Best herbicide for horsenettle

Invasive Plant Management

Silverleaf nightshade is declared noxious in Arkansas, California, Hawaii, Idaho, and Nevada and is an “A”-designated weed for quarantine in Oregon and Washington. Carolina horsenettle is declared noxious in Alaska, Arizona (prohibited weed), Arkansas, California (“B”-list), Hawaii, Iowa, and Nevada (USDA-NRCS, 2019).

Silverleaf nightshade and Carolina horsenettle reproduce by seed, rhizomes, and root fragments. Plant stems die in the fall, and new shoots develop from adventitious buds on roots. Stems are 1 to 3 feet in height. Flowers have five petal-like lobes that are about 3/4 inch across, with bright yellow stamens (Sidebar). Flower color ranges from dark violet to blue for silverleaf nightshade, and white to light violet for horsenettle. Individual plants produce up to about 200 fruit that resemble small tomatoes, and each fruit contains from 40 to 120 seeds. Fruit remain on dead branches where they can be spread by machinery, wildlife, livestock, and wind. Seed remain viable for up to 10 years in soil.


Silverleaf nightshade and Carolina horsenettle have the potential to invade natural areas, pastures, and cropland. Once established, plants form dense colonies from an extensive root system. Infestations reduce crop production, forage quality and quantity, and serve as a host for insects and plant diseases. Plants are adapted to a wide range of habitats, but thrive on disturbed land, including roads, ditch banks, rivers, livestock corrals, and overgrazed lands.

Both plants contain glycoalkaloids, which are toxic to livestock. Although all parts of the plant are toxic, immature fruit have a higher concentration of glycoalkaloids than mature fruit, leaves, or stems. Damage to the intestinal tract and nervous systems in livestock can occur. In severe cases, ingestion can cause hallucinations, paralysis, and death. Cattle and horses are reported to be more susceptible to toxicity than sheep, while goats are apparently unaffected. Most grazing animals and wildlife avoid grazing the plants.


Several management methods have been investigated for both weeds. The key to effective control is stopping seed production and killing the root system. Quarantine and exclusion are regarded as the most important control strategies in areas where the plant is not established.


In field trials, silverleaf nightshade and Carolina horsenettle responded similarly to various broadleaf herbicide treatments. Results from studies conducted in the U.S. show that Milestone®, GrazonNext® HL, or Chaparral® herbicides provided significantly better control 90 to 120 days after application than 2,4-D (Figure 2). On sites where other weedy broadleaf plants are present, GrazonNext HL at 1.5 to 2.1 pints per acre will provide more broad-spectrum control than Milestone at 4 to 7 fluid ounces and would be the most cost-effective treatment. Applications of 2,4-D alone will suppress nightshade shoot growth and fruiting, but result in minimal damage to roots allowing plants to regrow. The optimum time to apply selective herbicides is when nightshades are actively growing at the bud to flower growth stage.

Ministry of Agriculture, Food and Rural Affairs

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Horse-nettle (Solanum carolinense L.)

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Table of Contents

  1. History
  2. Life Cycle
  3. Distinguishing Characteristics
  4. Control in Corn
  5. Control in Soybeans
  6. Control in Winter Wheat


A member of the nightshade or potato family. Horse-nettle is not an overly common weed, but is certainly problematic in field crops once it has established. In general, horse-nettle prefers sandy soils.

Life Cycle

Perennial, reproducing by seed and underground rhizomes.

Distinguishing Characteristics

It is distinguished by its very spiny stems and leaves, underground roots (rhizomes), lobed leaves, white flowers and smooth yellow berries.

Horse Nettle Pictures

Each thumbnail image links to a larger image

Herbicide Control in Field Corn

Post Emergent Control

In conventional corn, none of the post-emergent broadleaf herbicides provide greater than 80% visual control (Table 1). However, tank-mixing a broadleaf herbicide with one of the post-emergent grass herbicides (i.e. ULTIM, ACCENT) will provide better control of horsenettle than if each product were applied alone. In “Roundup ready” (RR) corn, a sequential application with glyphosate at 1 L/ac should provide good control of horsenettle (Table 1).

Table 1. Horse-nettle control in corn using various post-emergent broadleaf herbicides.

Active Ingredient Trade Name % Control
glyphosate;glyphosate glyphosate;glyphosate (RR corn only) 98
dicamba/atrazine MARKSMAN 75
atrazine/2,4-D SHOTGUN 72
dicamba BANVEL II 64
primisulfuron-methyl/dicamba SUMMIT 62
diflufenzopyr/dicamba DISTINCT 49
prosulfuron + dicamba PEAKPLUS 45
bromoxynil + atrazine PARDNER or KORIL + atrazine 23
atrazine Various Trade Names Exist 22
Table 2. Horse-nettle control in corn with various post-emergent tank-mixes.

Active Ingredient Trade Name % Control
nicosulfuron + primisulfuron-methyl/dicamba ACCENT + SUMMIT 94
nicosulfuron/rimsulfuron + dicamba ULTIM + BANVEL II 89
nicosulfuron/rimsulfuron + diflufenzopyr/dicamba ULTIM + DISTINCT 89
nicosulfuron/rimsulfuron + dicamba/atrazine ULTIM + MARKSMAN 87
nicosulfuron/rimsulfuron + prosulfuron + dicamba ULTIM + PEAKPLUS 87

Source: Dr. Peter Sikkema, University of Guelph.

Number of Trials:

Table 1 is based on 3 field trials in Ontario.

Table 2 is based on 5 field trials in Ontario.

Herbicide Rates: Rates used in this trial are listed in OMAFRA Publication 75 – Guide to Weed Control.

Weed Stage: Horse-nettle was in between the 2 to 8 leaf stage at the time of all post-emergent applications.

What has been your experience?

We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

Herbicide Control in Soybeans

Post-Emergent Control in Soybean

Split glyphosate applications in “Roundup Ready” (RR) soybeans offer the greatest level of horse-nettle control. If growing conventional soybeans, FIRSTRATE has provided the best activity of horse-nettle, but it can only be described as supression of this difficult to control weed. Other conventional broadleaf herbicides like BLAZER and BASAGRAN FORTE, have provided poor control of horse-nettle.

Table 1. Horse-nettle control in soybean with glyphosate and FIRSTRATE.

Active Ingredient Trade Name (application timing) % Control
glyphosate;glyphosate glyphosate; glyphosate (post – RR soys only) 98
glyphosate glyphosate (2 L/ac post – RR soys only) 93
glyphosate + cloransulam-methyl glyphosate (1 L/ac) + FIRSTRATE (post – RR soys only) 87
glyphosate glyphosate (1 L/ac post – RR soys only) 84
cloransulam-methyl FIRSTRATE (post) 78

Source: Dr. Peter Sikkema, University of Guelph.

Number of Trials: Table 1 is based on 6 field trials in Ontario.

Herbicide Rates: Rates used in this trial are listed in OMAFRA Publication 75 – Guide to Weed Control.

Weed Stage: Horse-nettle was in between the 2 to 8 leaf stage at the time of all post-emergent applications.

We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

Herbicide Control in Winter Wheat

No research trials have evaluated the control of horse-nettle in winter wheat.

We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

Controlling Tall Ironweed and Horsenettle: Mike Setters

This past year the Master Grazer Educational program conducted several demonstrations across KY for producers to see best management practices related to pasture management. One of these demonstrations was implemented in Lewis County by cow/calf producer Mike Setters. Previously, he has completed the Master Grazer and Master Cattleman programs and uses many of the practices taught in these programs, such as rotational grazing and improved access to water.

Mike participated in a demonstration trial concentrated on controlling weeds in pasture fields. Phillip Konopka, Lewis county agent, and Dr. J. Green worked with Mr. Setters to determine the field and the specific weeds that needed to be controlled the most. They decided to implement practices to control tall ironweed and horsenettle. Three weeks prior to the herbicide treatment, Mr. Setters clipped the pastures he intended to use for the demonstration. This allowed the weeds to have young, herbicide-susceptible regrow at time of herbicide application.

On July 29th, 2014 Dr. Green used an UTV and sprayer to apply the herbicide treatment of ForeFront HL at a rate of 2 pints per acre. To allow the herbicide to work to control these weeds, they waited two months (September 26, 2014) before going back and taking forage samples from the field. In addition, Dr. Green left strips in the field untreated to allow comparisons to the treated area.

When samples were collected in September, forage dry matter (DM) available in the treated area was 1946 lbs./ acre while the untreated area was only 1246 lbs. of DM/acre, a difference of 700 lbs. DM. The amount of weeds present in the non-treated area was 421 lbs. of DM/acre while only 9 lbs. of weed DM/ acre was present in the treated area. If the forage had been grazed in September, an additional 12 cow-grazing days per acre would have been available for grazing.

Dr. Green said that the trial worked very well in showing how clipping and then applying herbicide can benefit pastures and reduce weed populations. Additional samples are going to be collected this upcoming year to determine the long-term effect of herbicide treatment on these pasture. After seeing the benefits from this study Mr. Setters said that he is going to start using appropriate herbicides on the rest of his farm to control weeds.

For more information about controlling weeds in pastures, contact your local extension agent or check out the UK publication AGR-207 Broadleaf Weeds of Kentucky Pastures. Another good UK publication is AGR-172 Weed Management in Grass Pastures, Hayfields, and Other Farmstead Sites.

Plants of Texas Rangelands

Carolina horse nettle

Solanum carolinense L.

Solanaceae (Nightshade family)


Carolina horse nettle is a coarse, branching, warm-season perennial in the Nightshade family. It grows 1 to 3 feet high.

Carolina horse nettle has large spines on the stems and leaves. Each of its mostly oval leaves has several large teeth or shallow lobes on both sides. On the underside are microscopic, star-shaped hairs.

The clustered flowers are pale violet to white and give rise to spherical fruit. The fruit is about › inch in diameter; it is green with light green vertical bands until maturity, when it becomes uniformly yellow.

Because of its many spines, the forage value of Carolina horse nettle is poor for wildlife and livestock. The fruit is poisonous to livestock.


This plant grows across the eastern part of Texas and the entire eastern half of the United States. It is found mostly in sandy soils in fields, open woodlands and waste places.

Toxic Agent

Horse nettle is a nightshade. Nightshades contain glycoalkaloids, which are broken down in the body to sugars and alkaloids. The toxicity may depend upon the maturity of the plants, because more toxins are present in the fruits than in the leaves.

Almost every animal species has been poisoned by nightshade, but S. carolinense is probably mostly responsible for cases involving cattle and horses. Hay and silage containing the mature plants have been associated with poisoning and deaths.

Signs of Livestock Ingestion

It is thought the glycoalkaloids are responsible for the clinical signs associated with the gastrointestinal tract, and the alkaloids are associated with the signs in the central nervous system. The signs may include: Anorexia; Depression; Excess salivation; Diarrhea or constipation; Trembling; Weakness; Colic.

The star-shaped hair and seeds of this plant are readily identifiable in the gastrointestinal contents of acutely poisoned animals by microscopic techniques.

Question:I’m worried that a weed that grows on my property may be horse nettle, and I’d like to know more about what this plant can do and how to identify it. I know it’s poisonous for horses, but how much do they have to ingest for it to be harmful? Is there a cumulative effect?

Answer: Horse nettle (Solanum carolinense), also referred to as Carolina horsenettle or bull nettle, is a member of the nightshade family and is found in most of the contiguous United States but especially in the Central and Eastern states.

The plant grows up to two feet tall, with an erect, branching structure; the leaves are alternate and can grow to four to six inches long, with irregular wavy or lobed margins. The leaves and stems are often covered with fine hairs and prickly spines. The flowers, which appear at the top of the plant from June through August, are three-quarters to one inch across and range from light purple, blue to white. The plant produces round, tomato-like berries that are half an inch in diameter and change from green to yellow as they ripen.

Horse nettle, like many plants in the nightshade family, contains solanine, a glycoalkaloid that irritates the oral and gastric mucosa and affects the autonomic nervous system, which controls various internal organs. The glycoalkaloids act on the digestive system to cause excessive salivation, colic and diarrhea or constipation. These signs may be followed by depression, weakness, depressed respiration, dilated pupils, collapse and death if horse nettle is eaten in large amounts.

All parts of the plant are poisonous, but toxicity varies depending on growing conditions. The glycoalkaloid levels are higher in the fall than in the spring, and green, unripe berries are more toxic than ripe or dried berries. Toxicity is reduced (but not eliminated) when the plant is dried.

Any livestock—including cattle, sheep, goats and pigs as well as horses—may be poisoned after eating large quantities of horse nettle. Horses tend to avoid the plant because it is distasteful, and they are unlikely to eat enough to cause serious problems unless the weed is rampant in their pasture or they have no other suitable forage. The amount of horse nettle it takes to produce a toxic effect varies, depending on how concentrated the solanine isin the plant, and how much is eaten. However, it generally takes a pound or more to cause poisoning. A single mouthful or a few berries will have little effect on a mature horse. The glycoalkaloids act rapidly once they are absorbed from the intestinal tract, but the effects are not cumulative.

Eradicating established horse nettle is difficult. The plant propagates from seeds, and it also spreads through an extensive underground root system. Mowing the plants before they produce seeds will slow them down but won’t eliminate them. And because they can grow back from even small portions of their rhizomatous roots, they are difficult to control with herbicides or by pulling them up manually.

Contact your local extension agent to identify the plant and for tips on the best strategies to control it in your area.

Anthony P. Knight, BVSc,?MS, DACVIM
College of Veterinary Medicine & Biomedical Sciences
Colorado State University
Fort Collins, Colorado

Toxic Principle Tropane alkaloids, especially solanine, which has similar effects as atropine on the autonomic nervous system. Also directly irritating to the oral and gastric mucosa. Green plant and unripe fruits most toxic. Toxicity is reduced by drying. Description An erect 1-2 feet high, branching plant with yellow spines on leaves and stems. Leaves are simple, alternate, oblong, and irregularly lobed. The flowers are simple, alternate, oblong, and irregularly lobed. The flowers are pale violet to white in color, clustered near the top of the plant. The 5 petals tend to be united. The fruits are berries 1-1.5 cm in diameter, yellow when ripe.
Gastrointestinal Salivation, colic, intestinal stasis, diarrhea.
Musculoskeletal Muscle tremors, weakness.
Treatment Symptomatic therapy is indicated including fluid therapy, activated charcoal via stomach tube. Physostigmine may be used cautiously in severely poisoned animals.
Cardiovascular system Rapid heart rate, weak pulse. Hemolysis and anemia may be present in sever cases.
Respiratory System Labored breathing, nasal discharge,
Nervous System Depression, drowsiness, incoordination, paralysis of rear legs, coma and death.
Renal System Kidney failure has been reported
Diagnosis Based upon clinical signs and evidence of the plant being consumed.
Special Notes Destruction of the plants before fruits are produced will prevent horsenettle spreading.

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