Survey Indicates Green Foxtail Most Abundant Weed in ND

Canada thistle, other weeds cause more yield loss, however

While green foxtail (pigeongrass) is generally the most abundant weed in North Dakota field crops, Canada thistle and wild oats result in more yield loss.

That’s according to results of a state weed survey conducted in 2000 by North Dakota State University and the North Dakota Department of Agriculture.  Complete results of the survey, which evaluated weeds in small grains and broadleaf crops, can be found online at www.ag.ndsu.nodak.edu/weeds/ER83/ER83.htm .

The 2000 weed survey compares weed shift results of a similar weed survey conducted by NDSU in the summer of 1978 and 1979.  However, unlike those surveys over 20 years ago, the 2000 survey also analyzed weeds in the spring (mid May-late June) prior to any herbicide application, in addition to weeds in the summer (Aug-Sept, prior to harvest).

Green foxtail was the most abundant weed in both spring and summer surveys in 2000. It was also the most populous weed in the 1978-79 survey.  While the competition from green foxtail with crops is not as intensive as from weeds like wild oats or wild mustard, high green foxtail densities and frequency as indicated in the surveys point out that green foxtail still causes large losses, according to Richard Zollinger, NDSU extension weed specialist.

While wild oats caused more production losses in wheat and barley than any other weed in 1978 and 1979, Canada thistle caused more yield loss in 2000 than any other weed, followed by wild oat, field bindweed, common milkweed, kochia, and green and yellow foxtail combined. Canada thistle resulted in the loss of 35.5 million bushels of hard red spring wheat alone in 2000. The results of these surveys indicate that perennial weeds have become a greater problem and reduced small grain yields more in 2000 than 1979, says Zollinger.

Although weed populations tended to fluctuate less in small grains than in other crops, the most abundant weeds in small grains were also most abundant in the other crops.

Weeds that were in the 2000 survey but not in the 1978/1979 surveys were wild-proso millet, eastern black, hairy, and cutleaf nightshade, biennial wormwood, tall waterhemp, lanceleaf sage, yellow nutsedge, Venice mallow, and swamp smartweed. Weeds that were in the 1978/1979 surveys but not in the 2000 survey were nightflowering catchfly and prairie wild rose.

—Tracy Sayler

HRS, durum & barley crop losses in North Dakota from various weeds in summer 2000 based on individual weed competition data   Weed Freq. % Weed Density pl/m2 Acresa 1000 Yield Loss b % Grain Loss c 1000bu Green foxtail 57 31.5 6,327 2.5 4,551 Wild oat 54 12.0 5,994 10.0 20,852 Yellow foxtail 32 27.9 3,552 2.5 3,091 Wild Buckwheat 38 11.3 4,218 4.0 5,870 Kochia 41 8.4 4,551 5.0 7,916 Canada thistle 32 8.2 3,552 27.0 35,502 Pigweed species 23 8.9 2,553 - - Field bindweed 12 9.3 1,332 25.0 12,327 Quackgrass 12 7.9 1,332 - - Common lambsquarters 11 5.0 1,221 - - Common ragweed 9 8.9 999 21.0 7,298 Russian thistle 9 6.6 999 - - Common milkweed 11 3.9 1,221 22.0 9,335 Perennial sowthistle 7 4.7 777 11.0 2,973 Sunflower 7 3.4 777 10.0 2,703 Wild mustard 6 6.2 666 5.0 1,158 Field pennycress 4 9.7 444 - - Barnyardgrass 5 3.6 555 - - Common cocklebur 4 4.1 444 12.0 1,854 Volunteer cereal - - - - - Flixweed/Tansy mustard 2 0.6 220 - - Total       28.1 115,430 a Acres infested was obtained by multiplying weed frequency by crop acres which was 6.4 million for HRS wheat, 2.9 m for durum wheat, and 1.8 m for barley in 2000 (NDAS 2002). b Percent yield loss caused by weed competition was based on weed density and competition data from previous literature and study data. Total % yield loss is based on all acres. c Grain loss based on average North Dakota production of 36.5 bu/A for HRS wheat, 27 bu/A for durum wheat, and 55 bu/A for barley.  (NDAS 2002). Losses from weed competition in barley were only available for wild oat where loss in barley was about 25% less than in HRS wheat for wild oat plants (Bell and Nalewaja 1968). The losses in barley from all weeds were assumed at 25% less than in HRS wheat.

Top 10 most abundant weeds in North Dakota based on weed index

Spring 2000 Weed species	Index	Summer 2000 Weed species	Index	Average of 1978 and 1979 Weed species	Index
Green foxtail	103.0	Green foxtail	73.8	Green foxtail	236.0
Wild mustard	50.0	Wild oat	38.8	Wild oat	61.8
Wild buckwheat	46.2	Yellow foxtail	37.5	Wild buckwheat	53.3
Wild oat	35.4	Kochia	33.1	Redroot pigweed	42.4
Canada thistle	30.4	Wild buckwheat	28.6	Yellow foxtail	28.5
Kochia	30.2	Canada thistle	26.5	Common lambsquarters	24.7
Yellow foxtail	28.0	Pigweed species	19.6	Wild mustard	22.8
Pigweed species	26.8	Volunteer cereal	10.6	Russian thistle	19.3
Common lambsquarters	23.3	Common ragweed	10.4	Kochia	16.9
Volunteer cereal	14.8	Field bindweed	8.7	Field bindweed	11.5

Soybean Maturity 101

Soybeans respond to day length so the actual calendar date is highly influenced by latitude location. Each variety therefore has a narrow range of north to south adaptation. Soybean yield and quality are affected if a season ending freeze occurs before a variety reaches its physiological maturity. Dates of maturity are listed in NDSU performance tables and indicate when the plants in a variety are observed and estimated to be physiologically mature. Usually harvest will commence approximately 7 to 14 days after the soybeans are physiological mature.

Relative maturity ratings are also provided for many of the varieties entered in the trials at various locations. These ratings consist of a number for the maturity group designation such as: (000, 00, 0 or 1) and followed by a decimal and another number, ranging from .0 to .9, which indicates maturity rankings within each maturity group.

For example the variety Jim is indicated as 00.6, making it a medium maturing variety in the 00 group. Walsh would be a 0.0 making it one of the earliest varieties in the 0 group whereas Sargent is a 0.8 making it one of the later varieties in the 0 group. Few if any group 1 soybeans are currently planted in North Dakota except in the extreme SE part of the state.

Group maturity rankings of public varieties were developed after observing them for a number of years and sites. Relative maturity ratings for private varieties are usually provided by owners and were developed in a similar manner.

See the following NDSU web site for 2002 soybean performance and maturity data: www.ag.ndsu.nodak.edu/aginfo/variety/soybean.htm .

—Duane Berglund, NDSU extension agronomist

Soybean Maturity Groups
(Early)	000	(Few available)
(Mid-early)	00.0	00.5	00.9
(Mid)	0.0	0.5	0.9
(Late)	1	1.5	1.9
For each 0.1 change in group rating this represents approximately 0.75 to 1 day later maturity