An unhealthy cherry

[John Robinson]

Just spotted this in our orchard and wondered if anyone could identify the problem. Seems to be occurring on a couple of trees, both of which are cherry rootstock which we have let grow. Other, grafted cherrys nearby seem unaffacted.

 

[agg221]

Looks like bacterial canker to me - what variety are they and whereabouts in the country (also, what's the soil like)?

 

Alec

[John Robinson]

Thanks for the reply.

 

I don't know the variety. They were suckers transferred from a previous home. We're in North Lincolnshire and the soil is very poor and sandy - the tree had it's first manure mulch last Autumn.

[agg221]

Any details on the tree they were suckers from - approximate age and size, and where in the country? Also, was it top-worked (grafted at the top, at about standard height) or grafted near to the ground?

 

The reason for the questions is that this will narrow down a likelihood as to whether it's Colt, F12/1 or seedling cherry. This will give a clue as to likelihood of susceptibility.

 

Ultimately though, it hasn't girdled the tree and bacterial canker is annual rather than progressive, so this particular canker won't get any worse. Further control is a combination of cutting out heavily diseased branches (such as that side branch), minimising stress on the trees, and deciding whether or not to spray (copper-based fungicide). Minimising stress means keeping grass away from the trunk so there's less competition for water. Your mulch of well rotted manure will help here, although you don't want to overdo it and get lax growth. Sandy soils are likely to give you more of a problem with drying out, although the normal 'bad' soil type is heavy clay leading to waterlogging.

 

Longer term, some varieties are more susceptible than others. The classic book on cherries ('Cherries' by Norman H. Grubb) contains some text where he's bemoaning the fact that, whilst trying to establish the national trials at East Malling, unfortunately the site wasn't very suitable and some varieties he couldn't even get to fruiting size before they died, so he couldn't identify them!

 

Alec

[John Robinson]

Thanks again Alec. The trees they suckered from were themselves suckers transplanted from another location. The variety they originated from is long lost in time. I can say that we transplanted these from South Yorkshire to North Lincs.

 

In terms of removing the branch, is that something I can do now or should I wait till later in the year?

 

Thanks again for your help, which is much appreciated.

[agg221]

Hi John,

 

Are you suggesting the variety is coming true on its own roots? I'd be interested in anything you can throw in on the original location of the variety, and a description of the fruit and the form of the mature tree. I might be able to help with a tentative identification, at least of type, and some of the obscure local varieties are beginning to become more recognised now by various groups.

 

I've dug out Grubb's comments on canker, reproduced below. It's long, and detailed, but may be of interest. Personally, I'd trim out the damaged area when the tree starts to grow. There's not a lot to be gained by doing it sooner - both the canker and the tree are dormant so neither is moving at the moment, and you want to avoid secondary silver leaf infection.

 

Alec

 

From Cherries, by Norman H. Grubb, 1949:

 

Bacterial Canker

This disease, common to plums and cherries, is probably the most serious and widespread disease of sweet cherries in England. It has been present in the variety collection at East Malling since the early years, and has in several cases, mentioned in the variety descriptions here given, made it impossible as yet to obtain a description of the mature tree habit.

 

There can be few cherry-growers in England who have never seen trees injured by Bacterial Canker. Signs of it have been seen in every cherry district, and in every nursery where cherry-trees are grown, which the writer has visited. Even in orchards which appear at first sight to be entirely free from it, if trees of any of the highly susceptible varieties, like Napoleon or the three "Mezels", are present, some indications of the disease will almost certainly be found. There are still some cherry-growers who do not know the reason for the death of branches or whole trees in their orchards, usually with the exudation of large quantities of gum. A short description of the symptoms commonly seen may therefore be useful.

 

The disease is often present in winter, without any obvious signs. More than once, as late as May, we have congratulated ourselves on the few signs of canker in the cherries, only to find later on quite as many trees and branches dying as usual, and sometimes more. The major symptoms are most obvious from midsummer onwards. Where whole trees or large branches are affected, they can be seen from long distances; the foliage loses its healthy green colour and, and becomes yellowish or brownish. It may drop long before the usual time; or if the tree or branch is quickly killed, it may remain and dry up, like the dead leaves often remaining on oak and beech trees in winter.

 

The exudation of gum from the lower parts of affected branches, or from the crotches or stems of dying trees, is a common symptom, but not quite universal; cases have been known of the death of branches and trees, due to Bacterial Canker, with little or no gum exudation. The gum, when present, is dissolved or softened by rain, and frequently drips on to the lower part of the stem or the ground. It is true that gum may be exuded in small quantities in the absence of Bacterial Canker; any mechanical injury to the bark may cause it. But where large quantities are present - the condition known to our ancestors, and still often called, "Gumming" - the only cause so far certainly known is Bacterial Canker. The fact that Hogg remarked of our most susceptible variety, Napoleon, "the tree is a very vigorous grower, very hardy, and not subject to gum" does not necessarily indicate that there is more than one cause of "gumming"; the explanation may be that the disease was less widespread in Hogg's day than in ours, or perhaps that the form Hogg described was more resistant to disease than the one we now have.

 

A very common symptom in wet springs is "Bacterial Leaf-Spot". The relationship between this and the death of spurs due to bacterial attack on the one hand, and the cankers in branches and stems, on the other, has not yet been fully worked out. It is known, however, that two organisms are concerned; their relative frequency is still obscure, as is also the possibility of one form of the disease giving rise to infections of other forms. There are other causes of "leaf-spot" in cherries besides bacterial infection; and spurs of some varieties are commonly killed by Brown-rot. Thus, in the absence of expert identification, these symptoms cannot be assumed to be due to bacterial infection.

 

A partial control of Bacterial Canker has been worked out, consisting of spraying with Bordeaux mixture twice annually. An application as nearly as possible at the time of leaf-fall is given at a strength of 10lb of copper sulphate and 15lb of hydrated lime to 100 gallons of water; this is repeated in spring, shortly before blossoming, at the lower concentration 6-9-100. Severe damage to the foliage can be caused by using too high a concentration for the spring spray, or by applying it after blossoming.

 

The control resulting from these treatments is not at once apparent. In the summer following the first applications there may be little or no difference between sprayed and unsprayed trees, doubtless because most of the infections then appearing took place before the leaf-fall application. But with susceptible varieties the repetition of the sprays over a two- or three-year period is said to give enough control to be well worth the cost.

 

The disease in its stem and branch forms seems also to be partly controlled by cutting out infected branches or trimming the discoloured bark from infections on the stem. The control is by no means complete, possibly because re-infection takes place through knife- and saw-wounds; painting the cut surfaces may reduce the risk of re-infection, but does not seem to prevent it altogether.

 

Trials are in progress to test the effect of frame-working susceptible varieties on the branches of root-stocks or named varieties known to be more resistant. There is little to indicate that the mere fact of working the susceptible scions on a resistant frame will increase the resistance of the scions; but at least in such frame-worked trees the crotch (one of the most commonly infected parts of susceptible trees) will be resistant. If one branch is killed by the disease, others may survive.

 

Wherever the disease is known to be troublesome, provided the soil is not unsuitable for cherries, much can be done by planting only the more resistant varieties. For this reason, the brief tree descriptions in this volume include any available information about the susceptibility of the varieties to the disease at East Malling, and sometimes elsewhere. This should be of some help to prospective planters. Reports received from growers in many districts, however, suggest that the relative susceptibility of varieties may to some extent differ in different conditions. Thus Roundel - at East Malling one of the most resistant varieties - is sometimes reported as susceptible; whilst Bradbourne Black, which at East Malling is often rather susceptible, appears in some orchards to be more resistant than some which are less affected at East Malling.

 

For these contradictory observations there may be more than one explanation. In the first place, the varieties may not be identical. It is known, for instance, that the names "Roundel", "Bedford Prolific", and "Bedford Black" are used for several varieties, some of them so closely similar in fruit as to be almost indistinguishable; and there certainly exist slightly "variant forms" of what may be regarded as the same variety, some of which probably differ in their susceptibility to the disease. Secondly, the susceptibility of certain varieties seems to vary with the age of the tree. Some, of which Schrecken and Bradbourne Black are examples, appear to be rather susceptible when young, and to "grow out" of it as they become mature; others, such as Elton, and perhaps Waterloo, appear to become more susceptible when mature. Such changes in susceptibility may be more common than is at present known; the variety collection at East Malling contains no more than two or three trees of most varieties - not enough to give reliable indications.

[John Robinson]

Are you suggesting the variety is coming true on its own roots?

 

I think I am (as you can tell I'm new to this!). The sequence of events which lead to this tree is described below:

 

I'd be interested in anything you can throw in on the original location of the variety, and a description of the fruit and the form of the mature tree.

 

Unfortunately I don't have any information on the original variety at all. All I know is that a cherry tree in the Sheffield area had been cut down and the garden was peppered with suckers. Some of these were planted elsewhere in South Yorkshire and grew into mature trees at a height of about 10ft with light pink flowers. When these were cut down, these also suckered and these suckers were transferred to their current location. I think that is what you mean by being true to their own roots?

 

I might be able to help with a tentative identification, at least of type, and some of the obscure local varieties are beginning to become more recognised now by various groups.

 

Sorry I can't help with more detailed information.

 

I've dug out Grubb's comments on canker, reproduced below. It's long, and detailed, but may be of interest. Personally, I'd trim out the damaged area when the tree starts to grow.

 

Many thanks. I will read through that tomorrow, and follow your advice on pruning the damaged wood.

 

Thanks again.

 

John.