Spot spraying or digging, cutting and poisoning, or bio-control?
The removal of introduced weeds by spot spraying and digging is ongoing at Crookshanks. Weed seeds can last in the soil for many years depending on the plant, the soil, and the weather. It is common sense that digging plants out, if possible, is far preferable to using any chemicals at all on your land. The testing of safety of chemicals on the soil, is likewise, ongoing. We cannot assume that, despite the assurances of chemical companies, that any chemical compound is safe for any plant or the soil biota. Chemicals must therefore be used with the utmost care. By all means, read the label carefully of any chemical you plan to use, cover all exposed skin and be very careful not to breathe in any spray wind drift . In addition, ask everywhere for advice, mainly, professional sprayers, about the different chemical spray usage. Quite often less chemical than recommended can be used. However, do not do this without checking with several experts, as using less chemical can cause plants to develop a resistance, which makes them harder to eradicate. No chemicals should be used close to watercourses, rivers or dams.
While spot spraying is suitable for most plants, digging (or pulling out) is not at all suitable for those with rhizomatous roots, such as St John’s wort. A rhizome, also known as a creeping rootstalk, or horizontal underground plant stem, is capable of producing the shoot and root systems of a new plant. Rhizomes are used to store starches and proteins and enable plants to perennate (survive an annual unfavourable season) underground. Even quite small St John’s wort plants can extend a long way into the ground and when pulling out the plants, even a small rhizome can remain to build another plant the following Spring. In the late nineties, this happened to me several years in a row.
Cutting and painting: The live branches of briar roses and hawthorn trees need to be cut with a brush cutter or light chainsaw before being painted with a mixture of 50/50 Glyphosate and water (and red dye) in native grasslands and in native plantations, to ensure the seeds are not carried further afield by birdlife. Once established, these plants are hard work to manage… it must be done, however, to ensure a weed-clean future for a native grass environment or for a plantation of native trees!
Biocontrol of weeds: In the early 2000s, after a few years of keeping fit spot-spraying on the mountains, now joined by my partner John Boyd, I jumped at the chance to attend the Landcare biocontrol of weeds workshop at Bredbo. There I met ex-Agriculture, ex-CSIRO biocontrol expert Barry Sampson, from WeedBioControl (http://www.weedbiocontrol.com.au).
Our most urgent concern was Vipers’ bugloss, a smaller species with a darker blue flower than Patterson’s Curse. The covering was wall-to-wall across the non-forest areas of Crookshanks but needed the same solution that Barry was advocating for both. This included the Leaf Mining Moth which spread easily, the Crown weevil larvae which left a black mush in the middle of each plant, usually killing it, , along with Root weevil and larvae, and Flea beetles, and Stem borer operatives. I was somewhat sceptical… Would we be wasting our money?
However, thrilled with the outcome some years later, with the disappearance of the weed and the occasional Viper’s bugloss plant being retained to keep the insects on the job, I approached Barry about our St John’s wort problem. Another box of material arrived for us to distribute at the end of autumn 2021. An assessment in April 2022 determined that the mites and Chrysolina beetle were multiplying and that would spread easily on the wind or on the fur of grazing animals. Effective all year round, the mite causes stunting and twisting of leaves and a stem with a dusty coated appearance but can only be positively identified by microscopic inspection. The Chrysolina beetle defoliates the wort.
Having bought an additional Murrumbidgee River block late in 2019 to continue our proposed wildlife corridor from Crookshanks’ Peak to the Murrumbidgee River, John and I inherited lots of blackberry plants along the River and Peak Creek, among many other noxious weeds. I have again asked Barry to supply us with biocontrol material for the blackberries, which, he tells me will be available for distribution after Anzac Day this year (2023). Other weeds that can be controlled using biocontrol include horehound, thistles, prickly pear, bridal creeper, dock, and blue heliotrope, among others.
John and I highly recommend biocontrol of weeds, as it certainly more than halves the physical weeding job of property owners!
Narelle Moody February 2023