ACCase Restrictions Bring Propyzamide to Centre Stage
The recent restriction imposed by PSD on the use of ACCase inhibitor herbicides means that oilseed rape growers will have to carefully consider their approach to grass-weed control this autumn, says Dr. David Stormonth, Technical Manager for Interfarm UK Ltd.
He explains that ACCase herbicides are contact-acting grass-weed herbicides, also known as the fops and dims. The restriction of using only one application of a specific ACCase grass-weed herbicide in the crop has been brought in to combat the problem of weed resistance, especially in black-grass.
“This restriction highlights the advantages of other grass-weed herbicides in oilseed rape and brings propyzamide to centre stage. Propyzamide is a benzamide group herbicide and is unaffected by these new restrictions. Although used for many years, this soil-acting residual herbicide has never had a problem of weed resistance, due to its complex mode of action. This situation makes propyzamide a useful herbicide to include in any programme, especially when labels of contact-acting graminicides will restrict their use this autumn. Split doses of a graminicides are no longer possible,” advises Dr. Stormonth.
“Propyzamide products, such as Flomide or Propose, are well known products and have a history of successful use. Not only does propyzamide have excellent grass-weed activity but it also controls many broad-leaved weeds found in the crop in the autumn and winter. If rapid control of cereal volunteers or other grass weeds is required, it can be used in mix or sequence with many ACCase products if necessary.”
“To get the best from propyzamide, it should be applied to moist soil in cool conditions from the 1st of October. Cool conditions allow the grower to get the benefit of its persistence. Propyzamide lies in the top 2 cms of the soil profile and susceptible weeds germinating from this layer will be controlled. Crops established from minimum tillage are highly suitable. Ploughing before drilling oilseed rape will reduce the grass-weed burden but this technique can allow some grass-weeds to establish from below the effective herbicide layer, reducing the overall control. In such cases, the addition of a contact graminicide can help to achieve successful control. This would be the single permitted application of an ACCase inhibitor,” explains David.
“The best approach should be decided on a field-by-field basis. A number of questions need to be considered - What are the problem weeds likely to be? What was the cultivation method? When will the grass-weeds be at the optimum stage for effective control to be achieved? Is there a history of ACCase graminicide failure? Is it better to use the single permitted graminicide application to control early cereal volunteers, or to wait until it can be tank-mixed with propyzamide to achieve full grass-weed control later in the autumn? Whatever the answers, it is important to apply propyzamide products such as Flomide or Propose at the best time in the autumn, when conditions are cool, moist and the weather is suitable for spraying,” says Dr. Stormonth.
Propose contains 50% w/w propyzamide as a WP in a 5 kgs packs. Flomide contains 400g/l propyzamide as a flowable in a 5 litres packs. 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. In oilseed rape, Propose is recommended at 1.4 kg or 1.7 kg/ha and Flomide at 1.7 l/ha or 2.1 l/ha from the 1st October up to the 31st January.
