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Although pyracantha is a hardy plant, several pests and diseases can be a real problem for pyracantha. The two more serious diseases that attack pyracantha (also known as firethorn) are Pyracantha fireblight and pyracantha scab. More on these further down. When it comes to pests, you have the usual aphids that are easy to control and mainly attack new lush foliage in spring. However, woolly aphids and pyracantha leaf-mining moth are two insects that prey on pyracantha and can do significant damage if not treated. Read on to learn how to identify and treat these pyracantha pests and diseases.
Pyracantha leaf-mining moth
What are pyracantha leaf-mining moths?
The pyracantha leaf-mining moth is a relative newcomer to the gardening scene being first discovered in Britain in 1989. However, it’s now a widespread problem. This is a small moth (6mm to 8mm in wingspan) that burrows inside leaves to feed. The moth’s wings are bronze with white markings, and it’s active between January and March.
How to spot pyracantha leaf-mining moths
You may see the moths themselves, but you’re more likely to notice the silvery white discolouration of the upper surface of the pyracantha leaves. The moths lay eggs on the leaves that hatch into larvae/caterpillars. When the moths, as caterpillars, bore into the leaves, they create oval-shaped mines, and you can see the shape of these on the outside of the leaves. When you spot the mines, it’s usually in the summer after the earlier activity of the moths.
The discolouration may cover most of the leaf’s surface. When the caterpillar moves on, the leaves fold upwards due to the web spun within them, hiding the mines.
What to do
While your pyracantha plant may look a bit ragged, it’s not in any danger. The mined leaves from the previous year may drop off in the next spring, but new growth replaces them. There’s no effect on the plant’s ability to produce flowers or berries or to survive in the long term.
Some birds, such as blue tits like to open the mines to eat the caterpillars within them. That’s about it for control of these pests. There’s nothing else to do, you just need to be aware of it.
What is a woolly aphid?
The woolly aphid is a sap-sucking aphid that lives on the trunk and branches of your pyracantha plant. After sucking the sap from the plant, the aphid covers itself in a white and waxy secretion that looks like fluff. The aphid itself is a brown-black colour. Sucking the sap leaves your plant in a weakened state, unable to produce new growth and perhaps unable to keep up the existing foliage.
How to spot woolly aphids
Woolly aphids are active from April to October, so you will likely spot them as thats when most people are out and active in the garden. Look for the white fluffy material on parts of the trunk and branches of the plant. In spring, the aphids hang around the bark around old pruning cuts, but after new growth develops in the spring, they move on there. When you’re pruning your pyracantha in the winter, just feel along the bark and shoots for bumps and lumpy growths.
Woolly aphids overwinter in your pyracantha by hiding in the cracks of the bark. So it’s best to deal with them before the cold weather sets in.
What to do
It’s important to prune off the diseased parts as the swellings can split and let diseases in.
If you only have a small gathering of woolly aphids, use a stiff-bristled brush to sweep them off the plant. Do this as soon as you notice them, preferably in spring or summer before they have the chance to build up a large colony. These aphids are an important part of your garden eco-system so you can put up with a few of them on your plant.
These aphids have natural predators, including ladybirds, that you can buy and introduce to your pyracantha, and they will also help to control aphids. Ladybirds can, of course, move on, so there is a good choice for greenhouses here this is less likely to happen, which is why I recommend organic oil sprays below.
As just mentioned, organic oil sprays are also a good way to deal with these pests. Spray natural pyrethrum oil (Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer are affective sprays) or neem oil (Vitax Plant Guard Pest & Disease Control, Bug Clear Fruit & Veg) over the plant to help reduce the infestation. These natural pesticides have a short working life so you have to keep reapplying them. You can
What is fireblight?
Fireblight is one of those diseases that spreads by bugs, birds and the weather including wind and rain. It moves fast from plant to plant. This bacterial disease normally affects open blossoms, new leaves and growth in the spring. It’s around from late spring through to autumn.
How to spot fireblight
Fireblight is easy to spot. As its name suggests, affected leaves start to crack and turn black, as if they’ve been burned by fire. Blossoms wilt and you find slime oozing from the infection in wet weather. There may be cankers (sores) on the plant as well, especially where infected shoots join the larger branches.
As the infection spreads through to the inner bark of the plant, shoots shrivel and die. The outer bark becomes a brownish-red colour which you see when you peel back the infected bark.
What to do
At the first sight of fireblight, prune out the infected parts. Use a sterilised and sharp cutting tool, and re-sterilise it between cuts. Peel the infected bark back until you find healthy wood and cut back to that. You may need to cut back 30cm in small branches and 60cm in larger ones. Remove any late blossoms before they open so that the disease doesn’t spread to that part of the plant.
Unfortunatly, this is all you can do as there is no chemical solution to get rid of fireblight.
Make sure you prune out the infected branches thoroughly. The bacteria overwinter in the bark cankers and emerge in the warm and wet spring. The bacteria gets into the inner bark via the blossoms. The good news is that pyracantha does respond well to hard pruning, so don’t be scared to prune affected areas hard to ensure you remove all infected parts of the plant.
What is Pyracantha Scab?
While not as serious and harmful to your plant as pyracantha fireblight, pyracantha scab is very unsightly. This is a fungal disease that affects the blossoms and berries. It also causes the plant to drop its leaves, leaving it quite bare and disfigured. Scab is spread by the wind and rain, and by bugs and birds.
How to spot pyracantha scab
The blossoms and berries begin to turn black and get scabs on them (hence the disease name). The flowers and leaves fall off the plant and the berries become disfigured by black marks and cracks. Before they fall, you may notice dark spots on the leaves. Young shoots may die back. This happens from the spring to the autumn.
What to do
As with any disease, the first thing is to remove any infected part of the plant. Carefully prune away all parts that are hit by the disease using a sharp and sterilised cutting tool. If you need to cut back most of your plant, remember that this will reduce its flowering the next year.
Remove all the fallen leaves in the winter. This fungal disease survives the winter on those leaves, just waiting for the spring when it can reinfect new growth.
Westland Plant Rescue Fungus Control is the only fungicide which is labelled to control pyracantha scab. You might also try Bayer Garden Systhane Fungus Fighter which is approved for use by gardeners to control apple scab so could be effective on pyracantha scab.