Case study: Weeds Management.
Rosa Glen Road, ROSA GLEN
STATE NRM CAPABILITIES
FARMING – GRAZING OF Alpacas AND SHEEP
David & Jennie Young
The rolling hills of Rosa Glen is home to David & Jennie Young. Their 253 acre farm, purchased over 20 years ago, provides ample pasture for grazing Alpacas & Dorper sheep. The property features stands of remnant bush with a tributary of the Chapman Brook running through it.
With the purchase of their pretty property, the Young’s also unfortunately inherited severe infestations of both Arum Lily & of Blackberry along a substantial parts of their creekline. Less severe but still problematic was pasture weed Guildford Grass. Each weed required a different approach and in addition to the control methods described below, required copious amounts persistence, constant observation and a hands on effort to make a lasting difference.
The Weed: Arum Lily
Arum lily (Zantedeschia aethiopica) is native to South Africa and was introduced to Australia as an ornamental garden plant. It is the worst environmental weed in the Capes region. It occurs in both pasture and bushland, particularly in damp areas but also invading drier sites. Arum lily is spread by birds and invades areas of good quality native vegetation. Often forming dense monocultures it out competes native species reducing biodiversity and decreasing habitat and food resources for native animals.
Arum lily is poisonous to most stock, pets and humans. Symptoms can include swelling of the tongue and throat, stomach pain, vomiting and severe diarrhoea. Ingestion of the plant may be fatal.
Arum lily is listed as a Declared Plant under the Biosecurity and Agriculture Management Act 2007. Under the Act landholders are required to manage arum lily to reduce the size of infestations and prevent the spread of the weed. (Source: A Guide to Arum Lily Control - Nature Conservation)
Scale of Infestation:
The Arum Lily thickly infested around a 150m length of both sides of the creekline.
The Method of Control:
As the size of the infestation was too large for any physical control methods, chemical control was really the only method to use with a chance of success. A ‘heavy hit’ spay with metsulfuron was applied when the plants were actively growing between July and October of 2008.
Note: The optimum time to spray is when at least 50-70% of flowers are present but spraying is effective as long as applied before the flowers start to wither. Rhizomatous tubers that begin actively growing later in the season will be missed if spraying occurs early in the season. In winter wet areas, spray before the water levels have risen or after they have fallen. (Source: A Guide to Arum Lily Control - Nature Conservation)
The chemical control was extremely effective, eradicating over 90% of the Arum Lilly, however, as the small rhizomes attached to the main arum lily tuber were not all killed by the herbicide application that killed the parent plant, a follow up spray was required. Plants growing from the surviving daughter rhizomes were visible two years after the initial spraying so a follow up spray took place in 2010. Since that time there has been a small level of re-emergence which was dealt with in 2017 via spot spraying with Metsulfuron & follow up sprays in early 2018. Overall the problem is now well under control, although the likelihood of reinfestation from surrounding areas also necessitates an on-going program of monitoring & control.
The Weed: Blackberry (Rubus fruticosus aggregate)
Blackberry is a perennial, semi-deciduous shrub with prickly stems (canes) that take root where they touch the ground, often forming thickets up to several metres high. It varies from sprawling to almost erect. The stems, which grow up to 7 m long, may be green, purplish or red, and are generally thorny and moderately hairy. Young canes emerge from buds on the woody root crown each spring and grow very rapidly (50–80 mm a day).
Blackberry will persist indefinitely in an area unless it is treated. Plants that die are replaced by seedlings or daughter plants produced by nearby individuals. Plants may produce up to 13,000 seeds per square metre.
Source: Blackberry Weed Management Guide - CRC for Australian Weed Management and the Commonwealth Department of the Environment and Heritage
Scale of Infestation:
Blackberry had overtaken 5 acres of David & Jennie’s property & creekline. When David first tackled the blackberry in 2000 some stands were well over his head, requiring him to chainsaw pathways through the blackberry to enable access.
Method of Control:
As the problem was so extensive and difficult to get at (for any sort of mechanical control) chemical control was the only real solution. David himself undertook spraying along the most seriously infested of the creekline in 2000 again using metsulphuron. In early 2018 a contractor was engaged to undertake a control spray with metsulphuron in a smaller remaining infested section (area pictured).
Note: High-volume spraying is recommended for spot spraying, particularly in dense infestations or large blackberry thickets. If using this method, spray the inside of bushes first, ensuring good coverage of stems and leaves. Then spray outside leaves, runners and tips. Take particular care with this method because it is very easy to overdose and affect off-target species or contaminate waterways. If using herbicides taken up by the leaves, avoid slashing in the season before application; it can reduce the effectiveness since only the new canes will be available to take up the herbicide. Source: Blackberry Weed Management Guide - CRC for Australian Weed Management and the Commonwealth Department of the Environment and Heritage
A 80% to 90% kill rate was achieved however as well established blackberry thickets have a large number of root crowns of different ages, and the older and bigger ones are usually hard to kill. This has meant that annual spot spraying has been required to keep it under control.
“Missing a year will set you back significantly”, says David, so ongoing monitoring is essential, “set aside a day each year & do it”.
The Weed: Guildford Grass (Romulea rosea)
Originating from South Africa, Guildford Grass, (also known as Onion Grass) is a perennial herb that looks like a grass, grows like an annual, and can spread rapidly on farm land. The plant not only produces abundant seed, but also corms underground to survive the hot and dry summers in Mediterranean environments of temperate Australia. Not to be confused with Onion weed or Nut Grass (rarely seen in pasture, mainly undervine).
Scale of Infestation:
Whilst nothing compared to the scale of the declared weeds Arum Lilly & Blackberry, a number of paddocks on David & Jennie’s property were not usable for grazing due to the presence of Guilford Grass. The growth of stock numbers provided the motivation to endeavour to remove the Guildford Grass thus enabling the use of the paddocks.
Method of Control:
David deep ripped his paddocks in June of 2017, leaving the bulbs exposed. He followed this in July with a cover crop of Oats mixed with pasture seed. The Oats were grazed down, then the stock removed allowing the pasture to grow through.
David’s method of control appears to have been very effective with only limited re-emergence of Guildford Grass. By allowing the pasture grass to establish strongly prior to any further grazing has meant the remaining Guildford Grass is struggling to compete. Avoidance of re compaction of the paddocks, maintaining above 70 per cent ground cover of pasture grasses and maximising growth during autumn and winter will assist to prevent Guildford Grass from becoming a problem again.