On your marks, get set… go with Kerb or ASTROKerb

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After the 1st of October, theoretically you can start applications of propyzamide (such as Kerb Flo and ASTROKerb) in oilseed rape according to their labels, but practically this active ingredient with residual activity should only be applied when conditions are correct to optimize its performance. For that you need to wait until the soil temperature has gone below 10ºC and is still falling and soil moisture is sufficient. Soil temperatures are around 12-14 ºC at the moment so we have a few weeks to wait. Past experience and under normal circumstances, conditions are usually suitable from around Bonfire night, 5thNovember onwards.

Available from mid-October, Corteva Agriscience, the Agriculture Division of DowDuPont, will go live with its weather data decision support system to help optimize application timings for ASTROKerb (propyzamide and aminopyralid) and Kerb Flo 500 (propyzamide). With data available to a postcode level, the support system consists of a traffic light to aid decision making; it is available 24/7 on the Dow AgroSciences main web site (http://uk.dowagro.com/oilseed-rape-to-spray-or-not-to-spray/) and also on the Farming On-Line web site.

The system is based on the concept of traffic lights. Iuliia Kovalova of Corteva says that this system includes emoji’s to indicate wind and rainfall so producing even more accurate results and helping growers and advisors plan their spraying workload more effectively and for the first time it will feature a new national soil temperature summary.“We want the system to be more accurate and more user friendly for growers and advisors.” she says.

Iuliia explains that the tool is a guide to growers and advisors to help them identify when conditions are suitable for applying propyzamide in their locality. Growers and advisors enter their postcode and the system indicates the current status of criteria that influence the decision to make propyzamide application in their postcode area; if the traffic light shows red, soil conditions in the postcode area are unsuitable, so don’t apply these herbicides; otherwise propyzamide will breakdown too quickly and black-grass control will be compromised. The half-life of propyzamide at 10ºC is around 100 days whereas at 15ºC the half-life falls to 60 days. Hence the need for cooler soils.

“If amber, conditions are getting more optimal, so you should get ready to apply and if green, conditions are broadly suitable, so check your individual fields. The system is not a definitive GO/DON’T GO but a strong indicator for growers to look carefully at conditions for any particular field or farm.  The system is simple to interpret, but there is a lot of technical work behind it,” says Iuliia.

“Optimising ASTROKerb and Kerb’s performance, three areas need to be considered – soil temperature, soil moisture and weed seed depth. Soil temperatures must be cooling – around 10ºC and falling. At cooler temperatures the herbicide lasts longer in the weed germination zone and so its activity is greater and longer. “

“Soil moisture distributes residual herbicides evenly in the top few centimetres, or weed germination zone of the soil. Soils must not be waterlogged or saturated, however. Care must be taken to avoid any risk of contamination to water and importantly, all aspects of good water stewardship must be adhered to. Maintaining stewardship of residual herbicides in rape is important to ensure the long term availability of these herbicides and every manufacturer; agronomist and grower need to take on their own responsibilities.”

ASTROKerb and Kerb Flo 500 require the same conditions for application and have the same wide application window of four months, starting from the 1stof October through to the end of January.  “Don’t forget that the crop needs to have three leaves. ASTROKerb delivers the same weed spectrum as Kerb Flo 500, with the addition of mayweed species and common poppy. We would expect activity on sow thistle and groundsel too. ASTROKerb has caught the imagination of many growers with black-grass control and the appeal of post-emergence broadleaved weed activity,”

“The usual weather data reports for advisors and growers will also be on the web site or sent out directly. These reports carry information on getting the best from propyzamide-containing herbicides plus national graphs of soil temperatures and moisture deficits over time in several locations. “Weeds particularly grassweeds such as black-grass and rye-grass need to pick up a lethal dose of propyzamide. Both these weeds are difficult to control in cereals and many growers are using rape as a true break crop now where weed seed populations can be reduced. If Kerb and ASTROKerb are given the best conditions to work, they can produce levels of control of over 90%, almost unprecedented in the cereal crop nowadays,” she says.

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