Pasture Weeds Control Seminar
Watch our Weeds Seminar Video with guest speaker Dr Kerry Harrington.
We were thrilled to have DR Kerry Harrington, a renowned weed science expert from Massey University, present at our Central Districts Field Days seminar. Dr Harringtons’s seminar was a deep dive into effective weed management, specifically focused on tackling the common weeds that impact New Zealand’s pastures and farming operations. With over 2,000 weed species in the country, knowing how to properly manage them is crucial for maintaining healthy pastures and crops.
Dr Harrington covered a range of topics, including how to identify problematic weeds, the best control methods for different species, and the science behind effective herbicide use. He also discussed the latest research and practical strategies for managing weeds in a sustainable and cost-effective way, helping farmers reduce their impact on the environment while improving productivity.
To make sure this valuable information is accessible to everyone, we filmed the entire seminar. The video is now available for you to watch at your convenience. Whether you’re a farmer looking for solutions to persistent weed problems or just interested in learning more about effective weed management, this video is an excellent resource to help you make informed decisions about controlling weeds on your property.
Don’t miss out on Dr Harringtons expert insights—watch the full seminar video now and take away practical tips to improve your weed management approach.
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Speaker Profile
Dr Kerry Harrington completed a Bachelor of Agricultural Science degree with honours between 1977 and 1980, studying the leaching of hexazinone on hillsides for his honours project. Dr Harrington’s Masters of Agricultural Science degree investigated control of Californian thistle with glyphosate, and his PhD looked at phenoxy resistance in nodding thistle. He joined the teaching staff at Massey University in 1983 and has been lecturing and undertaking research in weed science since Dr Harrington went into semi-retirement at the end of 2023.
The research that Dr Harrington has undertaken has varied widely, usually in collaboration with colleagues or postgraduate students. Herbicide resistance has been a common theme, including resistance to triazines by black nightshade and to glyphosate by ryegrasses in vineyards. Pasture weed control has often been investigated, including recent work with spot-spraying, weed-wipers on Californian thistle, goats for herbaceous weed control and organic dairy pastures. The control of specific environmental weeds has included investigations of pypgrass, Madeira vine, great bindweed, broom and old man’s beard.
Dr Harrington has also been involved with development of herbicide control recommendations for novel crops such as stevia, a species that may one day replace sugar as a sweetener, for growing manuka for honey and in pastures based on plantain. Dr Harrington now offers a short course at Massey University each year for people who work with herbicides.
Pasture Weed Control – Supplementary Notes
Dr Kerry Harrington
Adjunct Associate Professor of Weed Science
[email protected]
Effects of Pasture Weeds:
Research has shown that weeds such as Californian thistle, Scotch thistle and rushes reduce animal production from pastures, mainly through reducing utilisation of the pastures, ie animals are discouraged from eating pasture near the weeds.
However, clover content of pasture is also incredibly important, and knocking back clover content by spraying a herbicide like MCPA or aminopyralid can affect animal production just as much.
Research Using Weed Wipers:
By wiping effective herbicides like glyphosate to tall growing weeds, excellent control can be obtained with minimal damage to pastures. Must graze pasture down low first to ensure pasture isn’t hit, then wipe the weeds not grazed; narrow-leaved plantain seedheads not affected by glyphosate.
Californian thistle best controlled with wipers after flowering in autumn to get good movement from tops of stems down to root system (but not drought stressed); we obtained 93% decrease in stem density measured in the following season with double pass using 1:20 mix of Glyphosate 360 with water.
Some movement of herbicide down to pasture can occur with later rainfall, but this glyphosate concentration gave clover dominant pasture whereas clovers were badly damaged by clopyralid, triclopyr/picloram or metsulfuron (if it rained later).
Other Comments:
For all other thistle species, the objective is not root control but rather stopping seeds from forming, so weed wiping should be done as soon as they are taller than the pasture and before seed production has started; also avoid them germinating in the first place by keeping pastures dense, especially in autumn; or treat in early winter with MCPB.
Rushes and tussocks definitely need a double pass of wiper as plants on other side of clump get almost no herbicide wiped on them; only glyphosate works.
Docks are harder to kill: need to add metsulfuron to glyphosate and wipe in spring when seedheads starting to form (0.5 g of Metsulfuron 600 product per litre)
Other pasture weed control recommendations can be found on my website: https://www.massey.ac.nz/weeds
Why Bother Weedwiping Thistles in Autumn?
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