(Arboricultural-styled) 'Fact of the Day'

[tree-fancier123]

I know this will have been done to death elsewhere on the forum, but the recent Id request posted with armillaria replies made me realize I still don't know if I see it on a stump, or even a live tree in a garden, does the mere presence of honey fungus in a location mean it will spread to healthy trees?

I have before read about burning infected tree remains, or taking them to the dump, say if an armillaria tree is felled in a garden with other trees.

 

I realise some of the stuff on this will have been written years ago and may be perfectly valid, but what's the latest in the books and journals on armilaria cross infection?

[Kveldssanger]

I have a few publications on honey fungus - I shall look to post something later on.

[Kveldssanger]

Will get a few facts done tomorrow to make up for lost time. Had a busy day and a half - not really had time to sit down and write out anything overly technical.

 

Got a few good ones for tomorrow, so worry not.

[Kveldssanger]

18/10/15. Fact #60.

 

Honey fungus is one of the most common root pathogens throughout the world, and it can kill a massive range of plants - both trees and shrubs. A very broad range of coniferous and broadleaved tree species can therefore be host to honey fungus.

 

In terms of how it infects, its typical modus operandi is active pathogenesis, which is a strategy that involves direct penetration of the host by a fungal pathogen - largely through the roots (usually through root-to-root contact between an infected and un-infected individual). Therefore, this strategy employs tactics that can lead to infection of both healthy individuals and already-stressed individuals.

 

It is perhaps relevant to make note of the fact that honey fungus is not considered to be a major problem in woodlands, unless the woodland is a young coniferous plantation (of around 10-15 years of age - after this point, the situation will usually stabilise and honey fungus becomes less of a problem). This is most probably because trees are in abundance within woodlands, so the impact of honey fungus is not at all as severe as if it clutches your prized monkey puzzle tree from life.

The following bit on control is copied from my notes on control of honey fungus. I have a huge number of references for the below section - they are all listed.

 

As honey fungus is found within the soil, control is going to be obviously be very difficult; particularly when it has been present on a site for many decades and has established a wide network of rhizomorphs. If a specimen is infected therefore, removal of the entire tree (including root mass) may be necessary and the soil subsequently replaced, though as the pathogen can lie 'dormant' in soil for a long time it is hard to prevent infection – particularly if the fungus has been dormant for many years, as one may not even be aware of its presence.

 

The selective planting of more resistant species can be an option on high-risk sites, and ensuring specimens remain healthy can also reduce risk of infection – particularly when one recognises that man-altered environments facilitate the pathogen's spread more so than unaltered environments (when forests are cleared over time, healthy root systems are left – these now-starving systems support artificially high numbers of such soil pathogens that facilitate attacks on existing healthy trees).

 

Chemical control is largely impractical, despite a large array of controlling agents. Trials into determining whether ring-barking infected hosts before felling would reduce future incidences of Armillaria mellea outbreaks during 1957 by the Forestry Commission also proved ineffective, contrary to in Africa where such a practice has more impact (likely due to lesser abundance of rhizomorphs in the soil).

 

As a more avant-garde measure, in light of Armillaria mellea very rarely infecting previously-altered wood, intentional infection of the butt or root area with bacteria or non-decay-causing fungi may be a possible option, as may intentionally altering wood to become false heartwood or true heartwood, though evidence to support such a theory is absolutely lacking.

 

Sources:

 

Bennett, F. (1924) Outlines of Fungi and Plant Diseases. UK: Macmillan & Co.

 

Fox, R. (ed.) (2000) Armillaria Root Rot: Biology and Control of Honey Fungus. UK: Intercept.

 

Garrett, S. (1970) Pathogenic Root-Infecting Fungi. USA: Cambridge University Press.

 

Grieg, B., Gregory, S., & Strouts, R. (1991) Forestry Commission Bulletin 100: Honey Fungus. London: HMSO.

 

Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management (Research for Amenity Trees 7). London: HMSO.

 

Mallett, K., & Hiratsuka, Y. (1988) Inoculation studies of lodgepole pine with Alberta isolates of the Armillaria mellea complex. Canadian Journal of Forest Research. 18 (3). p292-296.

 

Pawsey, R. (1973) Honey fungus: recognition, biology & control. Arboricultural Association Journal. 2 (4). p116-126.

 

Pawsey, R. & Rahman, M. (1976) Chemical Control of Infection by Honey Fungus, Armillaria melica: A Review. Arboricultural Journal. 2 (10). p468-479.

 

Schwarze, F., Engels, J., & Mattheck, C. (2000) Fungal Strategies of Wood Decay in Trees. UK: Springer.

 

Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates.

 

Strouts, R. & Winter, T. (1994). Diagnosis of Ill-Health in Trees (Research for Amenity Trees 2). London: HMSO.

 

Tainter, F. & Baker, F. (1996) Principles of Forest Pathology. UK: John Wiley & Sons.

[David Humphries]

Possibly the key point whilst assessing Armillaria is to identify which species it may be.

 

The UK has 6 species

 

Some of these are similar in appearance and may be only differentiated by size/shape of spore.

 

As there are species that are relatively benign, (as opposed to aggressively pathogenic) or act as secondary parasites and even wholly saprophytic, then it's important to know which one you're presented with.

 

http://arbtalk.co.uk/forum/tree-health-care/81240-armillaria-investigation.html

 

 

 

.

[tree-fancier123]

interesting reading, thanks

 

it seems a lot of time and money has gone into developing an effective fungicide, but still no generally accepted operationally feasible means of control

[Kveldssanger]

I have a chapter on chemical control in Fox's book. I can do a fact on that perhaps, if it's feasible.

[tree-fancier123]

found this by Fox on Armillaria

http://world-food.net/download/journals/2003-issue_1/V1N1A95-100armillaria.pdf

 

'In France trenches over a metre deep are

dug to isolate the infected plants from healthy parts of a vineyard

or a fruit orchard have been used to control spread of Armillaria

root disease'. Don't suppose many customers would want trenches dug in the hope it may protect other trees if one gets infected.

 

'Strawberry plants are killed within a few weeks enabling them to

be used as “live bait” to reveal where Armillaria is present or

absent in the soil' Not heard that before.

[Kveldssanger]

Facts will be a bit slower this week. I have a few assignments to churn out, so I will do one every other day until the weekend.

[Kveldssanger]

20/10/15. Fact #61.

 

Many species of eucalyptus are heteroblastic - as in, mature foliage significantly differs in morphology from juvenile foliage. In species such as Eucalyptus globulus, juvenile foliage may be incredibly different from the adult state. Where such foliage occurs on the same tree, the difference is particularly striking.

 

Juvenile foliage usually is found on seedlings of 2-3ft tall - beyond that, individuals will mainly have adult leaves. However, some individuals may rech 7m tall and still have juvenile foliage. Typically, after 20-30 nodes though of course varying with species (usually at arond 2m in height) however, juvenile foliage, if not already adult in morphology, will begin to transition towards adult foliage. Where foliage shows characteristics of transition between juvenile and adult, it is referred to as intermediate foliage.

 

Identification of exact eucalypts is actually made simpler by the presence of juvenile leaves. Many species have similar adult leaves, though do not share such similarities with their juvenile leaves. Therefore, where there is uncrtainty over the species, locating juvenile foliage can significant aid with exact identification.

 

The juvenile foliage is also strongly hereditary, to the point that even after only a few months they can be used as genetic markers.

 

Source: Pryor, L. (1976) Biology of Eucalypts. UK: Edward Arnold.

Edited October 20, 2015 by Kveldssanger