When given the best conditions to work, propyzamide can give levels of black-grass control of more than 90%.
1. Performance is best where rape crops have been established using min-till techniques. Black-grass seeds remain and then germinate in the top layers of the soil where the propyzamide is retained
2. Applications should be made to firm, moist soils with a fine tilth where possible.
3. Propyzamide is best applied when soil temperatures have got down to 10degC at 30cm and are falling to avoid too rapid degradation. The half-life of propyzamide at 10degC is around 100 days whereas at 15degC it falls to 60 days. Hence the need for cooler soils. Good grass-weed control is achieved when a lethal concentration of propyzamide is reached in the germinating weed. This is a function of plant size, rate of growth and continuing availability of propyzamide in the top 5cm or so of the soil for uptake.
4. Kerb (propyzamide) may be applied in frosty conditions, but avoid application onto frozen ground where subsequent rainfall could result in run-off into watercourses. For ASTROKerb (propyzamide + aminopyralid), ideally ensure frost is off the target broad-leaved weed.
5. There needs to be sufficient moisture in the soil for plant uptake, but avoid water-logged or saturated soils. Soil moisture deficit should be less than 50mm and falling.
6. Corteva data shows that the combination of optimal weather and soil conditions usually starts after November 5 in a normal year. Products containing propyzamide have a wide window of usage up until January 31.
7.Where there are populations of difficult to control black-grass, using the maximum label rate of propyzamide (850 gai/ha) is advised. Propyzamide will control black-grass resistant to other chemistries in the arable rotation and for this reason is an important tool in managing black grass populations.
8. Strategic use is recommended in tank mix or sequences with graminicides. In very difficult black-grass situations, adding a ‘dim’ to propyzamide or propyzamide + aminopyralid nearly always raises the level of weed control.
9. Propyzamide is soil acting so spraying wet weeds at run-off or light rainfall after application is not an issue. ASTROKerb is said to be rainfast after one hour.
10. All applications should be made with due regard to water stewardship, i.e. do not spray where there is a risk of run-off to adjacent watercourses.