Dahlia diseases - what are they, why they grow poorly and do not bloom

Dahlias are an ornamental crop characterized by lush shrubs and long flowering throughout the summer. The flower is liked by many growers, but due to the high susceptibility of the plant to pests and diseases, its popularity is gradually decreasing. The problem is quite solvable if preventive treatment of bushes is carried out in a timely manner and tubers are properly stored in winter.

Brief description of the plant

Dahlia is an annual or perennial herb, depending on the species. The culture belongs to the Astrov family. In the wild, the plant can be found in the mountainous regions of Mexico, Chile, Guatemala, Colombia. Modern dahlias are a complex hybrid that has gone through a long selection work. As a result, varieties have been obtained that have a varied color of the petals, as well as the size and shape of the flowers.

Dahlias are susceptible to disease and pests

Perennial dahlias have a tuberous branched root, which accumulates moisture and nutrients. Thanks to this, the plant is able to provide itself with everything it needs. Dahlias form erect, hollow stems 50-200 cm high. Along their entire length, there are pinnately dense leaves of a dark green hue. Dahlia flowers have the shape of a basket, in which reed, marginal, median and tubular petals can be located. Their color is monochromatic and variegated.

This culture does not winter outdoors.

With the arrival of the first frost, the tubers must be dug up and sent to winter in a cool dry place. In the spring they are planted. As soon as the ground warms up well, the plant begins vegetation. Dahlias bloom in late June - early July and lasts until late autumn.

What causes diseases

Hybrid forms of dahlias have partially lost their natural immunity, and the susceptibility of plants to pathogens has increased. Any mistakes in the care and storage of tubers can provoke the development of diseases. When growing a flower, it is important to adhere to preventive measures, since not all diseases of dahlias are treatable.

Improper care

Various factors can provoke the development of diseases. All of them are associated with improper plant care.

Common reasons:

• storing tubers at high or too low humidity;
• incorrect division of the rhizome in the spring;
• lack of nutrition;
• excessive or poor watering;
• lack of preventive treatments;
• thickening of landings;
• non-compliance with crop rotation.

Common diseases

Dahlias are most often affected by fungal diseases. When growing a flower on a site, you need to know how they manifest themselves and what to do if there are signs of infection.

Leaf spot

The provoking factor in the development of the fungus is the thickening of the plantings. Against this background, the level of ventilation between the plants decreases, which leads to an increase in humidity. Dahlia leaf disease can be identified by light yellow spots of irregular shape and with a blurred border. Subsequently, their shade becomes brown, and the border acquires a dark color.

You can get rid of the disease with drugs:

• Fundazol;
• copper sulfate;
• Oxyhom.

Leaf spot develops slowly

Gray rot

This disease can also be the reason why dahlias do not grow and bloom. During it, brown spots appear on the leaves, which, with high humidity, are covered with a gray-white edge.

Preparations for fighting gray rot:

• Topsin;
• Benleit;
• Rovral.

Verticillium and Fusarium wilting

These diseases have similar symptoms, but their pathogens are different. Initially, the fungus infects the roots and tubers of the plant, then moves upward and becomes the reason why the leaves of dahlias curl and wither. The affected parts of the plant are covered with a pink or brown bloom. For treatment, you must use Fundazol or Oxyhom.

Brown rot

The disease affects young shoots of the plant at the seedling stage. The provoking factor is too deep planting of tubers. This leads to the fact that the sprouts weaken, as they do not have enough strength to break out.

Preparations for the treatment of brown rot:

• Alirin;
• Fitosporin;
• Gamair.

Other diseases

Dahlias affect other diseases as well. Each of them has its own characteristic differences.

The reason why dahlias do not bloom and grow poorly may be:

• Powdery mildew. It appears as a white bloom on foliage. As the disease progresses, it acquires a dirty brown hue. Subsequently, the leaves completely wither, and the plant stops blooming. When powdery mildew appears on dahlias, it is necessary to treat the plant with Skor or Topaz.
• Blackleg. The disease develops when the plant is planted with seeds or cuttings. The provoking factors are excessive watering and cool air temperatures. A characteristic sign of damage is a black rim at the base of the seedlings. Subsequently, the stem in this place becomes thinner and cracked. For treatment, seedlings are recommended to be watered with solutions of Previkur Energy or Maxim.

You can cope with the problem if it is possible to determine the disease.

Incurable diseases

Some diseases cannot be treated. The only way in this case is to prevent the mass spread of pathology. To do this, the infected plant remains must be destroyed.

Incurable diseases of dahlias:

• Mosaic virus. It appears on the leaves with light stripes. Then they increase in size, and the entire plate becomes pale. In this case, the leaves do not fall off.
• Tuberous galls. During illness, swollen warts appear in the area of ​​the root collar. As a result, the shoots of the plant grow deformed and cannot fully develop.
• Mycosis. The initial sign of damage is that the leaves of the plant begin to turn yellow, as if there is a lack of water. But watering doesn't solve this problem. As a result, the entire above-ground part completely fades.
• Fusarium. It is characterized by brown spots that appear on shoots and leaves. Then they grow and cause the death of the plant.

Pests

Often the culture is affected by pests. Before you start fighting them, you need to find out who can eat dahlias, and what tools are best to use.

Aphid

If aphids appear on dahlias, the pest is located on their young shoots and leaves.The insect forms entire colonies, so it is impossible not to notice them. As a result of the defeat of aphids, the growth of the plant slows down, the buds are deformed, and the bush can completely stop blooming.

Aphids on dahlias, how to process the bushes? You can fight this harmful insect with the help of drugs: Inta-vir, Actellik or Decis.

Aphids will not allow the plant to fully develop if it is not destroyed

Nematodes

These worms damage the shoots, leaves and buds of the plant. A characteristic sign of damage is light spots, which subsequently darken and die off. As a result of the activity of nematodes, the bush noticeably lags behind in growth, shoots and leaves are deformed.

Affected dahlias must be dug up and burned. In the same place, the flower cannot be re-planted. To combat the pest, you need to use marigolds, placing them somewhere nearby. The smell of this plant scares off nematodes.

Plant bugs

Insects feed on the young leaves of the plant. As a result, metabolic processes in tissues are disrupted. Initially, brown spots appear on the leaves, and then the plates wrinkle completely.

With a small number of pests, you can get rid of them in a folk way using a solution based on Coniferous soap. If the lesion is massive, it is necessary to use the drugs Mospilan or Iskra-M.

Gastropods or slugs

These creatures are activated at night. They are attracted by the young leaves of the plant. Pests gnaw holes in them, and sometimes eat them completely. This negatively affects the decorative effect of the bush.

For the destruction of slugs, it is necessary to use preparations based on metaldehyde. In dry weather, you can pour wood ash, red pepper or superphosphate at the base of the bushes. Beer traps are made to kill slugs, as they love the smell of this drink.

Greenhouse whitefly

A small white butterfly that lays eggs on the back of the plant's leaves. Gluttonous larvae emerge from them. To destroy the whitefly, it is necessary to water the plants with Aktara's working solution and at the same time spray the foliage with Mospilan or Aktellik.

Fawn or shaggy bronze

During the flowering period, large black insects appear on dahlias. Their size is about 1 cm. They feed on petals, stamens and pistils of a flower. Spraying with insecticides does not give the desired results, since new ones arrive to replace the dead pests. The only way to save dahlias is by hand-picking beetles.

Others

Sometimes dahlias can suffer from the gamma scoop moth. This pest becomes more active in late spring - early summer. The insect feeds on the nectar of flowers without causing serious damage to the plant.

The danger is posed by its larvae, which damage the dahlia tubers. As a result of their vital activity, the plant begins to wilt. For the destruction of caterpillars, it is recommended to use the drug Fufanon.

Preventive measures

What if dahlias don't grow? This question can be heard from many flower growers. Slow growth is most often caused by diseases and pests. In order to prevent such a problem, preventive measures must be followed.

Basic Rules:

• Before planting, the tubers must be soaked in a solution of insecticide and fungicide for 15 minutes.
• Before laying a dahlia for storage, its rhizomes should be dried.
• Observe the crop rotation.
• Store plants in a cool, dry place with ventilation during the winter.
• Avoid waterlogging of the bushes.
• Spray plants with special preparations twice a season to prevent infection.

Dahlias do not grow well, what to do in this case, it becomes clear when identifying the root cause. In order not to face such a problem later, it is necessary to control the condition of tubers in winter and bushes throughout the season.