Sorghum halepense (weed)

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Sorghum halepense
Author: Tau‘olunga
Source:Wikimedia Commons

Sorghum halepense (L.) Pers. - (Johnsongrass)

Johnsongrass is an important and widespread weed which affects crops like maize, soybean or cotton, mainly in subtropical regions. It forms dense clumps or solid stands. Reported yield losses have exceeded 50% in some areas and crops. It is native to the Mediterranean and has been introduced into North America as a forage crop in the early 1800s (farmer Johnson introduced it into Alabama). The weed is common in agricultural lands and disturbed habitats. It can tolerate a variety of ecological and soil conditions. Each panicle develops hundred of seeds throughout the summer and a single plant produces about 1 kg of seeds per season. Seed dispersal involves wind, water, livestock, contaminated harvests and farm equipment.

The persistent rhizomes remain viable at depths of more than 1 m and seeds can still germinate after several year. This makes control difficult and eradication almost impossible. Combined and repeated applications of mowing, soil cultivation and herbicides are recommended in autumn and spring, followed by rapid re-vegetation. Torching fields of Johnsongrass every 2 weeks throughout the summer using gas burners, has been practised in some areas but is now considered uneconomical.

Vernacular names
• Deutsch: Wilde Mohrenhirse
• English: johnsongrass
• Español: canota
• Français: sorgho d'Alep

The plant can grow more than 2 m high and develops an extensive rhizome system. The leaves are smooth on both sides and have a conspicuous white midrib. The panicles are loose and have a purple colour. The species is self-compatibility and plants growing close together will cross-fertilize.

For details see the respective page in the BugwoodWiki.