Kerb Weather Data – Final Report – week ending 30 November 2018

Welcome to the final edition for this autumn, providing timing guidance for propyzamide applications to oilseed rape.

Soil temperatures (at 30cm) have cooled and applications are now being made. With falling temperatures and conditions still good to travel at the moment we are entering an ideal period of time for applications to be made.  Consider applications when conditions allow. When applying propyzamide it is important to consider water stewardship, and that when applications are made users are taking all precautions to avoid water contamination. Both Kerb Flo 500 and ASTROKerb can be used until 31st January.

It is important to wait until soil temperatures have cooled to less than 10°C as this optimises the blackgrass control activity from your propyzamide application. Cooler soil temperatures slow propyzamide breakdown and ensures blackgrass roots are exposed to propyzamide for longer periods of time, thus optimizing control.

Use the maps and links below to find the data for soil temperatures and moisture-deficits in your region.  Please note at 30 cm soil temperature reading is less variable than the more commonly used 10 cm reading.

Kerb Weather Map week ending 30 November 2018

Whilst conditions in most regions across the UK appear to be green i.e. ready for application of Kerb® (or ASTROKerb®), please check your local status using the postcode checker for a more accurate reading.

For optimal blackgrass control Corteva Agriscience recommend Kerb Flo 500 and ASTROKerb applications are made when soil temperatures are 10°C and falling, and there is sufficient soil moisture in the soil for grassweed uptake. Both these criteria are usually met from the first week in November.

Check out application conditions for your local postcode



Click on the link to the left to use the postcode checker.

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Please ensure good practice when using Kerb Flo 500 or ASTROKerb to avoid restrictions on these products


Will large crop canopies interfere with blackgrass control?

Trials have shown that even where canopies are dense, excellent blackgrass control can be achieved once optimum soil conditions are met.

As ASTROKerb will mainly be used for blackgrass, this should drive application timing. ASTROKerb has both contact and root activity on poppies and mayweeds and in our extensive trials programme, when optimally timed for blackgrass control even where canopies were large, control of these broad-leaved weeds has been good. Where broad-leaved weeds are the sole driver an earlier application could be considered before broad-leaved weeds become too large.

Can I apply Kerb Flo 500 in a frost?

Kerb Flo 500 may be applied in frosty conditions but avoid application onto frozen ground where subsequent rainfall could result in run-off into watercourses.

For ASTROKerb please ensure frost is off the target broad-leaved weed.

Do I need a dry-leaf for application?

The propyzamide active in Kerb Flo 500 is soil-acting so spraying wet weeds at run-off or light rainfall after application is not an issue. Ideally, the rainfastness of ASTROKerb is 1 hour for the aminopyralid element. Spraying on a drying leaf is OK but if rainfall falls within 1 hour and causes run-off efficacy may be reduced. All applications should be made with due regard to water stewardship, i.e. do not spray where there is a risk of run-off to adjacent watercourses.

Should I be worried spraying small, backward rape?

Crop selectivity for propyzamide is by depth protection of the roots.  Applications to very small oilseed rape plants can cause problems such as stunted growth with leaves fused to the axil or stem and yield depression. Once a crop has reached the three true leaf stage the roots are at sufficient depth to not take up a dose of propyzamide that could cause problems. Some judgement may be needed in backward crops as to the risk on any smaller plants and on shallow rooted areas. Applications of Kerb Flo 500 and ASTROKerb may be made to 31st January.

 What can I add to the Kerb programme to improve blackgrass control?

With high populations of blackgrass the use of programmes to give control is increasingly vital. Adding a “fop or dim” with good blackgrass activity as a sequence or tank-mix in the programme nearly always improves control and is frequently better than carbetamide/propyzamide programmes.

Download Topic Sheet 16 “Advice for Blackgrass Control in Oilseed Rape” for further advice.