We all know that weeds in pastures are undesirable, but a recent study sponsored by the Ministry for Business, Innovation and Employment¹ has reported that we have likely been underestimating their full cost to New Zealand agriculture. 

The study estimated that the total cost for just 10 common pasture weeds was likely to be over $1.3 billion a year in lost production, while Californian thistle alone takes over $700 million per annum 

from farmers. 

Farmers need to get on top of weeds to protect pasture yields, and fortunately they have some good tools at their disposal like Tropotox™ Ultra. Tropotox Ultra is a selective, grass and clover friendly herbicide that controls many broadleaf weeds in pasture, peas, clover and grass seed crops. It has a broad spectrum of activity with strength on thistles, buttercup, and seedling docks.

Tropotox Ultra contains 25 grams a litre MCPA and 375 grams a litre MCPB in a soluble concentrate formulation. It is a member of the phenoxy herbicide group, which were first discovered back in the 1930s, developed and commercialised in New Zealand in the 1980s, and still form the backbone of many of our pasture weed control programmes today.

Phenoxy herbicides mimic the natural plant growth regulator auxin in plants, causing abnormal growth, twisting of stems and cupping of leaves in susceptible species followed by plant death. However, monocots (for example grasses) are largely unaffected by the rates of phenoxy used, but many dicot plants (for instance broadleaves weeds) are highly susceptible. 

Tropotox Ultra is absorbed into foliage of growing plants where it moves to the growing points and interferes with key plant functions. Visible symptoms, such as twisting and curling of foliage, can be seen in a day or two but death of weeds can take several weeks. Clover, and some other legumes, lack the mechanisms that converts the product to the herbicidal active form, and once clover has at least two true trifoliate leaves it is tolerant to Tropotox Ultra.

Best use guides:

• Apply Tropotox Ultra to small, actively growing weeds once clovers have passed two true tri-foliate leaves.
• Do not apply to weeds under stress for example drought, water logging.
• Use the higher rate where weeds are more advanced.
• Avoid spraying where rainfall is expected within two hours of application.

For more information on how to get the best out of your pastures by using Tropotox Ultra, talk to your local PGG Wrightson Technical Field Representative.

Supplied by Agritrade

¹Saunders JT, G. G. (2017). The economic costs of weeds on productive land in New Zealand. International Journal of Agricultural Sustainability.