Invasive Weeds Management
Giant Hogweed. (GHW)
The sap from this plant is dangerous to humans reacting with sunlight and causing severe blistering and recurring dermatitis. Consequently, no attempt should be made to strim plants. Mowing can also be dangerous and in general should be avoided.
Recommended methods of control.
- Spraying using knapsack sprayer and systemic, glyphosate based herbicide. Roundup Pro Biactive is widely accepted as the most effective chemical suitable for use near watercourses. Only approved pesticides will be acceptable to SEARS who issue spraying licenses. Application must be by qualified person only. (PA6AW is the required standard).
Timing of spraying is important. Too early and many plants won't have emerged from the soil. Too late and plants may already be flowering or developing seed. Our experience in Ayrshire indicates that late March/ April until early June is usually an ideal time to spray however this year (2010), due to the prolonged hard winter, it is likely that spraying will be delayed by around 1 month. Plants should be around 18" (0.45m) tall when sprayed. Care must be taken to ensure that plants are sprayed using the appropriate strength/dilution and that the whole plant is sprayed. (when plants receive less than a lethal dose, they often survive and develop flowers prematurely as a stress response.)
- Cutting stems only delays flowering. For cutting to be effective, the plant should not have flowered and the root should be cut through at least 50mm below the soil surface. This method is only suitable where an individual plant occurs or where chemical application is not possible. Anyone cutting GHW should wear adequate personal protective equipment and be aware of all emergency procedures to follow should contact with the plant occur.
This method should only be used as a last resort.
- Grazing. Grazing is not a substitute for other treatments but it may be used in certain circumstances to assist in control.
ART staff are qualified and always available to advise on chemical control methods.