They are not very susceptible, but they can still be infested: we tell you which pests and diseases can affect hydrangeas.
It doesn't matter whether you have hydrangeas in the garden or hydrangeas in a tub: under optimal conditions, they are usually very resistant to diseases and pests of all kinds. Should it happen that the hydrangea is attacked by diseases or pests, this is usually the cause because the conditions for the plant are not optimal. Pests and diseases often occur with incorrect care or the wrong choice of location.
Hydrangeas are most commonly attacked by aphids, spider mites or powdery mildew. But root nematodes, vine weevils and leaf spot disease can also cause problems for the beautiful plants. However, if you take a good look at your hydrangeas, you will be able to quickly identify and combat the diseases.
Diseases and pests on hydrangeas
❧ Spider mites
One of the most common pests on hydrangeas are spider mites. These tiny creepy-crawlies lay hands on the leaves and can be recognized by silvery dots on their surface. Webs will later appear on the underside of the leaves and the spaces between the leaves will also turn yellow or grey-brown. Especially when the hydrangeas are in direct sunlight and the soil is dry, these little creatures can multiply wonderfully.
Combat:
To get rid of the mites, sometimes a shower with clear water is enough. If this is not successful, you can also treat the hydrangea with a spray containing rapeseed oil.
» Recommended reading: Fight spider mites on indoor plants - 5 effective tips.
You may be able to prevent re-infestation by transplanting the hydrangea after treatment.
❧ Aphids
Not very often, but sometimes you will also find aphids on hydrangeas. These pests mostly show up in spring when the weather is very warm and dry. The critters are not so tiny, so you can see themcan actually be seen with the naked eye. In addition, the surfaces of the leaves are coated with honeydew and are therefore very sticky. If there is an infestation with aphids, black sooty mold and ants are usually not far away either.
Combat:
Most of the time it is sufficient if you spray the plants with a hard jet of water. If this does not expel the lice, you can also spray the hydrangeas with nettle manure. Here are instructions on how to make nettle manure yourself.
❧ Mildew
In addition to these pests, hydrangeas are often also affected by fungi. If the hydrangea has an ideal location and is well supplied with nutrients, fungal diseases are quite rare, but they can still happen from time to time. Therefore, you should regularly check your plants for such diseases in order to be able to intervene early.
Mildew is very stubborn. When infested, gray coatings with a mealy appearance form on the top and bottom of the leaves. The bad thing about it: the wind causes the fungal spores to spread when there are strong temperature fluctuations. That's why you should always act quickly.
Combat:
If you recognize this fungal disease on your hydrangeas, you should remove the affected parts of the plant as soon as possible to prevent further spread. However, if the infestation is already very large, a chemical fungicide is usually the only solution if you want to save your hydrangea from dying.
❧ leaf spot disease
If the plant does not have enough nutrients and if the humidity is also high, the so-called leaf spot disease can also develop. This fungus can be recognized by dark spots with a brown colored center. If the plant continues to grow, the leaf tissue can also tear open at these points.
Combat:
In this case, too, the only solution is to remove the affected parts of the plant. You should also ensure that the hydrangea is better supplied with nutrients in the future to prevent new infestations.
❧ Chlorosis
Chlorosis occurs relatively frequently in hydrangeas. With this disease, the leaf veins turn green and the leaves turn yellow. The reason for this disorder is often iron deficiency, but it can also be that the soil is too alkaline.
Combat:
To make the soil a little more acidic, you can incorporate some peat or rhododendron soil. In addition, an iron fertilizer is helpful. After a few weeks it shouldyour plant will get better again. If this is the case, the leaves will return to their original color.
❧ Gray mold (Botrytis)
Gray mold is also caused by a fungus, which not only appears on the leaves, but also on the shoots and inflorescences. A greyish, powdery coating can be seen on these parts of the plant when infested. In the course of the disease, the inflorescences also atrophy and discolour (brown). Especially when the soil is very heavy and damp weather persists, the fungus has an easy time.
Combat:
You should water your hydrangeas in the morning as a preventive measure. Regular thinning also helps so that more air can get to all places. If an infestation does occur, you must cut off the relevant parts of the plant. Anything that falls should also be disposed of with household waste as soon as possible to prevent it from spreading.
» Reading tip: Fighting gray mold on potted plants - Here's how.
❧ Hydrangea virose
Viroses can be triggered in hydrangeas 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.
Combat:
Unfortunately, this highly contagious disease cannot be combated and prevention is also not possible. If a plant is infested, you unfortunately have to burn it completely. You also have to replace the soil at the appropriate place. You must not plant hydrangeas in the same place in the future.
❧ Hydrangea Greening
When the hydrangea turns green, the entire corolla and stamens are gradually transformed into tiny green leaves. Some growths can also be seen. The hydrangea weakens, loses its pretty appearance and eventually dies.
Combat:
Parasites and insects spread the dangerous mycoplasma, so unfortunately it is not possible to save the plant. 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 sometimes tamper with hydrangeas. The so-called thrips are sucking insects that leave spots on the plant. These later dry up and lead to the death of the affected shoots. The plant then develops very poorly and the flower buds die off.
Combat:
To combat this tiny creature, you should use preparations with the active ingredients of the neem tree. In addition, those with rapeseed oil or potash soap preparations can also be considered.
❧ Root Nematodes
Root nematodes are tiny roundworms that ingest the cell sap. The roots then lose tension and volume, and an unpleasant odor escapes from the soil. Over time, the parts of the plant above the ground also suffer from sagging until they finally die. Most nematode infestations occur when the soil is depleted.
Combat:
You can't fight these worms. You can only prevent an infestation. You can achieve this by providing a good supply of nutrients and placing marigolds between the hydrangeas.
❧ Vine Weevil
The vine weevil gnaws the edges of the leaves so that semicircular notches can be seen. The beetle itself is not so dangerous, its larvae are worse. They don't attack the leaves, but the roots, so that the plant stops growing and often even dies.
Combat:
The vine weevil cannot be combated chemically. You can only drive him away by collecting him at dusk. Reading tip: Fighting vine weevils - This is how it works.