Agronomy Facts 58 Management of Eastern Black Nightshade in Agronomic Crops An Integrated Approach Eastern black nightshade (Solanum ptycanthum Dun.), an include American black nightshade (Solanum americanum annual broadleaf plant, is a problem weed in northeast- Mill.), black nightshade (Solanum nigrum L.), and hairy night- ern field crop production. It is native to the Americas and shade (Solanum sarrachoides Sendtner). Of these three, only commonly found throughout the United States east of the hairy nightshade is found in the northeastern United States. It Rocky Mountains. Nightshade begins germinating in May can be distinguished from eastern black nightshade by the lack and can continue throughout the growing season. Although of red-purple coloration on the lower surface of the leaves, and it can cause reductions in crop yield, more important, it can upon close inspection of the fruit, the calyx (sepals) may cover interfere with the harvest and lower crop quality. as much as half the berry. Eastern black nightshade is the pre- At soybean harvest time, nightshade foliage is green dominant annual nightshade species in Pennsylvania. and the berries are still intact. During harvest, the berry juice In addition to the annuals, the perennial smooth causes soil, nightshade seeds, and other foreign materials to groundcherry (Physalis subglabrata) and horsenettle adhere to the grain, producing a pasty mixture that can clog (Solanum carolinense) seedlings look like the eastern black and gum the sieves, cylinders, and augers of combines. If nightshade seedling. However, both of these typically allowed to dry, this mixture can harden, resulting in down- emerge from rootstock, distinguishing them from annuals. time or even costly repairs. The berry juice can stain seed, Eastern black nightshade is toxic, as are most plants in potentially resulting in dockage at the mill; in addition, the the nightshade family. All parts of the plant are considered moisture in the berries can cause poor bulk flow of soybeans poisonous, but the green leaves, stems, and seeds are espe- and promote mold formation during storage. cially toxic. The green fruit may be quite poisonous, while Eastern black nightshade is a member of the nightshade the ripe fruit may be relatively nontoxic. The concentrations (Solanaceae) family. Although weeds belonging to this family of the toxins are higher following dry conditions and often have many similarities, individual species should be identified lower following damp, rainy periods. The toxic properties carefully because they react differently to many herbicides. The are relatively heat stable and not removed by drying. Por- cotyledons of eastern black nightshade are small and green on tions of the plant stored with forage will remain poison- both surfaces with short hairs on the margins. The true leaves ous, so producers must be cautious when feeding livestock are simple, alternate, petioled, ovate, or ovate-lanceolate. The nightshade-contaminated hay. seedling leaves have a red-purple coloration on the lower sur- The toxicity of the green plant material varies from 0.1 face and margins that vary from entire to slightly serrated. Leaf to 1 percent of an animal’s body weight. The toxic prin- pubescence (hair) depends on the environment and varies from ciples include tophane and steroidal alkaloids, which com- nearly hairless to moderately hairy. The stem of the eastern monly induce symptoms in farm animals similar to those of black nightshade plant is erect, becomes widely branched, and an atropine overdose, which includes colic, diarrhea, saliva- reaches 1 to 2 feet in height. As the plant matures, white flow- tion, and vomiting. Very high doses may induce intestinal ers form in umbel-like clusters of four to five star-shaped flow- dysfunction and constipation, loss of coordination, weak- ers each. The fruit is a 3/8-inch, round, green berry that turns ness, tremors, depression, posterior weakness, paralysis, and purplish black at maturity. Each nightshade plant is capable of low heart rate and blood pressure. Clinical signs develop producing up to 1,000 berries. Contained in each berry are 50 rapidly. Most animals succumb or recover within 24 to 48 to 100 round, flattened, tan-colored seeds, each 1/16 inch in hours. Limited therapies are available for treatment. diameter (approximately the size of a pinhead). As with most weeds, an integrated control program Other annual members of the black nightshade complex combining preventive, cultural, mechanical, and chemical that are sometimes confused with eastern black nightshade methods is most effective. EASTERN BLACK NIGHTSHADE Illustration by Rae Chambers 2 Prevention planting helps control weeds missed by a preemergence Once eastern black nightshade has become established, herbicide treatment and provides a good alternative to a prevent it from spreading into new areas. Clean seeds and postemergence herbicide application. Cultivation will not berries from tillage implements and harvest equipment control weeds within the crop rows, nor is it effective on before using them in uninfested areas. Hay, straw, and crop late germinating weeds. Studies have shown that harvesting seed may contain evidence of eastern black nightshade, so soybeans can be difficult with as little as one nightshade purchase it from a reliable source. Avoid spreading con- plant per 10 feet of row; therefore, for soybeans, cultivation taminated manure onto uninfested fields. alone may not be worth the time and extra effort required. To reduce spreading, spot treat isolated patches of eastern black nightshade with an effective herbicide before Chemical Control the plants reach maturity. Birds have been known to eat ripe To ensure effective, safe, and economical herbicide use: eastern black nightshade berries and transport them to unin- • Select the appropriate herbicide for your weed problem fested fields. Spot treating with an herbicide or mowing any and crop. The stage of weed and crop growth, tempera- isolated patches in noncropland or fallow fields can reduce ture, and soil moisture and pH can affect herbicide perfor- the occurrence of this type of spreading. mance. For additional information, refer to the Penn State Agronomy Guide or consult with the extension educator General Cultural Control in your county or another agricultural professional. The germination of eastern black nightshade is sporadic throughout the growing season, making it difficult to • Read the herbicide label carefully and follow the direc- control in many crops; however, crop competition can aid tions. The label provides important information on safe in minimizing spread. Good cultural practices promote use, application, disposal, and storage. healthy crop stands, and the resulting canopy shading helps • Apply herbicides at the proper time. control weeds. The following guidelines will help you Apply the recommended rate to avoid injury, soil resi- maximize cultural control opportunities: • due, and poor control. • Follow soil test recommendations for lime and fertilizer. • Calibrate application equipment several times during the • Plant high-yielding varieties adapted to climate, soil, season to ensure the correct amount of herbicide is applied. and field conditions. • Wear proper protective equipment (PPE) when work- • If soil temperatures and conditions are optimal, plant ing with pesticides. early using narrow row spacing and high plant popula- Learn to predict weed problems. Scout fields regularly tions, when possible. • and record the types and locations of weeds present. • Follow practical integrated pest management programs Use field records to plan an integrated control program. that monitor disease, insects, and weeds, and use ap- Eastern black nightshade is typically not a major prob- propriate control tactics when necessary. lem in corn—it is not very competitive and can be easily • Avoid certain herbicide programs that increase the poten- controlled with many common corn herbicide programs tial for eastern black nightshade problems, such as Classic/ that contain atrazine. However, several other herbicides can chlorimuron plus Harmony/thifensulfuron in soybeans. also be used to control nightshade (Table 1). Control in soybeans can be achieved with effective Mechanical Control herbicides applied PRE (preemergence) and/or POST Mowing, plowing, disking, and cultivating are some of the (postemergence or foliar). The chloroacetamide herbi- more commonly used mechanical methods for field crop cides (e.g., Dual/metolachlor and Harness/acetochlor) will weed control. Existing nightshade infestations in hay crops provide some control of eastern black nightshade. For more or pastures can be controlled by timely mowing or swath- severe infestations, a PRE program that includes flumioxa- ing to prevent seed production. Repeated mowing may be zin (Valor) or sulfentrazone (Authority/Spartan) or POST necessary due to the sporadic germination of the plant. control with a diphenyl ether (e.g., Cobra, Reflex, or Ultra Fall or spring tillage can bury weed seed deep enough Blazer) or Pursuit may be necessary (Table 2). to reduce emergence. This strategy is especially effective An effective herbicide program combined with early for small-seeded weeds such as eastern black nightshade. canopy closure can increase eastern black nightshade Such tillage requires the use of a moldboard plow or anoth- control in soybeans. Early canopy closure can be achieved er tool that will invert the soil and bury the seed. However, through planting