Weather conditions and their impact on propyzamide usage
The residual herbicide propyzamide is a useful product to integrate in the battle against black-grass and rye-grass, but Interfarm UK who market two formulations, Engage and Flomide, are advising growers to check their oilseed rape crops carefully for appropriate soil temperatures and soil moisture requirements in order to gain successful use of these products this autumn.
"Being a residual herbicide, good levels of soil moisture are needed to help propyzamide penetrate the top layer of the soil profile from where grass-weeds germinate. Whilst soil moisture deficits were high earlier in the season, recent rainfall may have alleviated this problem in many areas but advisers are urged to check locally. Rainfall soon after application can significantly aid propyzamide activity by helping it penetrate the soil down to the weed root zone. Propyzamide is slow to move in the soil and rarely penetrates further than 2cms. This is why weeds emerging from depth such as black-grass after deep cultivations can require the addition of a contact graminicide in order to gain satisfactory control. Flomide and Engage can be tank-mixed with a wide range of graminicides," says Dr. David Stormonth, Technical Manager for Interfarm UK Ltd.
"Equally important is soil temperature. Low soil temperatures of around 8-10˚C are required so that long persistence is achieved throughout the problem weeds' germination period. More recently soil temperatures have been over 14˚C. Recent cool night conditions are reducing soil temperatures in line with "normal", which is creating suitable conditions for use of propyzamide. If you consider that soil temperatures are still above average, then delay application until cooler conditions prevail. With propyzamide there is no rush. Highly successful control has regularly been achieved from November, December or even January applications," says David.
In all cases, Interfarm strongly recommends the use of the higher dose rates on the label in order to gain maximum persistence. For Flomide this is 2.1 litres/ha and for Engage 1.7kg/ha.
"An added complication this season is the variable crop growth stages due to a dry and warm early autumn. The labels for both Flomide and Engage state that crops should be at or after the 3 leaf stage. This is to ensure the crop root system is below the herbicide residual layer. Trials have shown that the aerial size and stage of the crop is insignificant. As long as the root system is more than 4 cms down, then crop selectivity is good," says Dr. Stormonth.
David warns that conditions vary from region to region, or even field to field. He urges advisors and growers to consider the crop/field/soil status carefully before using propyzamide. "Propyzamide has a wide window of application of four months, from 1st October right through to the 31st January and there is plenty of opportunity to use this key active when conditions are more conducive to its best performance. Understanding how this herbicide actually works and the best conditions for its performance will mean that growers will benefit from good weed control," says David.
Propyzamide is available from Interfarm as Engage (50% WP), (which has been rebranded this year from Propose), 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. In oilseed rape, Engage is recommended at 1.4 kg or 1.7 kg/ha and Flomide at 1.7 l/ha or 2.1 l/ha. Use the high rate for black-grass control. Engage and Flomide are compatible with pyrethroid insecticides, graminicides and relevant fungicides including Quell Flo (mancozeb).
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
