Keeping pesticides out of raw drinking water supplies is essential to prevent products being restricted or even lost if residues are detected at levels that exceed statutory limits.
As the wetter high-risk winter period nears, we give a timely reminder of the key active ingredients in the spotlight and any stewardship guidelines or information available to help reduce the risk of them showing up in water.
This autumn and winter sees the industry’s last chance to prove it can keep the slug killer metaldehyde out of water before Defra makes a decision on its future in March 2017.
With reports of high slug pressure already this autumn, stewardship guidelines and the catchment-based initiatives could be given a stern test.
With only one alternative in ferric phosphate, it is vital growers get involved and help to safeguard metaldehyde’s future.
Metaldehyde Stewardship Group guidelines are:
- Use the minimum active per hecare to avoid drainage and run-off losses
- Maximum individual application rate: 210g/ha metaldehyde. For additional protection of water, suppliers/Basis advisers may recommend rates reduced to 160g/ha or less
- Maximum total dose from 1 August to 31 December: 210g/ha. For additional protection of water, suppliers/Basis advisers may recommend rates reduced to 160g/ha or less
- Maximum total dose rate: 700g metaldehyde active/ha in a calendar year
- No pellets to be applied within 6m of a watercourse
- Do not apply when heavy rain is forecast
- If drains are flowing, do not apply metaldehyde-based slug pellets
- More information about metaldehyde stewardship can be found on the Metaldehyde Stewardship Group website
Metazachlor and quinmerac
These two key oilseed rape herbicide actives are crucial to early-season weed control, but a recent trend to later post-emergence applications has increased the risk to water.
Metazachlor is contained in straight products such as Butisan S or Sultan 50 SC, while quinmerac is found in co-formulations with metazachlor, such as Katamaran, Elk or Shadow.
As part of the “Metazachlor Matters” stewardship campaign, voluntary guidelines were introduced in 2014 to minimise risk. They are summarised as:
- Maximum dose – 750g/ha metazachlor and 250g/ha quinmerac
- Where there are no drains – no timing restrictions
- Drained fields (including tempory) – aim for 1 October application, cut-off date 15 October
- Applications after 1 October can be made if soil/seed-bed conditions are good and drains not flowing
- Drained fields in Drinking Water Safeguard Zones – cut-off 1 October
By the time you receive this issue of Crops, these voluntary cut-off dates will have passed, so growers are advised to think carefully about soil and seed-bed conditions, along with current and forecast weather before applying metazachlor or quinmerac, even if it may be in accordance with statutory label guidelines.
To apply or not – don’t forget useful smartphone app
Agchem firm Adama’s Water Aware smartphone app provides a useful decision-support tool for use when applying a number of high-risk herbicide actives. It has recently been updated to include metaldehyde pellets.
Using soil type, current and forecast weather and soil moisture deficit data, it can provide an indication of potential pollution risk at the time of spraying or pellet application.
It also includes Environment Agency “What’s in Your Back Yard” (WIYBY) information to indicate if a field location is in a groundwater or surface water safeguard zone.
The app is free to download and is compatible with both IOS and Android operating systems.
Carbetamide and propyzamide
Two more oilseed rape autumn herbicides – carbetamide and propyzamide – are also frequently detected in raw water. Theyare firmly on the regulatory radar and use restrictions are a possibility.
This could have negative implications for blackgrass control in particular and users of these actives can find best practice advice on the Voluntary Initiative website, with water protection advice sheets (WPAS) available for each.
Farmers Weekly is working with Gatekeeper agronomists to highlight key pesticide rule changes and the potential implications, keeping you on the right side of the law and aiding on-farm record keeping.
Sentinel is a decision support tool linked to Gatekeeper crop management software, a programme that helps arable farmers with record-keeping and legislation issues. For more details visit the Farmplan website or call 01594 545 011