Optimise timing and performance of residual propyzamide in rape and beans
With autumn 2008 proving to be a challenge for arable farming, and weed control in particular, Interfarm UK are advising growers how to get the best from the residual-acting herbicide propyzamide, whilst ensuring it is handled with care when it comes to water issues.
"Achieving good weed control under current conditions is not easy, but with the propyzamide herbicides, Flomide and Engage, growers do have a degree of flexibility. Optimum weed control with Flomide or Engage requires cold and moist soils, so that the propyzamide can penetrate and persist in the top 2 cms of the soil surface layer to the weed root zone. Soil temperatures of 8ºC or less are optimum for performance and we have only just reached this level in most parts of the UK. It has been too warm until recently. Propyzamide does work at lower temperatures, but it takes longer for symptoms to be seen. Contrary to common opinion, frosts are not necessary for propyzamide to work, but as degradation of the herbicide in soil is temperature-related, lower cooler temperatures mean longer residual persistence. It can be applied in frosts as it has no contact activity," says Dr. David Stormonth, Technical Manager for Interfarm UK Ltd.
"Good levels of soil moisture are also needed to help the herbicide penetrate the top layer of the soil profile and to help weed roots take up the herbicide. Propyzamide binds strongly to soils and doesn’t leach and rainfall after application will aid soil penetration. It is vital that all precautions are taken to avoid any risk of surface water run-off," advises Dr. Stormonth.
"In winter oilseed rape, crop size is not particularly significant as long as the crop roots are below the herbicide layer. The crop size guide of 3 true-leaves is used on the label as an indicator of this. As long as the crop’s root system is below 3 cms, then crop selectivity will be good. This means that the many backward or mixed growth stage crops we are seeing this year can be treated within the next few months. If however it is too difficult to get on the land and conditions are not favourable, then it may be wise to wait to apply Flomide or Engage. You have up until the end of January to apply propyzamide in rape."
David points out that growers may want to consider combining Flomide or Engage with a contact-acting graminicide. "The combination of propyzamide and a fop/dim type graminicide often results in surprisingly good control, even if the black-grass is known to exhibit fop/dim resistance. This mix will need careful timing with regard to weed size but it will enhance grass-weed control. A suitable fungicide can be added to this mixture, optimising spray application costs."
In winter beans application timing is pre-emergence. "With less than half of winter beans drilled to date and the majority yet to emerge, there will be plenty of opportunity to apply propyzamide in the next few weeks," advises David.
Propyzamide is available from Interfarm as Engage (50% WP) and Flomide (400g/L SC) Both are 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. Engage is recommended at 1.4 kg or 1.7 kg/ha and Flomide at 1.7 l/ha or 2.1 l/ha.
For further comment and information, please contact Dr. David Stormonth, Technical Manager, Interfarm UK Ltd. on 01354 741414 or 07818 036506 (mobile) or via e-mail david.stormonth@interfarm.co.uk
