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Kevin Bradley
Division of Plant Sciences

Mandy Bish
Division of Plant Sciences

In corn and soybean cropping systems throughout the Midwest, weeds represent an economically significant threat to yield. The continued increase in the number of weed species developing herbicide resistance adds another level of complexity in management of these pests. This University of Missouri publication is a resource for identifying weeds and understanding herbicide injury to crops.  The first section of this guide provides photos and identification tips for 141 weed species found in Midwest agronomic production systems and includes seedling identification keys to aid in accurate and early identification of common broadleaf and grass weeds. The second section of this guide provides information on herbicide injury to crops, including introductions to herbicide resistance and the site-of-action groups, herbicide-injury diagnostic charts, and photos and descriptions of symptoms for herbicide-injured plants from 15 of the different herbicide site-of-action groups.

Topics

• ACCase inhibitors (Group 1)
• ALS inhibitors (Group 2)
• Amaranth, Palmer (Amaranthus palmeri)
• Amaranth, Powell (Amaranthus powellii)
• Amaranth, spiny (Amaranthus spinosus)
• Anoda, spurred (Anoda cristata)
• Barley, foxtail (Hordeum jubatum)
• Barley, little (Hordeum pusillum)
• Barnyardgrass (Echinochloa crus-galli)
• Bedstraw, catchweed (Galium aparine)
• Bermudagrass (Cynodon dactylon)
• Biennial broadleaf weeds
• Bindweed, field (Convolvulus arvensis)
• Bittercress, smallflowered (Cardamine parviflora)
• Bluegrass, annual (Poa annua)
• Broadleaf weed seedling identification
• Brome, downy (Bromus tectorum)
• Buckwheat, wild (Polygonum convolvulus)
• Burcucumber (Sicyos angulatus)
• Burdock, common (Arctium minus)
• Bushy wallflower (Erysimum repandum)
• Buttercup, bulbous (Ranunculus bulbosus)
• Buttercup, corn (Ranunculus arvensis)
• Carpetweed (Mollugo verticillata)
• Cheat (Bromus secalinus)
• Chickweed, common (Stellaria media)
• Chickweed, mouseear (Cerastium fontanum sp. vulgare)
• Chicory (Cichorium intybus)
• Cocklebur (Xanthium strumarium)
• Copperleaf, hophornbeam (Acalypha ostryifolia)
• Copperleaf, Virginia (Acalyphya virginica)
• Corn herbicide injury diagnostic key
• Cornflower (Centaurea cyanus)
• Crabgrass, large (Digitaria sanguinalis)
• Crabgrass, smooth (Digitaria ischaemum)
• Croton, tropic (Croton glandulosus var. septentrionalis)
• Cupgrass, woolly (Eriochloa villosa)
• Dandelion (Taraxacum officinale)
• Dayflower, Asiatic (Commelina communis)
• Deadnettle, purple (Lamium purpureum)
• Diterpene biosynthesis inhibitor (Group 13)
• Dock, broadleaf (Rumex obtusifolius)
• Dock, curly (Rumex crispus)
• Eclipta (Eclipta prostrata)
• Economic thresholds for weeds
• EPSP synthase inhibitor (Group 9)
• Evening-primrose, common (Oenothera biennis)
• Evening-primrose, cutleaf (Oenothera laciniata)
• Factors contributing to herbicide injury
• Fescue, tall (Lolium arundinaceum)
• Filaree, redstem (Erodium cicutarium)
• Fleabane, annual (Erigeron annuus)
• Foxtail, Carolina (Alopecurus carolinianus)
• Foxtail, giant (Setaria faberi)
• Foxtail, green (Setaria viridis)
• Foxtail, yellow (Setaria pumila)
• Galinsoga, hairy (Galinsoga quadriradiata)
• Garlic, wild (Allium vineale)
• Geranium, Carolina (Geranium carolinianum)
• Geranium, dovefoot (Geranium molle)
• Glutamine synthetase inhibitor (Group 10)
• Goosegrass (Eleusine indica)
• Grass weed seedling identification
• Groundcherry (Physalis spp.)
• Groundsel, cressleaf (Packera glabella)
• Healall (Prunella vulgaris)
• Hemp dogbane (Apocynum cannabinum)
• Henbit (Lamium amplexicaule)
• Herbicide injury by site of action
• Horsenettle (Solanum carolinense)
• Horsetail, field (Equisetum arvense)
• Horseweed, or marestail (Conyza canadensis)
• HPPD inhibitors (Group 27)
• Jimsonweed (Datura stramonium)
• Johnsongrass (Sorghum halepense)
• Knawel (Scleranthus annuus)
• Knotweed, Japanese (Polygonum cuspidatum)
• Kochia (Kochia scoparia)
• Lambsquarters, common (Chenopodium album)
• Lettuce, prickly (Lactuca serriola)
• Long-chain fatty acid inhibitors (Group 15)
• Mallow, common (Malva neglecta)
• Mallow, Venice (Hibiscus trionum)
• Maypop passionflower (Passiflora incarnata)
• Microtubule inhibitors (Group 3)
• Milkweed, common (Asclepias syriaca)
• Milkweed, honeyvine (Cynanchum laeve)
• Millet, browntop (Urochloa ramosa)
• Millet, wild-proso (Panicum miliaceum)
• Morningglory, entireleaf (Ipomoea hederacea var. integriuscula)
• Morningglory, ivyleaf (Ipomoea hederacea)
• Morningglory, palmleaf (Ipomoea wrightii)
• Morningglory, pitted (Ipomoea lacunosa)
• Morningglory, smallflower (Jacquemontia tamnifolia)
• Morningglory, tall (Ipomoea purpurea)
• Mouse-ear cress (Arabidopsis thaliana)
• Mousetail (Myosurus minimus)
• Mugwort (Artemisia vulgaris)
• Mustard, hedge (Sisymbrium officinale)
• Nightshade, eastern black (Solanum ptycnanthum)
• Nutsedge, yellow (Cyperus esculentus)
• Oatgrass, bulbous (Arrhenatherum elatius var. bulbosum)
• Orchardgrass (Dactylis glomerata)
• Panicum, fall (Panicum dichotomiflorum)
• Panicum, Texas (Urochloa texana)
• Pansy, field (Viola kitaibeliana syn. V rafinesquii)
• PDS inhibitors (Group 12)
• Pennycress, field (Thlaspi arvense)
• Pennycress, thoroughwort (Microthlaspi perfoliatum)
• Pepperweed, field (Lepidium campestre)
• Pepperweed, Virginia (Lepidium virginicum)
• Perennial broadleaf weeds
• Perennial grasses
• Photosystem I electron diverter (Group 22)
• Photosystem II inhibitors (Group 5)
• Photosystem II inhibitors (Group 6)
• Photosystem II inhibitors (Group 7)
• Pigweed, prostrate (Amaranthus blitoides)
• Pigweed, redroot (Amaranthus retroflexus)
• Pigweed, smooth (Amaranthus hybridus)
• Pimpernel, scarlet (Anagallis arvensis)
• Pineapple-weed (Matricaria discoidea)
• Plantain, hoary (Plantago media)
• Plants resembling grass
• Poinsettia, wild (Euphorbia heterophylla)
• Poison-hemlock (Conium maculatum)
• Pokeweed, common (Phytolacca americana)
• PPO inhibitors (Group 14)
• Principles of weed identification
• Purslane, common (Portulaca oleracea)
• Quackgrass (Elymus repens)
• Radish, wild (Raphanus raphanistrum)
• Ragweed, common (Ambrosia artemisiifolia)
• Ragweed, giant (Ambrosia trifida)
• Red sorrel (Rumex acetosella)
• Rocket, yellow (Barbarea vulgaris)
• Ryegrass, annual (Lolium multiflorum)
• Sandbur (Cenchrus spp.)
• Shattercane (Sorghum bicolor)
• Shepherd's-purse (Capsella bursa-pastoris)
• Sicklepod (Senna obtusifolia)
• Sida, prickly (Sida spinosa)
• Signalgrass, broadleaf (Urochloa platyphylla)
• Smartweed, Pennsylvania (Polygonum pensylvanicum)
• Smartweed, swamp (Polygonum amphibium)
• Sowthistle, spiny (Sonchus asper)
• Soybean herbicide injury diagnostic key
• Speedwell, corn (Veronica arvensis)
• Speedwell, purslane (Veronica peregrina)
• Spurge, spotted (Chamaesyce maculata)
• Spurge, toothed (Euphorbia dentata)
• Spurry, corn (Spergula arvensis)
• Star-of-Bethlehem (Ornithogalum umbellatum)
• Starch grapehyacinth (Muscari botryoides)
• Stinkgrass (Eragrostis cilianensis)
• Summer annual broadleaf weeds
• Summer annual grasses
• Sunflower, common (Helianthus annuus)
• T1R1 auxin receptors (Group 4)
• Thistle, Canada (Cirsium arvense)
• Trumpetcreeper (Campsis radicans)
• Velvetleaf (Abutilon theophrasti)
• Violet, common blue (Viola sororia)
• Virginia-creeper (Parthenocissus quinquefolia)
• Waterhemp (Amaranthus rudis or tuberculatus)
• Weed scouting and mapping procedures
• Wild carrot (Daucus carota)
• Winter annual broadleaf weeds
• Winter annual grasses
• Witchgrass (Panicum capillare)
• Woodsorrel, creeping (Oxalis corniculata)
• Woodsorrel, yellow (Oxalis stricta)

Acknowledgments

This manual was first published in 2001 under the title Practical Weed Science for the Field Scout: Corn and Soybean. The original authors were Bill Johnson, Fred Fishel and Reid Smeda of the University of Missouri. It was revised in 2007 and 2009 by Kevin Bradley and Reid Smeda of the University of Missouri, Bill Johnson of Purdue University, and Chris Boerboom of the University of Wisconsin.

Pages

• 128