|Version 2||Date January 2020||Reference 16|
Recent rainfall across much of the western winter cropping areas, has resulted in good soil moisture profiles. As a result effective summer weed control programs will be essential to maintain yield potential into 2015.
Timing of application is critical for effective control and as most summer weed herbicides provide little residual activity, controlling later germinations depends on stopping seed set.
Whether you decide to spray early or late, adjuvant selection is critical to the performance of most active ingredients.
Adjuvants improve herbicide efficacy by reducing evaporation and drift, increasing droplet survival on leaf surfaces and increasing penetration of herbicide active ingredients into the plant.
Which of these is best suited to your needs depends on the active ingredient being used, the weed spectrum and stage, water volume and desired droplet size, spraying conditions and timing of the year, which may require the use of a particular type of adjuvant.
SACOA’s ANTIEVAP® is excellent at improving the efficacy of most summer fallow herbicides such as Triclopyr and/or Glyphosate.
An acidifying surfactant such as COHORT 700® may be of use as a buffering agent if water quality is poor, otherwise provides little benefit in improving droplet survival and penetration.
The final efficacy of a herbicide results from the active ingredient getting from the nozzle into the plant for translocated herbicides or onto the leaf surface for contact herbicides. In most cases herbicides are sprayed out using water as a carrier and an adjuvant to improve this process.
Droplet survival on the leaf surface is an important indicator of herbicide efficacy, and is influenced by three key factors;
|Chart 1: Oil based adjuvants such as ANTIEVAP® have a positive effect on increasing droplet size versus non-ionic surfactants. (Source: USDA 2014).|
Adjuvants have an important role in improving herbicide efficacy by:
Oils and adjuvants can be split into two broad types – penetrants and spreaders.
A 2012 trial conducted by AgSense at Goomalling examined the effect of time of day on herbicide efficacy and the efficacy of ANTIEVAP®, LI700 and ENHANCE® in some commonly used melon control mixtures.
The trial found;
SACOA have been conducting research into the role of oils and adjuvants in improving droplet survival and final herbicide efficacy, under summer spraying conditions for a number of years.
SACOA’s research work will continue over the 2014/15 summer with work in Western Australia & the Victorian Mallee correlating the impact of droplet size on final herbicide efficacy. Data from a recently implemented trial in Western Australia comparing SACOA’s locally developed and manufactured products with imported alternatives will be published over the next few weeks.
|Chart 2: ANTIEVAP® 1.0% and ENHANCE® 0.5% proved superior to LI700 with Triclopyr & Triclopyr + LVE mixtures. (Source: AgSense Western Australia 2012).|
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This document should act as a guide only and no purchase or usage decisions should be made based on the information provided without obtaining independent, expert advice. SACOA and contributors do not necessarily recommend or endorse any products or manufacturers referred to. SACOA Pty Ltd will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information contained in this document. More information is available from SACOA via sacoa.com.au or 08 9386 7666, or by contacting your local reseller.
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