Japanese Knotweed

Japanese Knotweed (Fallopia japonica) and Gunnera* Infestations in Dún Chaoin

The project to eradicate Japanese Knotweed and Gunnera from the parish began in 2017.  In the first year, trials were carried out in Ceathrú, Baile na hAbha and Baile Bhiocáire and it was decided to extend the work to the whole parish.  A grant of 75% was obtained from the Leader Programme and the contract was awarded to Envirico to do the work.  The total cost of the project was €46,996 towards which a grant of €35,247 was awarded by Leader and a local contribution of €10,110 was collected from the landowners and the balance of €1,639 was paid by the Comharchumann.

We now have a better understanding of these alien invasive species and we know how strong and widespread they are and that it is very difficult to get rid of them.  The landscape of the parish is an aid to the spread of the plants and they follow the rivers and grow strongly in the most inaccessible places.

Progress has been made as can be seen from these figures:

Estimated original area affected by Japanese Knotweed                               27, 059 m2

Estimated original area still affected in 2020                                                    1,365 m2 (5% of original)

New sites of Japanese Knotweed found in 2020                                              616 m2

Total in 2020                                                                                                   1,981 m2

Estimated extent of Gunnera in 2018                                                                 58 m2

Estimated extent of Gunnera in 2020                                                               218 m2  (c. 4 fold growth)

Areas of the parish where the growth of Japanese Knotweed is of concern (numbers refer to map references in the Envirico 2020 Report)

            Mám na Ceathrún (dump sites) JK01 & JK02

            Along the river bank at Baile na Rátha towards Bóthar na hAbhann JK14 – JK18

            Along the river bank behind Tigh Kruger JK28 & JK29

            Gleann Loic JK39 & JK56

            Baile na Rátha towards Droichead Bán JK52

The 17 new sites (JK63 – JK80) will need further treatment

Despite success in knocking the Japanese Knotweed back, the resilience and resistance of the plant to the treatment to date suggest that the areas of concern given above would benefit from continued spraying.  The plant will recuperate and grow strongly again if it is left unhindered and it will continue to spread along the waterways to find new sites.  It is suggested that one spraying a year in the Autumn will be sufficient to continue the work that has been started.

All areas of Gunnera will need treatment though this is not as problematic because it is more easily controlled.  *There are two species of Gunnera in the parish, Gunnera tinctoria which spreads chiefly by seed dispersal and Gunnera manicata which spreads mainly by its root system.  They have to be treated appropriately.

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