Content
Hydrangea diseases are relatively rare. The plant has sufficient immunity to withstand various external weakening factors under normal conditions and with proper care. However, violations of the conditions and rules of maintenance can from time to time cause diseases of large-leaved hydrangea. Most of them are reversible and relatively easy to cure.
What are the diseases of hydrangeas?
Hydrangea diseases are divided into three groups:
- associated with metabolic disorders
- fungal;
- viral.
There are several dozen species of hydrangea, differing in the shape of the trunk (or bush), plant size, foliage, etc., but the diseases, their pathogens and carriers will be common to all species.
It can be argued that diseases of tree hydrangea, as well as paniculata, will almost completely repeat each other, both in symptoms and course. Below we will discuss different types of diseases for garden and indoor plant varieties.
Diseases of garden hydrangea
Garden species are exposed to more severe environmental conditions than indoor species. In addition, diagnosing diseases in these plants can be complicated by a large number of analyzed parameters (after all, it is easier to observe a plant in a pot than in open ground).
Chlorosis
Externally manifests itself in the form of yellowing and drying of foliage. Usually, the disease first affects the entire lower leaves, and after 1-2 days the entire hydrangea bush begins to turn yellow.
With chlorosis, the veins may remain green
Yellowing of hydrangea is caused by iron deficiency in the plant's body. The cause of the disease is either its deficiency in the soil or its excessively high alkalinity. It prevents hydrangea from properly absorbing this microelement.
Treatment of the disease: adding iron salts to the soil, acidifying the soil, changing the plant care regimen.
White rot
One of the most common fungal diseases of hydrangea. The fungus quickly attacks the leaves, stems and roots of the flower. By consuming important substances, it completely deprives the plant of nutrition, which can cause it to die. Mainly infects hydrangea in greenhouses. Garden or indoor crops suffer from it less often.
Symptoms: a white coating similar to cotton wool and darkening hydrangea shoots that rot near the ground.
The fungus spreads very quickly and is able to completely cover the surface of the leaves.
Complex treatment is necessary: the affected areas should be removed and burned, treating the sections with a solution of potassium permanganate. Partially damaged and neighboring healthy bushes should be sprayed with copper-containing preparations.
Powdery mildew
It mainly affects young hydrangeas that have a lack of root nutrition. In some cases, the disease is provoked by excessive fertilization of the bush with nitrogen. Symptoms: numerous faded yellow-green spots.
At a later stage, the disease is characterized by purple spots on the leaves
This type of fungus exclusively affects hydrangea (each crop has its own powdery mildew pathogen), so it is safe for neighbors of other species.
Treatment of the disease consists of destroying the damaged areas and treating the foliage with Fitosporin or Topaz.
Septoria
A fungal disease that manifests itself at low temperatures and high humidity. Symptoms: spots up to 0.5 cm in diameter, light in the center and dark at the edges.
After white spots appear in the center, they are covered with small holes from which fungal spores are sown
Treatment: removal of damaged areas, treatment of the cut with potassium permanganate, spraying with copper-containing preparations and special agents, for example, Rodomite Gold.
Ring spot
It is predominantly a disease of hydrangea paniculata. A viral disease whose spread does not depend on weather conditions or care. Symptoms: ring-shaped spots appear on the hydrangea.
In later stages, the spots darken and the leaves shrink
There is no treatment for the disease because there are no effective drugs. The hydrangea is highly likely to die, so to avoid the spread of infection, the bush should be destroyed.
Hydrangea cancer
Oncology is characteristic not only of animal organisms, but also of plants. Symptoms of the disease: numerous brown spots, ulcers appear on the back of the leaf under the spots.
As the disease develops, the spots merge into larger ones and the leaves dry out.
The exact causes of hydrangea cancer are unknown; it is believed that it is provoked by mechanical damage to the bush. Treatment consists of removing the affected areas. Currently, the disease is not considered contagious.
No flowering
Hydrangea may not bloom for several reasons:
- erroneous pruning of last year’s shoots, on which buds form;
- freezing of buds;
- too much direct sunlight;
- irregular watering and fertilizing.
The solution to the problem is aimed at overcoming these factors: using diffused light, covering the plant for the winter, etc.
Diseases of indoor hydrangea
In general, diseases of indoor hydrangea leaves are similar to garden ones. The only difference is that plants in open ground are more susceptible to fungal diseases, since the humidity in the garden will always be higher than at home.
Downy mildew
Like all fungi, this disease occurs in high humidity, but requires elevated temperatures for normal development. Symptoms consist of oily spots on the stems and leaves, which over time change color to grayish-brown.
Leaves affected by downy mildew lose their shape and curl
Treatment of the disease consists of removing damaged areas (up to the entire stems) and spraying the plant with a 1% solution of Bordeaux mixture or drugs with similar effects (Kuproskat, Optimo, Kumir, etc.)
Gray rot
This fungus mainly attacks young leaves, and in rare cases, shoots. The reason is excessive waterlogging of the room, too frequent and abundant watering, shading of the room, crowding of plants.
With high humidity, gray rot quickly spreads throughout the plant.
Treatment of the disease consists of timely removal and destruction of the affected areas. After which the flower should be sprayed with a solution of potassium permanganate. If the damage has become global, the best option would be to completely destroy the plant so that the disease does not spread to neighboring ones. It is also recommended to spray bushes with a damage level of less than 30% with Fundazol.
Dry blackening of foliage
In some cases, when a hydrangea is sick, it will develop brown spots on the leaves. Gradually they cover the surface of the entire plant.
The middle stage of the disease partially affects all leaves
The cause is watering hydrangeas with hard water and sunburn. Treatment of the disease in this case is very simple - use settled water and place the flower in the shade.
Wet blackening of foliage
In the event of a sudden change in temperature or increase in humidity, droplets of water appear on the leaves, after which they begin to turn black.
The plant loses its shape, its branches droop
You can cope with the disease very simply by placing the flower in conditions (temperature and humidity) that are acceptable for growing. In this case, it is recommended to halve the irrigation dose for the next month.
Phyllostictosis spot
The manifestation of the disease is observed in the form of merging dark red spots with a lighter center. Subsequently, the spots expand, and a purple border appears along their edges. Then spores appear in the form of small black dots.
Phyllostictosis spotting at a late stage of the disease irreversibly destroys leaves
Treatment is standard for fungal diseases - removal of damaged areas and preventive treatment of foliage with copper sulfate 1%.
Ascochyta blotch
Symptoms include the appearance of round spots, which, as they grow, take on an irregular shape. Sometimes the spots are surrounded by a dark brown or purple border. In the dead tissue in their centers, the fruiting bodies of fungi are formed, which overwinter in this form.
Ascochyta blight primarily affects leaves in the upper part of the plant.
Treatment consists of removing the affected areas with their obligatory destruction. This is followed by preventive treatment with copper-containing preparations.
Rust
A fungal infection that occurs when there is excess water and nitrogen fertilizers. Symptoms: small yellow or brownish-brown spots, which later turn into brown growths. Rusty-colored spores spill out of the growths.
Most often, rust is localized at the edges of foliage.
Treatment consists of removing damaged leaves and treating the plant with copper chloride at a concentration of 40 g per 10 liters of water. You can use the drug Topaz.
Hydrangea pests and their control
Most often, the plant is attacked by various types of insects. But the list of pests is not limited to arthropods. A weakened hydrangea may suffer from protozoa and slugs. Below are the most common pests.
Aphid
This is a small parasitic insect that feeds on plant sap. A colony of aphids is always clearly visible on the leaves. Often a sign of its presence are ants eating the honeydew (droplets of sweet liquid) secreted by it.
In large numbers, aphids can pose a serious threat to any crop.
Treatment consists of treating the plant with insecticides: Fitoverm, Streda, Iskra. In the case of small colonies, you can get by with folk remedies - a soap solution or simply washing off the insects from the leaves with water from a pressurized hose.
There is also a biological method of control using ladybugs, natural enemies of aphids. To attract them, you can plant marigolds near the hydrangea.
Spider mite
Small arthropods that also feed on plant sap. They appear mainly in the hot season or during drought. Symptoms: the presence of cobwebs on the leaves. When there are a large number of colonies, they are visible to the naked eye from the underside of the leaves.
Leaves affected by spider mites may curl
Treatment is the same as in the case of aphids. If the colony is small, treatment with a soap solution is sufficient. If it grows to a large size, chemical action is necessary. Conventional insecticides may not be enough, so special anti-tick agents are used - acaricides. These may be: Akrin, Acrofit, Apollo, Vermitek.
Shellfish
Garden snails and slugs can pose a threat to hydrangeas, especially young plants. In adults, they eat fresh leaves, growth zones and newly opened buds. Mollusks become most active during periods of high humidity.
The presence of slugs can be detected by characteristic damage to the leaves.
Another sign of their activity is the marks on paths and plant stems.
Mostly mollusks are collected by hand, destroying their resting places and egg-laying sites. Beer traps can be an effective remedy.
Sometimes their natural enemies, birds or toads, are used to exterminate slugs. Treating hydrangea against these pests using chemicals (for example, Molluscicide) has certain risks, since all products of this kind are toxic.
Nematode
This pest is a protozoan that attacks the roots of a plant. From there the worm gets into the trunks. The danger comes from its waste products, which are poisonous to plants. External manifestations of the nematode are red galls on the leaves and characteristic lesions on the roots.
Tuberous lesions of the root system are characteristic of nematodes
Pest control is preventive in nature. To do this, sugar is added to the soil, which is food for other types of microscopic worms that parasitize nematodes. Preparations Actofit and Fitoverm should be applied several days before planting the plants in the ground.
May beetles
The larvae of these insects feed on plant roots. Hydrangea may also be among the victims of these pests. Damage to the root system leads to deterioration of the plant's nutrition; it may wither or even die completely.
If clutches of cockchafers are discovered, they should be destroyed immediately
Preventive treatment against larvae involves watering the hydrangea with an infusion or decoction of onion peels. Spraying the bushes with a solution of ammonia (20 ml per 10 liters of water) will also be effective.
Medvedka
The omnivorous nature of the mole cricket is well known. This insect, in the absence of natural food sources, can damage the roots of ornamental plants, including hydrangeas.
A sign of the appearance of a mole cricket will be numerous small-diameter holes in the area
The fight against mole crickets is complex. The use of traps, poisonous baits, as well as preventive treatment of hydrangea with insecticides should be combined.
Night owls
The larvae of these butterflies are capable of causing irreparable damage to a plant in a relatively short time, since the rate at which they eat leaves is very high. Sometimes the devastating effects of caterpillars can destroy an entire bush in less than one day. Therefore, it is necessary to regularly inspect hydrangea leaves to detect this pest.
Cutworm caterpillars eat large holes in leaves
To combat cutworms, contact insecticides are used, which are sprayed on the leaves monthly, starting in May. An effective way to control the pest will be birds attracted to the site.
Prevention of diseases and pests
Practice shows that preventive measures carried out at the required frequency require much less effort than treating a plant if it is infected.
The main measures to prevent hydrangea include:
- maintaining the correct acidity and mineral composition of the soil;
- compliance with the light and shadow regime: hydrangea needs diffused light and partial shade;
- Carrying out careful selection of seedlings for planting;
- regular mulching of the soil;
- disinfection of garden tools after each and destruction of all cut shoots or leaves;
- treating hydrangeas in early spring with antifungal drugs.
Spring treatment of hydrangea consists of antifungal copper-containing drugs, for example, a solution of copper sulfate 1%. In the summer, preventive actions are usually not taken, but in the fall you can treat hydrangea from diseases and pests using a solution of 3% Bordeaux mixture.
Conclusion
With proper care of the plant and appropriate weather, hydrangea diseases almost never appear. Both bush and standard forms have strong immunity and, with the correct approach to agricultural technology, successfully fight against any pathogens. In those rare cases when the disease does attack the hydrangea, its treatment does not present any particular problems and boils down mainly to adjusting the conditions of the plant and treating it with appropriate drugs.
Please write a reply
Ragged holes have appeared on the leaves of Hydrangea paniculata, what is it?
Good afternoon.
Unfortunately, without a photo it is quite difficult to determine the cause. Most likely, your hydrangea was attacked by pests. Presumably night owls.
Send us a close-up photo of the leaves and we will help you determine the cause.