Weeds in our Area (Part One Hundred and Thirteen)
By Bob and Ena McIntyre – Garden Route
BIOLOGICAL CONTROL CONTINUED
Cereus jamacara
In this and the next issue we look at two plants in the Cactus family (Cactaceae). The one is a true
succulent and the other is considered a climber. The true succulent Cereus jamacara (Queen of the
Night) is this week’s subject for which two bio-control agents have been released with some
success.
Cereus jamacara (Queen of the Night) was introduced into South Africa as an ornamental and
barrier plant. It has become a significant alien invader in Mpumalanga, and there are a few of these
“ornamentals” still to be seen in gardens in our area. Good reason for eliminating these prickly
invaders before they become established outside of our garden walls. It is a category one invasive
alien weed. In spring it produces large pretty white flowers that open mainly at night, closing again
in the morning. Birds and monkeys drop seeds in the shaded areas under trees where they feed.
Such shaded areas are ideal for successful germination of the seed and the growth of the plants.
Impacts: Once established under and amongst trees the
Queen of the night rapidly replaces indigenous vegetation
and prevent wildlife from finding food and shelter.
Identification: Queen of the night is a spiny tree with thick
succulent branches growing from a short woody trunk. It
closely resembles the indigenous Euphorbia ingens
(naboom) but its spines are in groups of 5-10 and the cut
stems do not have milky latex. The branches are green to
blue-green with 4 to 9 but mostly 6 prominent ribs. The plant
does not produce leaves. White flowers appear between
November and January. The fruits are yellowish-pink, pink or
red succulent berries ±60mm long with small black seeds.
Control: Two bio-control agents and the stem borer Alcidion cereicola and the sap sucker
Hypogeococcus festerianus were released. The stem borer has had considerable impact and the
sap sucker more moderate success. A herbicide MSMA is registered for this plant. Small plants can
be sprayed and larger specimens must be injected with the herbicide. Manual removal and
particularly disposal must be done with great care as chopped or broken branches can easily take
root. All parts of the plant must be destroyed either by deep burial or by burning. Please refrain
from carting away and simply discarding “over the side” as this is one of the most effective ways of
distributing this pest.
Substitute: As a barrier plant Aloe arborescens (kransaalwyn) is an excellent low maintenance
choice. If you are looking for a form/feature garden plant, Euphorbia ingens (naboom) will do the
trick.
Next issue another Cactaceae and an even greater threat to our area: Pereskia aculeata.
References: Alien Weeds and Invasive Plants by Lesley Henderson, Copyright © 2001 Agricultural
Research Council. Problem Plants of South Africa by Clive Bromilow 2001.
http://www.wikipedia.org and http://www.arc.agric.za.