| dc.description.abstract | This work has investigated a range of aspects of the physiology and management of
Fallopia japonica (Ronse Decraene) and closely related invasive introduced plant
species, colloquially referred to as Japanese knotweed. Prior to this work very little
detailed scientific research had been done into the nature of the plant and its related
species or into the effectiveness of control methods over the long term.
This work has highlighted the need for education of the public to prevent further
spread by inappropriate disposal, and advice on suitable and practical methods of
control in a wide range of environments. The creation of an online GIS database has
led to an increase in reporting of sites on private land by the public and this has in
turn strengthened the Cornwall database which is the most comprehensive of its type
ever created. This database has enabled detailed analysis of distribution,
identification of likely areas of colonisation and indicated mechanisms of spread. It
has also provided a basis for targeting of resources and prioritisation of treatment.
Initial field observations also prompted research on physiological aspects of the plant
which have particular implication for determining methods for its control. The work
has shown that much smaller fragments of rhizome than those previously tested are
capable of regeneration (down to 0.01g) and that there is a significant likelihood of
fragments of 0.06g regenerating in suitable conditions which has implications for
separation techniques. It has demonstrated that typical rhizome material is capable
of survival for at least three months under saline conditions thus highlighting a risk of
marine spread along coasts. Extension rates of above ground material of up to 13.8
cm over a 24 hour period have been recorded. Cutting of above ground material
caused a stimulation of new above ground stems – thus any proposed treatment
should continue consistently over a number of years. A temperature of 40C
maintained over a period of 7 days removed rhizome viability in chopped fragments
of up to 10cm thus suggesting that temperature controlled in-vessel composting may
be a possible disposal route for chopped rhizome. Main underground extension
growth has been shown to occur in the Autumn with no particular orientation to the
growth. Up to 50kg (wet weight) of underground material has been discovered in a
cubic metre of excavated material. Rhizome disturbance has been shown to promote
underground extension. The way in which rhizome desiccates, leaving viable buds
separated by necrotic material, means that underground connections within an area
cannot be assumed. This has implications for the effectiveness of chemical
treatment. The suggested regeneration from leaf material has not been
demonstrated, nor has a reliable chemical method of testing the viability of rhizome
material.
The implications of these physiological aspects on a wide range of treatment
methodologies have been considered and control methods have been tested.
Excavation and separation of material can be effective in appropriate soil conditions.
The need to use glyphosate based herbicides primarily in the Autumn has been
demonstrated. This work has called into question the current methods of assessment
of effectiveness of control and the use of viability assessments on sites. It has
highlighted that monitoring of treated sites needs to be continued over a number of
years in order to determine whether eradication has been achieved. In view of the
legal proscriptions about the plant, it is considered that some control measures
currently deployed could have the potential to breach current legislation by being
likely to cause the plant to spread. | en_GB |
