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Harrisia Cactus

Harrisia cactus plant

Harrisia flower & fruit

   




family

Cactaceae

status

Harrisia cactus (Eriocereus species) are declared noxious throughout all LCA’s within the Southern Tablelands and South Coast region in class 4. It cannot be propagated or sold anywhere in the state. Harrisia cactus was originally introduced as a garden plant.

Description

Spiny rope-like, night-flowering perennial cacti. Forms large tangled mats on the ground 30 to 60 cm high. Stems are bright green, fleshy, jointed at 30 to 45 cm and 2.5 to 4 cm in diameter. They are ribbed length wise, each rib with 6 low, pyramidal humps, 5 to 7.5 cm apart. Each is crowned with rounded areoles of grey felted hairs, giving rise to 1 to 3 sharp spines to 35 mm long. The fruit are red, subglobular, 4 to 5 cm diameter. When ripe, fruit reveal 400 to 1000 small black seed embedded in white pulp.

Plants can form dense matted thickets. They are impenetrable to stock and can cover most of the ground in an area. Seeds remain viable for 4 to 5 years. To date this weed is a problem in the southern and central Queensland area, with occasional outbreaks in northern NSW.


Control

Constant cultivation can remove infestations. Biological control by a mealybug may reduce infestations but does not entirely prevent seed production in Queensland. Control agents do not persist when the infestation becomes sparse, and results from biocontrol agents have been disappointing in the cooler climate of NSW. Cactoblastis and cochineal insect, which provide control of prickly pear (Opuntia species) are not effective on Harrisia cactus.  There are herbicides registered for use on this plant.