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PLUM TREE PESTS AND DISEASES
Plum trees are one of the more resilient fruit trees and if they are given good care then they will most likely remain unaffected by pests and diseases.
Like all plants however things can go wrong and this page is designed to help you identify what the problem is and the best method of dealing with it.
Because plum trees can deal with a good amount of neglect, many of the problems are associated with old age. Another cause of problems with plum trees is frost. Plant them in a frost pocket and the tree will survive but fruit will suffer.
The picture above shows the damage done to plums by the plum sawfly (Hoplocampa flava). From the outside the plum looks OK, may be a small brown mark on the skin but nothing more. But inside, the plum is completely inedible. You may also notice one or two small hardened drops of resin on the fruit which are the tree's response to being attacked.
In spring the sawfly emerges from the soil and lays eggs on the blossom of plum trees. When the plums develop the little caterpillars eat their way into the centre of the plum and feed off it as the plum develops.
Plum Sawfly is difficult to control using organic methods, the only one being available is a pheromone trap which goes some way to controlling the disease.
Look for the giveaway brown mark on fruits and when they are forming pick the fruit off and burn them, this will help in controlling the disease next year. Burn any fallen fruit which is unusable.
The chemical deltamethrin sprayed when the blossom is falling off will definitely help control plum sawfly.
Another effective method to control this pest is to break up and turn over the top 8cm / 3in of soil with a trowel around the tree in February to March. This will bring the bugs to the surface and birds will eat them.
This is often referred to as Plum Leaf Curl Virus or Plum Leaf Curl Disease, both are misleading. There is no such virus or disease, the curling of leaves is caused by some other factor. In the vast majority of cases it is aphids which cause the leaves to curl. Often these aphids are called leaf curl aphids.
To check for aphids, uncurl the leaves and look for signs of aphids. If you can't see any, look through a magnifying glass or take a close up picture and expand it. Often, aphids are not visible to the naked eye.
It's important to diagnose aphids correctly because if you assume it's a virus, disease or a fungus then you will may well end up spraying with a fungicide or other spray which will not kill the aphids.
Plum trees are often attacked by aphids and the first signs are young leaves curling up, this is often referred to as Plum Leaf Curl. They are not normally discoloured just curled. If you uncurl the leaf the aphids will be seen inside - small green, white or light brown insects. By themselves they probably won't cause too much damage but often they secrete a sticky juice which attracts unwanted diseases.
We have written a whole page on identifying and treating aphids and it can be found here. Follow that advice and almost certainly your plum tree will live through the attack with no bad side-effects. Two specific types of aphids attack plum tree, the Plum Leaf-Curling Aphid and the Mealy Plum Aphid. Both are treated exactly the same as other aphids. The Plum Leaf Curl tend to attack from April to June whereas the Mealy Plum Aphid attacks in July to early September.
There are chemical sprays which may help (one of the most common is Resolva Bug Killer) but there is nothing that could convince me to spray chemicals over plums and then eat them. The other problem with chemical sprays like Resolva is that they kill pollinating insects. The alternative is the plum moth pheromone trap which attracts the male moths. The moths then stick onto the trap thus reducing the population of male moths. If you try this method follow the instructions exactly for the best effect.
Both Czar and Victoria plum trees seem to be particularly vulnerable to plum moth attack, other varieties less so. The lifecycle of this pest starts in May when the female moths lay eggs on the underside of growing plums. The eggs hatch and then dig into the plum and feed on it. When fully developed the caterpillar comes out from the plum and builds itself a small cocoon where it pupates (changes) into a fully grown moth. Favourite places for doing this are under cracks in the bark or on the soil below the tree.
The damage occurs typically in April to June time and the trees will fail to develop fruit in that year. There is no agreement as to exactly why pigeons do this. Preventing the damage depends to some extent on how big your plum tree is. Smaller plum trees can be protected with netting which is simply draped over the tree and this works well. Fruit cages are another permanent solution which prevent 100% of the damage.
For larger fruit trees, where it is not an option to surround them with a physical barrier, the options are more limited. Methods which have worked in some cases include those listed below:
- Hang old CDs from the branches to scare the birds
- Cut the bottom out of plastic bags and tie loosely to branches -
unattractive maybe but it seems to be the most successful way to scare
pigeons. The bags move about in the wind
- Plastic model of birds of prey tied high up on the tree and moved
occasionally. These can be bought online
One method which has been proven to be a failure is to try and attract the pigeons to other areas of the garden / allotment with bird food. What then happens is that more pigeons are attracted, they eat the bird food and then turn their attentions to the tree.
The symptoms of brown rot in plums are unlikely to be mistaken for any other disease. The skin of the affected plums will have grey, small raised bumps on it and if you cut into the plum the flesh will be discoloured and rotting where the bumps are most numerous. If left, the plum will shrivel completely. The picture below shows a plum affected by brown rot at a relatively early stage.
Insects, birds and fruit splitting because of lots of rain, all damage the fruits allowing this fungus to gain entry. Once a plum is infected it can infect other nearby fruit as well and very quickly the whole tree can become infected. Most at risk are plum trees that bear fruit very closely together (Victoria plum trees are particularly prone to Brown Rot) There are no chemical sprays available to the amateur gardener but if you follow the action plan below this disease can be eradicated:
- As soon as you notice affected plums remove and destroy them.
- Remove and use any fallen plums, do not let them remain on the
- Pick fruit as soon as it is ripe, do not let them over-ripen on the
- If your plum tree is very tall with fruit high up that you cannot
reach then you have a problem. With trees of this size the plum fruit
higher up cannot be harvested and is a prime target for Brown Rot.
Invest in a pair of long-handled loppers and cut the highest fruit
bearing branches off. Late spring / early summer is the ideal time to do
- Thin the fruit on plum trees as recommended on this page. Too much fruit causes them to rub together allowing fungi such as Brown Rot to enter, it also prevents good air circulation.
See also the question near the end of this page about the effect of untreated Brown Rot in later years.
The signs to look for are small green caterpillars on the leaves, buds which fail to develop and leaves with holes in them. This pest is the Winter Moth and will normally become apparent in late March to May. The first indication will be tiny caterpillars on and around fruit and leaf buds. They may spin silken threads and hang from the tree twigs. They then grow into larger caterpillars and will eat leaves, buds and almost all parts of the foliage.
Read our Winter Moth page for more details.
There are many forms of scale insects which attack a variety of plants but one in particular can be a problem with plum trees, it is named the Lecanium Scale. The picture below shows just how scary looking this pest is but, although serious if left to its own devices, it is not impossible to control. At maturity they look like pea-sized growths which are purple-brown on stems and young branches.
First, exactly what is it? What you see in the picture above is a scale insect which feeds on the sap of a twig, branch or leaf. Their life cycle begins when the scales overwinter and then lay eggs around May time - 200 or so eggs which are beneath the parents body. In May to mid July the eggs hatch and crawl away to new parts of the tree. This is the stage at which pesticides can be effective, when the insects are moving about. When the insects find a suitable position they clamp their jaws onto the bark of tree and begin to feed on the sap of the tree without moving again.
If you can identify the period in May /June when the young scale insects are on the move spraying with an insecticide will kill them. Ask at your garden centre for an appropriate spray. In general though, sprays suitable for killing aphids will also kill moving scale insects.
If you miss this stage of their lifecycle then a plant oil winter wash treatment (again ask at your local garden centre) in December to January will effectively suffocate many of the overwintering bugs.
The easiest method, if your tree is a manageable size, is to manually remove the scale insects around May when they are clearly visible but have not yet hatched their eggs. If you are squeamish about removing them with your fingers use a toothbrush and some diluted washing up liquid to brush them off. A gentle spray after with a hose should then remove all traces of them.
Relatively unknown in garden cultivated plum trees in the UK, Plum Pocket is becoming increasingly common. The symptoms are quite unusual and hard to mistake for any other pest or disease. Young fruit begin to to appear longer than normal and slightly larger, this normally becomes visible around mid June time. The next symptoms are white marks on the skin of affected plums, this is a fungus forming. Soon after the plums will begin to wither and die. Normally only around 50% of the plums are affected.
Both the picture above and below are courtesy of GardenFocused reader Walter A who is quite clearly a better photographer than I am! The above picture show young fruit on the right developing in the typical elongated fashion. The left hand plum is more developed and is clearly suffering from Plum Pocket.
If the fruits are cut open at any stage no stone will be found, just an empty "pocket" of white flesh as can clearly be seen from the picture above. As the plums wither they turn brown and fall off. The disease is caused by the fungus Taphrina pruni and affects plum and damson trees.
LIFE CYCLE OF PLUM POCKET
The spores of the fungi are spread through air and water from nearby affected trees. It is more commonly found on wild plum and damson trees so if you have any nearby take a careful look at them for signs of infection. The spores become airborne in early spring, land on your tree and lodge in the bark and newly forming branch buds. There they stay, causing no damage, until the next spring. They then multiply and begin to attack fruit buds and young fruit and cause the damage mentioned above.
TREATING PLUM POCKET
The spores of the fungi are spread through air and water from nearby infected trees and also from the affected tree itself. Once the fruit are initially affected there is no way to save them that year. Treatment is aimed at limiting the spread of the spores and at the same time spraying the tree before fruit buds form in early spring.
The first course of action is to remove and burn all affected fruit including those which have fallen to the ground. Take a close look at the tree and if you notice any unusually thick clusters of twigs growing from branches, prune them off because in all likelihood they are infected. As part of the normal pruning process remove any twigs and branches which look unhealthy.
A fungicide sprayed onto the tree will also limit damage very considerably. The best one we know of for Plum Pocket is Westland Plant Rescue Fungus Concentrate, the active ingredient is Difenoconazole. Spray the tree once in November and then again in March.
The copper fungicide Bordeaux Mixture has previously been recommended as a spray to prevent Plum Pocket. However it has now (or soon will be) withdrawn from sale in the UK. Currently there are no alternatives which have been scientifically proven to be anywhere near as effective as Bordeaux Mixture
Various alternatives are suggested, for example aspirin solution or milk, but none have been proven to have any effect.
WHITE POWDER ON PLUM TREE LEAVES
Plum trees often suffer from POWDERY MILDEW which is a fungal disease. The powder you see on the leaves are the spores of the fungus. We have a page dedicated especially to identifying and treating powdery mildew which can be found here. As far as plum trees are concerned the problem is most frequently caused by bad air circulation especially in the centre of the tree. Although plum trees withstand infrequent pruning better than most other fruit trees, this fungus often occurs where the foliage and branches are crowded.
Where the disease is left to progress secondary infections and pests may well attack the weakened tree. Aphids in particular (please use a magnifying glass to examine the leaves) are attracted to weakened trees and they may cause the mildew to turn sticky in places.
Most commonly found in plum tree it can also affect other trees. There are two symptoms which are commonly noticed. The first is silver sheen to some, though not all, of the leaves. The second symptom you may notice is visible only if you prune branches 3cm / 1in or more wide. There may well be a brown stain in the wood.
Read our detailed article to positively identify Silver Leaf disease, the causes and how to treat it.
The most likely cause of this problem is Shot hole (also known as Coryneum Blight) and this section covers that disease. Similar holes can also be caused by Canker (damage to the bark will also be clearly present) and the Shot hole Borer (stems and trunk have holes in them but not the leaves).
The most obvious symptom is the appearance of lots of holes in the leaves. Initially they are brown circles of dying or dead tissue, as the leaf grows the brown circles fail to grow and eventually they fall off leaving the trademark round holes. These can join up over time leaving bigger holes in the leaves. Less obvious signs are brown marks around developing buds and / or grey spots on the fruit which may also include a resinous gum.
The disease is a fungal infection which thrives in damp and crowded conditions. It does respond to chemical treatment both in spring and autumn. In spring spray with an anti-fungal mix such as Westland Plant Rescue Fungus Concentrate.
The copper fungicide Bordeaux Mixture has previously been recommended as a spray to prevent fungal diseases in fruit trees. However it has now (or soon will be) withdrawn from sale in the UK. Currently there are no alternatives which have been scientifically proven to be anywhere near as effective as Bordeaux Mixture
Various alternatives are suggested, for example aspirin solution or milk, but none have been proven to have any effect.
The fungus can also be controlled simply by reducing the number of affected leaves, buds and correct pruning especially of the lower parts of the centre of the tree. Firstly, remove all fallen leaves and twigs from around the base of the tree. If the area is water logged, try to provide good drainage to reduce humidity. Prune off all affected twigs which have infected buds.
Plum trees such as Victoria are more likely to be affected by Shot hole because they tend to grow branches and foliage close together - perfect conditions for this fungus.
The picture below describes the symptoms very well. Round holes in the bark of the tree are visible, most frequently in the main stem. Repeated attacks result not only in holes in the bark but the bark begins to lift off the surface of the inner wood. The Shot hole Borer is most common on plum, apple, pear and cherry trees.
The holes are caused by the Shot hole Borer beetle and the life cycle is as follows:
- The adult beetles (black / dark brown) bore small holes into the wood in May / June time where
they lay about 50 eggs.
- The eggs pupate into larvae which feed on the wood.
- About two months later the larvae have turned into adult beetles and they bore their way out of
the wood leaving the characteristic small round holes.
- In August / September the adults then bore their way back into the bark where they lay eggs.
- The eggs overwinter and appear as adults in May / June time starting the lifecycle again.
In most cases plum trees which are affected are already weak and the shot hole borers cause even more damage. In the UK there are no insecticide / pesticide sprays to prevent or cure shot hole borers. Your only option (with only a very slim chance of success) is to improve the general health of the tree. In reality, it is probably best to dig up the tree, burn it and start again. Do not plant new fruit trees in the same position.
Rust affecting plum trees is caused by the fungus Tranzschelia pruni-spinosae. It's normally first noticed in August time with the underside of the leaves having a rusty-brown coating to them. The top sides of the leaves may also have small, irregular black marks on them, see the pictures below. Some varieties of plum tree, Victoria especially, are more prone to rust compared to others.
It does not affect the fruit, if the fruit are showing signs of disease you have another problem as well as rust. There are currently a few sprays that are available to the amateur gardener to control rust but none are designed to be sprayed on plum trees (or other edible crops). You will see this specifically mentioned on the labels of the products.
Whilst rust can be a very serious problem for some plants (e.g. some pine trees) it is not a serious problem in plum trees because it occurs late in the year. Rust is spread on the wind and it overwinters on / just below the ground on plant matter, leaves especially. It also overwinters to a small degree in crevices on the bark of plum trees.
In any year there will be several sources of rust and it is almost impossible to eradicate them all. The following actions however will limit the spread of the disease and in many cases all make it unnoticeable:
- Rust thrives in humid conditions and this can be minimised by
ensuring there is good air circulation through the middle of the tree.
If you have a problem with rust in one year pay particular attention to
thinning out the centre of your plume tree when you
prune it in June / July the next year.
- Plum tree rust primarily overwinters on leaves which have fallen to
the ground. In the year you notice rust as being a problem thoroughly
clear up all fallen leaves as often as possible. Do the same in the next
year even if the rust appears to be minimal.
- Do NOT remove infected leaves from the tree, wait until they fall to
the ground. Leaves infected with rust are still capable of supplying
nutrients to the plum tree especially just before they fall off.
- Rust grows best on nitrogen rich foliage, do not feed your plum tree with nitrogen rich fertilisers. If you do need to feed the tree, use long-lasting fertiliser such as blood, fish and bone.
SUNKEN, MISHAPEN AREAS OF BARK, DARK GUM OOZING FROM SURFACE
These are the classic signs of Bacterial canker. The other sign is yellowing leaves with holes in them. Click here to read our detailed article about identifying and treating bacterial canker as well as the lifecycle.
Plum trees which suffer from environmental stress such as hot or cold weather, fluctuating levels of moisture at the roots or similar conditions often produce plums which have small blobs of clear and hardened liquid on them, the picture below shows these blobs on plums.
There can be lots of them or just a few. As well as environmental conditions this can be caused by very localised insect damage or it can be the result of some other more serious pest or disease. The blobs themselves are not a pest or a disease but they are produced as a result of some other pest, disease or condition.
Cut an affected plum in half and look for signs of a pest, if none is found then the plum is still edible. If there are other signs then diagnose what has caused them rather than worry about blobs themselves, they are just a sign of another problem.
There is no one answer to this problem so you need to work through the section below to work out what is happening:
- When the blossoms are forming in early spring, through to the time when they open out, a late
frost can damage the blossom. In this case the blossoms will die within a day of the
frost and you will end up with a browned and clearly damaged blossom. This will not be pollinated
and therefore will not set fruit.
Occasionally this happens in cold years and there is nothing to be done except to put up with it and hope for fruit next year. It could also be that the tree is in a position where it will very frequently suffer from late frosts either because the area you live in is always cool or the tree could be in a frost pocket. If either of these are the case then you have two options.
- If the tree is young it can be moved to a better position.
- If it's five years or more old then it's probably best to think about a new, more frost resistant plum tree. Czar and Victoria are two common varieties which resist cold well.
- If the tree is young it can be moved to a better position.
- The blossoms are not being pollinated. In this case the blossom will be produced but will
simply die off before being pollinated. The likely reasons for this are:
- The tree is not self-fertile and there is no nearby suitable pollination partner. See our page on
plum tree pollination for full details. To save some time
for many of you reading this, I can confirm that the two most common plum trees, Victoria and Czar,
are self-fertile and do not need a pollination partner to set fruit.
- Bees are unable to pollinate the blossoms. In some areas there is simply a shortage of bees. In
other areas the weather may have been too cold or too windy / rainy for a prolonged period of time
which will prevent bees going out and pollinating the tree.
The above picture shows two blossoms which have finished flowering. On the left the fruit has set (i.e. the blossom has been pollinated) and this can be identified because, just below the old blossom, the fruit has a slight bulge in it. On the right the fruit has not set (i.e. the blossom has not been pollinated) and this can be identified because, just below the old blossom, the "fruit" has no bulge in it.
- The tree is not self-fertile and there is no nearby suitable pollination partner. See our page on plum tree pollination for full details. To save some time for many of you reading this, I can confirm that the two most common plum trees, Victoria and Czar, are self-fertile and do not need a pollination partner to set fruit.
- If none of the above applies to your plum tree then the problem is most likely due to how the plum tree is being cared for including pruning.
REDUCED AMOUNT OF BLOSSOM
Plum and greengage trees are renowned for failing to produce blossom in their first three to four years. One year they may be fine, the next there may be lots of blossom. They are especially liable to fail to produce blossom when a cold snap occurs at the time blossom production is just starting.
There is nothing that can be done to help other than keep them in good condition (see care instructions here) and they will most likely blossom and produce fruit the next year. With smaller trees and those in containers it is possible to net them with horticultural fleece to reduce the risk of frost damage. However, it looks unsightly and is not a practical solution with larger trees.
In some gardens, the position of the tree may prevent the shade side of the tree from producing blossom but the side facing the sun is relatively unaffected. This is caused by the shaded side suffering worst from the cold weather compared to the sunny side.
FRUIT HAVE SPLIT OPEN
The picture below says it all, the plums have large cracks in them. Typically this happens in late July to August and often just as the plums appear to be ripening.
Initially this is not a pest or disease it is as a result of variations in the water supply available at the roots. Typically there will be a dry period and during this time the forming plum skin will start to harden slightly as a result. Then, if there is suddenly a large amount of water available the fruits will swell but the skin can't keep up with it and splits open.
If the plum tree is grown in a container the solution is to water more frequently but don't water log. Try to keep the water supply constant. If the tree is in the open ground and there is a dry spell, especially if the tree is grown against a wall, water every week or so. A mulch around the tree, as far as the extent of the canopy, will also help to ensure an even supply of water.
When the fruits have split they are still perfectly edible. However they will quickly attract wasps, other pests and diseases which will spoil the fruit even more. The bottom right plum in the picture above shows a blob of semi-hard resin which is simply a side effect of the plum splitting.
A reader of these pages sent in the picture below to illustrate the problem. The picture clearly shows wilted leaves and also yellow / brown leaves, some with small holes in them. We deal here exclusively with wilted leaves because in all probability the major problem is the cause of the wilted leaves. The brown and yellowing leaves may well be a secondary symptom.
Wilted leaves are a sign that the upper part of the tree is not receiving sufficient water but the problem may not be alack of water. The wilting could be caused by too much water.
Unfortunately there can be several reason s why leaves wilt on a plum tree and we discuss each of them below. It is up to you to decide which is applicable in your case.
If a tree is starved of water eventually it will suffer and wilting leaves will be one of the first indications of a problem. This situation is most common in containerised trees and young trees planted in the ground. It is rare in established trees unless something significant has occurred to the local area around the tree.
The solution is simple, water more frequently. Where the tree is in a container, temporarily moving it to a shady position as well will speed up the recovery process
TOO MUCH WATER
Too much water can have the same effect. If a plum tree is waterlogged the roots cannot absorb essential oxygen and the tree will go into a decline. This may take several weeks to damage the tree.
The soil around the tree, or in the container, will be consistently over wet (ruling out a lack of water). The solution is to cease watering the tree until the surrounding ground (or in the container) is much drier.
WATER-FLOW IS INTERRUPTED
If the main trunk of the tree is damaged or infected, water supply to the upper part of the tree may be totally or partially restricted. This can cause leaves to wilt. The most common cause of this is severe canker affecting the main trunk.
If the canker only affect specific branches, the wilting leaves will be restricted to that part of the tree. See here for our in depth article about canker and plum trees. An alternate cause can occasionally be damage caused by animals such as deer.
ROOTS ARE DAMAGED OR INFECTED
The least likely cause of wilting leaves are damaged roots but it does occasionally happen. The problem is hard to diagnose without digging the tree up and that will do it serious damage. Damage to the roots can stop the absorption of moisture and deprive the foliage of water.
The best course of action is to only dig up the tree when all hope of it recovering is lost. At that point examine the roots carefully for signs of damage and / or disease. This will allow you to take action to protect nearby trees and any new plantings.
Wasps can eat and disfigure plums and sometimes the damage is considerable. There have been many contraptions and devices developed over the years but, so far, the evidence is that none of them has any significant effect in reducing wasp activity.
This includes jam jars full of sugary liquid which can trap a few wasps but the numbers are so insignificant that they can be considered useless.
The latest device is a false wasp nest which is intended to scare other wasps off. We can find not a shred of evidence that this works.
If the damage caused by wasps to your plum tree is significant you can be sure that there is a wasp nest nearby. Wasps are not lazy insects but neither are they stupid, they build their nests near to a source of food and they consider plums, apples, pears etc. a very good source of food.
To make matters worse, where wasps damage the plum fruits this can often quickly attract flies who will feed on the damaged areas. They can cause further porblems and will also help transfer diseases to the plums.
The only way you can reduce damage to your fruit trees by wasps is to kill them in their nest. By all means spend time searching the internet for other solutions but there are none at the moment. Locating and killing them in their nest is the only solution.
As far as killing wasps is concerned, our advice is to leave that to expert pest companies. Only five people, on average, are killed each year from wasp and bee stings but many more suffer very bad reactions and many more acquire a lifelong fear of wasps. Leave it to the experts.
This then leaves your only contribution being to locate the wasps nest. You will need to spend a bit of time doing this. Watch the wasps when they land on fruit and then determine the direction they fly off to and follow this. With a bit of patience this will eventually lead you to their nest which is unlikely to be far away.
Apologies for not providing a quick and free solution to wasp damage on plum and other fruit trees, but the above are the facts.
COMMENTS / QUESTIONS LEFT BY OUR READERS
|13 March 2016||From: Rosie|
|For a few years we have had a white/grey powdery growth on the branches of our plum tree. This is also on other trees in our and our neighbours garden. The tree still fruits but each year there is less fruit and more branches become brittle and break off. What is this and is it treatable? Can I prevent this spreading to other trees?
ANSWER: This sounds very much like Powdery Mildew. We have a page devoted to the causes and possible treatment of this problem which can be found by clicking here.
|29 January 2016||From: Betty C|
|I have a ten year old Marjorie seedling used to be called a damson but now a plum? It Has always cropped well but last year was badly pruned by someone "helping" my sick husband. Yesterday I noticed the whole of the trunk and larger
branches are covered in white mushroom like fungi growths. We have had a very wet winter but not actually had any flooding here. A Victoria plum close by seems to be OK at the moment. I am worried that whatever it is might spread.
ANSWER: The bad pruning and the fungal infections may or may not be connected, it's difficult to know. If the pruning was done in winter it's more likely that they are connected. Plum trees should only be pruned when the tree is actively and strongly growing, June is a good time.
Any fungal growth is likely to release massive amounts of spores and if they have infected one plum tree they can infect another one nearby.
The decision is up to you as to what to do with the Marjorie's seedling, without seeing it I can't say. But plum trees are prone to fungal infections and they are difficult to control especially because most of the fungicide sprays are now banned or not for use on plants which produce edible crops.
If you keep the tree, don't prune it this year and don't prune the Victoria plum tree either. Open cuts are prime sites for fungal infections to enter.
|10 October 2015||From: Michael Back|
|I have a plum tree 6yrs old normally good crop but this yr half of the tree died and the bark is splitting, I will prune out the dead and treat the cuts
ANSWER: Sounds like a good course of action to me. I do hope it recovers. Choose a dry day if at all possible.
|01 October 2015||From: Roy F|
|My plum tree is 2 yo not a very good crop this year if the birds didn't eat them wasps invaded them what can i do to guard them is there any insecticide or other means to protect next year|
|27 August 2015||From: Madeleine S|
|My Victoria plum tree had a white blight on the leaves and plums but with all the rain we have had recently the blight has gone. Can I eat the plums now if I rinse them off with tap water?
ANSWER: Without knowing more about the "white blight" I can't offer advice about eating the fruit. I can say two things however, I am unaware of any disease of plum tree fruit that makes them inedible after a wash with water. The "blight" does sound to me like a form of mildew and that can simply be washed off and the fruit then eaten.
|22 July 2015||From: Arthur|
|My 20 year old Plum tree seems to have attracted loads of what looks like mini wasps. Can they damage the fruit? I Have already sprayed with Bayers. Thank-you in anticipation.
ANSWER: We have added a new section above about plum trees and wasp damage which can be found here.
|12 June 2015||From: Wendy|
|I have a Victoria plum tree which I planted 4 years ago. I had leaf curl disease badly in year 2, sprayed in year 3 which cured most of it.
Last year there was 3 plums on the tree which grew to eating stage. This year sprayed again, twice, as recommended on bottle. Still got some leaf curl and got clumps of leaves which turned brown and looked unsightly. There was about a dozen plums growing which all dropped off when they were about 2cm long.
There is also spots of sticky goo in places. Is this the canker you mention and why did the plums drop off? I only found your site yesterday and went straight out and pruned the tree. Great advice to other questions by the way. Keep up the good work, US amateurs rely on people such as yourself.
ANSWER: There are a couple of questions to answer. First, there is no such thing as "leaf curl disease", it's important to understand that. See our section on this above here. The problem is almost certainly aphids and they are causing the leaves to curl. To treat this you need to get rid of the aphids organically or spray with an appropriate insecticide.
A bad infestation of aphids can severely restrict fruit production (causing developing fruit to drop off) and this seems to be what has happened to your plum tree.
As far as the sticky goo is concerned, if it's on the fruit then it is not canker, see here for what it may be. If it is on the stems and branches, especially if they are cracked, then in all likelihood it is canker. See our page dedicated to this bacterial infection here.
|12 June 2015||From: Wendy|
|This is a leaf off my Victoria plum tree would like to know if you could tell me what it is and what I can do about it.
My hubby and I are not gardeners and we don't have a clue. Edges of the leaves are curly with green lumps all over them like
ANSWER: Not sure what that is. If you send a picture I will will do my very best to diagnose. Send the picture to the email address on our "Contact Us" page.
Without a picture to confirm, the most likely cause of the lumps is small insects between the two layers of the leaves. The insect is either growing or laying eggs. In the vast majority of cases there is nothing to be done and the tree is likely to be relatively unaffected. Spraying the tree with an insecticide will do no good because the insecticide will not permeate the leaf surface.
|9 June 2015||From: Pamela Hammond|
|Just bought a mini plum tree which have left in pot as it appears to be 'bleeding'. The buds are
still tightly shut but brown liquid is trickling down the trunk!!
ANSWER: It sounds very much like your tree has bacterial canker. Full details of this bacterial infection can be found by clicking here. If you have just bought the tree I would take it back to the supplier and ask for a refund because the infection was clearly there when you bought the tree.
|5 June 2015||From: Mark|
|I have a Victoria plum it had lots of blossom this year but after they seem to go brown and drop off have you any idea what this could be?
ANSWER: I have added a new section in the main article to answer this question in depth. Click here to go there now.
|26 May 2015||From: John Windibank|
|We have been here 2 years now. There is a plum tree in the garden that is well established. Last year
it had a lot of fruit but developed a problem by way of white pussie type spots on the fruit which culminated in the
plum shrivelling up, the leaves also dried up. Having sprayed the tree with what ever it was that our local nursery
gave us we accepted that we would get no edible fruit from it. This year there has been no blossom = no fruit. Could
this be due to last years problems? Many thanks in anticipation.
ANSWER: It sounds very much like your plum tree suffered from Brown Rot last year. If that's the case and all that was done was to spray the tree (there are no sprays which are proven to be effective against this fungus) then your tree has suffered significantly. It's no surprise that it has not flowered this year.
It may well recover next year and I would wait until then to see what happens. If still no blossom appears, then I would be tempted to prune the plum tree rather more severely than is normal. The reason behind that advice is because Brown Rot sometimes affects the fruiting spurs and the only solution when that happens is to prune away the fruiting spurs and allow others to develop.
|20 May 2015||From: Adrian|
|I have a plum tree that seems to have a few problem last year most of fruit lost along with leaves.
This year didn't blossom very well only few branches with leaves a lot with out which appear to be dead and brittle.
Some of the large main branches have small buds which developed leaves.
This hasn't happened before. Looked like it has brown rot from googling so have started too cut dead branches and seal
and heal. I cut one of main and this appears to be soft in middle.
Do I have too cut back until solid as this might go back too main trunk. Another question can I graft on to this from healthy
branches from other parts of tree.
ANSWER: It's essential to cut back into good wood to remove the infection. I would suggest cutting back at least 5cm / 2in into good wood.
I have never tried grafting from different parts of the same tree but can see no reason why this shouldn't work. Personally I would leave it until next year to ensure that the tree is healthy.
|15 March 2015||From: Graham|
|I have a number of plum trees in my garden all of which are probably over 20 years old, I have noted
rows of hard fungus growing in Trunks and branches which just break off. I have done this and burned them. Is this
fungus damaging for the trees, will I need to replace them? Thanks Graham
ANSWER: I would need a picture to be 100% sure but normally hard fungi don't do any significant damage. They can sometimes however be a sign of over-damp conditions.
|15 March 2015||From: Hamish|
|Regarding wasps. If you use a bottle glass or plastic instead of a jar put about 1 inch of sugar solution 1 measure sugar to 1 hot water dissolve and put into bottle. The wasps want to get out through the side and hardly ever make it to the top narrow exit. Once you have 2 to 3 inches dead wasps clean out and refill with another inch of solution|
|16 February 2015||From: Ian|
|Last year my Victoria plum tree(about 8- 10years old) was in full fruit when for no apparent
reason some of the branches and fruit started to die back. It became quite widespread so I cut back the affected
branches and found a black centre -some spreading outwards in the branches. Now I have left a 3' stump where
my tree was!! . Can you tell me what the likely cause was?.
FROM DAVE: The most common cause (almost exclusively) of marked wood in plum trees is Silver Leaf Disease. It is also commonly accompanied by "silvered" leaves but you may have missed this. The quick spread of the problems also points to Silver Leaf Disease. Click here for more information, but it does sound very much like a dead tree in your case.
|11 September 14||From: Dreamer|
|My Victoria plum tree was fine last week and now looks as if it is
dying. Some leaves have holes but the underneath of all leaves looks as
if it's covered in rust and has some tiny white maggots. Would appreciate
FROM DAVE: We have added a new section above (see here) on plum rust. Because this fungus tends to occur at end of the season it does little damage to plum trees - it's worse than it looks. As far as the tiny maggots go I would suggest ignoring them this year. If you tackle the rust as described above the leaves should be healthier next year and hopefully the maggots will not appear.
|11 September 14||From: Ron Dark|
|For anyone's interest: For a number of years I had a problem with pear mite on a purchased espalier pear tree. Although no solution appears in any source I have consulted, I found that a fairly strong solution of Jeyes Fluid applied liberally after leaf fall in the Autumn completely eradicated this pest.
FROM DAVE: Thanks for that information Ron. Just to be extra clear where did you apply the Jeyes Fluid? On the ground around the tree or sprayed on the tree?
|21 August 14||From: Lila|
|Hi, our plum tree this year hasn't grown nearly as many plums as last year, the leaves look as though they have
Shot hole disease and we had to get rid of one of the branches as almost snapped. The leaves also have little yellow dots on them. Does this mean my tree is dying? we have picked around 900g of plums, also some of them had maggots. What can we do to ensure next year we have a health tree. We didn't prune it last year and you seem to suggest we do this June time.
FROM DAVE: Yes, wait until June time before pruning. Late August is definitely too late for a couple of reasons and would do more damage than good. As far as Shot hole goes read the section on this problem above. Your tree can recover if you take the action suggested.
For the maggots you don't say what they look like but the most common are the maggots of plum moth. Read the section above here for lots more information on how to deal with them.
|21 August 14||From: Carol Cunningham|
|My single plum tree is covered in tiny plums each spring but they all
turn yellow and drop off when they get to 5-6mm in size. I keep the tree well watered and mulched. It's in part-sun area of the garden. What's going wrong?
FROM DAVE: Plum trees naturally drop some of their fruit in June time but to loose all the developing plums is a different matter. In almost all cases it's an environmental or nutrient problem. Too much or too little water, a late frost etc. If you can rule those out I would suspect a nutrient problem. In autumn and early spring sprinkle a handful of blood fish and bone per square metre around the base of the tree out to the edge of the canopy. Gently trowel it into the surface of the soil and water in. Anyone else have any other thoughts?
|19 August 14||From: Val|
|We have just moved and have a large plum tree in the garden we have identified brown rot, have started to prune and there is a
black ring through the inside of each branch cut, what is this and can it spread to a large cherry tree we also have?
FROM DAVE: This sounds like Silver Leaf Disease, the brown marks in the wood indicate this. See our section above for more information.
|10 August 14||From: Cherie Crozier|
|What can I spray my plum tree with as I have identified it having the
plum moth, due to pink maggots inside fruit. thanx
FROM DAVE: It's too late to spray this year, the bug is already in the fruits and no spraying can kill them now. The time to spray is about mid June and there two common sprays which are Westland Resolva Bug Spray and Bayer Sprayday Greenfly Killer.
|07 August 14||From: Mamta|
|I read your very interesting article above. My Victoria plum tree has become infested with
saw fly this year. It is 4 years old. It fruited very well for the first 2 years, very little fruit last year. I had only 2 bunches of plum this year. When I picked a ripe looking one and cut it open (thank God I did not bite into it!), it had a few small larvae crawling inside, ugh! On the outside, there was a resin like drop at the base of each fruit. I have disposed off the fruits. I will mulch around it with chip bark soon. What else should I do?
FROM DAVE: Burn any affected fruits, picked ones and those that have fallen. In February / March break up and turn over the top 8cm / 3in of soil with a trowel around the tree. This will bring the bugs to the surface and birds will eat them. The chemical deltamethrin, sprayed when the blossom is falling off, will definitely help control sawfly. You need to time the spray so that it occurs before the bugs burrow into the forming fruit. Once inside the fruit, spraying will have no effect.
|04 August 14||From: Brian G|
|I have a 5 year old Victoria plum tree that was full of fruit. I took a load off but it has not improved the size of fruit that I left on the tree.
However I am starting to have problems with the fruit. There is a bit of brown rot which I am used to, having a
Victoria plum. I pick them off and put them in the dustbin.
But all the fruit is rather scabby but only on the side that faces the light. The backs of the fruit are green and clean. The scabbed fruit is turning a red colour
I gave the tree a winter wash and have sprayed it with horticultural soft soap to keep it free from aphids which seems to have worked.
I attach photo of three of the fruits and one of the tree. If you zoom in on the pic of the it highlights the problem quite well.
I would appreciate your views on this. Is it terminal? If not what can be done?
FROM DAVE: Any help in identifying this problem will be much gratefully appreciated.
|03 August 14||From: Not Given|
|My 3 year old Victoria plum tree has very hard scabby fruit on it. How can I treat it?.
FROM DAVE: I'm not sure from the limited description what the problem is. Send a picture (send one using our email address) and I'll do my best to identify the problem.
|22 July 14||From: Tristan|
|I have two Victoria plum trees and the leaves have lots of little holes in and thousands of flies on the trees and the fruit is starting to fall off or rot. Also ground underneath seems to have lots of black mildew on. Any ideas? Thanks. Picture attached here.|
|21 July 14||From: Peter|
|I have a plum moth (plum sawfly?) infestation of my greengage in Cambridgeshire. Rather than "burning" the infected fruit as you suggest, I have placed a bucket of water next to the tree, and every time I pass the tree, I throw any infected fallen fruit into the water. The fruit immediately sink to the bottom, as do the white grubs themselves (they cannot swim - I tested this on one grub).|
|21 July 14||From: Jean C|
|My plum trees have holes all over the branches and tree trunks and there is a clear sticky sap coming from each hole, one tree looks dead and now the other tree has shrivelled up leaves and also hole all over the branches and trunk with sap coming from them as well. What is this and can it be treated.
FROM DAVE: Are you from the UK? I ask because that sounds very much like shot-hole borer and I wasn't aware that it commonly affected plum trees here.
|20 July 14||From: Caroline|
|Please could you help me identify what is the problem with my Victoria plum tree. I can’t decide if it may be
brown rot. Picture is attached
FROM DAVE: You've identified Brown Rot correctly, the small grey blobs on the fruit are a definite identifying sign. I have added a section on Brown Rot of plums in the article above for more identification details and what to do about this disease.
|13 July 14||From: Patricia|
|1st yr of setting plum tree. Lots of fruit but started to notice
clear jelly sticky stuff on plums which set hard, have been wiping off and destroying plums but still it comes - can you please tell me how to get rid? Thank you
FROM DAVE: Without a picture (send one using our email address if you want to) it's difficult to say for certain but it sounds like a normal reaction plums have when they suffer from environmental problems (water, heat, cold etc) or as a reaction to some other pest or disease. See the section "Clear Blobs of Hardened Resin / Jelly on Plums" above for more information.
|11 July 14||From: Robert Martin|
|All the plums that were on two of my three plum trees have gone none left on the trees none on the ground
FROM DAVE: If there is absolutely no trace of them then the only conclusion is that they have been eaten by a human who has then disposed of the stones. You don't mention if you have eaten them or possibly someone you know. If that's not the case then I fear that they have been stolen.
|6 July 14||From: Jim Wells|
|Plum tree about 12 years old for first time showing
sticky, white/grey powdery leaves though at present developing fruit seem unaffected. Any idea what may be and how to treat? Thanks, Jim
FROM DAVE: Sounds very like Powdery Mildew. I have added a section on this pest above entitled "White powder on Plum Tree Leaves".
|6 July 14||From: Jackie Rees|
|Victoria plum tree leaves turning brown around the edges also brown in the centre some have
small holes in the leaf. Your help please tree about 4years old with plenty of fruit.
FROM DAVE: There are many fungal diseases which can affect plum tree leaves and environmental problems, especially water-logged soil, can also have the affect you describe although the holes are slightly more unusual.
It may well be shot hole which causes brown spots in the leaves and some holes. I would spray a fungicide on the tree as a first course of action. There are several on the market, one well known one is Scotts Fungus Clear Ultra.
|26 June 14||From: PJ|
|My plum tree has come into leaf as normal, but now nearly all the leaves look withered and are dying, but there is a lot of unripe fruit forming normally. No sign of any disease that I can see, but it looks very poorly. Could it be old age? It\'s probably about 20 years old at least
FROM DAVE: I doubt very much that age is the problem, plum trees normally live a lot longer than 20 years. If there are no signs of aphids (use a magnifying glass to look at the underside of leaves to be 100% sure) or other pests / diseases then the problem sounds environmental. Has the area flooded last winter / spring? Has it been pruned regularly? Anything else changed in the last year or so?
|01 June 14||From: Walter Awlson|
|I have a mature Victoria Plum tree which is badly affected with
"pocket plum". Following advice to remove branches with affected fruit, there is very little left and obviously no crop this year. Is there any treatment which will help save this tree and prevent a recurrence?
FROM DAVE: Plum pocket was previously very rare in the UK but over the last three years it is becoming more widespread. I have included a new section above in the main article on this pest to describe its lifecycle, identification and treatment.
|Date: 23 May 14||From: Irene G|
|My mature Victoria plum tree has failed to come into leaf this year. There was early evidence of small buds but they have failed to open. There are no visible signs of canker or damage to the the outside of the tree. The only change to its environment was the stacking of logs from a tree we cut down last autumn approx 2m from the tree base. Could this have damaged roots? Some twigs can be snapped but others still appear to have sap. Any help/suggestions welcomed.
ANSWER: A difficult one to diagnose because the first possibility is environmental. Too cold, too wet or (most unlikely) too dry. That pile of wood you mention may be causing water to remain in the ground longer than it normally would and after all the wet weather we have had that could be the problem.
Plum trees are notorious for changing their growth habits from one year to the next. I would suggest waiting until next year to see what happens especially because the tree is obviously alive with no external signs of damage,
|Date: 19 May 14||From: Brian H|
|I have pea sized black blisters on the underside of the branches
of my yellow plum tree. What are they and how can I treat it. Pictures attached.
ANSWER: These are scale insects, almost certainly Lecanium Scales. I have added a section in main article above on how to identify and treat them. Thanks for the pictures which greatly help to identify the problem.