Management of a Veteran Kentish Orchard

[agg221]

Alec, I've used Armillatox for eradicating Armillaria in the past, though this was a fair while ago pre understanding (a bit) about the complex relationships within the soil.

 

I only mention the identification angle as it's possible your historical infection was another species of Armillaria feeding saprophytically on dysfunctional wind rocked/severed roots, or old dead roots from previous removed trees.

 

Possibly too long ago to recall but I wonder how the vitality of the two trees in question were at the time or whether it was just the presence of Armillaria fruiting bodies that led to the decision?

 

Can you recall where they were fruiting?

 

 

Old thread on the (mis)identification of Armillaria fruit bodies, which is quite an interesting case study.

 

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

 

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Hi David - I read the thread which was interesting but also confirmed that I know very little about mycology

 

Bearing in mind this was over 25yrs ago, my recollection is as follows:

 

On the Annie Elizabeth shown, the fruiting bodies were concentrated at the base of the trunk, on the tension side. The branch shown currently supported would have been around 2' lower at the time. The presence of dysfunctional roots is therefore a possibility. On the Newton Wonder the fruiting bodies were also adjacent to the trunk. This tree showed no sign of movement due to wind, but may have experienced a ground level change at some point - if so the soil would have been raised around a foot about 40yrs earlier when a Nissen hut was erected. There was some significant decay in the trunk at the then ground level, so there was material available.

 

Vigour in both trees was poor. There was a lot of blossom but almost zero extension growth. That said, up until 1988 there was effectively no extension growth on any of the trees, no pruning having taken place for many years and the crowns having become a twiggy mass. However by the time they were being treated they would have had some pruning undertaken, probably over a couple of years. From what I recall the Newton Wonder was showing some extension growth but the Annie Elizabeth was not, specifically compared to the adjacent Annie Elizabeth (shown in the other pictures) which was making modest extension growth. After treatment, the trees made good extension growth.

 

I can be fairly confident that this was not arising from the remains of adjacent dead/removed trees. The Newton Wonder had Comice pears on both sides, and a Worcester Pearmain nearby. The whole line was complete so no trees would have been removed since the Nissen Hut was erected. There would have been a tree at some point about 20ft to one side of the Annie Elizabeth but we have re-planted in that area and found no remains, so it is reasonable to presume that it had gone a long time previously. Also the fruiting bodies were only present right against the trunks of the affected trees and treatment was only applied adjacent to the affected trees, which eradicated the Armillaria, all indicating that the source had been treated.

 

I don't think there is enough to go on to be definitive, but looking back my view is that, in an orchard with many trees on weak rooted dwarf stock, they would have been very vulnerable had Armillaria spread, unless it happened to be a purely saprophytic species. Even gallica is regarded as a weak pathogen which in this case may be strong enough to kill trees on dwarf stock, or sufficiently weaken the root system that they fail. As such, I would still be inclined on balance to eradicate it (were a suitable treatment still available) and risk local damage to the soil ecosystem, on the grounds that recolonisation with beneficial agents from the surrounding soil should be fairly rapid, whereas negative spread would be equally rapid and probably far more damaging.

 

Alec

[AHPP]

Excellent thread. Thank you for taking the time to post.