Key Points:
- A range of pre and post emergence herbicides were applied to three species types of brassica used in vegetable seed production (Asian Radish, Red Radish and Pak Choi (open pollinated)) in order to assess whether these crops have differential tolerance to a range of herbicides.
- Herbicides were applied using a logarithmic plot sprayer which applied agrichemicals at a gradually decreasing rate from two times full rate to less than quarter rate.
- It should be noted that the brassica species were tested for their tolerance to these agrichemicals rather than the herbicides weed control properties.
- N.B. Of the herbicides tested some were approved for use in forage and vegetable brassicas whilst others had no approval, therefore all data should be treated with caution and any crop
- action referred to your agrichemical supplier and/or seed contract provider.
- There were large differences in herbicide tolerance due to product tested and individual brassica species.
- Of the pre emergence herbicides the most damaging herbicides were acetochlor and gardoprim. The least damaging products tended to be those products with some recommendation for forage or transplanted brassica such as alachlor (e.g. Lasso) and propachlor (e.g. Ramrod), though with both these products damage was apparent.
- In this trial the least damaging pre-em products were propyzamide (Kerb), metochlor (Dual Gold) (half rate and below) and clomazone (Magister) and dimethenamid (Frontier) in the Asian Radish. Both Kerb and Magister have UK approvals for weed control in oilseed rape though in the main Kerb is
- used post emergence.
- With the post-emergence herbicides (applied 4th December) there were greater differences in tolerance between the brassicas tested, Red Radish in general looking to be more sensitive than Asian Radish. Pak Choi in the majority of cases appeared to be the least sensitive.
- Dicamba despite an approval in forage kale was damaging to all three species at full rate.
- Over two seasons (2005 & 2006) Diflufenican (DFF) (Quantum) has been more damaging to Red Radish and although it carries no approval for brassica, Asian Radish and Pak Choi have displayed much greater tolerance.
- The greater sensitivity of Red Radish was also noted with Cougar which contains DFF and isoproturon, but which again carries no approval for brassica crops.
- Of those products that didn’t completely kill the brassica, Kerb, Ramrod, Cougar, Dicamba, Radiate and Quantum gave the best weed control (Wireweed, Cornbind, Pansy, Fumitory, Speedwell) in this trial.