One of the world’s worst weeds (Holm) Blackberry nightshade (Solanum americanum & S.nigrum) is a weed of 37 crops in 61 countries. Alternate host for diseases including anthracnose, Cercospora, blight, leaf spot and powdery mildew, at least 13 nematodes, 3 bacterial diseases, 7 fungal diseases including Rhizoctonia and over 30 crop viruses.
Description: Blackberry nightshade is a cosmopolitan weed from the Americas. It is an upright or spreading annual herb to 1.3m with green to purplish leaves egg shape to rhomboid, stems angled or winged (S.nigrum rounded stems). Clusters of white star shaped flowers (similar to potato flowers) producing glossy round green to black berries (fruit). It is claimed that each plant can produce up to 178,000 seeds!
Where found: Grows in disturbed open areas and dispersed by birds, animals and through garden waste.
Considered edible in Africa and other countries. May contain toxic alkaloids and toxic levels of nitrates. Most cases of suspected poisoning are due to consumption of leaves or unripe fruit. Of the species which occur in Australia S. americanum, S. scabrum and S. villosum are all considered to be edible.
Control by: Mulching reduces germination. Hand removal before seed set. Chemical -2,4-D amine(500g/L) 20 mL in 10 L water or Starane® or 20 mL in 10 L water, applied when the weed is actively growing in summer with reasonably selective control.
A handy key to distinguish between the species can be viewed here
Inspections in Fraser Island townships continue every May and November, with great work occurring with the volunteer groups and residents. There are still plants being brought over from the mainland, seen without any known quarantine. Please think before bringing plants to the island to reduce the potential for spreading disease and pests. For further information, go to: www.frasercoast.qld.gov.au
Article submitted by Juliet Musgrave, Fraser Coast Regional Council