The growth and spread of the plant must be controlled according to the measures specified in a management plan published by the local control authority and the plant may not be sold, propagated or knowingly distributed
Why Is It Bad?:
Harrisia Cactus was introduced to Australia in the 1890ís as a pot plant by the mining community around Collinsville, Queensland. Recognised as a pest species in 1935, Harrisia has spread south from the original site and now infests large areas of Queensland and New South Wales.
Originally from South America, these species form dense impenetrable thickets. These thickets choke out pastures, restrict human and stock movement, limit access to watering points, and interfere with operations such as mustering. The spines are long and inflict serious injury to stock, causing economic losses for landholders. The sharp spines also make pasture unfavourable to stock, they do not like to move among even small infestations.
Harrisia Cactus is a succulent with jointed branches that form tangled mats, reaching approximately 0.5m in height. Branches are fleshy and have longitudinal ribs with triangular humps at regular intervals. Spines grow to 3cm or more, are very sharp and occur in a group from each areola.
The flowers are mostly white, sometimes tinged with pink, and generally open at night.
Harrisia can begin to produce fruit after just 6 months, and can produce fruit all year round. Fruit is bright red when ripe and covered with spiny protuberances. They are filled with 400-1000 sweet black seeds in white pulp.
Harrisia Cactus also has fibrous surface roots and deep-growing tuberous roots that form an energy reserve.
All parts of the plant must be removed (including all tubers) and destroyed by burning as any portion of tuberous root or branch left in the soil will resprout.
Results are often irregular so follow-up treatment is required. It can take several weeks before effects of herbicide become noticeable.
Slashing & Cutting:
Mealy bug (Hypogeococcus festerianus) attacks the tips and buds of the cactus. The bugs spread via wind and human intervention, but are less effective in dryer, cooler areas. In ideal conditions, Mealy bug infestations take 3 seasons to kill a plant. Another biological agent, the Stem-boring Longicorn beetle (Alcidion cereicola) attacks the stems, but is less effective than the Mealy bug.
Cultivation & Scalping:
Harrisia cannot survive on lands under constant cultivation. However, this method should only be approached on a long term basis as seeds and segments will resprout if competition is not present.
Successful treatment programs rely on ongoing monitoring of sites. Regrowth and new seedlings can easily become larger infestations if follow-up treatments are not part of the management program
Click an image to view a larger version
Image Credit: Ashley Bullock Narromine Shire Council