Pests & Weeds
Ants appear from time to time, summer and winter, before and after rain, and early and late in the day. Ants nest in the ground and many nests are interconnected. Ants are part of the ecosystem in Port Augusta. Surface movement of ants is a naturally occurring activity and varies throughout the year as they relocate or search for food. In the main ants are considered a nuisance pest rather than a health problem. Council only arranges short term treatment of surface infestations of ants on footpaths surrounding school boundaries, playgrounds and other high use public facilities as determined by the Parks /Works Supervisors.
Caltrop (Tribulus terrestris) is a declared pest plant in South Australia and stopping the spread of caltrop is the best method of control. As a pest weed it successfully germinates following summer rains and within only a few weeks develops small yellow flowers that form sharp-spiny burrs that are a cause for discomfort.
To prevent the spread of caltrop please be mindful and avoid moving through infested areas since the burrs ‘seed capsules’ each which may contain 100 seeds are dispersed by easily attaching to shoes, clothing, pets, tyres of vehicles and also the movement of soil. One caltrop plant can reportedly produce up to 4000 seeds, with each seed able to remain dormant in the soil for at least five years which makes it difficult to control across the urban landscape.
Around the home caltrop can be found growing on areas of bare ground where there is little competition from other plants, so mulching or maintaining dense turf or native vegetation cover are useful gardening techniques. Hand weeding is the recommended control method to remove caltrop, by chipping or grubbing each plant to remove the tap root followed by disposal in the general (red) waste bin. Chemical treatment requires careful timing of application to ensure the plant has been sprayed before seed has set. Freezing or burying mature burrs ‘seed heads’ below a depth of 50cm have been found to destroy seed viability.
Opuntioid cacti are a group of plants that belong to the sub-family Opuntioideae within the family Cactaceae. Originally from the Americas, some species were introduced into Australia to support cochineal dye production, while others were planted as garden ornamentals or hedges. One of the most well-known opuntioid cacti is Opuntia stricta (common prickly pear).
Opuntioid cacti are spread from the movement of seeds, fruit and cladodes via birds, animals, water, vehicles, equipment and people. Good hygiene is essential when working in infested areas, including staying on tracks. All cladodes and fruits should be removed from an area during control activities as they are capable of regrowing, even under very harsh conditions. The most efficient and effective weed control strategy is prevention.
Four herbicides are registered for the control of opuntioid cacti. These are MSMA, triclopyr, picloram + triclopyr, and amitrole, under various trade names. The Australian Pesticides and Veterinary Medicines Authority (APVMA) regulates the use of chemicals in Australia. In some instances off-label permits are issued by the APVMA, to allow for uses that are not specified on the label. For more details on herbicide registration and permits visit the APVMA website.