kollman, G.E., and D.W. Staniforth. 1972.
Hormonal aspects of seed dormancy on yellow
foxtail. Weed Sci. 20:472.

69. Lehle, F.R., D.W. Staniforth, and C.R. Stewart.
1983. Lipid mobilization in dormant and
nondormant caryopses of yellow foxtail (Sefaria
Lutescens). Weed Sci. 31:28.

70. Li, C.H., W.K. Pao, and H.W. Li. 1942.
Interspecific crosses in Sefaria. II. Cytological
studies of interspecific hybrids involving (1) S.
faberii and S. italica, and (2) a three-way cross,
F2 of S. italica x S. viridis and S. faberii. J.
Hered. 33:351.

71. Lindquist, D.A., J. Hacskaylo, and J.B. Davich.
1961. Absorption and translocation of phorate
and phosphorus by cotton seedlings. Bot. Gaz.
123:137.

72. Lovely, W.G., C.R. Weber, and D.W. Staniforth.
1958. Effectiveness of the rotary hoe for weed
control in soybeans. Agron. J. 50:621.

73. Moolani, M.K., E.L. Knake, and F.W. Slife.
1964. Competition of smooth pigweed with com
and soybeans. Weeds 12:126.

74. Morre, J.D., and O.H. Fletchall. 1963. Germi-
nation-regulating mechanisms of giant foxtail
(Setaria faberii). Missouri Agric. Exp. Sta. Res.
Bull. 829.

75. Murray, J.S., M.M. Schreiber, and A.T. Guard.
1967. Anatomy of the first intemode of giant
foxtail. Weeds 15:347.

76. Nadeau, L.B., and I.N. Morrison. 1986.
Influence of soil moisture on shoot and root
growth of green and yellow foxtail. Weed Sci.
34:225.

77. Nieto, J., and D.W. Staniforth. 1961. Com-
foxtail competition under various production
conditions. Agron. J. 53:1.

78. Morris, R.F., and C.A. Schoner, Jr. 1980.
Yellow foxtail biotype studies: Dormancy and
germination. Weed Sci. 28:159.

79. Oliver, L.R., and M.M. Schreiber. 1971.
Differential selectivity of herbicides on six Setaria
taxa. Weed Sci. 19:428.

20

80. Orwick, P.L., and M.M. Schreiber. 1975.
Differential root growth of four Setaria taxa.
Weed Sci. 23:364.

95. . 1962. Taxonomy of Setaria (Gramin-

eae) in North America. Illinois biological mono-
graph No. 29. Univ. Illinois Press, Urbana.

81.

1979a. Interference of redroot pigweed 96.

and robust foxtail in soybeans. Weed Sci.
27:665.

82. . 1979b. Analysis of nonstructural carbo-
hydrates in redroot pigweed and robust foxtail
throughout the growing season. Weed Sci.
27:374.

83. Orwick, P.L., Schreiber, M.M.. and D.A. Holt.
1978. Simulation of foxtail growth. The
development of SETSIM. Weed Sci. 26:691.

84. Osvald, H. 1953. On antagonism between
plants. Proc. 7th Intl. Botan. Congr.. Stockholm

7:167.

85. Parochetti, J.V. 1974. Yellow nutsedge. giant
green foxtail, and fall panicum control in com.
Weed Sci. 22:80.

86. Pavlychenko, T.K. 1949. Plant competition and
weed control. Agric. Inst. Rev. 4:142.

87. Parker, C. 1963. Factors affecting selectivity of
2 ,3-dichlorallyl N , N-diisopropylthiolcarbamate
(diallate) against Avena spp. in wheat and barley.
Weed Res. 3:259.

88. . 1966. The importance of shoot entry

in the action of herbicides applied to the soil.
Weeds 14:117.

Rudyanski, W.J., R.S. Fawcett, and R. McAllister.
1987. Effect of prior pesticide use on thiocar-
bamate herbicide persistence and giant foxtail
control. Weed Sci. 35:68.

97. Santelmann. P.W.,andJ.A. Meade. 1961.
Variation in morphological characteristics and
dalapon susceptibility within species of Setaria
/utescens and S. faberii. Weeds 9:406.

98. Santelmann, P.W., J.A. Meade, and R.A. Peters.
1963. Growth and development of yellow foxtail
and giant foxtail. Weeds 11:139.

99. Schoner, C.A., R.F. Norris, and W. Chilcote.
1978. Yellow foxtail biotype studies: Growth and
morphological characteristics. Weed Sci. 26:632.

100. Schreiber, M.M. 1965a. Development of giant
foxtail under several temperatures and photo-
periods. Weeds 13:40.

101.- — . 1965b. Effect of date of planting and
stage of cutting on seed production of giant
foxtail. Weeds 13:60.

102. - — . 1977. Longevity of foxtail taxa in
undisturbed sites. Weed Sci. 25:66.

103. Schreiber, M.M., and L.R. Oliver. 1971. Two
new varieties of Setaria uiridis. Weed Sci.
19:424.

89. Peters, E.J., D.L. Klingman, and R.E. Larson.
1959. Rotary hoeing in combination with herbi-
cides and other cultivations for weed control in
soybeans. Weeds 7:449.

90. Plant material introduced by the Division of
Foreign Plant Introduction. Bureau of Plant
Industry. Inventory Nos. 102 through 116.
1930-1933.

91. Pohl. R.W. 1951. The genus Setaria in Iowa.
Iowa State College J. Sci. 25:501.

92. Rahman, A., and R. Ashford. 1970. Selective
action of trifluralin for control of green foxtail in
wheat. Weed Sci. 19:754.

93. - — . 1972. Control of green foxtail in wheat
with trifluralin. Weed Sci. 20:23.

94. Rominger, J.M. 1959. Taxonomy of Setaria
(Gramineae) in North America. Ph.D. thesis,
Univ. Illinois.

104. Schreiber, M.M., and P.L. Orwick. 1978.
Influence of nitrogen fertility on growth of foxtail.
Weed Sci. 26:547.

105. Schreiber, M.M., G.F. Warren, and P.L. Orwick.
1979. Effects of wetting agent, stage of growth,
and species on the selectivity of diclofop. Weed
Sci. 27:679.

106. Slife, F.W. 1954. A new Setaria species in
Illinois. Proc. NC Weed Control Conf. 11:6.

107. Slife, F.W., and W.O. Scott. 1951. Setaria
faberii — giant foxtail. Crops and Soils 3:22.

108. Staniforth, D.W. 1953. Levels of weed
infestations as related to yield losses and control
practices in com. Proc. NC Weed Control Conf.

10:44.

109. - — . 1957. Effects of annual grass weeds on
yield of com. Agron. J. 49:551.

21

110. - — . 1961. Responses of com hybrids to
yellow foxtail competition. Weeds 9:132.

111. - — . 1965. Competitive effects of three
foxtail species on soybeans. Weeds 13:191.

112. Staniforth, D.W., and C.R. Weber. 1956.
Effects of annual weeds on the growth and yield
of soybeans. Agron. J. 48:467.

113. Stevens, O.A. 1957. Weights of seeds and
numbers per plant. Weeds 5:46.

114. Stickler, R.L., E.L. Knake, and T.D. Hinesly.
1969. Soil moisture and effectiveness of
preemergence herbicides. Weed Sci. 17:257.

115. Taylorson, R.B. 1986. Water stress-induced
germination of giant foxtail. Weed Sci. 34:871.

116. Thompson, L., Jr. 1972. Metabolism of chloro
s-triazine herbicides by Panicum and Setaria.
Weed Sci. 20:584.

117. Todd, B.C., and E.H. Stobbe. 1977. Selectivity
of dichlofop methyl among wheat, barley, wild
oat, and green foxtail. Weed Sci. 25:382.

118. Upchurch, R.P. 1957. The influence of soil-
moisture content on the response of cotton to
herbicides. Weeds 5:112.

119. Vanstone, D.E., and E.H. Stobbe. 1978. Root
uptake, translocation, and metabolism of ni-
trofluorofen and oxyfluorofen by fababeans (Vicia
/aba) and green foxtail (Setaria uiridis). Weed
Sci. 26:369.

120. Vengris, J. 1963. The effect of time of seeding
on growth and development of rough pigweed
and yellow foxtail. Weeds 11:48.

121. Vengris, J., W.G. Colby, and M. Drake. 1955.
Plant nutrient competition between weeds and
com. Agron. J. 47:213.

122. Weber, C.R., and D.W. Staniforth. 1961.
Competitive relationships in variable weed and
soybean stands. Agron. J. 49:440.

123. Wicks, G.A. 1964. Directed postemergence
herbicide sprays on com in 1964. NC Weed
Control Conf. Res. Rept. 21:130.

124. Williams, R.D., and M.M. Schreiber. 1976.
Numerical and chemotaxonomy of the green
foxtail complex. Weed Sci. 24:331.

125. Wollny, E. 1881. Untersuchungen uber der
Einfluss des Standraumes auf die Entwicklung
und die Ertage der Kulturpflanzen. J. Landw.
29:25-62, 217-255, 493.

126. Wood, C.E., Jr. 1946. Setaria faberii in North
Carolina. Rhodora 48:391.

22

Author:

Ellery L. Knake, Professor
Department of Agronomy
University of Illinois at Urbana-Champaign

Editor: Eva Kingston
Designers: Marisa Meador

Lauren Toalson

Donna Johnson
Photographers: Paul Hixson
David Riecks

This bulletin is dedicated to Professor Fred W. Slife, weed science pioneer,
who was one of the first to recognize the significance of giant foxtail in the
Midwest. He studied the biology and life history of giant foxtail, as well as its
impact on crop production, and developed practical control measures.
Professor Slife was an inspiration to others whom he also encouraged to
conduct research on this species.

The Illinois Agricultural Experiment Station provides equal opportunities in
programs and employment.

2.5M— crouse— 12-90— ek

UNIVERSITY OF ILLINOIS-URBANA