What goes on wicks?
Choice of herbicide for the Eco-Wipe from the limited range approved rested mainly on site, says Mr McCall.
For fields with sterile brome and on pastures where grass kill from odd drips of chemical from the wicks was unimportant, Roundup (glyphosate) was the norm. On conservation areas he stuck to Broadshot (2,4-D + dicamba + mecoprop).
Key to good control, he stresses, is keeping wicks saturated, so some dripping is inevitable. "Broadshot gives you added safety." He has had little or no experience with the off-label alternatives – Grazon 90 (clopyralid + triclopyr) and Dow Shield (clopyralid). .A problem with chemical recommendations, he says, is they tend to be based on earlier experience with rope-wicks.
English Nature is working closely with herbicide-makers to provide better application advice for the new-style machine, says land management adviser John Bacon. Four different concentrations for each chemical have been tried, ranging from 1:2/3 for glyphosate to 1:200 for clopyralid. Legally however growers may not use a solution more concentrated than 10 times the application rate, he warns.
Replicated trials showed there is a "fairly wide range of dilutions that will work". But experience suggests a 1:10 ratio is about right, he says.