Integrated Approach- Management of Eastern Black Nightshade

Eastern black nightshade (Solanum ptycanthum Dun.), an annual broadleaf plant, is an increasing weed problem in northeastern field crop production.
Integrated Approach- Management of Eastern Black Nightshade - Articles

Updated: August 14, 2017

Integrated Approach- Management of Eastern Black Nightshade

It is native to the Americas and is commonly found throughout the United States east of the Rocky Mountains. Nightshade begins germinating in May and can continue throughout the growing season. Although it can cause crop yield reductions, more importantly it can interfere with the harvest and lower crop quality.

At soybean harvest time, nightshade foliage is green and the berries are still intact. During harvest, the berry juice causes soil, nightshade seeds, and other foreign materials to adhere to the grain, producing a pasty mixture that can clog and gum the sieves, cylinders, and augers of combines. If allowed to dry, this mixture can harden, resulting in downtime or even costly repairs. The berry juice can stain seed, potentially resulting in dockage at the mill; in addition, the moisture in the berries can cause poor bulk flow of soybeans and can promote mold formation during storage.

Description and Identification

Eastern black nightshade is a member of the Nightshade (Solanaceae) family. Although weeds belonging to this family have many similarities, individual species should be identified carefully since they react differently to many herbicides. The cotyledons of eastern black nightshade are small and green on both surfaces with short hairs on the margins. The true leaves are simple, alternate, petioled, ovate, or ovate-lanceolate. The seedling leaves have a red-purple coloration on the lower surface and margins that vary from entire to slightly serrated. Leaf pubescence (hair) depends on the environment and varies from nearly hairless to moderately hairy. The stem of the eastern black nightshade plant is erect, becomes widely branched, and reaches 1 to 2 feet in height. As the plant matures, white flowers form in umbel-like clusters of 4 to 5 star-shaped flowers each. The fruit is a 3/8-inch round green berry that turns purplish-black at maturity. Each nightshade plant is capable of producing up to 1,000 berries. Contained in each berry are 50 to 100 round, flattened, tan-colored seeds, each 1/16 inch in diameter (approximately the size of a pinhead).

Other annual members of the black nightshade complex that sometimes are confused with eastern black nightshade are American black nightshade (Solanum americanum Mill.), black nightshade (Solanum nigrum L.), and hairy nightshade (Solanum sarrachoides Sendtner). Of these three, only hairy nightshade is found in the northeastern United States. It can be distinguished from eastern black nightshade by the lack of red-purple coloration on the lower surface of the leaves and upon close inspection of the fruit: the calyx (sepals) may cover as much as half the berry. Eastern black nightshade is the predominant annual nightshade species in Pennsylvania.

In addition to the annuals, the perennial smooth groundcherry (Physalis subglabrata) and horsenettle (Solanum carolinense) seedlings look like the eastern black nightshade seedling. Both of these typically emerge from rootstock, however, distinguishing them from annuals.

Eastern black nightshade is toxic, as are most plants in the Nightshade family. All parts of the plant are considered poisonous; however, the green leaves, stems, and seeds are especially toxic. The green fruit may be quite poisonous, while the ripe fruit may be relatively nontoxic. The concentrations of the toxins are higher following dry conditions and often are lower following damp, rainy periods. The toxic properties are not removed by drying and are relatively heat stable. Portions of the plant stored with forage will remain poisonous, so producers must be cautious when feeding livestock nightshade-contaminated hay.

The toxicity of the green plant material varies from 0.1% to 1% of an animal's body weight. The toxic principles include tophane and steroidal alkaloids, which commonly induce symptoms in farm animals similar to those of an atropine overdose, including colic, diarrhea, salivation, and vomiting. Very high doses may induce intestinal dysfunction and constipation, loss of coordination, weakness, tremors, depression, posterior weakness, paralysis, and low heart rate and blood pressure. Clinical signs develop rapidly. Most animals succumb or recover within 24 to 48 hours. Limited therapies are available for treatment.

Management

As with most weeds, an integrated control program combining preventive, cultural, mechanical, and chemical methods is most effective.

Prevention

Once eastern black nightshade has become established, prevent it from spreading into new areas. Clean seeds and berries from tillage implements and harvest equipment before using them in uninfested areas. Hay, straw, and crop seed may contain evidence of eastern black nightshade, so purchase it from a reliable source. Avoid spreading contaminated manure onto uninfested fields.

To reduce spreading, spot treat isolated patches of eastern black nightshade with an effective herbicide before the plants reach maturity. Birds have been known to eat ripe eastern black nightshade berries and transport them to uninfested fields. Spot treating with an herbicide or mowing any isolated patches in non-cropland or fallow fields can reduce the occurrence of this type of spreading.

General Cultural Control

The germination of eastern black nightshade is sporadic throughout the growing season, making it difficult to control in many crops; however, crop competition can aid in minimizing the plant's spread. Good cultural practices promote healthy crop stands, and the resulting canopy shading helps to control weeds. The following guidelines will help you maximize cultural control opportunities:

  • Follow soil test recommendations for lime and fertilizer.
  • Plant high-yielding varieties adapted to climate, soil, and field conditions.
  • If soil temperatures and conditions are optimal, plant early, using narrow row spacing and high plant populations, when possible.
  • Follow practical integrated pest management programs that monitor disease, insects, and weeds, and use appropriate control tactics when necessary.
  • Avoid certain herbicide programs (such as Classic plus Pinnacle in soybeans) that increase the potential for eastern black nightshade problems.

Mechanical Control

Mowing, plowing, disking, and cultivating are some of the more commonly used mechanical methods for field crop weed control. Existing nightshade infestations in hay crops or pastures can be controlled by timely mowing or swathing to prevent seed production. Repeated mowings may be necessary, however, due to the sporadic germination of the plant.

Fall or spring tillage can bury weed seed deeply enough that emergence is reduced. This strategy is especially effective for small-seeded weeds such as eastern black nightshade. Such tillage requires the use of a moldboard plow or other tool that will invert the soil and bury the seed. If soil erosion is a problem, however, intensive tillage may not be possible or practical. Less intensive types of tillage such as chisel plowing, disking, or field cultivating prior to planting can destroy weeds that have already emerged, but may also stimulate additional weed emergence.

Cultivating row crops removes or buries small weeds and makes them less competitive. In corn or soybeans, one or two cultivations during the first six weeks after planting helps to control weeds missed by a preemergence herbicide treatment and provides a good alternative to a postemergence herbicide application. Cultivation will not control weeds within the crop rows, and is not effective on late-germinating weeds. Studies have shown that harvesting soybeans can be difficult with as little as one nightshade plant per 10 feet of row; therefore, for soybeans, cultivation alone may not be worth the time and extra effort required.

Chemical Control

To ensure effective, safe, and economical herbicide use, do the following:

  • Select the appropriate herbicide for your weed problem and crop. The stage of weed and crop growth, temperature, soil moisture, and soil pH can affect herbicide performance. For additional information, refer to the Penn State Agronomy Guideor consult with your county extension agent or other agricultural professional.
  • Read the herbicide label carefully and follow the directions. The label provides important information on safe use, application, disposal, and storage.
  • Apply herbicides at the proper time.
  • Apply the recommended rate to avoid injury, soil residue, or poor control.
  • Calibrate application equipment several times during the season to ensure that the correct amount of herbicide is applied.
  • Wear proper protective clothing when working with pesticides.
  • Learn to predict weed problems. Scout fields regularly and record the types and locations of weeds present. Use field records to plan an integrated control program.

Eastern black nightshade typically is not a major problem in corn; it is not very competitive and can be controlled easily with many common corn herbicides such as the triazine herbicides (e.g. Aatrex) or any mixtures that contain a triazine. For more information on effective corn herbicides, see Table 1.

Table 1. Herbicides for eastern black nightshade control in corn.
HerbicideCropProduct/AControl RatingaComments
a) 10 = 95-100%, 9 = 85-95%, 8 = 75-85%, 7 = 65-75%, 6 = 55-65%. Ratings based on optimal application timing.
Preplant or Preemergence
Atrazine 4LCorn1-2 qt9Triazines are very effective at controlling eastern black nightshade. On highly erodible ground with less than 30% surface residue, no more than 1.6 qt may be applied prior to crop emergence. (Restricted-use pesticide and water quality advisory)
Bladex 90DFCorn1.3-3.3 lb9Do not use on sands or loamy sands with less than 1% organic matter. May cause (cyanazine) injury if rates are exceeded for soil type, or if cold, wet, poor growing conditions follow application. Rates may be increased up to 25% in no-till situations with heavy crop residue. (Restricted-use pesticide and water quality advisory)
Dual II 7.8E (metolachlor) orCorn2-3 pt7+Dual II, Frontier, and Micro-Tech may be broadcast prior to weed emergence. These herbicides may provide adequate control of less severe nightshade infestations. For severe infestations, a tank-mix partner should be added or a post application should be conducted for season-long control. Micro-Tech is a restricted-use pesticide. (Water quality advisory)
Frontier 6.0E (dimethenamid) or20-32 fl oz
Micro-Tech 4ME (alachlor)2-4 qt
Harness 7E orCorn1.25-3 pt8+Acetochlor is similar in activity to Dual but is more active on certain broadleaves such as eastern black nightshade. Acetochlor may be applied on corn that is up to 11 inches tall, depending on the tank-mix partner. The rate may need to be increased up to 20% for fields with heavy surface plant residue. (Restricted-use pesticide and water quality advisory)
Surpass 6.4E or1.5-3.75 pt
TopNotch 3.2CS (acetochlor)2-3.75 qt
Princep 90DF (simazine)Corn1.1-3.3 lb9Princep is similar to atrazine but has better grass activity and less broadleaf control. Like atrazine, Princep can persist in soil and leave carryover residues. (Water quality advisory)
Pursuit 70DG (imazethapyr)Corn1.44 fl oz8For use only with IMI corn. Pursuit will provide fair to good control of eastern black nightshade. Do not plant non-IMI corn until 8.5 months after application.
Postemergence
Atrazine 4LCorn1-2 qt9Apply before weeds are 1.5 inches tall and before corn reaches 12 inches in height. Add 1 qt of crop oil concentrate/A to spray solution. Do not include oil if corn is under stress from prolonged cold, wet weather. (Restricted-use pesticide and water quality advisory)
Banvel 4S orCorn0.5-1 pt8May apply Banvel up to 1 pint before corn is 8 inches tall; adjust rate to soil type. Use 0.5 pint on corn between 8 and 36 inches tall. Apply Clarity before corn is 8 inches tall.
Clarity 4S (dicamba)
8-16 fl oz
Bladex 90DF (cyanazine)Corn1.3-2.2 lb9Apply from corn emergence until the four-leaf stage, but before weeds exceed 1.5 inch. Under dry conditions, a surfactant may be used to improve control. Use of the 4L formulation postemergence increases the likelihood of crop injury. Corn may be injured if cold, wet, cloudy weather precedes application. (Restricted-use pesticide and water quality advisory)
Buctril 2E (bromoxynil)Corn1-1.5 pt9Apply to actively growing nightshade up to 6 inches in height.
Pursuit 2AS (imazethapyr)Corn4floz8For use only with IMI corn. Apply to actively growing nightshade up to 3 inches in height. Larger plants are not controlled. Do not plant non-IMI corn until 8.5 months after application. Use surfactant or crop oil concentrate as directed.
Tough 5EC (pyridate)Corn0.8-1.6 pt9For best results apply to actively growing nightshade prior to the four-leaf stage. Tough also is effective on common lambsquarters and pigweed.

Control in soybeans can be more difficult because of the current unavailability of effective herbicides. The chloroacetamide herbicides (e.g. Dual and Lasso) will provide some control of eastern black nightshade. For more severe infestations, a pre program that includes sulfentrazone (Authority BL or Canopy XL), or post control with a diphenyl ether (e.g. Cobra or Blazer) or Pursuit may be necessary. For more information on effective soybean herbicides see Table 2.

Table 2. Herbicides for eastern black nightshade control in soybeans.
HerbicideCropProduct/AControl RatingaComments
a) 10 = 95-100%, 9 = 85-95%, 8 = 75-85%, 7 = 65-75%, 6 = 55-65%. Ratings based on optimal application timing.
Preplant or Preemergence
Dual II 7.8E (metolachlor) orSoybeans2-3 pt7+Dual II, Frontier, and Micro-Tech may be broadcast prior to weed emergence. These herbicides may provide adequate control of less severe nightshade infestations. For severe infestations, a tank-mix partner should be added or post application should be conducted for season-long control. Micro-Tech is a restricted-use pesticide. (Water quality advisory)
Frontier 6.0E (dimethenamid) or20-32 fl oz
Micro-Tech 4ME (alachlor)2-4 qt
Pursuit 2AS/70 DG (imazethapyr)Soybeans4 fl oz/
1.44 oz
8Pursuit will provide fair to good control of eastern black nightshade. Do not plant corn until 8.5 months after application.
Authority Broadleaf 56.3DF or

Canopy XL 56.3DF (sulfentrazone + chlorimuron)
Soybeans6.8 oz9Authority Broadleaf and Canopy XL will provide effective control of eastern black nightshade. This broadleaf weed mixture also is effective on many other broadleaves and yellow nutsedge. This product will need a tank mixture to improve grass control.
Postemergence
Blazer 2S (acifluorfen)Soybeans0.5-1.5 pt8+Applications should be made before nightshade exceeds 2 inches in height. Soybeans should have at least one or two trifoliate leaves. For consistent control, a nonionic surfactant is required. Do not apply when weeds or crop are under stress. This product does not provide residual control.
Cobra 2E (lactofen)Soybeans6-12.5 fl oz8+Applications should be made to actively growing eastern black nightshade up to the six-leaf stage. Soybeans should have one to two trifoliate leaves. Use surfactant or crop oil concentrate as directed. May cause foliar injury to soybeans. This product does not provide residual control.
Pursuit 2AS/70 DG (imazethapyr)Soybeans4 fl oz/1.44 oz8Apply to actively growing nightshade up to 3 inches in height. Do not plant corn until 8.5 months after application. Use surfactant or crop oil concentrate as directed.
Reflex 2E orSoybeans1-1.5 pt8Apply to actively growing eastern black nightshade. For best results, apply to nightshades that have four true leaves or less. A nonionic surfactant or crop oil concentrate is needed for best performance. This product does not provide residual control.
Flexstar 1E2-3 pt
Roundup Ultra 4S (glyphosate)Soybeans1-4 pt8Apply over-the-top to Roundup Ready soybean varieties only. Treat from soybean emergence to flowering stage in 10-20 GPA. For most effective control of eastern black nightshade, plant in narrow rows and apply 1.5-2 pt/A about one month after planting. Apply to nightshade less than 4 inches in height. Sequential applications may be necessary if new weed growth occurs.

A combination of an effective herbicide program and early canopy closure can increase eastern black nightshade control in soybeans. Early canopy closure can be achieved through planting in narrow rows or drilled beans.

At times, nightshade can present a problem for seedling forages such as alfalfa. To reduce the chance of competition from eastern black nightshade in alfalfa, plant the forage crop as early in the spring as possible, well in advance of nightshade germination. If nightshade becomes a problem in alfalfa, use Pursuit herbicide early postemergence or Buctril before daytime temperatures become too warm (see product labels for rates and additional information).

Harvest Aids

If herbicides fail, harvest aids can be used in soybeans. If the nightshade plants are still green and have not yet been frosted, apply 12.8 fl oz of Gramoxone Extra plus surfactant as a harvest aid (Note: Gramoxone Extra is a restricted-use pesticide). Apply after the soybean pods have set and lost all green color and at least 7 days before harvest. In the absence of a harvest aid herbicide, delay the soybean harvest for as long as possible to allow additional berry drop. Nightshade berries will drop slowly following maturity or after a hard frost.

Prepared by Edward L. Werner, research technician; William S. Curran, associate professor of weed science; and Dwight D. Lingenfelter, assistant extension agronomist.

Authors

Managing weedy plants in agroecosystems Conservation tillage and cover crops Herbicide use Integrated weed management Weed management in organic cropping systems

More by William S. Curran, Ph.D.