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Pieris Problems – pests, diseases and other problems
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Pieris are compact, slow-growing shrubs that delight gardeners from all over with their pink/red young leaves that take on cream colours during adolescence and end with green. The white, bell-like flowers add a certain Lily of the Valley look which is why the plant is commonly called the Lily of the Valley shrub.
Adding year-round interest to your garden, it can be devastating when there are suddenly pests, diseases, or other problems getting in the way. Thankfully, there are things you can be on the lookout for and prevent against.
The one pest with which you must contend is the Pieris lacebug. This is a winged insect and you will know when it has invested your plant because your leaves will become pale and bleach in appearance which is something mistaken for a nutrient deficiency. You can typically find the lace bugs on the underside of the leaves. For those who live in Southern England, this can be a particular problem as it was first discovered in a garden in Windor in 1998 and is now widespread. There are some varieties more resistant than others something you can investigate beforehand. If you notice damage from the lace bugs, you can use a regular bug spray killer so long as your plant is not currently in flower, usually, the make an appearance early summer which is when it should be sprayed but it may also need another treatment late summer. If you apply the bug killer while your plant is flowering it will also cause harm to the necessary pollinating insects. If the infestation is not to bad you can live with it or prune our effected growth after flowering.
Fungal leaf spot is the first problem you will likely face in terms of diseases. The way you can recognize that your plant is suffering from this disease is by examining the leaves. This disease causes brown spots to appear on the leaves which get incrementally larger until such time as they take over the entirety of the leaf causing it to fall off. Fungal leaf spot requires warm humid conditions so one of the ways to prevent it from taking place is to keep the foliage on your plant dry and encourage air circulation.
When you water do it early in the morning and at the base of the plant. This will help your plant absorb the water and dry out early. Moreover, you should remove any weeds and make sure the plant is not overcrowded. This can be the situation reconciled by some light pruning to prevent overcrowding and improve air circulation. If you mulch your plants in the springtime you want to keep the mulch about 30 centimetres minimum away from the base of the plant so that it doesn’t rot.
Leaf spot treatments
If your plant is suffering from fungal leaf spot you can treat it with any product that contains copper octanoate or sulfur. You can also mix a natural treatment that is comprised of baking soda and water, 1/2 teaspoon of baking soda for every 4 litres of water.
Phytophthora root rot
On a rare occasion, your plant may be susceptible to phytophthora root rot. If your plant has this it will turn yellow maybe even purple something that happens to one branch early on and then spreads to the rest of them. This is a fatal disease. To prevent that you want to make sure your plant is never waterlogged or left in any type of standing water which you can ensure with proper drainage and allowing the plant to dry out between watering.
Lack of nutrients
There are other problems you might face. If the leaves have turned a sickly yellow shade it could be caused by a lack of nutrients. This type of plant loves acidic soil so you might need to apply a fertiliser base for acid-loving plants specifically something for azaleas or rhododendrons. You can check the pH level of your soil. If you find that the soil in which your plants are grown is far too alkaline and there’s no way to change that level regularly you might have to move it but this needs to be done around October when the plant has gone dormant for the winter. Consider planting in a container with ericaceous compost if your soil to not acidic.
To much sunlight
Another cause of sickly yellow leaves could be sunlight. These plants are native to Mountain areas and they need dappled shade or even shade so if they are positioned in direct, strong sunlight all day it could cause the leaves to turn yellow.
Pieris not flowering
If your plant has never flowered, this is another problem that indicates it is simply not growing properly. Similarly to the sickly yellow leaves, you should check the soil levels to make sure the soil is properly acidic. If your soil is alkaline you will have to plant it somewhere else, most people with this problem end up planting in a pot complete with ericaceous compost.
If your plant is grown in a container could have become rootbound, if you lift up the container in which it is grown and you see the roots are sticking out through the drainage holes it is rootbound and it will need a larger container with fresh compost or regular feeding at a minimum.
As long as you don’t have a very young plant, it can take a few years to flower, you should be able to reconcile the issue of lack of growth and subsequent lack of flowering by checking these two things.
By making sure to keep an eye out for signs of pests, and to vigilantly treat diseases, your pieris shrub can continue living a healthy life with brightly coloured leaves and white flower clusters.