Crop Protection Online > Pests - Weed biology<br> <sub>Agro-region: Denmark</sub> - Sonchus spp.
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5.11 2024 undefined

Weed biology
Agro-region: Denmark

Sonchus spp. Previous page Next page

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Can be mistaken for

Taraxacum officinale, which has smooth true leaves.

Characteristics

Cotyledons
Broad egg-shaped with entire leaf margins. Stalked. Smooth surface. Length approx. 5-6 mm.

True leaves
Circular to inverted egg-shaped outline with more or less deeply incised leaf margins. Stalked. Sparsely hairy surface. The leaves contain latex, which can be seen by squeezing a torn-off leaf. Length approx. 9-12 mm. The first true leaves of plants that are germinated from budding roots of Perennial Sow-Thistle resemble the true leaves of young seedlings.

Mature plant
Sow-Thistle comprises 3 different weed species: Perennial sow-Thistle, Prickly Sow-thistle and Smooth Sow-thistle. The three species, which are very similar, have 50-80 cm long, erect stems. The species are usually full of latex. The leaf margins are serrate to spiny. Plants from the three species break easily on touch, which have given them the popular Danish name “brittle Thistle”. The diameter of the flower head is approx. 20-50 mm. Seed production: Perennial sow-Thistle up to approx. 200 seeds per plant.

Seed
Perennial sow-Thistle: compressed staff- to oblong almond-shaped and slightly pointed at both ends. Oval cross section. On each side of the surface are 3-5 longitudinal ribs, which are jagged across. Thousand grain weight approx. 0.5 g.Smooth sow-Thistle: shape and cross section like Smooth Sow-thistle. On each side of the surface are 3 longitudinal ribs, of which the lateral ribs often are divided into two, and 2 marginal ribs. The ribs have small, roundish Peaks. Thousand grain weight approx. 0.3 g.Prickly sow-Thistle: compressed almond-shaped with sharp side edges. Slender oval cross section. The smooth sides of the surface have 3 smooth longitudinal ribs. Thousand grain weight approx. 0.3 g.

Biology

Propagation and dispersal
Prickly sow-Thistle and Smooth Sow-thistle: only through seeds. Perennial sow-Thistle: through seeds and budding roots.

Habit
Perennial Sow-Thistle is perennial. Prickly sow-Thistle and Smooth Sow-thistle are both summer annuals.

Importance

The perennial species, Perennial Sow-Thistle, is frequently found in perennial crops throughout Denmark and in reduced-tillage fields. The other two sow-Thistle species are very common in spring-sown crops throughout Denmark. In all crops sow-Thistle can both be troublesome and cause heavy losses even at small densities.

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Taxonomy

Compositae.

Names in different languages

Danish : Svinemælk
German : Gänsedistel
English : Sow-thistle
Latin : Sonchus spp.
Norwegian : Åkerdylle
Swedish : Molke
Sonchus spp.: Seedling
Seedling
Sonchus spp.: Early stage
Early stage
Sonchus spp.: Vegetatively reproduced <br><i>(Sonchus arvensis)</i>
Vegetatively reproduced
(Sonchus arvensis)
Sonchus spp.: Flower
Flower
Sonchus spp.: Mature plant <br><i>(Sonchus asper)</i>
Mature plant
(Sonchus asper)
Sonchus spp.: Seeds
Seeds
 
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