Aucuba Japonica Diseases (5 Diseases + Proper Treatment)

Most of the diseases that affect Aucuba Japonica are fungal. Five of the major problems or diseases you can face with Aucuba Japonica are Phyllosticta Leaf Spot, Stem Dieback, Blackening Aucuba Leaves, Foliage Burn, and Nonpathogenic Root Rot. 

All of these diseases are prevented with just some extra steps in your garden. If the plants are already affected then there are some curative measures that are very simple to apply.

In this post, we will find all the reasons and symptoms that you need to identify the disease and take proper action.

If one curative measure is not working then you will also look into the symptoms of other diseases that are affecting the plants. 

Quick Overview of Aucuba Japonica Problems and Solutions

Reasons  Solutions 
Phyllosticta Leaf Spot Take preventive measure
Stem Dieback Use fungicides
Blackening Aucuba Leaves Less watering 
Foliage Burn  Avoid direct sunlight in cold
Nonpathogenic Root Rot Less water and dry organic fertilizer

5 Diseases Aucuba Japonica Can Have (Explained)

Disease 1: Phyllosticta Leaf Spot

The first thing that you need to know is, Aucuba Japonica leaves turning black are not similar to Phyllosticta Leaf Spot. They have different reasons, symptoms, and preventive and curative measures.


Phyllosticta is a fungus. The fruit of these fungi is more prominent in the moisture area. This means when your garden has more than it should it develops Phyllosticta fungus in the Aucuba Japonica plant. 

Also along with the moisture, over-watering the plant can cause the buildup of the Phyllosticta fungus. 


The black spots created due to the attack of Phyllosticta fungus are not similar to other black spots due to nutrient deficiency or other factors. In this case, you will see small black spots here and there. 

The major difference between the black spot from other factors is, the sports will have an outer ring of red color.  Sometimes this red color can turn to Brown as the disease gets severe and untreated.  


  • The reason for the formation of this fungus is unwanted moisture in the air or over-watering. Preventive measures that you can take to stay away from this disease. 
  • Keep the garden clean. Do not throw your kitchen compost directly into the garden before composting them.
  • Try not to have any accumulation of dead leaves and Debris in your garden. They will create unnecessary junk and Habitat for fungus and bacteria.
  • While watering the plant make sure you apply it from steam to downward. Aucuba Japonica doesn’t appreciate water on the leaves. This reduces the probability of the development of fungus in the leaves.   

Curative Measures:

Unfortunately till now no fungicides are developed targeting Phyllosticta. This is why the preventive measures are taken under more concentration than the curative measures. 

Also, the fungi sites targeting tebuconazole fungus work great on Phyllosticta fungus.

It can reduce the probability of death of the Aucuba Japonica. And with proper nutrients and care the plant can even recover from the disease. 

Disease 2: Stem Dieback


Stem Dieback is a serious disease that leads to other diseases like nutrient deficiency and so on.

It is also caused by a fungal infection known as Phomopsis fungi. Due to the wrong watering system, the disease appears on the stem and spirits from there.

If the situation gets severe and the fungus spreads to the leaves and apex of the plant when the plant dies.  


With this disease, we will see black and brown spots growing on the stems. Some small spots turn into lesions as the disease gets severe. After a while, you will find the spots spread to the leaves. 


The fungal infection mainly happens due to improper watering of the plants. To avoid such a situation you will need to water the plant from steam to downward.

Water dripping from the leaves will affect the streams and cause habitation for the fungus.

Also if any of the plants are already affected by Phomopsis fungi need to be removed from the Garden immediately. Otherwise, this fungus will spread from one plant to another in a small amount of time. 

Also, it is best to keep your garden as clean as possible. Oh, so it is best to keep your garden as clean as possible. This actually works as a preventive measure for both fungicides and bacterial infections. 

Curative Measures:

There are no special fungicides targeting Phomopsis fungus. The best way to treat the disease is by applying fungicides and creating a dry environment around the plant.

If it is raining too much, then try to do a replantation inside your home. This way the plant can’t spread the disease to other plants and will have a dry environment to heal itself. 

Disease 3: Blackening Aucuba Leaves


It is often seen that the leaves and the shoots of Aucuba leaves are turning black. It’s not like the leaf is just changing color, rather it seems like the leaf is rotting.

Owners often think that this is due to an infection in the leaves but this is actually happening due to an infection in the root. 

The disease happens due to the stress caused in the roots by the cold soil in the winter season due to snow or rain.

In the spring and summer seasons if it is raining or you’re over watering then also the disease can take a severe turn.

Another reason for root stress is phytophthora. It is a soil infection that spreads to the other parts of the plant to the roots. 


The symptoms are very simple. The leaves and the shoots will turn black but you don’t find any other reason. Especially if it will seem like a pest infection but there won’t be any pests around.   


To prevent this disease, here are some steps that you can take.  

  • Try not to plant Aucuba in a place that tends to hold water for a long time. 
  • If you are applying natural compost to the plant then it is mandatory to compost them ahead. It is very important to make this compost with heavy clay soil before incorporating them with the plants. 
  • If it always remains wet in your area, then try to form a soil bed about 20cm high from the ground.
  • To prevent moisture you can also use mulch in the ground.

Curative Measures:

There is no special medicine that you can use to get rid of the problem. Rather you will need to get rid of the affected follicles as soon as possible.

Take out the plants from the ground and replant them into dry and loose soil so that you can check on the roots. 

Try to apply a fertilizer that boosts growth. Introduce nitrogen and magnesium-based fertilizer for the plants to have a healthy development and recover fast.

Disease 4: Foliage Burn


Foliage Burn happens in Aucuba Japonica when there is a combination of direct sunlight and cold weather. Aucuba Japonica is not a fan of direct sunlight no matter which season you are planning to plant them.

Open gardeners think that Aucuba Japonica doesn’t survive better in cold soil, so they put them under direct sunlight.

As a result, they get exposed and burn themselves. Any ornamental plant of the same genera suffers from the disease.  


The basic symptom of the Foliage Burn disease is the change of color. The leaves will turn brown and then black. The burned places will seem dry and cranky. 

The disease mainly prevails in the early spring. When the weather and the soil are still cold and the sun is visible. Look at the stem and leaves for the signs.


The best precaution to avoid Foliage Burn is if you put your plants in a Shady area. It can be a bit tricky as you have to balance the required sunlight and excess sunlight. 

In some cases, you can even use natural burlap to create artificial shade. But do not put them in any moisture area where the soil can get easily contaminated with fungus. 

Curative Measures:

If the plants are already suffering from Foliage Burn then the first thing to do is to get rid of the affected area with sharp scissors or knives.

If the stems are affected then in severe cases you might need to get rid of the whole plant before it spreads.

To give the plant a chance to cure you can transfer the outdoor plants indoors, in a warm environment away from direct sunlight. 

Disease 5: Nonpathogenic Root Rot


Nonpathogenic Root Rot is actually caused by bacteria and excess fertilizer. This is more prominent If you are using organic Fertilizers and not composing them ahead of time.

As a result along with the good bacteria, there lies bad bacteria switching in affecting the roots and stems. 


Unlike getting attacked by phytophthora, Nonpathogenic Root Rot is visible in the root and stem zone. They will get sticky and dirty black. Osho only the lower part of the steam will change color along with the root. 


The first thing to avoid Nonpathogenic Root Rot is not to use any excess fertilizer even if it is organic.

While using the organic fertilizer it must be ensured that it is dry and mixed with dry soil and then incorporated with the plant soil.

If any of the plants are affected you need to get rid of those plants immediately and transfer the healthy plants to somewhere else if possible.

Also always try and get a closer look for affected plants each week. This way before it spades all over the garden you can take action. 

Curative Measures:

If the plants are already infected then, the best thing to do is to get rid of those pants. This way you do not affect the other plants in your garden.

Unfortunately, there is not much of a curative measure you can take but allow these plants to have a dry environment and enough nutrients to cure themselves. 

How to Take Care of Aucuba Japonica

Aucuba Japonica is an ornamental plant. It doesn’t need much attention but it can get easily infected by a fungus which can lead to the death of the plant.

Here are some caring measures that can help you to flourish Aucuba Japonica in your garden. 

  • The plant prefers warmer places to survive. Therefore it is best to plant them during the spring season which leads to summer and you can overwinter the plant for the winter season. 
  • Try to use more organic fertilizers rather than chemical ones which will avoid chemical burns in the plants. But before introducing the fertilizer, mix them with dry soil.
  • Do not go overboard with the watering system. The water needs to be applied in a way that it doesn’t get hold of the soil and still the plants get enough to survive. 
  • Most importantly do not plant Aucuba Japonica along with other plants. Rather make a separate bed for them so that if they get a fungal infection it doesn’t affect the other plants in the garden. 
Basic Requirement  Scale 
pH of soil  6.0 to 7.0
Sunlight  6 to 8 hrs a day
Temperature  50-65°F
Watering  .5 inch per week
Fertilizer  Must contain nitrogen 
Moisture of soil  50 to 60 percent 


Can Aucuba take full sun?

Aucuba is a versatile bush that can be filled in full sun, part sun, or full shade. Aucuba Japonica, a Japanese tree, is an Asian bush esteemed for its resistance to weighty shade and huge, frequently vivid evergreen leaves. The female Aucuba produces groups of huge berries that become red in the fall.

How often do you water Aucuba?

Water a recently established aucuba profoundly once consistently, giving sufficient dampness to splash the roots. Allow the dirt to dry between each watering. When the plant becomes laid out and shows new development, watering declines every other week.

What do you feed Aucuba?

Feed compartment developed aucuba bushes once consistently from spring through summer utilizing a broadly useful, water-dissolvable manure. Keep manure throughout the fall and cold weather months.

Final Words

Aucuba Japonica is not very hard to manage but it needs attention when it gets affected by diseases. Aucuba Japonica Diseases can be tricky.

So you need to take a closer look at the symptoms of the disease and then take curative measures. 

Always remember that preventive measures for your garden plants are better than curative measures. Some of these diseases mentioned in the article are not even curable.

This means if not identifiable at the primary level the plants might die.

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