With the calendar date suggesting spring is just around the corner, and sprayers poised to act as soon as field conditions allow, pulse growers are urged to consider partnering pre-em sprays with a residual herbicide adjuvant to get crops off to a strong weed-free start.
Unlike cereals and oilseed rape crops which are considered fairly competitive, pulse crops are highly susceptible to weed competition in the early stages.
With associated yield losses of up to 40% and a very limited herbicide armoury post-emergence – mainly bentazone – achieving the best results possible from pre-em applications is crucial for the strong weed free start that’s needed, explains Stuart Sutherland, technical manager at Interagro.
“Weed control is one of the biggest challenges for pulse growers but so vital to get right to maximise returns. And this spring, the atrocious winter will be adding workload pressures into the mix. However, there are a few vital quick wins growers can achieve simply by incorporating residual herbicide adjuvant Backrow Max, says Stuart.”
“This becomes evident if we consider the objectives for pre-em application.”
Key Points:
- Pulse crops are highly susceptible to weed competition in the early stages.
- Consider combining herbicides with different chemical properties.
- Partner with adjuvant Backrow Max for more effective weed control.
Pre-em herbicide application – objectives and how Backrow Max will help backup your weed control
Minimise spray drift
As well as the risk to off-targets in neighbouring fields, spray drift can reduce the lethal dose of herbicide active on your intended target, compromising herbicide efficacy from the outset.
Aim to minimise drift by using drift reducing nozzles. Inclusion of Backrow Max will optimise the application even further by reducing the number of <100 microns droplets which are the most susceptible to drift.
Maximise coverage across the soil
Good even coverage is crucial to create a robust herbicide barrier to block germinating weeds.
Misses in coverage will allow weeds to find a way through. This can be particularly problematic with faster forward speeds, low water volume spraying, and using drift reducing nozzles – because they create coarser droplets.
Including Backrow Max will help because as well as reducing the number of very small droplets prone to drift, it also reduces the number of very coarse droplets prone to run-off, resulting in a more optimal droplet size for pre-em application and maximising coverage across the soil.
Maximise herbicide retention in the top 5cm – consider implications of heavy rainfall
After an exceptionally wet autumn and winter, saturated soils could be holding on to water for some time, even if they dry out nearer the surface and are ok to travel.
In these conditions, herbicide retention in the top 5cm – the weed germination zone – could be compromised, because herbicide mobility in the soil profile increases with higher moisture levels. Heavy rainfall events after herbicide application to wet soils will have the biggest impact.
Herbicide active ingredients with high mobility and low soil adsorption properties – imazamox and clomazone – will be the most vulnerable.
In the worst case scenario, herbicide may leach to the crop seed, resulting in phyto to emerging pulse seedlings.
Research shows Backrow Max is one, if not, the most effective residual herbicide adjuvant at improving herbicide retention in the weed zone, increasing residual activity. This will be crucial in situations where several flushes of weeds are expected, where herbicide half life is short eg with prosulfocarb-based products, or where weather conditions remain volatile during crop establishment.
Maximise herbicide uptake – consider implications of dry weather
On the lighter soils, it’s not inconceivable to imagine that with a period of prolonged dry weather, seedbeds could suddenly turn drier than is ideal for optimum herbicide efficacy.
Herbicides with low mobility and high adsorption to organic matter will be most susceptible to the effects of low moisture – they need more moisture to be displaced from soil organic matter for uptake to occur. Herbicide actives most at risk will be pendimethalin and aclonifen.
If it’s too dry for weeds to germinate then it’s worth considering postponing the application until rain is forecast unless you are using a herbicide with a longer half-life that will remain active in the soil – such as pendimethalin – that will be ready to work when weeds germinate.
Backrow Max can add as much as 33% efficacy in dry conditions by binding water molecules to soil particles. This has been proven in controlled lysimeter studies in the Netherlands where Backrow Max increased moisture levels by 30%.
In replicated field trials in spring beans, Backrow Max added 33% efficacy to Stallion (prosulfocarb and pendimethalin) against black bindweed, and 19% to black-grass control.
Consider combining herbicides with different chemical properties
Using herbicides with different modes of action is a crucial component of resistance management.
Where possible it would also make sense to partner herbicides together that have different chemical properties.
If one herbicide has high mobility and low-medium adsorption eg clomazone, it would make sense to partner it with a herbicide that has low mobility and high-very high adsorption e.g. pendimethalin.
This is because whilst the clomazone will be most at risk of heavy rainfall, the pendimethalin will be the least at risk. On the flip side, in very dry conditions, the pendimethalin will be more vulnerable and the clomazone less so.
The inclusion of Backrow Max will help optimise spray droplet targeting and overall efficacy. Trials in beans with Nirvana (pendimethalin and imazamox) for example, have shown benefits of 10% against broad-leaf weeds.
More and more growers are maxing their weed control with Backrow Max
Backrow Max – Backup for early weed control in pulses
Backrow Max is a residual herbicide adjuvant approved for use in an extensive list of crops.
You can find out more about it by downloading our latest brochure here.
If you wish to discuss Backrow Max and how it could potentially help you, please get in touch with Stuart below.
Backrow Max is available to purchase through Agrii.