Summary

Woodland management can have many objectives such as for example:

• Timber or wood fuel production
• Habitat restoration
• Protecting or enhancing biodiversity
• Providing a resource for recreation.

Without suitable vegetation management, the primary objectives for the woodland are often unachievable.

Pesticides in the UK are subject to a tight regulatory framework, and their safe use requires careful and often complex planning. Despite this, due to their effectiveness and relatively low economic cost, since the 1970s managers have come to depend on the use of herbicides to manipulate vegetation. However, recent developments in European and national policy mean that there is increasing pressure to reduce this reliance, and to consider alternative approaches.

Challenges facing woodland managers:

• A pressure to reduce reliance on herbicides and adopt non-chemical methods of vegetation management
• A lack of economically viable non-chemical approaches, set against a background of sustained pressure to minimise costs associated with woodland management (direct alternative non-chemical approaches are often 10 – 1000 times more expensive)
• Increasing complexity of regulations and methodologies required for sustainable plant protection product use
• A reduction in the range and function of approved plant protection products
• Controlling the spread of alien and native invasive weeds within established woodlands, a challenge which may be made more problematic by climate change.

Current research is divided into three broad themes:-

• Vegetation management
• Reducing pesticide inputs
• Direct seeding

In addition, activity in this programme derives from, amongst others, the following specific overarching policy themes:-

• The UK Forestry Standard and policy on sustainable forestry, which calls for felled woodland to be re-planted, and existing and new woodlands to be managed to deliver sustainable multiple benefits. A basic principle of the UK Forestry Standard is to minimise the use of herbicides by using them only according to the needs of the site, and only where other options are not available or uneconomic.
• The UK Woodland Assurance Standard (UKWAS), which requires managers to work towards the reduction and elimination of all synthetic pesticide use in forestry, and commits the forest industry to carrying out research into methods of reducing pesticide use in forestry and publishing the results of this research.
• UK Government policy, as detailed in the relevant country Codes of Practice, is to keep pesticide use to the lowest possible level, whilst making sure that pests, diseases and weeds are effectively controlled in a way that protects the health of people, and safeguards biodiversity, plants and the environment.
• The European Union Thematic Strategy on the Sustainable Use of Pesticides which calls on member states to minimise the risks to the environment from using pesticides and reduce their use, including substitution with non-chemical alternatives.
• The European Forest Action Plan which calls for enhanced protection of forests from damaging biotic agents.
• The Forestry Commission Science and Innovation Strategy ^(PDF-308K) which restates the importance of research into alternatives to chemical pesticides, calls for new approaches to dealing with biotic threats, and recommends the examination of alternative regeneration techniques such as direct seeding.

Status

The programme is reviewed at regular intervals.

Contact

Ian Willoughby

Forest Research collaborators

Victoria Stokes also works on the programme, and the Technical Services Unit provide essential field based technical support.

Integrated forest vegetation management – Reducing herbicide inputs

The programme is carrying out research into alternatives to herbicides and where there is currently no suitable alternative, reducing herbicide inputs in forestry.

Alternatives to Herbicides

For many weeding situations, non-chemical options already exist, but they are nearly always dramatically more expensive, as well as being less effective and often less sustainable, than the use of herbicides. However, opportunities exist for investigation into novel forms of non-chemical weeding methods such as biological control (mycoherbicides), use of dye markers, cover crops, mulches and manipulation of planting stock.

Jeskyn’s farm showing young ash trees growing with plastic mulch mats

Reducing herbicide inputs

In some situations there is currently no cost-effective way of controlling invasive, competitive weeds without the use of chemical herbicides. We are currently conducting a series of experiments to allow us to model critical period of weed competition for various vegetation / tree interactions. This will allow us to develop practical recommendations for mangers as to how to maximise the impact of any herbicide interventions, for minimum possible input and minimum reduction in survival and growth.

Herbicide reduction trial three years after planting

The photo shows two plots in one of our experiments three years after planting:

• The trees in the extreme left-foreground were only weeded for the first three years after planting
• The trees on the extreme right had just received their first weeding treatment which continued until year 5.

The photo demonstrates the influence of weed competition on tree form and height; the trees on the right which did not receive early weeding remained 27% shorter than weeded trees after 5 years, despite intensive use of herbicides in years 3, 4 and 5.

Publications and guidance on forest vegetation management can be found on our publications pages

What’s of interest

Forestry Commission publications on vegetation management and the use of pesticides, and Integrated Pest Management and pesticide reduction

Useful sites

• UKWAS

Integrated forest vegetation management – Vegetation management

Competition from weeds for resources such as water, nutrients and light is probably the single most important factor preventing successful survival and growth of young trees, particularly on more fertile sites.

The impact of weed competition on growth rate is demonstrated by the images below showing 4-year-old cherry trees with and without effective weeding.

Achieving successful, cost-effective weed control amongst small, vulnerable tree seedlings is not always straightforward.

Work in this programme is therefore focussed on addressing specific weed control problems in new planting, restocking and natural regeneration situations through replicated field experiments. Changes in legislation, commercial withdrawal of herbicide products, herbicide resistance, climate change and the spread of invasive alien and native weeds all make further work in this area vital.

Publications and guidance

The expertise built up in this area over a number of years enables Forest Research to offer free, expert, unbiased, advice on specific weed problems throughout Britain. Comprehensive guidance on the use of herbicides in different situations has been produced.

Pages on the Health and Safety Executive website give a wide range of useful information on pesticides.

Publications and guidance on forest vegetation management can be found on our publications pages

Contact

Ian Willoughby

What’s of interest

Forestry Commission publications on vegetation management and the use of pesticides, and Integrated Pest Management and pesticide reduction