Trust control
The Trust has been controlling Giant Hogweed on the Isla system for 4 years in an attempt to eradicate it which may take as long as 15 years as the seeds lay dormant for many years. Spraying with glyphosate (Round-up biactive) starts in May and continues throughout the summer. Any plants that have emerged later or those that have been unnoticed are cut and a treatment of glyphosate is applied to the stem to ensure the plant dies.
The Huntly Fishing Association have also been spraying Hogweed on the Bogie system.
This time consuming process should eventually bring rewards so that the general public and anglers can access the Deveron without encountering this non- native plant that causes painful blisters when subjected to sunlight.
How it should be controlled?
It is important that the plant is kept under control, even eradicated where possible. Using mechanical methods, the plant can be cut, mown or pulled. Physical control should never be undertaken unless protective clothing is worn.
Cutting before flowering will only achieve temporary control - the plant will regrom the following season.
Cutting after flowering has no benefit once the seeds have been formed. Small infestations can be controlled by digging out the whole plant. The relevant competent authority (English Nature, Wildlife Trust, Local Authority) must be satisfied that the management plan is appropriate.
The plant can also be controlled chemically. This method should only be considered after other practical methods have been ruled out. Properly used, the herbicide glyphosate (Roundup, Spasor, Sonic...) is most effective. Prior agreement with the Environmental Agency must be obtained before a herbicide can be applied in or near water.
The plants may be sprayed with Glyphosate at a rate of 5 litres per hectare when growing actively but less than a metre tall, usually between April and May.
Control measures will only affect mature plant and so due to the longevity of the seeds, regular annual checks should be made for germinating plants.
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