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Hydrangeas: identify and combat diseases and pests

Hydrangeas: identify and combat diseases and pests

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Although they are not very susceptible to it, they can still be infected: we will tell you which pests and diseases can occur on hydrangeas.

damaged hydrangea

Regardless of whether hydrangeas (hydrangea) in the garden or hydrangeas in a bucket: under optimal conditions, they are usually very insensitive to diseases and pests of any kind. Should it nevertheless occur that they are infected by diseases or pests, this is mostly because that the conditions for the plant are not optimal. Pests and diseases often occur with incorrect care or the wrong location.

Hydrangeas are most commonly infested with aphids, spider mites or powdery mildew. But root nematodes, black weevils and leaf blotch can also cause problems for the beautiful plants. With a proper look at your hydrangeas you will quickly be able to recognize and fight the diseases.

Diseases and pests on hydrangeas

❧ Spider mites:

Spider mites are one of the most common pests on hydrangeas. These tiny crawling animals grab the leaves and are recognizable by their silvery dots on the surface. Later on the underside of the leaves shows a web and also the spaces between the leaves turn yellow or gray-brown. Especially when the hydrangeas are directly in the sun and the earth is dry, these little animals can reproduce wonderfully.


To get rid of the mites, showering with clear water can sometimes be enough. If you are unsuccessful, you can also treat the hydrangea with a spray containing rapeseed oil. Reading tip: fighting spider mites on houseplants - 5 effective tips.

You may be able to prevent re-infestation by moving the hydrangea after the treatment.

❧ aphids:

Not very often, but sometimes, you can also find aphids on hydrangeas. These pests usually show up in spring when the weather is very warm and dry. The animals are not so tiny that you can actually see them with the naked eye. In addition, the surfaces of the leaves are also covered with honeydew and therefore very sticky. If there is an infestation with aphids, black soot fungi and ants are usually not far away.


Most of the time it is sufficient to spray the plants with a hard water jet. If this does not drive the lice away, you can also spray the hydrangeas with nettle slurry. Here is a guide on how to make nettle yeast yourself.

❧ Mildew:

In addition to these pests, the hydrangea often also has problems with fungi. If the hydrangea is in an ideal location and is well supplied with nutrients, fungal diseases are rare, but it can still happen from time to time. Therefore, you should regularly check your plants for such diseases so that you can intervene at an early stage.

Powdery mildew is very persistent with hydrangeas. In the case of an infestation, gray deposits with a mealy appearance form on the leaves above and below. The bad thing about it: The wind causes the fungal spores to spread when there are strong temperature fluctuations. Therefore, you should always act quickly.


If you recognize this fungal disease on your hydrangeas, you should remove the infected plant parts as soon as possible to prevent further spread. However, if the infestation is very large, only a chemical fungicide usually helps if you want to save your hydrangea from dying.

❧ leaf spot disease:

If the plant does not have enough nutrients and the air humidity is also high, the so-called leaf spot disease can also occur. This mushroom can be recognized by dark spots with a brown colored center. If the plant continues to grow, the leaf tissue can tear open at these points.


In this case, too, only a removal of the infected plant parts helps. Furthermore, you should pay attention to a better nutrient supply of the hydrangea in the future to prevent a new infestation.

❧ chlorosis:

So-called chlorosis also occurs relatively often in hydrangeas. With this disease, the leaf veins turn green and the leaves turn yellow. The reason for this disorder is often an iron deficiency, but the soil may also be too basic.


To make the soil a little more acidic, you can incorporate some peat or rhododendron soil. An iron fertilizer is also helpful. After a few weeks, your plant should be better. If this is the case, the leaves return to their original color.

❧ Gray mold (botrytis):

The gray mold is also caused by a fungus, which shows not only on the leaves, but also on shoots and inflorescences. In the case of an infestation, a grayish, powdery coating can be seen on these parts of the plant. In the course of the disease, the inflorescences also deteriorate and discolour (brown). Especially when the ground is very heavy and damp weather persists, the mushroom has a very easy game.


As a preventative measure, water your hydrangeas in the morning. Regular thinning also helps so that more air can get to all areas. If there is an infestation, you have to cut off the corresponding plant parts. You should also dispose of everything that falls as quickly as possible with your household waste to prevent it from spreading. Recommended reading: Fight gray mold in potted plants - Here's how.

❧ Hydrangea virosis:

In hydrangeas, the virosis can be triggered by mycoplasma or viruses. The plant and the inflorescences then remain very small, the parts of the plant turn purple to red and the leaves become dull.


Unfortunately, this highly contagious disease cannot be combated and prevention is also not possible. If a plant is infected, you unfortunately have to burn it completely. You must also replace the soil at the appropriate point. In the future, you will not be allowed to plant hydrangeas in the same place.

❧ Hydrangea greening:

In hydrangea greening, the entire corolla and stamens are increasingly being transformed into green, tiny leaves. In some cases, growths can also be seen. The hydrangea weakens, loses its pretty look and eventually dies.


Parasites and insects spread the dangerous mycoplasma, so that saving the plant is unfortunately not possible. In this case too, you must eliminate the entire plant and replace the soil.

❧ Thrips:

In addition to aphids and spider mites, other animal pests also sometimes cause problems with hydrangeas. The so-called thrips are sucking insects that leave spots on the plant. These dry up later and lead to the death of the infected shoots. The plant then develops very weakly and the flower buds die.


To fight this tiny one, you should use preparations with the active ingredients of the neem tree. In addition, those with rapeseed oil or potash soap preparations are also suitable.

❧ Root nematodes:

Root nematodes are tiny nematodes that ingest the cell sap. The roots then lose tension and volume and an unpleasant smell escapes from the ground. Over time, the parts of the plant above the earth suffer from sagging until they finally die. Most of the time, nematodes are infected when the soil is depleted.


You cannot fight these worms. You can only prevent an infestation. You can achieve this by providing a good supply of nutrients and placing student flowers between the hydrangeas.

❧ Weevil:

The black weevil gnaws the leaves at the edge so that semicircular notches can be seen. The beetle itself is not that dangerous, its larvae are worse. They do not attack the leaves, but the roots, so that the plant no longer grows and often even shrinks.


The black weevil cannot be controlled chemically. The only way to drive it out is to collect it at dusk. Recommended reading: Fighting weevils - how it works.