Herbicide Injury Symptoms

Plant part affected

Injury symptoms

Possible causes and comments

Entire plant Reduce plant growth and vigor while producing no other acute symptoms Examples include: low doses of simazine (Princep), dinitroanaline herbicides (trifluralin, oryzalin, prodiamine, pendimethalin) sprayed over the top of plants when new growth is present, imazaquin (Image), and others. Other possible causes include: poor drainage, root feeding insects, competition from weeds, low fertility, and water stress. Look for untreated plants growing in similar conditions and carefully evaluate all potential causes.

Leaves Feathering of leaves, strap shaped leaves Leaf malformations induced by translocated herbicides such as 2,4-D, MCPA, and glyphosate (Roundup).

Fiddlenecking in young growing points of plants; upward curling of older leaves is also obvious Symptoms are produced by growth-hormone herbicides such as dicamba (Banvel) and picloram (Tordon).

Cupping of leaves Distinct cupping (usually upward) caused by growth-hormone herbicides such as 2,4-D, MCPA, and dicamba (Banvel).

Crinkling of leaves; in grass species such as corn, leaves fail to emerge from the sheath normally and the plant remain in a stunted condition with twisted and crinkled leaves Caused by thiocarbate herbicides such as EPTC (Eptam).

Leaf rolling Injury symptom on grasses caused by dinitroaniline compounds such as trifuralin (Treflan, Preen).

Tip chlorosis; yellowing in the actively growing regions of plants;chlorotic areas may appear yellow, white, or pinkish Typical of translocated herbicides such as glyphosate (Roundup), halosulfuron, sethoxydim (Poast, Vantage), and fluazifop-butyl (Fusilade).

Veinal chlorosis - yellowing of leaf veins Usually results from root uptake of uracil and urea herbicides such as bromical, terbical, diuron (Karmex).

Interveinal chlorosis - yellowing of tissues between leaf veins Injury typically is caused by root uptake of triazine herbicides such as simazine (Princep).

Marginal chlorois - a narrow, yellow band almost entirely around the leaf margin; sometimes called a "halo effect" Can be caused by root or foliar uptake of triazine herbicides such as simazine (Princep) and diclobenil (Casoron).

Mottling; chlorosis or leaf discoloration which occurs randomly on the leaf; parts of the leaf remain green while others are chlorotic, sometimes puckered Rarely associated with herbicide injury. Sometimes preemergent herbicides such as oryzalin (Surflan) or isoxaben (Gallery) applied over very, young plant tissues can cause puckering and mottled leaves in susceptible species such as hydrangea, Heuchera and Euonymus alata compacta.

White tissue; results from loss of all pigments (cartenoids and chlorophyll); tissues may be white or yellowish-white, often with pink on the leaf margins Typical of carotinoid pigment inhibitors such as amitrole or clomazone (Command). Some bacterial infections may mimic these symptoms.

Marginal necrosis (death of isolated tissues, often following chlorosis) on the leaf margins; develops on older leaves after they have exhibited a chlorotic condition An over dose of a herbicide such as metribuzin (Sencor), simazine (Princep) or atrazine (AAtrex).

Necrosis occurring in small spots scattered through the leaf Caused by contact herbicides such as diquat (Reward), MSMA (Daconate), and pelargonic acid (Scythe).

Stem Epinasty - bending and/or twisting that occurs in either the stem or petioles of plants Response often occurs within a few hours after exposure to a herbicide. Growth-hormone herbicides such as the phenoxys (2,4-D, MCPA), benzoics (dicamba) and pyridinecarboxylic acids (clopyralid, triclopyr) cause such symptoms.

Abnormal stem elongation Stem elongation of broadleaved plants may be enhanced (at low concentration) or inhibited (at high concentrations) by growth hormones herbicides such as 2,4-D, MCPA, dicamba (Banvel), and triclopyr (Redeem).

Stem cracking; stems become brittle and may break off in heavy winds; stems often crack near the soil line Symptoms are typical of injury from growth regulator herbicides.

Adventitious root formation Growth-hormone herbicides such as 2,4-D, MCPA, dicamba (Banvel).

Swelling of coleoptiles, hypocotyl, and/or stem Caused by herbicides such as EPTC, trifluralin, and growth hormone herbicides; a common results of stem girdling at the soil line (resulting in stem swelling above the soil line) often associated with dinitroanaline herbicides.

Flower Changes in size, shape or arrangement of various flower parts. Branched flowers; multiple spikelets; some spikelets missing; flower partly or completely enclosed in the leaf; opposite instead of alternating spikelets along the rachis Usually caused by growth-hormone herbicides such as 2,4-D, dicamba (Banvel). Delay in flowering due to herbicide injury is common.

Fruit Changes in size, shape and appearance, or abortion of fruit Often associated with growth regulator-type herbicides, spray drift or misapplication of contact-type herbicides such as diquat (various brand names).

Roots Development of primary and/or lateral roots is inhibited; thickened and shortened roots; usually leads to stunting of plants Herbicides such as EPTC (Eptan), bensulide (Betasan, Dimension), and trifluralin (Treflan, Preen) are effective inhibitors of root growth. Growth-hormones herbicides may cause swelling of roots in some plants.

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© Erv Evans, Consumer Horticulturalist
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Plant part affected	Injury symptoms	Possible causes and comments
Entire plant	Reduce plant growth and vigor while producing no other acute symptoms	Examples include: low doses of simazine (Princep), dinitroanaline herbicides (trifluralin, oryzalin, prodiamine, pendimethalin) sprayed over the top of plants when new growth is present, imazaquin (Image), and others. Other possible causes include: poor drainage, root feeding insects, competition from weeds, low fertility, and water stress. Look for untreated plants growing in similar conditions and carefully evaluate all potential causes.
Leaves	Feathering of leaves, strap shaped leaves	Leaf malformations induced by translocated herbicides such as 2,4-D, MCPA, and glyphosate (Roundup).
	Fiddlenecking in young growing points of plants; upward curling of older leaves is also obvious	Symptoms are produced by growth-hormone herbicides such as dicamba (Banvel) and picloram (Tordon).
	Cupping of leaves	Distinct cupping (usually upward) caused by growth-hormone herbicides such as 2,4-D, MCPA, and dicamba (Banvel).
	Crinkling of leaves; in grass species such as corn, leaves fail to emerge from the sheath normally and the plant remain in a stunted condition with twisted and crinkled leaves	Caused by thiocarbate herbicides such as EPTC (Eptam).
	Leaf rolling	Injury symptom on grasses caused by dinitroaniline compounds such as trifuralin (Treflan, Preen).
	Tip chlorosis; yellowing in the actively growing regions of plants;chlorotic areas may appear yellow, white, or pinkish	Typical of translocated herbicides such as glyphosate (Roundup), halosulfuron, sethoxydim (Poast, Vantage), and fluazifop-butyl (Fusilade).
	Veinal chlorosis - yellowing of leaf veins	Usually results from root uptake of uracil and urea herbicides such as bromical, terbical, diuron (Karmex).
	Interveinal chlorosis - yellowing of tissues between leaf veins	Injury typically is caused by root uptake of triazine herbicides such as simazine (Princep).
	Marginal chlorois - a narrow, yellow band almost entirely around the leaf margin; sometimes called a "halo effect"	Can be caused by root or foliar uptake of triazine herbicides such as simazine (Princep) and diclobenil (Casoron).
	Mottling; chlorosis or leaf discoloration which occurs randomly on the leaf; parts of the leaf remain green while others are chlorotic, sometimes puckered	Rarely associated with herbicide injury. Sometimes preemergent herbicides such as oryzalin (Surflan) or isoxaben (Gallery) applied over very, young plant tissues can cause puckering and mottled leaves in susceptible species such as hydrangea, Heuchera and Euonymus alata compacta.
	White tissue; results from loss of all pigments (cartenoids and chlorophyll); tissues may be white or yellowish-white, often with pink on the leaf margins	Typical of carotinoid pigment inhibitors such as amitrole or clomazone (Command). Some bacterial infections may mimic these symptoms.
	Marginal necrosis (death of isolated tissues, often following chlorosis) on the leaf margins; develops on older leaves after they have exhibited a chlorotic condition	An over dose of a herbicide such as metribuzin (Sencor), simazine (Princep) or atrazine (AAtrex).
	Necrosis occurring in small spots scattered through the leaf	Caused by contact herbicides such as diquat (Reward), MSMA (Daconate), and pelargonic acid (Scythe).
Stem	Epinasty - bending and/or twisting that occurs in either the stem or petioles of plants	Response often occurs within a few hours after exposure to a herbicide. Growth-hormone herbicides such as the phenoxys (2,4-D, MCPA), benzoics (dicamba) and pyridinecarboxylic acids (clopyralid, triclopyr) cause such symptoms.
	Abnormal stem elongation	Stem elongation of broadleaved plants may be enhanced (at low concentration) or inhibited (at high concentrations) by growth hormones herbicides such as 2,4-D, MCPA, dicamba (Banvel), and triclopyr (Redeem).
	Stem cracking; stems become brittle and may break off in heavy winds; stems often crack near the soil line	Symptoms are typical of injury from growth regulator herbicides.
	Adventitious root formation	Growth-hormone herbicides such as 2,4-D, MCPA, dicamba (Banvel).
	Swelling of coleoptiles, hypocotyl, and/or stem	Caused by herbicides such as EPTC, trifluralin, and growth hormone herbicides; a common results of stem girdling at the soil line (resulting in stem swelling above the soil line) often associated with dinitroanaline herbicides.
Flower	Changes in size, shape or arrangement of various flower parts. Branched flowers; multiple spikelets; some spikelets missing; flower partly or completely enclosed in the leaf; opposite instead of alternating spikelets along the rachis	Usually caused by growth-hormone herbicides such as 2,4-D, dicamba (Banvel). Delay in flowering due to herbicide injury is common.
Fruit	Changes in size, shape and appearance, or abortion of fruit	Often associated with growth regulator-type herbicides, spray drift or misapplication of contact-type herbicides such as diquat (various brand names).
Roots	Development of primary and/or lateral roots is inhibited; thickened and shortened roots; usually leads to stunting of plants	Herbicides such as EPTC (Eptan), bensulide (Betasan, Dimension), and trifluralin (Treflan, Preen) are effective inhibitors of root growth. Growth-hormones herbicides may cause swelling of roots in some plants.