BSPP ‘Plant Doctor’ Quiz #32 – November 2023

The correct answer is:

Hymenoscyphus fraxineus

Ash dieback is a highly destructive disease of ash trees (Fraxinus species), especially the United Kingdom’s native ash species, common ash (Fraxinus excelsior). It is caused by a fungus named Hymenoscyphus fraxineus (H. fraxineus), which is of eastern Asian origin.

The disease is also known as ‘Chalara’, ash dieback, and Chalara dieback of ash. Calling it ‘Chalara’ ash dieback helps to distinguish it from dieback on ash trees caused by other agents.

IMAGE: Crown Copyright. Forestry Commission / Mick Biddle

The correct answer is:

Ash keys

The seeds produced by ash trees are known as ash keys and they typically hang in a bundle.  As they mature the colour changes from green to brown.  At this point they can be easily confused for wilting leaves which is a symptom of Chalara ash dieback.

IMAGE: Crown Copyright. Forest Research

The correct answer is:

Ophiostoma novo-ulmi

Dutch elm disease is a highly destructive disease of several species of elm (trees in the Ulmus genus). It is caused by two related fungi, Ophiostoma novo-ulmi and Ophiostoma ulmi, although almost all cases are now caused by O. novo-ulmi. The fungus is spread from tree to tree by elm bark beetles.

It has killed tens of millions of elm trees in the United Kingdom since the second wave caused by O. novo-ulmi was accidentally introduced, probably during the 1960s.

IMAGE: Crown Copyright. Forestry Commission

The correct answer is:

European mountain ash ringspot associated virus

The European mountain ash ringspot associated virus (EMARaV) is a pathogen that infects mountain ash trees (Sorbus aucuparia). The pathogen attacks the leaves of its hosts where it causes mottling and discoloration. In extreme cases the productivity of the tree can be affected, which can result in its gradual decline.

IMAGE: Adrian Fox, Fera Science Ltd.

The correct answer is:

All of the above

Conspicuous and often numerous sunken, bright orange-brown cankers can occur on the bark of young branches of infected trees. The cankers caused by chestnut blight can eventually girdle branches and stems, with all live tissue above the canker dying. On grafted trees, infections are most frequently found in areas close to the graft where callusing occurs, whereas in orchard and coppiced trees infections usually occur at the base of the stem (collars or insertion points). Masses of pin-head sized, yellow-orange to reddish-brown pustules may also be evident on infected bark. These fruiting bodies erupt through lenticels (gas exchange structures) in the bark and exude long, yellow-orange tendrils/threads of spores in humid and wet weather. Another obvious symptom of this disease is wilted and brown dying and dead leaves which are retained by the tree above a girdling canker. Below the canker, epicormic growth (prolific sprouting) may be visible.

IMAGE: Crown Copyright. Forest Research

The correct answer is:

Sirococcus tsugae:

Sirococcus tsugae is a fungal pathogen that causes shoot blight and cankers on cedar trees (Cedrus spp.), and shoot blight on hemlock (Tsuga spp.). It can attack seedlings and saplings as well as mature trees. This pathogen has the potential to cause considerable damage to valuable ornamental trees in public and private gardens and economic losses for the forestry and nursery sectors in the UK.

IMAGE: Crown Copyright. Forest Research

The correct answer is:

Red band needle blight

Dothistroma needle blight (DNB) is an economically important disease of conifer trees (trees with cones and needles), and particularly pines (trees in the Pinus genus). It is caused by the fungus Dothistroma septosporum

It causes premature needle defoliation, resulting in loss of timber yield and, in severe cases, tree death.

It is also known as red band needle blight because of the colourful symptoms it shows on pine trees, as in the picture above.

IMAGE: © Crown copyright. Forestry Commission

The correct answer is:

All the above

AOD typically affects older oak trees, but it has also been found in younger trees. It causes dark bleeds down the trunk of the tree. You may find the small, D-shaped exit holes of the oak jewel beetle in the bark. In severe cases the tree starts to lose leaves, causing the crown to thin. AOD can be fatal within 4 to 6 years of the symptoms first appearing.

IMAGE: © Crown copyright. Forestry Commission

The correct answer is:

Xylella fastidiosa

Xylella is a plant disease which can affect several species of broadleaved trees widely grown in the UK, such as oak, elm and plane, as well as a wide range of other commercially grown plants. Among them are grape, citrus, coffee, olive, almond and blueberry species, and many herbaceous plant species.

In nature, the bacteria are exclusively transmitted by insects from the Cicadellidae and Ceropidae families, which feed on plants’ xylem fluid. There are several species of insects in the UK which could act as vectors (agents of spread) of X. fastidiosa bacteria, including the common froghopper (Philaenus spumarius). Although such insects usually only fly short distances of up to 100 metres, they can be carried much longer distances by the wind.

IMAGE: David Cappaert, Bugwood.org

The correct answer is:

TreeAlert

Developed by the Forestry Commission, Tree Alert is an online reporting tool for forestry professionals and those with knowledge of trees and woods. Information about trees showing symptoms of pests or diseases can be recorded and submitted for further verification. https://treealert.forestresearch.gov.uk/

If you would like to find out more about the diseases mentioned in the quiz please visit the Forest Research webpage. https://www.forestresearch.gov.uk/tools-and-resources/fthr/pest-and-disease-resources/

Another valuable resource is the Observatree website where there are dedicated pages for pest and diseases. https://www.observatree.org.uk/