NovaChem > Industry News > 2021 > Beating the challenge of grassweeds this autumn

Beating the challenge of grassweeds this autumn

Published on 09/05/2021

WORDS: Neil Waddingham, Bayer New Zealand

Populations are clearly increasing New Zealand-wide, making it harder to reach levels of grassweed control sufficient to safeguard yields and reduce the seedbank. For the most effective grassweed control, it is critical to start early, before weeds start to germinate, which for autumn planted crops is any time now. 

Sakura is a pre-emergent herbicide for use on wheat and triticale which targets a wide range of troublesome grassweeds, including all types of ryegrass, hairgrass, annual poa, soft brome and barley grass.

While Sakura is increasingly recognised as an important part of ryegrass control programmes, it’s effectiveness against Vulpia hairgrass and annual poa shouldn’t be overlooked as these weeds are becoming more troublesome.

Applied pre-emergence, Sakura controls grassweeds before they can compete aggressively for space, water and nutrients. Early removal results in healthier, higher yielding crops. 

As grassweed populations increase, the chance of herbicide resistance developing also increases. It is simply a case that the more plants that survive, the more seeds are produced and so the greater the chance that herbicide resistant plants will develop. As a group K grassweed herbicide, Sakura provides a different mode of action against ryegrass thus helping to slow the development of resistant populations.

Getting the best from Sakura

Sakura is favoured in minimum till situations because this retains weed seeds closer to the surface ensuring they germinate more evenly and within the herbicide zone. This results in more consistent control.

When cultivating, remind farmers to create a fine, clod free seedbed to ensure effective herbicide soil contact. Sakura should be applied immediately after drilling to take advantage of all available soil moisture. It is primarily taken up by the roots of germinating weeds, so moisture post application is important to incorporate the product into the root zone. Typically, at least 10-15 mm of rainfall or irrigation is required. 

In some years the amount of rain received may be enough to enable ryegrass seeds to germinate but insufficient to activate the herbicide. If this occurs activation of Sakura will only happen when enough rain is received and by then some ryegrass is likely to have germinated. In these circumstances Sakura will act against germinated ryegrass by reducing root growth.

Getting the better of ryegrass

Ryegrass is a challenging weed to control as it germinates over a long period of time which is being exacerbated by the dry autumns we seem to be currently experiencing. For this reason, the aim should be to implement a herbicide programme using Sakura pre-emergence followed by Othello OD post-emergence in late winter. 

While the value of herbicide programmes for ryegrass control has been understood for many years, Bayer set out to demonstrate this with a trial at Orari, South Canterbury in autumn 2020. 

The paddock had a heavy but even population of ryegrass that equated to 308 heads/m2. Based on paddock observations, the ryegrass at Orari was assumed to be sensitive to different herbicide types but seed samples have been sent for testing. 

One pre-emergence spray of Sakura in autumn at 150 g per ha gave 82 per cent control of ryegrass. This was a very good result which would result in cost-effective yield increases but is insufficient to stop seed return. Adding Othello OD in late winter increased control effectively to100%. 

The clear conclusion from the trial was that for effective season long control of ryegrass it was vital to use Sakura as the corner-stone of an herbicide programme and that applying Othello OD in late winter was very beneficial.

This page is best viewed in an up-to-date web browser with stylesheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so. The latest version of Firefox, Safari, Google Chrome or Internet Explorer will work best if you're after a new browser.