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Nightshades
Nightshades have become a serious weed problem in North Dakota crop production. Human
activity associated with crop production, like moving tillage and harvesting equipment
from field to field or planting crop seed contaminated with nightshade seed is the
greatest contributor to nightshade seed dissemination. However, birds and other wildlife
consume nightshade and can transport seed through droppings.
Four different nightshades are found in North Dakota: black, eastern black nightshade,
hairy nightshade, and cutleaf nightshade. Black, eastern black, and hairy nightshade are
found in central and eastern North Dakota. Cutleaf nightshade is found in northern regions
of the state but is found in isolated areas in or near the Red River Valley. Hairy
nightshade is the only nightshade densely covered with small hairs and berries remain
green at maturity. Only the underneath side of black and eastern black nightshade leaves
are black or dark-purple in color and berries turn black or dark purple at maturity.
Eastern black nightshade is very difficult to distinguish from black nightshade before
reproduction and berry formation. Eastern black nightshade forms berries in umbrella-like
clusters with berry stems arising from a common point; the calyx is smallest, and the
lobes of the calyx recurve away from the berry. Black nightshade and hairy nightshade
berries connect in a racemose fashion (similar to grapes). The calyx of black nightshade
is mid-size and the lobes extend outward, while the calyx of hairy nightshade is large and
encloses half the berry.
Nightshade emergence is from June through September and is strongly influenced by
moisture. Rain events cause multiple flushes of nightshade and late flushes may occur
after normal crop spraying is complete. H. nightshade emerging in early fall can produce
viable seed before frost while E. B. nightshade requires a longer growing season.
Nightshade can compete in most crops even after crops form a shaded canopy. Consequently,
growth of nightshade can accelerate after small grain harvest, which exposes nightshade to
sunlight. Nightshade seeds become viable shortly after berry formation and seeds can
remain viable in the soil for 30 years when deeply buried. NDSU studies show that one
nightshade plant can produce 178,000 seeds under competitive situations or 800,000 in the
absence of competition. Therefore, successful nightshade management requires little or
no seed production.
Nightshade plants remain green through frost and can cause harvest problems. Berries are
poisonous and the juice from ruptured berries can stain crop seed, and glue nightshade
seed and dirt to harvested seed. In addition, dry nightshade berries are similar in size
to soybean or field pea seed and are difficult to separate. Nightshade can be spread to
other fields if contaminated seed is used for planting, therefore avoid planting crop seed
contaminated with nightshade seed.
Nightshades are tolerant to many classes of herbicide including SUs. Eastern black nightshade resistance to imidazolinone herbicides has been documented in the Red River Valley of North Dakota. Black nightshade is more tolerant to some herbicides (Matrix) than eastern black nightshade. Thus, herbicides may remove competing broadleaf weeds allowing nightshades to proliferate. Only a few herbicides with residual effect e.g. Authority, Balance, Pursuit, and Python can help control continuous nightshade emergence flushes. Other options for nightshade management include: planting of uncontaminated seed, using crop rotations, multiple herbicide applications to control late flushes, and inter-row cultivation
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