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The ancient Aztecs and Mayans decorated the temples of the Sun God with dahlias and used these flowers to carry out their pagan religious rites. They originally called dahlias acoctyls. The flowers received the name we know today in 1803. Today it is customary to decorate personal plots with dahlias. Many gardeners are keen on propagating them. And this is not surprising, because these plants bloom very beautifully. However, like all flowers, dahlias need care. The most annoying thing for flower growers is dahlia pests.
From this article you will learn which pests most often destroy dahlias. In addition, we will tell you about what dahlia diseases exist and how to deal with them. The article will also provide a video on the topic, which will expand your knowledge on this topic.
Preventive treatment of tubers
Tubers should be treated with fungicides or sulfur. You can powder the tips of the tubers with the preparation or dilute it in water and dip the roots into the solution.If you purchased liquid fungicides, then soak the dahlia tubers in the preparation for about 15 minutes. All work with chemicals must be carried out with rubber gloves. After processing, the tubers need to be dried. This can be done by laying the tubers on newspaper, cardboard or a wooden base.
Do not dry tubers on concrete. The fact is that it draws out moisture, as a result of which the dahlia tubers will wrinkle prematurely. If you have several varieties of plants, then you can prepare several containers with the solution. Each container will contain 1 variety, which means there will be no confusion. Some gardeners make a treatment solution from a systemic fungicide and insecticide.
It is worth noting that in many respects the need for preventive treatment depends on the climate in which the dahlias will be planted. Thus, in a humid climate, the likelihood of fungal diseases increases, while in a dry climate, this practically does not happen.
Types of diseases
Dahlias are susceptible to various diseases, most often fungal diseases. They develop in a humid climate and provided that the grower has planted flowers very densely. Next, the most common of them will be described, and advice will also be given on how to deal with diseases and their consequences.
Leaf spot
The fungus Entyloma dahliae is believed to be the causative agent of dahlia leaf spot. A sign of the disease are yellow-green spots on the leaves.Subsequently, they blur and become gray-brown with a pronounced border. Leaf spotting is caused by poor ventilation between dahlia bushes due to densely planted plants.
Fungicides are used to treat this disease of dahlias. It could be Oxychom or Fundazol. Healthy dahlia bushes are treated with these drugs, and diseased plants are destroyed.
Gray rot
The causative agent of gray rot, or botrytis, as it is also called, is the pathogenic fungus Botrytis cinerea. The first sign of the disease is the appearance of brown spots on the leaves, and then the entire plant is affected. Gray rot leads to drying of leaves, drying out of buds and deformation of peduncles.
If botrytis infects dahlias during the flowering period, then water spots appear on the inflorescences, as a result of which the tissues soften and the flowers rot. The disease develops due to excess moisture, which is a consequence of thick planting.
To combat the disease, fungicides are used in the same way as in the previous case. This could be Topsin, Fundazol, Benleit or Rovral.
Verticillium and Fuarium wilt
The symptoms of these diseases are the same, although the pathogens are different - Verticillium dahliae and Fusarium oxysporum. First of all, roots and tubers are affected; they simply rot. After this, the leaves and apical parts of the buds and shoots wither. The affected dahlia becomes covered with a pinkish (fusarium) or brown (verticillium) coating.
The cause of the disease is the same as in previous cases - poor ventilation and the presence of excess dampness due to dense planting. Affected tubers should be removed from the flowerbed and burned. As a preventive measure and treatment, plants should be treated with systemic fungicides.For example, Oksikhom or Fundazol.
Brown rot
The causative agent of this fungal disease of dahlias is the fungus Rhizoctonia solani. As a rule, brown rot affects young shoots and dahlias at the beginning of the growing season.
The disease develops due to too deep planting of tubers. Fungicides are used as preventive and therapeutic drugs. This may be Fundazol, Alirin, Fitosporin-M and Gamair.
Incurable diseases
There are several diseases of dahlias that cannot be treated:
- Mosaic virus. Pale green or yellowish stripes appear on the leaves of plants. If you find these symptoms on one of the bushes, then you need to urgently dig it up and burn it. Such an event will protect other bushes and minimize the possibility of infection.
- Tuberous galls. Nodular warts appear on the root collar. The affected tuber should be dug up as quickly as possible. Alternatively, try saving the tubers at the end of the season by trimming off the affected areas. After this, the cut sites are treated with fungicides. However, as practice shows, it is better to destroy such tubers and not use the contaminated area of soil for a year.
- Fusarium. Externally it appears as brown spots appearing on the stems. This leads to wilting and death of dahlias. Diseased shoots need to be cut off and then burned. The remaining bushes need to be treated, for example, with Bordeaux mixture (0.1%) or foundationol (0.1%).
- Mycosis. It manifests itself as a normal lack of water - the dahlia turns yellow and the shoots wither. So, first you need to water the beds and watch the bushes. If after 24 hours the leaves recover, then this is a lack of water, and if not, then mycosis. The disease is not treated, and the affected bush is dug up and burned. In the next 4 years, nothing can be planted on contaminated land.
Pests and their control
There are many types of pests that like to attack dahlias. Next, we will look at the main types and methods of dealing with them.
Aphids or Aphididae
Colonies of these pests are immediately visible to the human eye. A sign of their appearance on dahlias is yellowing and curling of the leaves, and the presence of sticky secretions on them. These are sucking pests that are also carriers of viral and fungal diseases.
If there are single colonies on dahlias, then you just need to cut them off with their leaves. If there are a lot of aphids, then the dahlias need to be treated. This can be done with a solution of Green soap or insecticides, for example, Aktara, Fitoverm, Confidor and Decis.
Chrysanthemum and strawberry nematodes
These pests damage dahlia leaves, petioles, and buds. Initially, light, darkening necrotic spots appear on the leaves. Nematodes can overwinter in the buds of dahlia tubers. Root pests of this species are sometimes encountered. A sign of their presence is stunting of the bush and subsequent bending of the stems.
Dahlias in which nematodes have infested should be dug up along with a large piece of earth and burned. After this, plants susceptible to the harmful effects of these pests can no longer be planted on the land where the infected dahlias were planted.As a preventative measure, you can water the soil with Ecogel, which strengthens the cell walls of dahlias. The pest is also repelled marigold, so you can plant them near dahlias and other plants susceptible to this pest.
Plant bugs
They feed on the leaf blades of dahlias, as a result of which the flow of nutrients is disrupted. Yellow, brown spots appear on damaged leaves. Later, the leaf tissues wrinkle and tear.
If you detect the presence of plant bugs on dahlias in time, it will be enough to treat the dahlias with a solution of Green soap. In case of mass infestation of dahlias by bedbugs, more powerful means are needed, such as Iskra-M or Mospilan. In the morning, bugs are practically motionless, so plants should be treated at this time of day.
Scoop Gamma
The moths of this pest fly in late spring and early summer. They feed on nectar and do not harm dahlias. However, these butterflies lay many eggs, from which caterpillars hatch, gnawing on the roots of dahlias at the surface of the ground, as a result of which the plant withers.
If there are few caterpillars, they can be collected by hand. But in case of a massive invasion, you will need to use agents such as Bitoxibacillin and Lepidocide. Insecticides such as Fufanon and Iskra-M will also help in the fight against caterpillars. All the above-mentioned preparations need to be treated with dahlias and their soil.
Gastropods or slugs
They appear in the shade, mainly in humid weather, and are especially energetic at night. They eat grooves in the leaves and gnaw through them. Often the leaves are completely eaten.
You can scatter ash between the rows, which irritates the mollusks; it is to them like glass to humans.However, this technique is ineffective, since after getting wet, the ash is no longer dangerous for slugs. Ordinary ground red pepper and superphosphate are also used to destroy them. Metaldehyde preparations kill slugs. They are also scattered on the ground. You can also set slug traps and collect them by hand.
Greenhouse whitefly
Small butterflies measuring 0.1 cm in size are sometimes found on dahlias planted in open ground. They usually attack flowers in greenhouses. Eggs are laid on the underside of dahlia leaves. They take cover under the leaves of dahlias. The larvae feed on the leaves, causing spots to appear on them. Greenhouse whitefly cocoons also form on leaves. It turns out that the foliage of dahlias serves as a home for this insect.
Insecticides such as Iskoriy, Aktaroy and Mospilan are used to control the pest. They are applied to the plant by spraying.
Fawn or furry bronze fawn
Olenka is a black beetle, larger than 1 cm. It eats the pistils, stamens and petals of dahlias. It affects flowers from late spring to late summer. Female beetles lay eggs in humus-rich soil, where brown-headed white larvae hatch and feed on dahlia roots and plant debris.
Usually there are not so many beetles, so they are simply collected from dahlias, and the larvae are removed during the process of loosening the soil.
Let's sum it up
So, with a competent approach to the issue of caring for dahlias, there will be no problems with them. Well, if you have done something wrong, you can always use the tips outlined in the article. In addition, we invite you to watch additional videos:
I would like to see more photos of diseased plants so that I could compare them with my own.