Two new TreeWatch surveys on oak trees

posted on May 13, 2012

This week we have launched two new surveys at TreeWatch. Both relate to the health of our oak trees and we asking members of the public for their help. Both surveys have been developed jointly with scientists from Forest Research and we will be sharing the scientific data we collect them to help in their studies. Both surveys, the oak jewel beetle and powdery mildew, have been linked to the very serious problem affecting our oak trees:- Acute Oak Decline.

Oak jewel beetle survey on TreeWatch

Oak jewel beetle survey on TreeWatch

The oak jewel beetle Agrilus biguttatus, lays its eggs in crevices on the bark of native oak trees. The larvae that hatch then tunnel through the bark to feed on the tree tissues underneath the bark. If large numbers of this insect infest a tree it may lead to tree death. When the larvae pupate, the emerging young adult beetles make very characteristic ‘D’-shaped exit holes.

Scientists at Forest Research want to know more about the distribution of this beetle, so it is just as important that your report an absence as much as a presence!


Oak powdery mildew survey on TreeWatch

Oak powdery mildew survey on TreeWatch

The second new survey is on Oak powdery mildewsurvey. Powdery mildew of oak is caused by the fungus Erysiphe alphitoides (also known as Microsphaera alphitoides) and it is a common foliar pathogen of oak trees across Europe. First found in England in 1908, it is thought to have been a factor in an oak dieback episode in the 1920s. Scientists today believe that it may one of the factors that is contributing to the decline of our oak trees. The mildew attacks young leaves and soft shoots of oaks, covering them with a felty-white mycelium (fine white threads). It causes eventually the leaves to shrivel and dry out or turn brown.

If you can help us by monitoring the health of oak trees near you, please get involved.  It is easy and fun.  To find out more and to take part visit


  1. Rather than focus attention on powdery mildew and beetles, which are just praying on a weak tree or temporal situation I would consider it of much more significant value to focus attention on the real issue that is affecting our Oaks, at least in mine and a few others opinions.

    Our Oak have the most complex ecology among our native trees, including a wide array of species specific symbiont’s, Soil health is fundamental to tree health. Trees grow up by roots, look there first and worry about the above ground issues last if you want to save them or uncover whats doing the damge try Nitrification, compaction, ploughing etc etc etc etc.

    these above ground issues are a small part of a much bigger equation, and healthy trees fend of such minor issues generally.

    What concerns me more is the future loss of our Naive white Oaks Quercus robur/petrea to hybridisation with non native Quercus cerris which is now widespread and weakening the genetic pool, 1-2000 years and there will be no English oaks to be concerned about!

    and NO, hybridisation will not answer climate change issues!

    Comment by Antony Croft — May 15, 2012 @ 10:26 pm

  2. Thanks for your comments Antony.

    Firstly, we believe that the two new oak surveys in our TreeWatch initiative are important as both subjects of the two surveys, the oak jewel beetle and powdery mildew, have been implicated as playing a part in the decline of the health of our native oak trees.

    We would agree with you about the importance of soil health, which is why Sylva is sponsoring its Sylva scholar at the University of Oxford in undertaking a whole research project in this area. You may want to read more about it here:

    Regarding hybridisation then this is of great interest. Don’t forget that hybridisation is also nature’s way of creating fitter populations. So yes, we may or may not have exactly the oaks we love today in 2000 year’s time but thanks to evolution we hope that there will be oaks of some description.

    Comment by Sylva Foundation — May 24, 2012 @ 5:28 pm

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