What to do if the rhododendron withered. Garden rhododendron: planting and care in the open field. Why do rhododendron leaves turn yellow?

Plants suffer from severe waterlogging, unbalanced top dressing, low soil acidity, winter physiological desiccation and sunburn. Can be damaged by fungal diseases ( spots, rust) and chlorosis(an acute lack of iron and manganese, which occurs when the soil is low in acidity and disappears with the correct feeding regimen). By collecting and burning damaged foliage, sanitary pruning, and treating plants with suitable fungicides, many diseases can be resisted.

Rhododendrons are most often damaged by garden snails and slugs (collection and destruction helps), rhododendron bugs, spider mites, mealybugs, weevils, scale insects, rhododendron fly, against which insecticides help well.

Major diseases and symptoms

Vascular (tracheomycosis) wilt caused by fungi of the genus Fusarium ( Fusarium oxysporum). The disease begins with root rot, damages the vascular system. Plants turn brown and dry, starting from the top of the shoots. On dried leaves and stems, a grayish coating forms - mycelium.

Late blight rot caused by fungi of the genus Phytophthora ( Phytophthora). Large purple-brown spots appear on the root neck and on the base of the stems, the roots turn brown and rot, the plant fades.

Gray rot caused by fungi of the genus Botrytis ( Botrytis cinerea). One of the most common diseases of many crops, since the spores of the fungus are carried both with air and with water spray. On all parts of the plant - leaves, buds, stems - vague brown-brown spots appear and quickly grow. Damaged tissues quickly dry out, they form a grayish coating - mycelium.

Septoria spotting caused by fungi of the genus Septoria ( Septoria). Small round reddish spots appear on the leaves, the center of which gradually turns white and black dotted fruiting bodies of the wintering stage of the fungus form on them. Diseased stems shrivel, dry out, the leaves turn yellow prematurely and fall off.

Prevention and control measures

Must be carefully examined planting material when buying, select suitable conditions for plants and follow the basic rules of cultivation.
Severely affected branches and leaves are pruned, in autumn plant residues are collected and burned.
In spring and autumn, as well as after flowering, the bushes are sprayed with Bordeaux liquid or its substitutes (Hom preparation).

Major pests

spider mite (Tetranychus urticae) infects plants in hot and dry summers. Adults are so small that they are very difficult to see (about 0.5 mm). Most often, an attack can be seen when the underside of the leaves is covered with a thin cobweb, and the leaves become lifeless, brownish and fall off.

Acacia false shield (Parthenolecanium corni). The larvae, resembling small shiny brown outgrowths on the bark, stick tightly to the branches and "pull" juices from the plant. As a result, it weakens, gradually dries up.

furrowed weevil (Otiorrhynchus sulcatus). This black small (up to 1 cm) beetle is harmful at all stages of development. The larvae damage the roots, and adults feed on leaves, do not shun buds and bark.

Control measures

Compliance with the rules of agricultural technology.
In early spring, plants are sprayed with the biological preparation Fitoverm, or chemical: Aktara, Actellik, Arrivo, Iskra, Inta-vir. In case of severe damage, the treatment is repeated after 7-10 days.
During flowering, plants are not sprayed so as not to harm bees and other pollinating insects.
In order to avoid addiction of pests, preparations must be changed.

Rhododendron - deciduous, semi-evergreen or evergreen from the heather family. Has high decorative properties- glossy foliage (in evergreen varieties) of rich green color, lush inflorescences of various colors. There are species that reach 30 meters in natural conditions, there are also creeping dwarf shrubs. Sometimes the crown of the rhododendron turns yellow. The article describes the possible causes of this phenomenon and methods of dealing with it.

The plant is moisture-loving. Insufficient watering will lead to a loss of leaf turgor, they will begin to wither and turn yellow. Check moisture level earthy coma, squeezing in his hand a handful of earth under a bush of rhododendron. The release of water droplets signals that the plant is flooded. This can lead to root rot. The lump crumbled - watering is required. It turned out to form a lump from the soil - moisturizing is optimal.

Place the bushes near a body of water or in the shade of a taller plant ( a good option- Pine). This will protect the rhododendron from excessive water evaporation. Moisture will also help support occasional watering with a sprinkler.

Watering is carried out with acidified water, for which oxalic, citric, acetic acid is used.

The root system of plants is sensitive and shallow. When weeding, loosening, overheating the soil, it is easy to damage it, which will lead to yellowing of the crown. Mulching will help prevent this. trunk circles(layer height - about 5 cm) pine needles, oak leaf, moss, high peat. It is impossible to loosen the earth under a bush.

Thrips black

The upper side of the sheet is covered with gray holes, the lower side is black. The affected parts of the plant become gray, then yellow, fall off. Spray with nicotine solution (0.3%).

Rhododendrons are also susceptible to damage by other insects: plowed slug, narrow-winged mole miner, spider mite, furrowed weevil.

Rhododendrons are subject to various spotting that cause fungi. The most dangerous of these diseases is septoria.

Septoria in rhododendron

Symptoms: reddish small spots form on the leaf plates in the center, which increase in size and turn white. The leaves turn yellow and dry up. A plant without timely assistance may be left with a bare stem.

Help: remove the affected parts of the bush. Spray with a fungicide (after flowering or in spring).

Prevention: choose healthy plants for propagation.

Chlorosis

Yellow spots appear at the ends and along the edges of the leaves due to a lack of nitrogen in the soil or stagnant water at the roots.
Between the veins on the leaf plate, pale or bright yellow spots form with a too dense root system, a lack of iron or magnesium, and alkalization of the soil.

Control measures: timely application of the necessary fertilizers, normalization of irrigation, thinning of the bush, the use of acidified water.

I have only a few evergreen rhododendrons growing in my flower bed. Lately, the leaves have begun to turn yellow. apparent reason. It so happened that their place is the sunniest, there is almost never a shadow.

I recently learned that it turns out that it is precisely such plants growing in the sun that are most susceptible to disease.

To save my rhododendrons, I had to study quite a lot of information about the main mistakes of flower growers, diseases and infections, as well as how to treat them. Willingly share with you, as well as attach photos and videos. After all, no one wants to lose such a flower garden decoration, right?

According to experienced flower growers, major diseases afflict this chic decorative flower due to ignorance of the elementary rules for caring for a plant.

Therefore, before planting it on your site, you should be well acquainted with the basic requirements, how to properly plant and choose a place, what kind of soil is suitable, and how to water and fertilize rhododendron. Here are the main causes of disease.

Too high soil moisture.
Insufficient percentage of soil acidity, which contributes to the weakening of the root system.
Planting a plant in areas where there is constant sunlight, contributing to burns of leaf plates.
The use of top dressings and fertilizers that are not properly bred or do not suit the rhododendron at all.
Drying out of the soil and lack of moisture, especially in winter.
Elementary disadvantage necessary elements for active growth plants.
Temperature fluctuations and freezing of the root system in the cold season.
Withering of rhododendron is often due to the fact that the soil contains too much sand and clay.

This plant is quite capricious and sensitive. When planting it in a flower garden or in a flower bed, many factors must be taken into account.

Major diseases

Rhododendron bush needs regular inspection. Periodically, you need to inspect the leaves, stem and branches of the plant, and if you notice any deviations, then hurry to take action.

Tracheomycosis (vascular wilt)

The causative agents of this disease are fungal microorganisms of the genus Fusarium. They affect the vascular system of the plant, causing the stem and leaf plate to dry out. There is also a gray coating. Gradually, the bush dies, and its root system undergoes a rapid process of decay.

As a preventive measure, a rhododendron bush can be treated (spray and water a little root zone) with 0.2% Fundazol.

If the bush is not treated in time with Bordeaux liquid, then it will not be possible to save the rhododendron. All affected parts of the plant are carefully removed and burned.

Bacterial root cancer

The root system is affected by a soil-like bacillus of the genus Agrobacterium, which is capable of destroying the root cells of this plant. The main symptoms are:

Rounded and large outgrowths form on the root and root neck, acquiring a dark color and a solid shape over time.
Flowering is weakened and the bush begins to grow more slowly.
The next manifestation of the disease is the decay of the root collar and rhizome. The plant dies.

The infection is capable of transferring to planting material and can persist for a long time. Rhododendron should be treated with Bordeaux liquid or its analogues. Very affected plants should be destroyed along with the rhizome.

Mosaic of rhododendron

The causative agent of this disease is Rhododendron mosaik virus. Descriptions in different sources may vary slightly, but the main manifestations remain the following:

Yellowish spots and small swollen areas appear on the leaf plates of the plant.
Along with yellowish spots on the leaves, dark brown and green also appear, resulting in a mosaic pattern. The thickness of the sheet becomes smaller.
The flowering of rhododendron sharply declines and growth becomes completely slow.
The disease most often affects the bushes of alpine varieties.
The carriers of the disease are harmful insects: bedbugs, aphids and others.

To get rid of the disease, one should initial stage Remove affected leaves and branches. It is also recommended to treat with Confidor and Aktellik. If the defeat is too strong, then the flower must be destroyed.

Rust

The bush is susceptible to this infection more often in the autumn months. Blisters of yellow, reddish and red and dark brown tint appear on the surface of the leaf plate. During the spring period for reverse side leaf, you can see reddish spores with a reddish tinge.

This disease manifests itself only on the leafy part of the plant, so it is worth removing rust-affected leaves at the first stage of infection.

Then it is possible for prevention and in medicinal purposes spray the bush with Bordeaux liquid or preparations, the main constituent element of which is copper.

Chlorosis

The edges of the leaves of rhododendron are stained with yellowish spots. A disease appears due to too high a percentage of acidity in the soil or due to a deficiency of nutrients necessary for the development and growth of the plant.

To defeat the disease, rhododendron is sprayed with a solution of magnesium or iron sulfate at the rate of 7 grams per liter.

Types of rot that affect the plant

There are several of them, and they appear on different parts of the rhododendron. Let's consider everything in turn:

Late blight rot

The causative agent is a fungus of the genus Phytophthora. The reasons for the defeat of the plant by this type of fungus can be several reasons:

Lack of a drainage layer when planting or too small a layer that does not pass moisture well.
Excessive accumulation of moisture and soaking.
The plant was originally a carrier of this disease when purchased.

Main signs: stems and leaves are covered with dark spots of a burgundy hue, sometimes they become purple. Then the root system begins to rot, the plant slows down in growth, and the general condition of the bush deteriorates sharply.

Rhododendron should be treated with Fungicide, Quadris, Fundazol or Bordeaux liquid and significantly reduce the amount of watering.

Gray rot

The causative agent is Botrytis gray and Botrytis ash gray. Infection occurs with the help of spores that can be transmitted by air. They have many forms.

The defeat occurs in the spring, and ash-gray botrytis extends only to dead parts of the plant. And from there, the disease passes to the healthy parts of the flower.

Contributes to the disease and excessive soil moisture, and dampness of the air. Mushrooms secrete toxins, which are transferred from the damaged areas to the entire healthy bush, infecting it. External signs are:

All parts of the plant are infected.
It is characterized by the appearance of spots of dark brown or brown shades. After a while they dry out upper layer starts to crack.
In raw rainy weather the affected areas are covered with a grayish, strongly pubescent coating.

It is necessary to remove all necrotic areas from the bush, and treatment with 0.2% foundationazole is also possible.

root rot

The main parts that suffer are the stems and the root part. At the first stage, for no apparent reason, the sheets begin to dry out. Then the buds on the stems become dark brown. The last stage is the darkening and rotting of the flower root.

It is recommended in this situation to destroy diseased plants or parts thereof. To prevent infection with root rot, it is necessary to control the watering of the rhododendron and soil moisture. You also need to maintain the level of soil acidity, depending on the plant variety.

Also, there are such types of rot as:

Dry white rot.
The death of shoots.
Bud rot.
Rot of seedlings and young seedlings.

Varieties of spotting

This section also has several types. The most common are the following:

Pestalocyanic

The disease affects the stem part and leaf plates of the flower. Dark brown spots appear on them. irregular shape. They are framed by a thin brown edging.

There are more spots on the shoots than on the leaves. Spore pads are usually found on the mottled, infected part of the leaf.

Sick areas are carefully cut off and the bush is treated with Bordeaux liquid or Camulus.

Anthracnose spotting

Brownish patches appear on the upper parts of the leaves. The leaves then dry up. dark spots then grow to the stem part. The affected leaves and shoots are cut off, and the bush is sprayed with Bordeaux mixture.

In addition, the following types of rhododendron spotting are distinguished:

Septoria.
Phyllostic.

wax disease

It is characterized by the appearance of several types of fungal infections that have different effects on parts of the plant.

Brownish-red outgrowths may appear and the stems thicken, sometimes parts of the flower are overgrown with white pillows - outgrowths. There are fungi that cause leaves to turn yellow or white coating with spores on the inside.

Here is an incomplete list of diseases that affect rhododendron. Only proper care, prevention and timely measures taken will help keep the plant healthy and blooming.

Yellowing of the leaves and flowers of a room or garden azalea can be noticeable even before the start of the active phase, when yellow leaves appear on the plant, which rapidly fall off (you can find out more about why azalea leaves dry and fall off and how to save the plant). To begin with, it may alert that dry grayish spots appear on the plant.. They may be barely visible.

This means that the direct rays of the sun hit the plant, and the azalea hates the heat.
Also, with such a symptom, one can talk about the appearance, but this is a topic for a separate article.
Important! If brown and brown spots appear on the leaves, this is a sure sign that the plant may die due to unsuitable conditions.
Brown-yellow ends on the leaves indicate that the roots of the plant feel some kind of discomfort. Perhaps the water for irrigation is very hard or the plant is too dry.
Another reason is too dry air.
If on one of the days yellow-green leaves appeared on the plant, then most likely the plant has chlorosis from a lack of iron, or these are the consequences of a draft and a temperature drop.
The constant fall of the leaves indicates improper “feeding” of the azalea, as well as problems in the soil - perhaps the earth will need to be replaced and the plant transplanted into another pot.

What is the danger to the plant?

If the plant is not treated, then after the formation of dry leaves, this tendency will pass to the branches. They, too, will gradually begin to dry, and then the drought will get to the roots of the azalea.

Damaged roots bring inevitable death to the plant., here you will already have to bring the azalea back to life in very difficult ways, with a not always successful result, especially for beginner flower growers.

In any case, the problem of drought must be identified and dealt with in a comprehensive manner. Only in this case will there be a chance to save the plant from death (for more details on how to save the azalea, see).

When is yellowing natural, and when is it a disease?

autumn

Yellowing in autumn is a normal process that occurs regularly in a certain variety.. Rhododedron in such a period needs pruning of those branches and leaves where gray-brown spots are observed. They can be carefully removed with secateurs. Withered leaves are collected along with dried twigs.

dangerous

But if yellowing is accompanied by various signs in the form of spots or browning of the leaves, then urgent action must be taken.

If you notice discolored spots on the leaves that make separate sections almost transparent, then a rhododendron bug made its way into the plant. It can lay brown testicles right in the tissues of the azalea, so it must be destroyed immediately. For this, the Diazion tool is suitable.
The appearance of brown spots on the leaves, which gradually increase, indicates fungal disease- septirozoic. Excessive humidity, heat and sunlight leads to it.
Attention! In order to get rid of the disease, you need to purchase a special anti-flu solution, and then put the azalea in the shade and make sure that it is not watered too much.

Causes

Why is this happening? Yellowing leaves can be due not only to natural causes., but also possible due to a lack of moisture or an excess of heat.

Sometimes this condition of the azalea is caused by the defeat of the plant by the mealybug. You can save him, but this will require constant treatment with a certain drug. In this case, you can help only with the help of an insecticide.
Sometimes the plant is attacked by aphids, which can be easily found on azalea leaves. You can destroy it with a simple remedy: take soapy water and water the plant three to four times a week.
The most common cause of yellowing leaves is the lack of the right amount moisture. In order for it to fall into overdried soil, the pot must be lowered into a basin with water for a few minutes. cold water. If the leaves of the azalea turn yellow after that, this means that the earth is oversaturated with calcium, which means that the water will need to be acidified during irrigation, and the temperature should be kept no higher than 15 degrees.

Do not forget that a prerequisite for the growth of azalea is acidified soil. It can be made from sand, peat and coniferous soil, you can limit yourself to the substrate that is sold in the store.

What parts of the plant are subject to the process and what needs to be done?

Dry spots on the tips of the leaves

If the leaves just turn brown around the edges, and then fall off, then you can try spraying them with Epin. However, in some types of azaleas, this process can be called natural - they periodically shed their leaves (you can find out more about why the plant sheds leaves and what to do to solve the problem).
If the plant does not dry completely, and dry spots appear along the edges of the leaves, then you should think about the fact that the water for irrigation is too hard.
You also need to check the humidity. When it is too stuffy, then you need to make sure that the plant is available Fresh air, and in the room was required level humidity.

Flowers turn yellow and fall off

If the leaves turn yellow and fall off, and such a process has reached the azalea flowers, this indicates fusarium. A special sign is that the leaves turn pale, then curl, turn brown and fall off. And the flowers dry, and then quickly crumble.

Fusarium in azalea develops only in a humid environment and at high temperatures.. Then it progresses and affects young roots.

Reference! To overcome the disease, it is necessary to spray the azalea with a solution consisting of an antibiotic, a fungicide and copper sulfate.

The recipe is this:

Crush three aspirin tablets, mix with an ampoule of fungicide, add vitriol.
Then water for two weeks daily, after which it will be necessary to water the azalea with a solution of potassium permanganate for another two weeks.

Stem

If the stem of the rhododendron also began to turn yellow, then you need to pay attention to feeding the plant.

Feeding schedule:

You need to feed with a special preparation "Azalea", it is desirable to carry out the procedure once a week.
Do not forget the most important thing - citric acid or lemon juice, which are added every 10 days.

Many add malic acid or acetic acid, you can do that. You can also spray the azalea with a solution of lemon juice.

An important top dressing for azaleas - ferovit. It is essentially an iron chelate, and iron is very important for azaleas. It is also used for chlorosis - when azaleas turn yellow leaves and stems due to a lack of iron. Ferovit also contributes well to the growth of greenery and generally improves the appearance of the azalea. They can be both watered and sprayed. More effective when spraying.

Prevention of the recurrence of the disease

Attention! Another effective preventive measure- water the azalea with a solution of potassium permanganate for two weeks once every two months. This prevention will help beat the plant from fuaziros and other unpleasant diseases.

Further care for indoor and garden rhododendron

In order to detect the problem in a timely manner, the plant should be periodically inspected, as well as damaged and dried parts should be removed. Wrong care behind the azalea leads to disease and death of the plant. Also, the azalea should be periodically transplanted into a new soil, watered with melt water, and covered with ice in the summer in the heat.

Conclusion

Azalea will bloom beautifully, but at the first inconvenience, it will begin to shed its foliage. To avoid unpleasant consequences, it is necessary to carefully monitor three conditions: air humidity, moisture in the soil, the absence of direct sun rays. Then the plant, if it does not belong to the subspecies of deciduous azalea, will have beautiful green leaves, periodically bloom and delight the owners with its beauty.

Rhododendrons are affected by many pests and diseases. To avoid the death of plants, it is necessary to regularly monitor the condition of rhododendron bushes and take timely measures to eliminate insect pests and fungal diseases.

Insect pests of rhododendrons

Acacia false shield (Parthenolecanium corni Bouche)

Rhododendron bug (Stephanitis rhododendri Horv)

Rhododendron bug is considered the most dangerous and common pest that affects these shrubs. A sign of its presence can be small black-brown dots on the back of the leaf, places of punctures by the bug of the leaves and their excrement.

In the photo, the larva of the rhododendron bug.

Damage leaf blade rhododendron larvae of the rhododendron bug.

You can destroy the bug by spraying with contact-intestinal and systemic preparations - clipper, omayt, aktara, demitan, apolo, fitoverm, Bi 58. The preparations must be changed so as not to cause addiction in insects to the active ingredient of insecticides.

Spider mite (Tetranychus urticae)

The spider mite inhabits rhododendron shrubs in a dry, hot season, feeding on the juices of its leaves. Due to extremely small size it is difficult to see it with the naked eye. Determine presence spider mite the appearance of the plant will help: the underside of the leaves, as it were, is entangled with a thin cobweb, and they themselves become brown in color, fade and fall off.

Here it must be added that middle lane In Russia, the full development cycle (generation) of the spider mite is from 7 to 9 days. Per summer season 22 generations of ticks hatch. To achieve success in the fight against ticks, it is necessary to carry out treatments every 6 days with systemic pesticides: Aktara, Omayt, Apolo, Demitan.

Field slug, or plowed slug (Deroceras agreste)

The arable slug infects the leaves of young rhododendrons, making large holes in them. Its activity can lead to the death of shrubs in the shortest possible time. To prevent this, individuals of the plowed slug will have to be collected by hand, and watering with a solution of TMTD (concentration 0.8%) also contributes to its destruction.

Rhododendron whitefly (Dialeurodes chittendeni)

Whitefly rhododendron, or white rhododendron fly (Dialeurodes chittendeni)

They are found mainly on large-leaved rhododendrons: Caucasian, Pontic and Ketevbinsky and their varieties and hybrids. Spraying leaves from below with nicotine and oil emulsion in spring and autumn is recognized as the most effective.

Tobacco (black) thrips (Thrips tabaci).

Tobacco (black) thrips is an insect of small size and characteristic black color. Damages leaves and buds of rhododendrons.

As a result, the foliage fades prematurely, turns yellow and falls off, and the flowers fade without opening. In addition, this pest greatly inhibits the growth of young shoots and deforms the buds. They fight tobacco thrips by spraying plants with a 0.3% nicotine solution, 0.2% karbofos emulsion. Also suitable for this purpose are preparations: Aktarv, Omayt, Apolo, Clipper, Fitoverm,

Garden beetle (Phyllopertha horticola)

Garden Asian beetles are the most dangerous pests for rhododendrons. They infect the stems and root system of plants, eat their leaves. Most effective tool for the destruction of the insect is considered: Clipper, Bee 58, Apolo, Fitoverm, Aktelik, Karate.

Furrowed weevil (Otiorrhynchus sulcatus L.)

Corrugated bevel Otiorrhynchus sulcatus L. is one of the most dangerous pests. It affects many cultures, including rhododendrons. It is very dangerous for plants, because adults eat leaves, buds, buds, flowers and even young shoots of rhododendrons, and larvae, while in the soil, eat all the roots up to the root collar. In young shoots, the bevel gnaws the bark to wood, the shoot above the affected area withers and dries. The pest eats leaves and petals in an arcuate manner, starting from the edges. Affected plants lose their decorative effect.

The adult beetle has a length of 8-10 mm, black, brown-black (young individuals are yellowish-brown), with yellow spots on thick, leathery, ribbed wings and with a short nose. Adults are inactive, flightless. Adults feed only at night, and during the day they hide in the substrate, under soil particles, so they are difficult to notice. On flowering specimens, they hide in inflorescences. If early in the morning they can sometimes be seen, then at the first touch the beetles freeze, fall to the ground and become difficult to distinguish.

The larvae are fleshy, yellowish-pale, 10-14 mm long, 3.5-4.0 mm wide, without legs, with a light brown head and black jaws. By appearance resemble the larvae of the cockchafer.

They eat the roots and bark of the base of the stem, as a result of which the plants die. AT greenhouse conditions Beaver breeds all year round, but especially intensively from July to December. It is during these months that the risk of damage to rhododendrons by larvae is greatest. Adults appear around February.

AT open ground the larvae overwinter in the soil, pupae form in spring. Adults appear in May and June. Females lay their eggs in humus-rich soils or in compost heaps.
Even in small numbers, pests can severely disfigure the leaves, flowers and shoots of rhododendrons, and their larvae can completely destroy hundreds of young seedlings growing in greenhouses.

Control measures.

The fight against this pest is very difficult, since it is not always possible to notice damage to the larvae in a timely manner. In addition, older larvae, as well as adults, are insensitive to insecticides. If larvae of the scythe appear in the picking boxes in which young seedlings of rhododendrons grow, the plants should be immediately transplanted into a fresh substrate, and the old one should be burned. During transplantation, care must be taken to ensure that pest larvae do not get into the new substrate, which are usually easy to find near the roots of the affected plant. For the purpose of prevention, the remaining boxes located near should be watered with a 0.1% emulsion of phosphamide (Bi-58; Rogor), 0.2-0.3% emulsion of metaphos, karbofos or chlorophos. The permissible concentration of insecticide in each case is determined individually. During the active life of adults, rhododendrons are pollinated with metaphos dust, sprayed with a 0.2% emulsion of metaphos, phosphamide or a 0.3% emulsion of karbofos or systemic insecticides and acaricides: Apolo, Omite, Demitan, Fitoverm, Flumite. Since adults actively feed at night, spraying should be carried out late in the evening, at night or early in the morning.

Narrow-winged miner moth

Its caterpillars gnaw many holes in the leaves, eat the leaf parenchyma, and then fold the edges of the leaf into a tube for pupation.

As a result of their activity, the leaves begin to dry out, crumble and fall off. To scare away the narrow-winged moth, knowledgeable people recommend fumigating or spraying bushes with sulfur.

Mealybug

rhododendron fly

The rhododendron fly infects the leaves of shrubs, leaving small light spots and debilitating plants. To destroy this specific pest, spraying with nicotine sulfate, Apolo, Demitan, Fitoverm is used.

Blue Moth (Arichanna melanaria)

Butterfly, wingspan 36-44 mm.

Blueberry moth caterpillar eats the edges of rhododendron leaves.

Control measures

During the appearance of blueberry moth caterpillars, rhododendron should be processed

Contact Insecticide: Clipper
Contact intestinal insecticides: Decis, Senpai, Intra-Vir, Barey, Aktellik, Karate, Karbofos
Systemic insecticides: Aktara, Konfidor, Kinmiks, Bi-58

rhododendrum sawfly

Sawfly larvae leave intricate patterns on the reverse side of the leaf.

Sawfly larvae, unlike adult insects, cause minor damage to the decorativeness of rhododendrons. Therefore, it is recommended, upon detection, to collect them from the leaves and destroy them.

fungal diseases

Tracheomycosis

Tracheomycosis leads to rotting of the rhizome, as well as significant damage vascular system plants. When painful signs appear, it is necessary to cut and burn the branches affected by the disease, and then spray the shrub with Bordeaux liquid.

Late blight rot

Late blight is caused by pathogenic fungi of the genus Phytophthora. As a result of this disease, the stems and root neck of the shrub are covered with brown or purple spots. Then the rhizome of the rhododendron turns brown and begins to rot, which leads to gradual wilting. In the absence of timely and competent treatment, the lesion passes first to the stems, and then to the leaves of the plant, leading to its death. When signs of the disease appear, the affected branches and shoots must be burned, and then the rhododendron bushes should be treated with quadris or 0.2% fundazolo. You can also use drugs: Gamair, Abiga Peak, Topaz, Fundazol.

Septoria spotting (Septoria lycopersici)

Pathogen: mushroom Septoria azaleae Voglino. Symptoms are described by different authors with slight differences.
1. Small rounded reddish spots appear on the leaves, gradually turning white in the center.

Over time, dotted black fruiting bodies of the overwintering stage of the fungus form on the surface of the spots. The leaves turn yellow and gradually dry out.
2. As a rule, greenhouse plants are susceptible to the disease. In countries where rhododendrons are cultivated very widely, this fungus is also found on deciduous rhododendrons in open ground. Yellowish, red-yellowish, later yellowish-gray spots of irregular shape appear on the leaves of plants. By autumn, they become dark brown in the middle, and sometimes even brownish black. At first, the spots appear in the middle of the leaf blade, gradually increase and, having reached the large veins, stop. The fungus grows into all leaf tissues, the leaves die and fall prematurely, so that the plant becomes completely naked. As a result of falling leaves in plants, all physiological processes are disturbed, they are not normally laid flower buds. On the spots, one can see small, black, dot-shaped spore receptacles - pycnidia, immersed in leaf tissues.

Control measures: pruning of the affected parts of plants, spring spraying with a solution of Bordeaux mixture, its substitutes or cumulus. If the air is excessively humid, do not spray plants with preparations containing copper, as this leads to burns of leaves and young shoots. Preparations containing copper are used only at normal air humidity and at a sufficiently high temperature. You can spray only those plants whose leaves have fully grown and developed. AT summer period it is necessary to treat with fungicides: Gamair, Abiga-Peak, Skor, Topaz, Fundazol.

Rot of seedlings and young seedlings of rhododendron

(pathogens - Rhyzoctonia sp., Pythium sp. and Botrytis sp.).

Often, when propagating by seeds and cuttings, one has to observe a sudden mass wilting of rhododendrons, their decay and death. The causative agents of this disease are fungi of the following genera: Rhyzoctonia, Pythium and Botrytis. Affected seedlings fall sideways and die, white hyphae of fungi or brownish mold are visible on the leaves. Pale, cobweb-like threads appear on the surface of the substrate. Fungi usually develop if the substrate is fresh, not yet decomposed, or if the crops are watered with fungus-infected water. Too much planting density, excessive humidity in greenhouses and insufficient air exchange increase the likelihood of disease.
Control measures: dying shoots should be sprinkled with finely ground charcoal to stop the spread of the disease. In addition, the disease can be instantly eliminated by sprinkling the affected areas with foundation powder. In order to prevent young shoots and seedlings, it is desirable to spray with a 0.2% suspension of foundationol. Captan and TMTD can be used to combat this disease.

Rhododendron bud rot

Pathogen: fungus Sporocybe azaleae (syn.: Pycnosteanus azaleae)

The disease was first detected on rhododendrons in the United States. The disease is typical for the largest rhododendrons (Rhododendron maximum L.) and Katevbinsky (Rhododendron catawbiense Michx.). Buds affected by this disease turn brown and die. Mushroom from buds can grow into branches and lead to their death. Control measures: during the growing season, plants should be sprayed regularly (every 2-3 weeks) with copper-containing preparations.

Buds "beaten" by autumn-spring frosts. Unlike the buds affected by the fungus Sporocybe azaleae (syn.: Pycnosteanus azaleae), they look clean and do not have pycnidia. But still, the buds "beaten" by frosts (frosts) serve as potential objects for the settlement of Sporocybe azaleae (syn.: Pycnosteanus azaleae), so they should be removed.

Carriers of the fungal disease Sporocybe azaleae (syn.: Pycnosteanus azaleae) are rhododendron bugs and cicadas Graphocephala coccinea, Graphocephala fennahi (rhododendron leafhopper). Cicadas themselves can be the cause of the drying of flower buds and buds of Azalea Pontica.

To prevent infection of the rhododendron by the fungus Sporocybe azaleae (syn.: Pycnosteanus azaleae) in July, yellow panels coated with adhesive are installed in the azalea bushes to catch the flightless green and orange striped cicadas.

In case of serious infestation, systemic and enteric-contact insecticides are used against cicada larvae. Treatments are carried out early in the morning.

In order to minimize losses from the development of fungal diseases, it is necessary to remove all shrunken shoots and dead dark-colored buds.

Gray rot of rhododendron

Symptoms: blurry brown spots without bordering appear on leaves, stems, buds and petals, the surface of which quickly dries and cracks.

The death of the shoots of rhododendron

Plants planted in full shade are most susceptible to this disease.
The causative agent is the fungus Phytophtora cactorum Leb. Symptoms: in the affected plants, the apical buds do not bloom, they turn brown, and then completely die off. The shoots also dry out at first, and later die off. Mature leaves curl up, turn brown and dry. Severely affected plants die.
The causative agent is the fungus Physalospora rhododendri. This fungus also infects lilacs. Symptoms: in diseased plants, on some shoots, the leaves turn brown, dry out, and then the entire shoot dies.
Control measures: affected leaves and shoots are burned. After flowering, rhododendrons are regularly sprayed with copper-containing preparations. Spraying is done every 10-14 days.

Rhododendron root rot

The causative agent is the fungus Phytophtora cinnamomi Rands. This fungus most often damages the roots and base of the stem. Symptoms: on individual shoots or on the whole plant they wither, and then all the leaves dry up without externally noticeable reasons. The apical buds turn brown and die. Cross sections of the shoots show that the cambium layer is brown. The roots turn brown and rot, the plant dies. This disease mainly affects rhododendrons growing on insufficiently acidic, highly moist soils. Most often, young and oppressed plants suffer. Plants are infected through the root system or through damage to the bark and roots.
Control measures: affected shoots or the entire plant is burned. To prevent the disease, it is necessary to maintain the acidity of the soil corresponding to the requirements of the plant species or variety and observe correct mode glaze.

Dry white rot of the root neck of rhododendron

The causative agent is the fungus Armillaria mellea (real honey agaric).
Symptoms: diseased plants have mycelial films and flat rhizomorphs under the bark. This disease usually affects those plants that have damage to the root collar. The plant affected by the fungus dies. Strongly growing rhododendrons do not get sick with dry rot of the root neck.
Control measures: affected plants are dug up and burned. Plants near which the disease is found should be transplanted so that the root neck is not covered by mulch (it must be dry).

Wax disease of rhododendron, or swelling of the leaves of rhododendron

Large, rounded or oblong spots of red or red-brown color appear on them. A dense waxy coating of sporulation develops on the surface of necrosis. Over time, the spots dry out and crack. Affected plants lose their decorative effect and bloom weakly. Usually this disease affects alpine species of rhododendrons - Rhododendron ferrugineum L., Rhododendron hirsutum L. and others. With the defeat of rhododendrons by the fungus Exobasidium rhododendri, a change occurs in the metabolism of amino acids.

Exobasidium vaccinii - the causative agent of a very common disease of lingonberry leaves, causes the formation of white cushion-shaped growths on young leaves of evergreen rhododendrons (Rhododendron maximum L., Rhododendron catawbiense Michx.) and deciduous rhododendrons in natural places their growth.

Exobasidium burtii forms characteristic spots on the leaves, which at first are small, round, and later, increasing in size, acquire indefinite form. White spores are visible on the underside of the leaf. This disease usually affects Rhododendron ponticum L. and Rhododendron luteum Sweet.

Exobasidium vaccinii-uliginosi Bond., the causative agent of a very common blueberry leaf disease, causes the formation of the so-called "witch's broom" in the Carolina rhododendron. The leaves turn yellow-brown, their underside is covered with powdery coating. A year later, the affected leaves die off.
Measures to combat diseases caused by representatives of the genus Exobasidium: pruning of the affected parts of plants, spring spraying with a solution of Bordeaux liquid, its substitutes or camulus.

Exobasidium japonicum attacks leaves and shoot tips. Affected plants develop abnormally thick, large, pale green leaves covered with a chalk-white coating.

These leaves quickly shrivel, grow moldy and dry out. On annual plants, the fungus is less common than on older ones. Susceptibility to this disease largely depends on the type and variety of rhododendrons.

Pestalocium blotch of rhododendron

Pathogen: fungus Pestalotiopsis sydowiana (syn.: Pestalotia macrotricha Kleb., Pestalotia rhododendri). Leaves and stems are affected. On the leaves appear small brown spots of irregular shape with a thin brown border.

The spots are often scattered along the edges of the leaf blade, which turns yellow and dries prematurely. Fungal sporulation pads form on the spots gray color. The spots on the stems are large, depressed, elongated. The surface of the spots dries up and brightens, numerous small gray pads of sporulation of the fungus are formed. Affected shoots gradually dry up.

In humid weather, all necrotic parts are covered with a fluffy smoky-gray coating of sporulation.

The same rhododendron leaf after the wet chamber.

Over time, brown rounded sclerotia form in the drying mycelium.

Control measures: pruning the affected parts of plants. At industrial cultivation- preventive spraying of plants and watering the root zone with a 0.2% solution of foundationol.

Anthracnose blotch of rhododendron

Pathogen: fungus Gloeosporium rhododendri. On the upper part of the leaves, marginal necrosis appears in the form of brown spots of irregular shape. The leaves gradually dry up. On the surface of the spots, sporulation is formed in the form of numerous rounded fruiting bodies. dark color. If the infection continues to develop, the stems are also affected, which dry out over time. This disease is widespread in Holland and England on young seedlings of the Pontian rhododendron.
Control measures: pruning of the affected parts of plants, spring spraying with a solution of Bordeaux liquid, its substitutes or camulus.

Phyllostic blotch of rhododendron

Mushroom Phyllosticta concentrica Sacc. (syn.: Phyllosticta maxima Ellis & Everh.). Symptoms are described by different authors with slight differences.
1. Large rounded spots with a reddish border appear on the leaves.
2. The spots are indistinct, irregular, dark brown or ash gray, with dark edges. Localized along the edges or at the ends of the leaves. Black balls - sporangia - fall out of the spots. In the vast majority of affected leaves die, and the process begins at the tips of the leaves. Similar spots are formed by the fungus Phyllosticta saccordoi.

Mushroom Phyllosticta rhododendricola.
Symptoms: the appearance on the leaves of reddish rounded spots with a thin brown border.
In the future, the affected areas brighten, crack and fall out. Black dotted bodies of the hibernating stage are formed on the necrotic tissue.
Control measures: pruning of the affected parts of plants, spring spraying with a solution of Bordeaux mixture, its substitutes or cumulus.

Cercosporosis of rhododendron. Pathogen: Cercospora rhododendri Ferraris.

Symptoms: Irregular, angular, dark brown spots with reddish edges appear on the leaves, especially noticeable on the underside of the leaf. In conditions high humidity the upper side of the leaf blade is covered with a gray coating of sporulation. Leaves are most affected lower tiers. The causative agent is widespread in the United States, especially on Pontic rhododendron and varieties based on this species. Another mushroom of the same genus, Cercospora handelii Bubak, is also dangerous.

Rhododendron leaf mosaic

Leaf mosaic is a disease of a viral nature, the carriers of which are bugs, aphids and a number of other insects. Rhododendrons are most susceptible to this disease. alpine species. Due to the development of the disease, the leaves of the plant turn yellow and thinner, and greenish swellings form on their surface. To prevent infection of all rhododendrons, the affected shrubs are destroyed. To combat insect vectors, it is recommended to use means such as confidor, actellik, etc.

rust of rhododendrons

The rust of rhododendrons affects both deciduous and evergreen rhododendrons. On diseased leaves, the so-called sporulation of the pathogen is formed, resembling dark-colored pads in appearance. In the fight, spraying with copper-containing preparations is effective. Rust of rhododendrons is a dvukhozyainny fungus. The second stage of development occurs on spruces. Strong damage to spruces by rust can cause spruce forests to dry out.

Bacterial cancer of the roots of rhododendrons

The causative agent is the bacterium Agrobacterium tumefaciens, a Gram-negative, obligately aerobic, rod-shaped soil bacterium of the genus Agrobacterium. Able to transform plant cells using a special plasmid. Phytopathogen, causes the formation of crown galls in plants, conditional pathogenicity is also known in people suffering from immunodeficiency diseases. Chemoorganoheterotroph, obligate aerobe.
Symptoms: large, rounded outgrowths form on the roots and root neck, which gradually darken and become hard. Plants slow down growth and bloom poorly. Over time, the growths and the root neck rot and the plant dies. The infection persists in plant debris, often spreading with planting material.

Control measures: regularly spray weakly affected plants with a solution of Bordeaux mixture or its substitutes; severely affected plants are burned along with the roots.

Nitrogen starvation is typical for plants growing in sandy soil. Its signs are the shallowing of the leaves, reduced flowering, weak ovary of the kidneys. You can fight the disease with the help of regular top dressing. mineral fertilizers with high nitrogen content.

Chlorosis of rhododendrons

Chlorosis manifests itself in the appearance of spots on the edges of the leaves of rhododendrons. yellow color. The causes of this disease are increased acidity of the soil or insufficient content of nutrients and essential elements in the soil. The problem should be dealt with by spraying shrubs with magnesium sulfate and iron sulfate (7 g of the substance per 1 liter of water).

Wetting rhododendrons

Soaking is typical for plants planted in heavy, clayey soil, as well as with excessive soil moisture. At the same time, there is a change in the color of the leaf plate, premature fall of foliage and destruction of the root ball. To prevent a problem, be careful when choosing a site for planting rhododendrons, and also do not overdo it with watering to avoid soil waterlogging.

sunburn of rhododendrons

Large-flowered rhododendrons, especially Yakushimanum hybrids, are the first to suffer from the scorching sun. They are the most famous and popular among gardeners, because already young, small plants are abundantly covered with large flowers during flowering.

In bright sun, the leaves become rusty brown in places, as if burned. This should definitely be avoided. This phenomenon is especially susceptible to rhododendrons, which are planted in young gardens, where there are still no large shrubs and trees that create shade.

Winter drying of rhododendrons

One of the most common diseases of rhododendrons. It is observed after severe frosty winter months. Signs of damage are manifested in browning and drying of the foliage.

Then, after a while, the entire shrub dies. The causes of the development of the disease are a violation of the waterways and excessive loss of moisture by rhododendrons. For the treatment of plants, intensive abundant watering, as well as daily spraying of shrubs. For prevention purposes, the so-called winter watering is used.

Pecking of buds and rhododendrons by birds

In early spring, the facts of pecking of the buds of rhododendrons by crows were noted, most often Smirnov's rhododendron suffers.

The information was collected and presented to your attention by the head of the plant protection department of the Agro-Industrial Complex "Vitus" Sinelnikov Konstantin Yuryevich

Specialists of the plant protection department of APK Vitus carry out entomological and phytopathological examination green spaces, develop individual action plans for plant protection, carry out the processing of green spaces with protective equipment and carry out comprehensive care behind the plants.

Department of plant protection APK "Vitus": [email protected]

Categories

Popular