North Dakota State University
NDSU Extension Service
ER-83, May 2003
R. K. Zollinger, NDSU Extension Weed Specialist
| Table 2. North Dakota weed infestations in current crop of HRS wheat, durum wheat, barley, and tame oat based on 986 surveyed fields, spring 2000. | ||||||||
| Weed | ||||||||
| Weed | Field Uniformity | Weed Density | Density Range | Weed | ||||
| Weed species | Frequency | All | Infested | All | Infested | Low | High | Index |
| (%) | (%) | (%) | - - Plants/m2 - - | - - Plants/m2 - - | ||||
| Green foxtail | 69.9 | 25.2 | 36.0 | 28.1 | 40.2 | 2.3 | 28.2 | 114.0 |
| Wild buckwheat | 52.5 | 18.7 | 35.6 | 7.7 | 14.7 | 0.1 | 5.6 | 54.2 |
| Wild mustard | 47.3 | 16.7 | 35.4 | 7.0 | 14.8 | 0.1 | 6.4 | 48.8 |
| Wild oat | 32.5 | 11.0 | 33.9 | 6.2 | 19.2 | 0.1 | 8.1 | 36.4 |
| Kochia | 34.5 | 11.3 | 32.7 | 5.6 | 16.2 | 0.2 | 11.6 | 35.8 |
| Pigweed species | 28.4 | 9.6 | 33.9 | 4.6 | 16.1 | <0.1 | 7.9 | 29.8 |
| Canada thistle | 36.5 | 9.5 | 25.9 | 2.8 | 7.6 | <0.1 | 3.6 | 26.3 |
| Yellow foxtail | 16.1 | 5.7 | 35.6 | 5.1 | 32.1 | 0.3 | 16.4 | 23.1 |
| Common lambsquarters | 26.1 | 7.4 | 28.3 | 2.9 | 11.1 | <0.1 | 5.7 | 22.8 |
| Sunflower | 14.2 | 5.6 | 39.2 | 3.2 | 22.7 | 0.1 | 8.3 | 17.9 |
| Russian thistle | 17.3 | 5.1 | 29.6 | 2.6 | 14.9 | <0.1 | 6.8 | 16.9 |
| Field bindweed | 15.4 | 3.8 | 24.8 | 1.3 | 8.3 | <0.1 | 3.8 | 11.9 |
| Field pennycress | 12.6 | 3.8 | 30.2 | 1.5 | 11.6 | <0.1 | 7.2 | 11.4 |
| Quackgrass | 12.6 | 2.7 | 21.1 | 1.5 | 12.1 | <0.1 | 6.3 | 10.4 |
| Common ragweed | 11.0 | 2.8 | 25.2 | 1.0 | 9.5 | <0.1 | 5.8 | 8.9 |
| Canola | 6.3 | 2.3 | 36.9 | 1.8 | 28.5 | 0.1 | 16.5 | 8.5 |
| Soybean | 7.9 | 2.5 | 31.2 | 0.4 | 5.5 | <0.1 | 2.2 | 6.1 |
| Eastern black nightshade | 7.1 | 1.7 | 23.3 | 0.6 | 8.2 | <0.1 | 3.9 | 5.4 |
| Perennial sowthistle | 7.3 | 1.5 | 20.7 | 0.5 | 7.2 | <0.1 | 3.6 | 5.2 |
| Volunteer cereal | 4.5 | 1.4 | 31.4 | 0.5 | 11.6 | <0.1 | 5.5 | 4.2 |
| Common mallow | 4.6 | 1.2 | 25.3 | 0.4 | 8.5 | <0.1 | 4.7 | 3.6 |
| Flixweed/Tansy mustard | 5.4 | 1.3 | 23.6 | 0.2 | 3.7 | <0.1 | 1.8 | 3.5 |
| Prickly lettuce | 5.0 | 1.1 | 21.5 | 0.2 | 4.8 | <0.1 | 2.5 | 3.3 |
| Common cocklebur | 4.3 | 1.1 | 25.0 | 0.3 | 5.8 | <0.1 | 3.3 | 3.1 |
| Annual smartweed | 3.8 | 0.7 | 19.1 | 0.4 | 11.7 | 0.1 | 10.3 | 3.0 |
| Dandelion | 4.3 | 1.0 | 24.3 | 0.2 | 4.0 | <0.1 | 1.9 | 2.9 |
| Common milkweed | 3.8 | 0.5 | 13.7 | 0.1 | 3.1 | <0.1 | 2.3 | 2.1 |
| Shepherd's-purse | 2.0 | 0.5 | 24.7 | 0.3 | 13.2 | <0.1 | 7.2 | 1.8 |
| Barnyardgrass | 1.6 | 0.5 | 33.3 | 0.2 | 11.9 | <0.1 | 4.1 | 1.5 |
| Fairy candelabra | 2.0 | 0.5 | 23.7 | 0.1 | 6.7 | <0.1 | 3.3 | 1.5 |
| Flax | 1.0 | 0.5 | 53.3 | 0.3 | 27.4 | <0.1 | 16.6 | 1.5 |
| Prairie wild rose | 1.9 | 0.4 | 18.9 | 0.1 | 3.9 | <0.1 | 2.5 | 1.2 |
| Sweetclover | 1.5 | 0.4 | 25.0 | 0.1 | 8.0 | <0.1 | 3.9 | 1.2 |
| Downy brome | 1.2 | 0.3 | 23.6 | 0.1 | 10.0 | <0.1 | 5.5 | 1.0 |
| Common purslane | 1.2 | 0.2 | 20.9 | 0.1 | 5.7 | <0.1 | 2.5 | 0.8 |
| Curly dock | 1.4 | 0.2 | 15.4 | <0.1 | 3.6 | <0.1 | 2.7 | 0.8 |
| Hedge bindweed | 1.1 | 0.3 | 28.0 | 0.1 | 5.0 | <0.1 | 1.8 | 0.8 |
| Wild-proso millet | 0.9 | 0.2 | 26.3 | 0.1 | 13.1 | <0.1 | 6.0 | 0.8 |
| Prostrate pigweed | 1.0 | 0.3 | 27.8 | 0.1 | 6.7 | <0.1 | 3.2 | 0.7 |
| Horseweed | 1.2 | 0.2 | 20.0 | <0.1 | 3.0 | <0.1 | 1.5 | 0.7 |
| Yellow woodsorrel | 0.5 | 0.2 | 32.0 | 0.1 | 16.1 | <0.1 | 6.6 | 0.6 |
| Nightflowering catchfly | 0.5 | 0.2 | 38.0 | 0.1 | 13.3 | <0.1 | 3.8 | 0.6 |
| Greenflower pepperweed | 1.1 | 0.1 | 12.0 | <0.1 | 1.6 | <0.1 | 1.2 | 0.5 |
| Giant ragweed | 0.6 | 0.2 | 28.3 | <0.1 | 7.4 | <0.1 | 3.2 | 0.5 |
| Biennial wormwood | 0.6 | 0.2 | 33.3 | <0.1 | 4.7 | <0.1 | 2.0 | 0.5 |
| Lanceleaf sage | 0.4 | 0.2 | 37.5 | 0.1 | 11.8 | <0.1 | 4.0 | 0.4 |
| Whitlowwart species | 0.6 | 0.1 | 21.7 | <0.1 | 3.4 | <0.1 | 1.8 | 0.4 |
| Marshelder | 0.8 | 0.1 | 14.3 | <0.1 | 2.0 | <0.1 | 1.4 | 0.4 |
| Common chickweed | 0.6 | 0.1 | 15.0 | <0.1 | 4.7 | <0.1 | 6.8 | 0.4 |
| Alfalfa | 0.5 | 0.1 | 24.0 | <0.1 | 4.5 | <0.1 | 2.2 | 0.4 |
| Dry bean | 0.6 | 0.1 | 16.7 | <0.1 | 2.7 | <0.1 | 1.7 | 0.4 |
| Field sandbur | 0.2 | <0.1 | 10.0 | 0.1 | 48.4 | <0.1 | 27.0 | 0.3 |
| Cutleaf nightshade | 0.5 | 0.1 | 18.0 | <0.1 | 4.5 | <0.1 | 3.4 | 0.3 |
| Foxtail barley | 0.6 | 0.1 | 10.0 | <0.1 | 2.3 | <0.1 | 2.2 | 0.3 |
| Purslane speedwell | 0.5 | 0.1 | 16.0 | <0.1 | 3.7 | <0.1 | 2.6 | 0.3 |
| Venice mallow | 0.5 | 0.1 | 10.0 | <0.1 | 2.8 | <0.1 | 4.8 | 0.3 |
| Safflower | 0.2 | 0.1 | 55.0 | <0.1 | 14.0 | <0.1 | 3.0 | 0.3 |
| Hairy nightshade | 0.3 | <0.1 | 6.7 | 0.1 | 15.8 | <0.1 | 7.7 | 0.2 |
| False chamomile | 0.4 | 0.1 | 15.0 | <0.1 | 1.6 | <0.1 | 1.0 | 0.2 |
| Field pea | 0.2 | 0.1 | 45.0 | <0.1 | 9.7 | <0.1 | 2.0 | 0.2 |
| Leafy spurge | 0.2 | <0.1 | 15.0 | <0.1 | 4.3 | <0.1 | 2.5 | 0.1 |
| Lentil | 0.2 | <0.1 | 5.0 | <0.1 | 7.0 | <0.1 | 24.0 | 0.1 |
| Wild vetch | 0.2 | <0.1 | 15.0 | <0.1 | 1.6 | <0.1 | 1.0 | 0.1 |
| Erect knotweed | 0.2 | <0.1 | 10.0 | <0.1 | 1.6 | <0.1 | 1.5 | 0.1 |
| Tall waterhemp | 0.1 | <0.1 | 20.0 | <0.1 | 2.2 | <0.1 | 1.0 | 0.1 |
| Corn | 0.1 | <0.1 | 20.0 | <0.1 | 2.2 | <0.1 | 1.0 | 0.1 |
| Horsetail | 0.1 | <0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | <0.1 |
| Smallseed falseflax | 0.1 | <0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | <0.1 |
| Weed free | 32.9 | 10.7 | 32.7 | - | - | - | - | - |
| Table 3. North Dakota weed infestations in current crop of canola, tame mustard, and buckwheat based on 88 surveyed fields, spring 2000. | ||||||||
| Weed | ||||||||
| Weed | Field Uniformity | Weed Density | Density Range | Weed | ||||
| Weed species | Frequency | All | Infested | All | Infested | Low | High | Index |
| (%) | (%) | (%) | - - Plants/m2 - - | - - Plants/m2 - - | ||||
| Green foxtail | 63.8 | 23.8 | 37.3 | 23.6 | 37.0 | 2.1 | 33.8 | 100.1 |
| Wild oat | 44.9 | 16.7 | 37.1 | 10.9 | 24.3 | 0.2 | 11.2 | 57.1 |
| Volunteer cereal | 40.6 | 16.5 | 40.7 | 8.6 | 21.1 | 0.1 | 8.1 | 50.1 |
| Canada thistle | 52.2 | 17.0 | 32.5 | 5.6 | 10.7 | <0.1 | 4.3 | 47.4 |
| Wild buckwheat | 36.2 | 13.0 | 36.0 | 4.9 | 13.4 | <0.1 | 5.7 | 36.5 |
| Wild mustard | 39.1 | 13.2 | 33.7 | 3.9 | 10.0 | <0.1 | 3.7 | 35.4 |
| Quackgrass | 31.9 | 8.6 | 26.8 | 6.0 | 18.7 | 0.3 | 11.5 | 33.1 |
| Kochia | 24.6 | 8.1 | 32.9 | 3.8 | 15.3 | <0.1 | 7.6 | 25.1 |
| Yellow foxtail | 13.0 | 5.2 | 40.0 | 3.9 | 29.8 | 0.3 | 15.8 | 18.6 |
| Pigweed species | 15.9 | 6.7 | 41.8 | 2.5 | 16.0 | <0.1 | 4.5 | 17.9 |
| Russian thistle | 17.4 | 5.4 | 30.8 | 1.4 | 8.2 | <0.1 | 5.5 | 14.5 |
| Field pennycress | 18.8 | 3.5 | 18.5 | 1.4 | 7.4 | <0.1 | 3.5 | 13.0 |
| Common lambsquarters | 13.0 | 2.6 | 20.0 | 0.8 | 5.9 | <0.1 | 8.9 | 8.7 |
| Flax | 4.3 | 0.7 | 16.7 | 1.5 | 35.5 | <0.1 | 6.7 | 5.8 |
| Annual smartweed | 7.2 | 1.7 | 24.0 | 0.6 | 8.2 | <0.1 | 8.6 | 5.5 |
| Common ragweed | 7.2 | 1.9 | 26.0 | 0.4 | 5.4 | <0.1 | 2.8 | 5.2 |
| Prickly lettuce | 2.9 | 1.4 | 50.0 | 0.5 | 17.2 | <0.1 | 5.5 | 3.6 |
| Field bindweed | 5.8 | 1.0 | 17.5 | 0.2 | 3.5 | <0.1 | 2.0 | 3.4 |
| Common purslane | 5.8 | 1.0 | 17.5 | 0.1 | 1.9 | <0.1 | 1.0 | 3.2 |
| Sunflower | 4.3 | 0.9 | 20.0 | 0.1 | 2.5 | <0.1 | 1.3 | 2.6 |
| Perennial sowthistle | 4.3 | 0.7 | 16.7 | 0.1 | 3.2 | <0.1 | 2.3 | 2.5 |
| Common mallow | 2.9 | 1.0 | 35.0 | 0.2 | 6.5 | <0.1 | 3.0 | 2.4 |
| Flixweed/Tansy mustard | 4.3 | 0.7 | 16.7 | 0.1 | 1.8 | <0.1 | 1.0 | 2.4 |
| Whitlowwart species | 4.3 | 0.6 | 13.3 | 0.1 | 2.2 | <0.1 | 1.7 | 2.2 |
| Prairie wild rose | 4.3 | 0.6 | 13.3 | 0.1 | 1.4 | <0.1 | 1.0 | 2.2 |
| Common cocklebur | 2.9 | 0.9 | 30.0 | 0.1 | 4.8 | <0.1 | 2.0 | 2.2 |
| Dandelion | 2.9 | 0.4 | 15.0 | 0.1 | 2.2 | <0.1 | 1.5 | 1.5 |
| Lanceleaf sage | 2.9 | 0.3 | 10.0 | 0.1 | 2.2 | <0.1 | 2.0 | 1.4 |
| Foxtail barley | 2.9 | 0.3 | 10.0 | <0.1 | 1.6 | <0.1 | 1.5 | 1.4 |
| Barnyardgrass | 1.4 | 0.3 | 20.0 | 0.1 | 5.4 | <0.1 | 3.0 | 1.0 |
| Cutleaf nightshade | 1.4 | 0.3 | 20.0 | 0.1 | 4.3 | <0.1 | 2.0 | 0.9 |
| Horsetail | 1.4 | 0.1 | 10.0 | 0.1 | 7.5 | <0.1 | 7.0 | 0.9 |
| Tall waterhemp | 1.4 | 0.3 | 20.0 | <0.1 | 3.2 | <0.1 | 2.0 | 0.9 |
| Greenflower pepperweed | 1.4 | 0.3 | 20.0 | <0.1 | 3.2 | <0.1 | 2.0 | 0.9 |
| Common chickweed | 1.4 | 0.3 | 20.0 | <0.1 | 2.2 | <0.1 | 1.0 | 0.8 |
| Horseweed | 1.4 | 0.1 | 10.0 | <0.1 | 3.2 | <0.1 | 3.0 | 0.7 |
| Swamp smartweed | 1.4 | 0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | 0.7 |
| Wild vetch | 1.4 | 0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | 0.7 |
| Nightflowering catchfly | 1.4 | 0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | 0.7 |
| Fairy candelabra | 1.4 | 0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | 0.7 |
| Shepherd's-purse | 1.4 | 0.1 | 10.0 | <0.1 | 1.1 | <0.1 | 1.0 | 0.7 |
| Weed free | 36.2 | 10.7 | 29.6 | - | - | - | - | - |
| Table 4. North Dakota weed infestations in current crop of soybean, dry bean, lentil, and field pea based on 197 surveyed fields, spring 2000. | ||||||||
| Weed | ||||||||
| Weed | Field Uniformity | Weed Density | Density Range | Weed | ||||
| Weed species | Frequency | All | Infested | All | Infested | Low | High | Index |
| (%) | (%) | (%) | - - Plants/m2 - - | - - Plants/m2 - - | ||||
| Green foxtail | 46.0 | 17.6 | 38.4 | 11.9 | 25.9 | 0.9 | 21.9 | 60.8 |
| Wild mustard | 56.1 | 19.4 | 34.5 | 7.0 | 12.5 | <0.1 | 4.2 | 54.5 |
| Yellow foxtail | 31.6 | 12.4 | 39.2 | 7.7 | 24.5 | 0.6 | 12.8 | 40.9 |
| Canada thistle | 41.7 | 9.7 | 23.3 | 3.3 | 7.9 | <0.1 | 3.6 | 31.3 |
| Volunteer cereal | 31.6 | 11.6 | 36.8 | 3.4 | 10.6 | <0.1 | 3.5 | 30.0 |
| Common lambsquarters | 26.7 | 6.3 | 23.6 | 4.4 | 16.4 | 0.1 | 6.3 | 25.5 |
| Wild oat | 23.0 | 7.0 | 30.2 | 2.8 | 12.4 | <0.1 | 5.4 | 21.3 |
| Pigweed species | 20.9 | 6.5 | 31.3 | 2.3 | 10.9 | <0.1 | 4.3 | 18.8 |
| Wild buckwheat | 23.5 | 7.0 | 29.8 | 1.6 | 6.8 | <0.1 | 3.0 | 18.6 |
| Quackgrass | 20.3 | 5.0 | 24.5 | 1.6 | 7.7 | <0.1 | 4.0 | 15.4 |
| Common ragweed | 18.7 | 5.3 | 28.6 | 1.3 | 7.2 | <0.1 | 3.4 | 14.7 |
| Common cocklebur | 14.4 | 4.6 | 31.9 | 1.7 | 11.5 | <0.1 | 3.8 | 13.3 |
| Eastern black nightshade | 15.5 | 4.7 | 30.0 | 1.3 | 8.4 | <0.1 | 4.0 | 12.8 |
| Common milkweed | 16.0 | 2.8 | 17.3 | 0.8 | 4.8 | <0.1 | 2.7 | 9.9 |
| Kochia | 12.3 | 2.7 | 22.2 | 1.1 | 9.0 | <0.1 | 6.9 | 9.4 |
| Wild-proso millet | 6.4 | 2.0 | 31.7 | 1.1 | 16.4 | <0.1 | 7.5 | 6.6 |
| Field pennycress | 5.3 | 1.6 | 30.0 | 0.3 | 6.4 | <0.1 | 2.3 | 4.2 |
| Field bindweed | 3.7 | 0.9 | 22.9 | 0.1 | 3.7 | <0.1 | 2.1 | 2.4</ |