A series of farmer and agronomist Focus groups have concluded that Kerb Flo (propyzamide) is considered to be the "default" herbicide for grass-weed control in oilseed rape and that grass-weeds including black-grass continue to be the priority targets.
John Sellars of Dow AgroSciences explained that farmers and advisors in Cambridgeshire, Nottinghamshire, Lincolnshire, Essex and Oxfordshire were asked about growing oilseed rape and their weed control strategies. "Rape is seen as the most profitable break crop and one that will continue to flourish in the future, due to its many marketing outlets and its profitability. But the research confirmed that grass-weeds, particularly black-grass, continued to be a difficult problem to tackle. It also identified that black-grass was getting worse across the rotation and that more attention would be needed in order to manage this problem successfully. Broad-leaved weeds in rape were seen to be more diverse and overall easier to control, although certain species such as charlock, runch, hedge mustard and poppy were still seen as a challenge."
Asked about weed priorities, black-grass, cereal volunteers and charlock were regarded as major problems that are important to control by both advisors and farmers on heavy and light land. In addition the light land farmers also saw poppy, cleavers and thistles as major weeds and on heavy land mayweeds and cranes-bill were additional problems.
Other concerns arising from the research were the withdrawal of herbicides, the lack of active ingredients with different modes of action available across the rotation as well as dose rate restrictions on some residual herbicides. "Both farmers and advisors saw growing oilseed rape as an opportunity to control black-grass with different chemistry. When asked to describe their weed control programme, Kerb was at the centre of both the heavy land and light land farm plans – it was described as the "default" treatment for black-grass," reports John.
As the window of application for Kerb Flo approaches, Dow AgroSciences are offering growers and advisors hints and tips of how to get the best from it.
Herbicide specialist for Dow AgroSciences, Andy Bailey points out that last year Kerb Flo worked really well. "This is because it was applied at the right time under the right conditions. The label for Kerb Flo says that it can be applied from the 1st of October onwards when the winter rape crop has three leaves. Many crops are at or passed this stage, but I would advise growers to hold off until temperature, soil moisture and weed seed depth are optimal. Soil temperatures need to be low - around 10ºC at 30cms and falling. Propyzamide works well at these lower temperatures and, as its degradation in soil is temperature-related, cooler temperatures mean longer persistence throughout the weed germination period. Temperatures are getting lower now and we need to keep a close eye on this."
Andy also advises that good soil moisture is needed to help the herbicide distribute evenly in the top few cms of the soil and that soil moisture deficit should be less than 50mm and falling. "A rule of thumb for soil moisture is 80% field capacity, before drains are flowing ; soils must not be waterlogged or saturated. Care must be taken to avoid any risk of contamination to water and very importantly all aspects of good Stewardship must be applied. With Kerb Flo being seen as such a vital ingredient by both farmers and advisors, we all need to act responsibly to make sure that its future is protected and that no water contamination occurs. With regard to weed seed depth, seed should not come from any deeper than 5cms as the black-grass would then be germinating below the Kerb Flo barrier layer. If application conditions are right, farmers can expect black-grass control in the high 90%’s, a level that very few herbicides in either cereals or rape can achieve, as the survey reveals."
Kerb Flo (400g/L propyzamide formulated as a suspension concentrate and packed in a new 10 litre pack) is recommended in winter oilseed rape, winter beans and a wide range of other crops for the control of cereal volunteers, annual meadow-grass, black-grass, brome, wild-oats, chickweed, bindweed, fat hen, redshank, small nettle speedwells and black nightshade. In oilseed rape Kerb Flo has a wide window of application of four months, from the 1st of October through to the end of January. It is recommended at dose rates of 1.7 l/ha or 2.1 l/ha and is compatible with a range of graminicides, insecticides, and fungicides.
