Weeds & Pests

Noxious weeds and pests are those which are considered to be harmful to agricultural or horticultural crops, natural habitats or ecosystems, or humans or livestock, especially one which may be the subject of regulations governing attempts to control it. The following weeds and pests have been designated as noxious in the state of South Dakota.

Canada thistle

Cirsium arvense

Other Names: Creeping thistle, Californian thistle, field thistle
Growth Form:
Forb
Life Span: Perennial
Flowering Dates: June – August
Reproduction: Rhizomes and seeds
Height: 0.3 – 1.2 m (1 – 3.9 ft.)
Flower: Pink to purple (rarely white) disk florets
Underground: Rhizomes, fleshy, extensive, creeping

Hoary cress

Cardaria draba

Other Names: Whitetop, whiteweed, pepperweed whitetop
Growth Form:
Forb
Life Span: Perennial
Flowering Dates: April – August
Reproduction: Rhizomes and seeds
Height: 0.1 – 0.8 m (0.3 – 2.6 ft, usually 1 – 1.5 ft.)
Flower: White corolla, petals 4; petals spatulate (3 – 5 mm long)
Underground: Rhizomes, creeping, extending horizontally and vertically as much as 3 m

Leafy spurge

Euphorbia esula

Growth Form: Forb
Life Span: Perennial
Flowering Dates: May – September
Reproduction: Seeds and adventitious shoot buds
Height: 0.1 – 0.9 m (0.3 – 2.6 ft, usually 1 – 2 ft.)
Flower: Greenish-yellow (1.5 – 3 mm long), unisexual; pistallate flowers divided into 3 cells
Underground: Roots deep, woody, spreading, brown and numerous pinkish scaly adventitious shoot buds

Purple loosestrife

Lythrum salicaria

Other Names: Purple lythrum, spiked loosestrife, salicaire
Growth Form:
 Forb
Life Span: Perennial
Flowering Dates: July – September
Reproduction: Seeds and rhizomes
Height: 0.4 – 2.5 m (1.3 – 8 ft)
Flower: Rose-purple corolla, cylindrical (4 – 6 mm long, up to 2 cm in diameter), petals 6 (5 – 7); petals crinkled; calyx teeth 6, teeth alternating with the petals, stamens 12
Underground: Taproot and short rhizomes

Perennial sow thistle

Sonchus arvensis

Sonchus arvensis is a species of flowering plant in the daisy family Asteraceae. S. arvensis often occurs in annual crops in the northern parts of Europe and may cause substantial yield losses.

Physical characteristics
Sonchus arvensis produces conspicuous yellow flowers that are visited by various types of insects, especially hoverflies of the genus Eristalis.

Russian knapweed

Centaurea repens

Other Names: Hardheads, Turestan thistle
Growth Form:
Forb
Life Span: Perennial
Flowering Dates: June – September
Reproduction: Rhizomes and seeds
Height: 0.2 – 1 m (0.7 – 3.3 ft)
Flower: Pink to purplish disk florets (1.2 – 1.3 cm long), numerous
Underground: Rhizomes spreading, deep, black, producing adventitious shoots

Saltcedar

Tamarix ramosissima

Other Names: Tamarix, tamarisk
Growth Form:
Shrub or small tree
Life Span: Perennial
Flowering Dates: April – September
Reproduction: Seeds, root sprouts, buried stems
Height: 1 – 6 m (3.3 – 20 ft)
Flower: White to deep pink corolla, petals 5, peals obovate to broadly elliptic (1 – 1.8 mm long)
Underground: Taproot, deep, extensive

Gypsy moth

Lymantria dispar

Reproduction: Egg masses are typically laid on branches and trunks of trees but may be found in any sheltered location. Hatching of gypsy moth eggs coincides with budding of most hardwood trees.

Hosts: Gypsy moth larvae generally prefer oaks, but may feed on several hundred different species of trees and shrubs, both hardwood and conifer.

Weed and pest information from "Weeds of the Great Plains" (book) - Nebraska Department of Agriculture and the SD Dept of Agriculture website.
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