Damage is caused by bean and peach aphids, spider mites (most often in dry years), slugs (usually in wet years), whiteflies, chrysanthemum and strawberry nematodes, cabbage cutworm caterpillars, hairy deer, slobbering pennies, and common earwigs. In addition to these pests, dahlias suffer from woodlice, tubers are often gnawed by mole crickets and May beetle larvae, as well as wireworms. During storage, mice and rats can cause significant damage to dahlia tubers.
Among the diseases during the growing season, powdery mildew, gray and white rot, smut, bacterial cancer, and viral infections are common.
Pests Dahlia
Nematode. Dahlias are affected by chrysanthemum and strawberry nematodes.These white, almost transparent and almost invisible pests are very dangerous, as they reproduce at enormous speed, especially in May-June, overwinter in all stages of development and are not at all afraid of frost.
The length of the female strawberry nematode is 0.8-1 millimeters, the male - 0.5-0.7 millimeters. Females lay eggs, from which larvae hatch, and after 12-15 days they are capable of reproducing.
Nematodes feed on cell sap. Damaged tissues turn brown and die. But more often various deformities occur: the leaves grow crooked, thickened, abnormally colored, the flowering stem thickens, and the receptacle is deformed.
The danger of the nematode also lies in the fact that it is a carrier of bacterial diseases - fasciation (wrinkling of leaves) and root bacteriosis.
The source of spread of the nematode is usually contaminated planting material, rain and irrigation water, as well as plant debris and weeds.
Control measures. Choosing a site for planting where strawberries have not grown before
Use of healthy material for planting. For prevention, seedlings can be treated in hot (46-47 °C) water for 15 minutes.
Regular weed control
Hairy deer. A black beetle 8-12 millimeters long, densely covered with grayish hairs. The body is oval. There are numerous small white spots on the elytra. The beetles fly in May-August, feeding on the petals, stamens and pistils of flowers. Females lay eggs in the soil, from which emerge white larvae with a brown head and three pairs of legs. They feed on plant debris and small plant roots.
It multiplies especially strongly in soil rich in humus.
Control measures. Manual collection and destruction of adult beetles. Collecting larvae when digging the soil
Spraying plants before flowering is ineffective; after it is prohibited.
Slobbery Penny. The leafhopper, an adult insect, has a body 5-6 millimeters long. Coloring ranges from yellowish-gray to black. Females lay eggs at the base of leaves, where yellowish-green larvae subsequently appear, covered with foamy secretions and feeding on cell sap.
Cicadas are the most dangerous because they are carriers of viral infections.
Control measures. Spraying plants before flowering with insecticidal preparations, for example, “Karate”, “Fury”, “Zipershans”.
Thrips. They are damaged by several types of thrips.
Harm is caused by adult insects and their larvae. Females lay eggs in leaf tissue. The larvae hatch after 8 days and develop in 10-12 days, feeding on the tissues of leaves and flower petals, making passages in them, severely disfiguring them. Dahlia leaves damaged by thrips acquire a characteristic silvery, sickly tint.
Plants are especially damaged by thrips in dry and hot weather.
Control measures. The best preventive measure against thrips is sufficient watering, since thrips most often attack plants that suffer from hot weather with insufficient watering.
Against thrips, plants should be sprayed with Actellik, Arrivo or Karate.
DISEASES
White rot. A fungal disease that develops on the bases of stems during the growing season (they become covered with a white cotton-like coating) and on tubers in storage during storage.The spread is facilitated by growing in heavy, damp, acidic soils.
The infection persists on plant debris.
Control measures. Compliance with crop rotation, use for growing well-lit and ventilated areas with loamy or sandy loam soils.
Liming of acidic soils
Using healthy material for planting, combating thickening of plantings. Those affected are destroyed.Verticillium wilt Fungal disease. The infection persists on plant debris and in tubers.
Causes rotting of roots and tubers. The bases of the stems and lower leaves turn brown, shoots with leaves and buds wither. When infected with verticillium, the entire plant wilts. The affected tissues are covered with a light brown velvety coating. Tubers are affected by dry rot during storage.
Control measures Dahlia is planted in a new place every year; before planting and storing the tubers, they are treated with a 0.2-0.4% Maxim solution for 30 minutes, then dried.
Tomato aspermia virus. On dahlia it appears on young plants. It is carried by aphids and during maintenance work; it persists on weeds and ornamental cultivated plants.
The virus infects the growing point, bushiness develops, and the main stems are not clear leaders. The leaves become small, asymmetrical, their edges acquire a bright pink or bluish color.
Control measures. Control of sucking pests.
Growing dahlias. A disease of bacterial nature. Numerous thin and short shoots of light green color sprout at the base of the stems.
Control measures. Regular change of site. Requirements for soil conditions: loamy or sandy loam, well-drained soil with an acidity not higher than pH 5.0.
For propagation, only healthy plant material is used.
When plants affected by the disease are identified, they are removed from the site along with a lump of earth and destroyed; in the fall, plant debris is carefully collected and destroyed.
Smut. Fungal disease. The first symptoms can be noticed already in the greenhouse on young cuttings. When propagated by tubers, it appears in June-July. First of all, the disease affects the lower leaves, on which numerous light green spots with a diameter of 2-10 millimeters appear, then the spots turn gray, but part of the damaged tissue remains yellow-green. Even later, the spots turn brown, and a dark brown border becomes noticeable around them. Gradually, individual spots merge and can cover the entire leaf. Development is promoted by high air humidity at an average temperature of 18-20 °C. Under such weather conditions, by mid-July, approximately half of the leaves on the plants dry out.
Control measures. For growing dahlias, select a well-ventilated and illuminated area.
If a disease is detected, before flowering, spray 2-3 times with 1% Bordeaux mixture or 0.5 copper oxychloride with an interval of 7 days.
Ring spot or spotted wilt. The disease is caused by the tomato bronzing virus, transmitted by thrips, and persists on perennial weeds.
Appears on young leaves in the form of light yellow rings and spots. Subsequently, brown necrotic areas form along the veins, and then the affected tissue falls out. Sick plants are stunted and bloom poorly.
Control measures. Control of sucking pests: aphids, thrips, leafhoppers, plant bugs.
Timely identification and destruction of diseased plants.
Mosaic. A viral disease transmitted by aphids, the slobbering frog.
Affects leaves, shoots and flowers. Light green spots with vague outlines of various sizes appear on the leaves. Over time, the tops of the shoots become brownish and cracks form on them. Plants grow poorly, dwarfism and excessive bushiness are observed. Large flowers look unusual against this background. With severe damage, flowering does not occur or ugly flowers open; some varieties may develop variegation.
Oak mosaic is caused by the cucumber mosaic virus. A characteristic symptom is a narrow yellow stripe on the leaves.
Control measures. To prevent spread with planting material, before storing dahlia tubers, they are heated in hot (50 °C) water for 30 minutes or dried in the shade at a temperature of 35 °C for 5 days, then disinfected in a solution of potassium permanganate (1 g /l) or lime solution (200 g/l) for 15-20 minutes.
During the growing season, weeds and virus carriers - aphids, leafhoppers, thrips - are controlled.
If diseased plants are detected, they are immediately removed from the site and destroyed.
Wet bacterial rot. Bacterial rot, an infection that lives on plant debris and in the soil.
If infection occurs in the soil, the affected tissues turn yellow, soften, smell unpleasant, plants are stunted, turn yellow and wither. When tubers become infected during storage (this occurs at high humidity in the storage), the infection causes their massive rotting.
Control measures. Before planting, dahlia tubers are treated in Gamaira solution, and the soil is also treated with it.
High level of agricultural technology, growing dahlias every year in a new place.
Timely removal from the site and destruction of diseased plants.
At the early stage of the disease, plants will be helped by spraying with Gamair.
In autumn, be sure to destroy plant debris.
Before storing, pickle the bulbs in a dark pink solution of potassium permanganate.
Powdery mildew. A fungal disease of dahlias, which manifests itself mainly in the second half of summer. First of all, the fungus infects the lower leaves, then the flower petals. Diseased organs of the plant become covered with a white coating, which then disappears. With advanced development of the disease, the flowering period is shortened and the resistance of the tuber against pathogens is reduced.
Control measures. If detected, the plants are sprayed with a solution of a copper-containing preparation or dusted with sulfur.
The following drugs are used: “Ordan”, “Skor”, “Horus”.
Gray rot. A fungal disease of dahlias that develops most severely in wet weather. Preserved on plant debris and in tubers.
Appears on leaves and stems in the form of numerous brown spots. The spots quickly grow and merge. The affected tissue dies, cracks and falls out. If young leaves are affected, they grow deformed. Peduncles are bent, buds do not open. With high humidity, a gray coating develops on the affected areas. In the fall, flowers may become infected. Light spots with necrotic tissue form on the petals, then they turn brown, merge, and the petals stick together, forming sticky lumps. Brown spots form on the surface of the tubers, growing wider and deeper. Diseased tubers are not stored.
Control measures. Dahlia is planted in a new place every year; before planting and storing the tubers, they are treated with a 0.2-0.4% Maxim solution for 30 minutes, then dried.
During the growing season, plants are treated with a solution of Trichodermin or Glyocladin.
Fusarium. A fungal disease of dahlias that affects the roots, stems and leaves of dahlias. The disease begins from the root collar area and spreads downwards. In humid weather, the affected parts become covered with a whitish-pink coating. During storage, diseased tubers shrink and dry out, and dry rot develops on them.
Infection occurs both during the growing season and during storage.
Control measures. Dahlias are planted in a new place every year; before planting and storing, the tubers are treated with a 0.2-0.4% Maxim solution for 30 minutes, then dried.
Treatment of tubers with Alirin B and Profit is also effective.
In summer dahlias need abundant watering. In hot weather, plants should be watered daily; at the end of summer, reduce watering; Weekly evening spraying with settled warm water is useful.
During the season dahlias It must be tied to supports 2-3 times (as it grows).
As dahlias grow, side shoots should be removed. Dahlias are planted until buds form at the top of the stem.
The stepsons of the two upper internodes under the flowering shoot should be left - they will then give the main mass of the inflorescence on the plant.
It is also necessary to remove shoots growing from the root collar, leaving only 2-3 shoots.
Side shoots can be left in pompom and small cactus varieties, as well as in single plantings.
You should also remove excess buds in a timely manner. On a peduncle of 3 buds, 1, sometimes 2, are left. Faded inflorescences must be cut off, because they retard the development of buds.
Good growth and flowering are promoted by fertilizing, which should be carried out at least 3 times during the summer. In addition to the above fertilizer mixtures, you can use slurry (1:10), infusion of bird droppings (1:20) at the rate of 1-1.5 liters per bush.
Diseases
There are viral, bacterial and fungal diseases dahlia.
Viral diseases
Yellow ring spot. With this disease, bright yellow rings and zigzags appear at the ends of the leaves.
Bronzing. Light green rings and various patterns appear mainly in the middle part of the leaves; the affected tissues die.
Viral mosaic. In the 2nd year, diseased plants develop wrinkling of leaves, shortening of internodes, strong development of side shoots - stepchildren, dwarfism, and inflorescences lose their decorative properties. Severely affected plants die.
Oak mosaic. A pale stripe appears on the leaves, similar in outline to an oak leaf, and the plants lag behind in growth and development.
Control measures: plants affected by a viral disease must only destroy. Thoroughly disinfect equipment and tools, disinfect the soil and dig up the layer.
Bacterial diseases of dahlias
Bacterial diseases include bacterial cancer And regrowth cancer. With bacterial cancer, white lumpy growths appear on the root collar, which then turn brown. By autumn, the growths reach a diameter of 10-12 cm. They rot, decompose and infect the soil with bacteria that remain in it for up to 5 years. In case of growth cancer, thickened, short, light green young shoots sprout on the lower part of the stem in a thick brush. Plants become infected through damaged areas of root tubers.
Control measures:destruction of diseased plants.
Fungal diseases
Dahlias are amazed black leg, verticillium, various types rotten, powdery mildew, spotting.
Pathogen black leg mainly affects young seedlings and cuttings. The stem of diseased plants darkens at the soil surface, becomes thin, bends, and the plant dies. For prevention purposes, seedlings and rooted cuttings should be planted in soil that has lain in heaps for at least 4 years, i.e., biologically disinfected.
Control measures: spill the soil on which diseased plants are found with a 1% solution of potassium permanganate.
At verticillium(wilting disease) plants suddenly wilt and turn yellow. The disease develops more often in the hot summer and spreads very quickly; plants die.
Control measures:Immediately burn the dead plants, treat the soil with bleach and dig up.
Sclerotinia, or white rot, occurs when fungal spores penetrate through damaged areas on the stems and during pinching. The affected areas turn yellow and rot, the above-ground mass of plants completely dies.
Control measures: cut the plants below the affected area and immediately destroy them, sprinkle the cut areas with ash (practically does not help). In case of severe damage, destroy the plants completely, disinfect the soil with bleach and dig up.
Fusarium, or dry rot, manifested in yellowing of leaves and stems. Pink pads form on the affected areas - sporulation of the fungus. During storage in winter, root tubers are affected.
Control measures: in case of minor damage, cut out the diseased areas to a healthy place, powder the wound with ash or a mixture of coal dust and sulfur. In case of severe damage, the plants should be destroyed, the soil should be disinfected and dug up.
Powdery mildew appears on dahlias in the form of a white coating on the leaves and stems, which disrupts their vital functions.
Control measures: at the first signs of disease, sprinkle the plants with a copper-soap mixture (2 g of copper sulfate, 20 g of green soap, 1 liter of water) or other copper-containing preparations; Spraying should be repeated after 2 weeks.
Pests
Greatest harm dahlias caused by sucking insects - different species aphids And meadow bug, which are carriers of viral diseases.
Control measures: spraying with a solution of liquid potassium or laundry soap (250-300 g per 10 liters of water), a solution of 0.2-0.3 percent karbofos or chlorophos. Against aphids, you can use tobacco infusion (practically does not help), actelik.
Slugs and woodlice, cabbage, potato and winter cutworm caterpillars eat young shoots and leaves of cuttings, inflorescences and leaves of adult plants.
Control measures: manual collection and destruction.
Wireworm(the larva of the click beetle) eats the tissue of the tuber, making passages in it that cause rotting.
Control measures: collect and destroy larvae and beetles, spill the soil with a solution of karbofos, chlorophos 10-30 percent.
Nematodes damage roots and stems by leafing. Invading them, they form swellings on the roots and stems (galls) and cause leaves to turn brown and die. Eventually the plants die.
Control measures: Plant marigolds between the rows of dahlias, which help reduce the number of pests.
More information about propagation, agricultural technology, care and planting of dahlias can be found in the selection of articles “”
Both needle-shaped, collared, and spherical dahlias are susceptible to diseases and pests - they damage plants, prevent them from developing and can lead to the complete death of the bush. The causative agents of most diseases of dahlia leaves are pathogenic fungi, which actively develop when plantings are too thick. The most common pests of dahlias are caterpillars, nematodes, slugs and aphids.
Dahlia diseases: leaf spot, rot and wilt
Here you will learn about dahlia diseases and how to control them using fungicides.
Leaf spotting. Fungal disease, causative agent - mushroom Entyloma dahliae. Yellow-green spots appear on the leaves of the plant, which blur and take on a gray-brown color with a dark border. The development of the disease is facilitated by dense plantings and poor ventilation in them. When treating this dahlia disease, systemic fungicides such as Fundazol and Oxychom are used. Affected plants are destroyed.
"Botrytis" or gray rot. Fungal disease, the causative agent is the pathogenic fungus Botrytis cinerea. When infected, brown spots first appear on the leaves. Then the entire plant is affected.
As you can see in the photo, with this disease, dahlia leaves dry out and die, flower stalks become deformed, and the buds dry out without opening. If the disease affects a plant in the flowering phase, watery spots form on the inflorescences, the tissues soften, and the flowers completely rot. Affected tubers rot. The development of the disease is facilitated by excess moisture and too thick planting. Dahlias are treated with fungicides against gray rot, such as Fundazol, Rovral, Topsin, Benleit.
Brown rot. A fungal disease, the causative agent is the fungus Rhizoctonia solani. It usually affects plants at the beginning of the growing season or young shoots. The bases of the shoots of the affected plants turn brown and become thinner. The development of the disease is promoted by planting dahlias too deeply. For the prevention and treatment of brown rot, fungicides are used, such as Alirin, Gamair, Fitosporin-M, Fundazol.
Fusarium and verticillium wilt. Two diseases with identical symptoms, but caused by different fungal pathogens Fusarium oxysporum and Verticillium dahliae. When affected by these diseases, the roots and tubers rot, the leaves, the apical part of the shoots and buds wilt. The affected parts of the plant are covered with a brown (verticillium) or pinkish (fusarium) coating. The development of diseases is facilitated by dense plantings, excessive dampness, and poor ventilation in the area with dahlias. To prevent and treat wilt, systemic fungicides such as Fundazol and Oxychom are used. Affected plants are removed from the flowerbed and burned.
If the dahlias have been affected by diseases that require plant removal, this measure alone is not enough. The soil underneath may still contain pathogens. Therefore, disinfection of the vacated space is necessary. An effective disinfection would be to generously sprinkle the soil with garden lime. Dahlias cannot be planted in this place in the coming years.
Dahlia pests: caterpillars, nematodes, slugs and aphids
The pests of dahlias and measures to combat them using insecticides and folk remedies are described below.
Caterpillars. Dahlias can be affected by the caterpillars of various pests - whiteflies, whiteflies, different types of armyworms, etc.
Look at the photo: These pests of dahlias gnaw foliage and young shoots, and can gnaw at the base of the stem.
All this leads to weakening of the plant, and in case of severe damage, to its death. If there are few caterpillars, they can be picked off by hand. In case of mass damage, systemic insecticides are used, which have a detrimental effect on both the caterpillars and the butterflies themselves, their oviposition and larvae.
Nematodes. Dahlias are often affected by strawberry and chrysanthemum nematodes. These almost invisible pest worms damage the buds, leaves and young shoots of dahlias. They feed on the juices of the plant, causing its weakening and deformation of the affected parts, stunting. To combat them, the affected plants are dug up with a large lump of earth and destroyed.
Slugs. These dahlia pests become active at night or in damp weather. They eat succulent dahlia leaves, sometimes destroying entire leaf blades. This leads to weakening of the plant. Slugs are collected manually or irritating substances are used - the soil around the plants is sprinkled with ground pepper and superphosphate. You can use pesticides, for example the drug Groza.
Aphid. Small sucking pests that settle in entire colonies on the back of leaves. They suck juices from leaves and young shoots. The leaves curl and turn yellow, and the affected shoots become deformed. A sticky discharge is noticeable on the plant - “honeydew”. Aphids not only harm the plant themselves, but are also carriers of diseases. At the first signs of aphid damage, it is necessary to cut off and destroy parts of the plant along with the pest colony. After this, the plants are treated with insecticidal preparations against aphids, such as Fitoverm, Confidor, Decis.
Here you can see photos of dahlia diseases and pests, which are especially dangerous for plants:
Loading...