Early and effective removal of black-grass and cereal volunteers is vital to get oilseed rape crops off to a good start and to allow good establishment before the winter. Some contact graminicides, such as tepraloxydim, can be locked up by hard water and so are less available to act on weeds. Freeing up effective herbicides through the addition of a water conditioning agent, such as Assist, will make sure they are able to work to best effect.
Cereal volunteers and black-grass have emerged very early alongside the oilseed rape crop this year and in some instances are already competing with the crop for moisture and nutrients. They need to be removed as early and as effectively as possible, according to Alan East, Technical Manager for Interagro Ltd.
One of the most effective and widely used contact herbicides in rape and other broad-leaved crops is Aramo (tepraloxydim). "But this herbicide and others such as glyphosate can be ’locked up’ by metallic cations such as magnesium and calcium found in hard water. These cations convert pesticides with a negative charge into inactive forms, making them unavailable. Trials work with the water-conditioning agent, Assist, has shown positive results with many "dim" herbicides, including Aramo, as well as with glyphosate. Assist does not enhance the pesticide performance per se but, when added to the spray tank first, acts sacrificially to form irreversible complexes with the cations in the hard water. This means that all of the herbicide is made available for weed control. The practical result is a higher effective dose and better results in areas with hard water," says Alan.
Alan East explains that trials with Aramo and Assist show that by adding Assist to the tank first can add around 8-9% more black-grass control. "A treatment of 1 litre/ha of Aramo gave around 78% control of black-grass, but with Assist, at 0.25% by water volume, it gave black-grass control of around 86%. For black-grass, which has become a real challenge to control in rape and wheat, this level of extra control is particularly significant."
"A large proportion of water from underground water is hard, particularly if derived from chalk or limestone strata. This means that the major arable areas of East Anglia, Southern England and the West and East Midlands are prime areas for hard water. They also happen to be prime areas for grass-weeds, particularly black-grass," points out Alan East.
"Assist also acts as a buffering agent, reducing the pH of water in the spray tank to provide a medium that is better for pesticides that are prone to alkaline hydrolysis. So it is useful in areas where the water has a pH of above 7," says Alan.
A blend of polybasic acids and sequestrants, Assist is recommended at 0.25% dilution of the total spray volume e.g. 250 mls in 100 litres of water per hectare or 500 mls in 200 litres of water per hectare. Half fill the spray tank with clean water and start agitation. Then add in the recommended quantity of Assist and mix well. Add in the recommended quantity of the pesticide and then the remaining water, maintaining agitation throughout. Assist is packed in a 5 litre pack.
For further details please contact Alan East, Technical Manager, Interagro on 01376 552703 or 07775 696268 (mobile).
