Question to the Department for Environment, Food and Rural Affairs:

To ask His Majesty's Government what estimate they have made of the percentage of ash trees that are surviving chalara ash dieback disease.

From observations in Europe and the UK, we expect 1-5% of ash trees to show useful levels of genetic resistance to the disease. Resistance is heritable which offers hope for a future breeding programme.

Reports from Europe have shown maximum mortality rates of 85%, but rates vary between countries and sites, as well as the timescales of monitoring and felling activity, so are difficult to validate. Ash trees, especially larger and older trees, can also decline slowly with the disease, over a period of years or decades, and with recovery shown in some years. This makes it difficult to estimate long term survival with any certainty. In the UK, the level of infection remains widely variable between areas, with the south-east of England being most affected.