Cereus jamacara / Queen of the Night / Nagblom

Dense clump of nagblom                                            Spines occur in clusters of 5-10

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Description: A spiny, tree up to 7 m high with multiple winged, thick, succulent vertical branches arising from a short woody trunk.

NB: Superficially resembles the naboom (Euphorbia ingens), but can easily be distinguished from all indigenous Euphorbia by:

1) its clusters of 5-10 spines (the others are spineless or have a single or a pair of

   spines); and

2) the fact that it does not exude a milky latex when cut.

Its name is due to the attractive white flowers produced in spring/early summer and which open mainly at night and close again at dawn. Like many cacti, it produces an edible, yellow-pinkish red fruit, the seeds of which are spread by monkeys and birds.

          

Origin: Introduced from South America (Brazil) as an ornamental plant and barrier hedge.

Occurrence: It invades rocky ridges and savanna, growing under and among trees. It is particularly prevalent in Mpumalanga and in southern Limpopo and is readily seen along the road from Vaalwater to Melkrivier.

 

Why it is a problem: It replaces indigenous vegetation and prevents animals from accessing food and shade. Chopped or broken branches readily take root and form new plants.

It is a declared Category 1 invader weed and its removal is mandatory. It is particularly important to eradicate this invader while serious infestations are still uncommon.

Elimination / Control Methods: This plant is relatively easy to eliminate, either physically or using herbicides. As with other cacti, it is also very successfully controlled using biological agents, which have the advantage of not creating any herbicidal risks – see below – but which are much slower in achieving the same results.

The plant can be cut down and its extensive root system dug up; however, great care should be taken during removal of the parts of the plant to ensure that none are left behind or along the way. All parts of the plant should be burnt (although it is also possible to bury them deeply).

Herbicides should be applied early in the growing season.

Note that:

-        All herbicides should be used when freshly mixed (do not leave the solution overnight).

-        NB: Follow carefully the instructions provided on herbicide label. Many herbicides can be toxic to other plants and or game and livestock if used inappropriately. (Mis-use of herbicides is also a criminal offence in terms of Act No. 36 of 1947).

The principal herbicide registered for use against the plant, with great success, is MSMA 720 SL (L7279). Dilute 1 litre of MSMA in 2 litres of water and inject the solution into pre-made holes in the stem of the plant at ~2.5m intervals, with only 2 ml per hole. Repeated treatment of up to 8 injections may be necessary.

NB: SANBI has advised that MSMA has recently been withdrawn from use by state departments because in isolated cases, it has been found to be highly toxic to grazing stock and wildlife, as it readily contaminates the grass surrounding the target plants. However, MSMA can be used safely if it is injected into the target plant, not sprayed onto it. It is strongly advised that the area to be treated is enclosed by a simple temporary fence to keep livestock and game out; and that the treated plants, once they have died off, are collected, burned in a pit and covered over with soil, before allowing animals into the area again.

The active herbicide ingredient glyphosate has also been registered for use against this and some other cacti, although it does not deliver results as good as MSMA. Numerous herbicides containing this chemical that have been registered, for example Duiker 180, Roundup Max, Nexus, Cobra, Springbok.

Biologically, some success has been reported from the use of the stem borer Alcidion cereicola, which was released in 1990.

 

References:

ARC-LNR Weeds & Invasive Plants website: www.agis.agric.za/wip

ARC-LNR SAPIA News 25 (July 2012): ARC – Plant Protection Research Institute, Pretoria. www.arc.agric.za

Bromilow, Clive (2010): Problem Plants and Alien Weeds of South Africa. Briza. Pretoria

Henderson, Lesley (2001): Alien Weeds & Invasive Plants. Agricultural Research Council (ARC), Pretoria.

Van Zyl, Kathy, compiler (2005): Control of Unwanted Plants. Xact Information, Pretoria.

Van Zyl, Kathy, compiler (2012): Problem Plant Control Compendium. AVCASA, Midrand

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Special thanks to Dr Gerhard Verdoorn of Griffon Poison Information Centre, to Mr Ferdie Jordaan of Arysta Lifescience and to Ms Lesley Henderson of ARC for their invaluable advice and guidance. Their enthusiastic support for this voluntary project is greatly appreciated.