Brodsky Yury Vasilievich is an experienced gardener from Primorye. Dear friend and subscriber
Failed landing
Too light, dim small leaves; oppressed look. This indicates a lack of oxygen to the roots (wet dense soil, stagnant water) or a lack of nutrition or water.
How to save. Correctly . They plant a rhododendron in and make sure that there is no competition with a superficial root system. Even too active perennials such as tenacity, completely covering the near-stem circle of the rhododendron, can deprive it of nutrition and moisture.
Often the outer part of the root ball is also a container formed by dead roots. Their dense felt does not allow living roots to break into the soil - as a result, the plant starves. It is necessary to remove this inner container when planting, or at least notch it in several places. It is useful to check if there are mole or mouse passages in the root zone.
How can I help you. , if necessary, water and mulch plantings, spray the crown. If the plant is planted well, but still lags behind in growth, they can help foliar top dressing solution of complete mineral fertilizer with trace elements. Top dressing is required 3-4 times in June-July at half the dosage recommended in the instructions.
Such a root ball before planting should be freed from a layer of dead roots.
Unsuccessful wintering
Death of leaf tissues or buds on parts of the rhododendron that are above the snow. The problem arises from the alternation of daytime sun and nighttime frost in February and March. If cold weather is accompanied by wind, then the leaves of the plant actively evaporate water. The water supply is not replenished, because the roots in the frozen ground do not work, and the leaves simply dry up. In deciduous species of rhododendron, flower buds or the upper parts of the shoots may dry out.
How to save. When choosing a landing site. In dry autumn, plants are watered abundantly. Install a winter shade - mesh or gauze, a rare burlap on the frame, protective screen etc. In autumn, bushes are mulched with a layer of 7-10 cm so that the soil does not freeze deeply.
How can I help you. In the spring, severely damaged leaves are pruned. The shoots are pruned in June, when it becomes clear where the buds wake up. Do not rush to cut branches from small-leaved evergreen rhododendrons - they very often grow back over the entire length of the shoot. If the leaves remain in winter state- lowered and rolled up into a tube, - the crown is often sprayed with water. They rake, so that the earth thaws rather, and the roots work.
Fracture of bushes by settling infusion or wet snow
How to save. In autumn, structures are installed above the bush, which will take on part of the snow load: arcs fixed crosswise, wigwam from stakes, etc. If the shape and size of evergreen rhododendrons allow, you can tie the bushes with elastic strapping.
How can I help you. Broken branches are cut in the spring. Do not rush and cut off slightly broken shoots: you can try to save them. To do this, you need to connect the edges of the fracture, tie up the shoot and fix its position with a support. The strapping and support are left for at least a year.
Ice crust damage to leaves
Evergreens are most often affected. If the crust does not melt for too long, the lower branches, which are in ice captivity, may completely lose their leaves.
How to save. Spruce branches or brushwood are placed under the lower branches of the bushes.
How can I help you. In the spring, severely damaged leaves and shoots are pruned.
Frostbite shoots
The leaves, bark and cambium tissues die, the shoot on the cut is dead - brown. Varieties that are not suitable for this climate zone suffer. In winter-hardy varieties, unripened shoots die. As a “growth disease” it occurs in young plants obtained by the meristem method - tissue culture, as well as in the case of late top dressing.
How to save. Choose to land. Top dressing is carried out in doses and only at the beginning of summer. In deciduous species, actively growing blind shoots are pinched at the end of July.
How can I help you. In the spring, frostbitten shoots are cut to healthy wood.
Weak flowering
Varieties rhododendron Caucasian and dense sometimes open part of the buds in the fall. In the spring, they bloom less. Rhododendron Ledebourg and varieties with its participation are trying to bloom in the winter thaws. In this case, nothing can be done.
Weak flowering of the bush with a lack of light, nutrition or moisture
How can I help you. Improve the conditions of detention. Remove faded inflorescences, preventing seeds from setting.
With a disease like rhododendron spotting, the leaves of the plant are covered with spots. The size, color and shape of these spots can be different, and it depends on the fungus-causative agent: gray, brown, yellow, black, angular, blurry, round, with a black border. A gray coating may appear on the upper side of the sheet. Such a disease as rust on rhododendron appears on the lower part of the leaves in the form of dusty yellow, brown or red pimples.
Diseases of rhododendrons - a real concern for the gardener
Fungal diseases of rhododendrons
Fungi also cause the death of shoots, while the buds of rhododendrons are affected, which first turn brown and then die. Then, the same thing happens with the leaves, and then with the shoots of plants. It is necessary to treat such diseases with drugs based on copper; treatment cannot be carried out with humid air as the leaves may get burned.
Rhododendron diseases caused by external factors
Rhododendron leaves dry and fall off
The winter drying of rhododendrons looks like the death of shoots, the leaves of evergreen species first curl, then dry up and die, in fact, this is the result of a violation of the plant's water metabolism. It is possible to prevent such a disease if evergreen rhododendrons are abundantly watered before wintering, and if signs of the disease appear in the spring, then after the soil has completely thawed, the plants need to be watered and sprayed abundantly.
Rhododendron whimsical plant
Rhododendron leaves turn yellow and fall off
Nitrogen starvation is provoked if rhododendrons are grown on sandy soils - the leaves become much lighter and smaller, the growth of young shoots stops, flower buds are not laid. At the end of summer, the leaves on evergreen species begin to turn yellow, and then fall off. In this case, the plant needs a transplant or systematic provision of top dressing. mineral fertilizers based on nitrogen.
Rhododendron root rot
For a disease such as root collar rot outward signs the soaking of rhododendrons is like - the shoots become soft, the leaves of a dull, grayish hue begin to fall off. Such a disease usually develops if it grows on clay soils with poor drainage. In this case, the rhododendron must be transplanted into a moisture- and breathable soil.
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A beautiful gesture to give fresh flowers in pots as a gift for the holidays has become a tradition. In almost every home there is a flower pot with exquisite plant. Very often, an azalea is chosen as a gift - a flower - rhododendron.
Despite the beauty of inflorescences and foliage, Azalea very quickly loses its attractive appearance - it dries up. Here the question arises of how to save the azalea, because you want so much that this flower retains its vitality for as long as possible and pleases with its bright colors. It is possible to revive the plant, and this is confirmed experienced growers. For resuscitation of azalea, several simple tricks are used.
Reasons for the death of azalea
Dry indoor flower may be due to several factors. And all of them are related to the conditions of caring for the plant.
Azalea foliage and shoots lose strength - wither and subsequently die when:
- lack of regular watering;
- excess moisture;
- elevated air temperature in the room;
- falling on the foliage of direct sun rays;
- lack of light;
- pest infestation;
- lack of fertilizing with fertilizers;
- a sharp drop in temperature;
- damage to the root system;
- when planting in unsuitable soil.
What to do if the azalea dries up
If at least one of the above factors took place before the azalea shed its foliage, and only bare shoots of the flower remained in the flower pot, the dying azalea should be carefully examined. Identification of live buds provides a basis for helping the plant.
Before resuscitating the azalea, you need to make sure that it has not died completely, otherwise all measures to save it will be in vain.
Irrigation disruption
In the absence of proper watering, the root system suffers first of all, the plant receives less nutrients for the formation of new shoots, and begins to fade. Weak roots are unable to develop without water, even in properly selected soil. To resurrect the azalea, in this case, it is not enough to fill the flower with water.
Need:
First of all, you should remove the plant from the flower pot, carefully remove excess soil so as not to damage the weak roots.
Secondly, soak azalea roots for half an hour in a solution containing special growth stimulants for flowering plants.
Thirdly, plant the azalea in the updated soil and subsequently observe the regularity of watering. Azaleas should be watered with settled warm water no more than twice a week.
What to do if the flower withered due to too abundant watering? With an excess of moisture, the roots of the azalea begin to rot. If the flower has already shed its foliage, this indicates that almost all of its roots are damaged.
In this case, it is also impossible to do without the so-called transshipment of azalea:
Withering azalea should be removed from the pot.
Next, gently clean the roots from wet soil, rinse in water room temperature, inspect all branches, cut off rot, process live roots by special means for plants from pathogenic bacteria.
The azalea with the rest of the living roots is transplanted into the renewed soil and subsequently moderate regular watering is performed.
Influence of high temperatures and lighting
If the azalea has dried up due to the high temperature in the room, it will be difficult to revive it. But you can still try to revive the plant.
Often, high temperatures have a negative effect on plants if a reserve supply of moisture does not accumulate in the soil. That is, the plant is either watered a little, or there is little soil in the pot to retain moisture.
How to save the azalea in this case?
If it is not completely dry, then proceed as follows:
To ensure the optimal amount of soil, the plant is transplanted into a larger pot.
Before planting the azalea, the soil is fertilized with shoot growth stimulants.
If there are no shaded places in the room and the transplanted azalea cannot be protected from the influence of high temperatures, then after each watering on flower pot put on plastic bag for 1-1.5 hours to create the so-called greenhouse effect. This procedure should be performed before forcing new azalea leaves.
The sun's rays burn the leaves of the azalea, they begin to turn yellow and fall off. In this case, the plant needs not much resuscitation, but first aid.
It must be provided in the following order:
The affected azalea must be removed in partial shade and removed from the shoots all damaged - yellow and dry leaves.
With insufficient lighting, the plant can also die, so after a week of settling in the shade, the azalea should be gradually turned towards the sun, perfect option- ambient lighting.
Azalea quickly dies with a sharp change in temperature. For example, if it grew at +20°C, and then it was created growth conditions at +10°C. Azalea is not afraid of cold weather if it is gradually hardened. You should not despair if the azalea began to shed its foliage in the coolness. It should create a neutral temperature regime for growth + 18 ... 20 ° С. And at the same time provide the plant with more sunlight.
Pests and diseases
Azalea is very sensitive to spider mites, aphids and scale insects. The foliage of the plant, which turns yellow and falls off, suffers from these insects.
Resuscitation of azalea in case of pest damage is:
In removing damaged leaves;
Plant processing special solutions from pests for indoor plants;
If necessary, replace the soil.
With planting soil a fusarium fungus can be brought into a flower pot, which negatively affects the development of azalea roots, from which they can completely die. The salvation of the flower in this case consists in watering it with a solution of potassium permanganate and the antifungal drug "Fundazol".
Poor quality soil
Plants of the rhododendron family prefer to grow in acidic soil.
Often, the azalea disappears due to non-compliance with this requirement:
If not all the leaves of the flower have dried up, you can revive it with regular watering with a settled slightly acidic solution of citric acid (1 liter of water + 2 grams of acid).
If the plant is almost dry, then you can try watering with a solution of boric acid (1 liter of water + 3 drops of acid).
With the usefulness of the root system, it would be appropriate to make the usual transshipment of the flower, picking up better soil for it (peat + coniferous soil).
When the azalea has dried up, it is important to determine the root cause of what happened. It is one thing how to save a plant planted with your own hands, another - bought in a store. Having received an azalea as a gift in a small pot, it must be transplanted without waiting for withering by the transshipment method immediately after it has faded.
Azalea is a whimsical flower plant. When resuscitating, it is extremely important to provide the plant with timely assistance. The above recommendations will help to preserve its beauty and strength, the implementation of which is mandatory in the care of an indoor flower.
The question "How to reanimate an azalea?" most often occur in people who are unprepared for the appearance of this flower in the house - they usually give it in an attempt to please the hostess. At first everyone admires flowering plant, and later unrest begins due to yellowing, blackening or drying of the leaves, as well as falling flowers. In such cases, it is urgent to decide how to save the dying azalea.
It is advisable to know at least something about rhododendrons before settling them at home. Because of the complexity of care, Azalea is called a capricious beauty. But if she settles in comfortable conditions, it will please the owners with a healthy look and lush bloom. You just need to line up behind it so that everything is in balance.
Azalea feels great at an air temperature not higher than +22 ° C in summer and +15 ° C in winter. It should be bright enough, but without direct sunlight. It should be humid in a pot and air (80%), but it is impossible to spray during flowering. The soil needs to be acidic. Trouble begins when these conditions are violated.
If the leaves began to dry out, change color, become stained, you need to find out why this is happening and eliminate the cause. Leaves can fall off very quickly. They turn yellow as a result of the attack of pests - then you need to take action quickly. And if a lot of calcium has accumulated in the soil, then adding a little citric acid to the water will help.
The main cause of leaf fall is excessive dryness and high air temperature. As soon as the drying of the greens began, you need to lower the air temperature (this way the plant will recover more easily), pour settled acidified water, spray the flower.
If the azalea dries, it is necessary to give her a cool shower. Most likely, tap water contains a lot of salts and unnecessary impurities (which is why it is defended), so you will have to use a watering can with a fine sieve to bathe it with clean, settled water with the addition of citric acid. You can immerse the pot in a bowl so that the water is 2 cm above the edge, leave it for 20-30 minutes, then let it drain excess water. Just fill the flower with acidified water!
If the azalea is dry
What to do in the event that the azalea has dried up, completely losing its leaves? Do not rush to throw it away, even if it is dry. If the roots are still alive, i.e., not dried out, then the plant can be reanimated with water, cooling and boric acid. Just need to be patient.
First you need to get rid of the old soil. To do this, the plant is taken out of the pot, the roots and a clod of earth are poured. clean water. As the soil soaks, slowly and carefully remove (wash) it with your hands, you can substitute the soaked roots under running water and rinse. Then the plant can be planted in a new soil, purchased specifically for azaleas and laid on a high-quality drainage layer in a new pot. It is desirable to add wood ash to the soil or Activated carbon, put a layer of pine needles on top. The transplanted flower should be placed in a softly lit place with an air temperature of no higher than +20 ° C and left until the morning.
The next day, the plant must be watered with water that has been settled for at least two days, adding a few drops of boric acid and Zircon to it. When all the soil flows well with water, the excess must be poured out of the pan.
Roots will absorb better useful material at low temperature, so the pot can be overlaid with ice. Some flower growers argue that in the summer, a pot of azalea should be put in the refrigerator for a day. Such procedures - watering with boric acid and Zircon, cooling - must be repeated daily until new leaves begin to grow. Then you can water every other day, sometimes replacing boric acid lemon, and replace the refrigerator with sprays.
How to reanimate after pests
Having got rid of the reason why the azalea, damaged by pests, dried up, you can start restoring the plant.
Affected leaves must be removed (if they have not fallen off on their own), bare branches should not be cut. In order for the azalea to revive its branches, it must be in comfortable conditions, but it is advisable to increase the humidity of the air even more by covering the plant with a transparent lid (bag, jar). To enhance immunity, it is sprayed with a solution prepared from the Elina preparation. Water frequently (daily or every other day) with acidified settled water.
How to reanimate after illness
Azalea diseases are the result of errors. These can be caused by fluctuations in air temperature, humidity levels. If the leaves of the azalea turn black, then the cause may be a black trias or infection with fungal diseases. Septoria (red-yellow spots with black dots), cercosporosis ( brown spots with red edges on the underside of the leaf), phyllostictosis (brown or gray spots) are characterized by the presence of spots that appear and grow on the leaves, stems of the plant. Late blight affects the roots, and the twisting and drying of the leaves indicates it, which first darken, starting from the very tips, change color, and then curl and.
These diseases will not be allowed to progress with special drugs that need to be started as early as possible: Bordeaux liquid, "Fundazol", "Ditan", "Topsin-M" or other fungicides. With verticillium, the base of the stem darkens, and not the leaf, this can most likely lead to death. will save timely processing blue vitriol or fungicides. The sooner the disease is established, the sooner treatment will begin, which means there will be more hope for a full recovery of the plant.
After using special preparations, all affected parts of the plant must be destroyed in order to prevent the disease from returning. An azalea that has survived a disease needs restorative procedures no less than after an invasion of pests or drying out due to bad care. The main goals are the same: restore immunity, improve conditions, help absorb nutrients.
Azalea will certainly be transplanted into a new soil, be sure to check the condition of the roots. Then apply frequent watering and spraying with water with boric and citric acid alternately, sometimes using the Elina solution to enhance immunity.
It is important that at this time the air temperature does not rise above + 20–22 degrees, and the lighting is soft without direct sunlight.
Video "Why does the azalea wither"
From this video you will learn how to cure an azalea that has begun to wither.
Rhododendrons, like any other plants, are affected by diseases and pests. Susceptibility to various diseases and pests mainly depends on the type and variety of the plant. Long-term practice shows that evergreen rhododendrons growing in open sunny areas are more susceptible to diseases and pests than those that grow in light partial shade. Depleted specimens tend to be more susceptible to diseases and pests than well-developed plants. The main thing in protecting rhododendrons from pests and diseases is to create optimal conditions for their growth and development. Compliance with the rules of agricultural technology and the choice of planting site corresponding to the requirements of the plant are essential. With proper agricultural technology for growing rhododendrons in culture, plants are only slightly damaged.
Diseases
Fungal diseases on seedlings of rhododendrons appear due to poor soil aeration, which occurs with excessive watering. Often this is one of the reasons for the mass death of seedlings. Plants infected with fungi should be regularly sprayed with a solution of Bordeaux mixture. Sick and weakened plants, as well as stumps, must be burned in order to eliminate the foci of the spread of fungal diseases.
Tracheomycosis wilt of rhododendron
Symptoms: the roots turn brown and rot, the fungus penetrates into vascular system plants and fills it, blocking the movement of nutrients. Leaves, starting from the upper parts of the shoots, gradually lose turgor, turn brown and dry. The leaves fall along with the petioles, and a grayish-white mycelium begins to spread from the vessels of the stem along the bark. The infection persists in plant debris and infected plants.
Control measures: timely burning of dead plants along with the roots. At industrial cultivation- preventive spraying of plants and irrigation of the root zone with a 0.2% solution of foundationazole.
Phytophthora root rot
Pathogen: Phytophthora cinnamomi fungus. Causes: drift from a nursery with acquired plants, soiling and poor drainage of the root zone. Symptoms: first, the leaves begin to wilt, often not on the whole plant, but on individual branches. At the same time, this wilting is not associated with overdrying; withered leaves do not restore turgor at night or early in the morning. In the region of the root neck - lesions under the bark. Further - the branch turns yellow, then the whole plant. Roots turn brown, rot, soak. Large brown spreading spots appear on the root neck and the base of the stems, the wood rots. Dense dark gray sporulation of the fungus develops on the spots. Affected plants wither and dry out. The infection persists in the soil and on plant debris.
Bacterial root cancer
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.
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. In humid weather, all necrotic parts are covered with a fluffy smoky-gray coating of sporulation. Over time, brown rounded sclerotia form in the drying mycelium.
Control measures: pruning the affected parts of plants. In industrial cultivation - preventive spraying of plants and watering the root zone with a 0.2% solution of foundationol.
Rot of seedlings and young seedlings of rhododendron
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: seedlings beginning to die 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) which is spread by the cicada Graphocephala coccinea. 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.
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. The disease has been noted in Latvia.
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 cinnamoni 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: in diseased plants, the root neck is entwined with a grayish-white ring - mycelium. 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
Symptoms: there is a slight deformation and thickening of the leaves. 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. This disease usually affects alpine views 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. As of 1981, this disease was not observed in Latvia.
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. As of 1981, this disease was not observed in Latvia.
Measures to combat diseases caused by representatives of the genus Exobasidium: pruning of the affected parts of plants, spring spraying 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. As of 1981, this disease was not observed in Latvia.
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. Spots are often scattered around the edges leaf blade which turns yellow and dries out 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 out.
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.
Septoria blotch of rhododendron, or azalea septoria, or small leaf spot
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 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-like receptacles of spores - pycnidia, immersed in leaf tissues.
Control measures: pruning of the affected parts of plants, spring spraying with a solution of Bordeaux liquid, its substitutes or camulus. 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 for normal humidity air and enough high temperature. You can spray only those plants whose leaves have fully grown and developed.
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 liquid, its substitutes or camulus.
cercosporosis
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 rust
The causative agent is the fungus Chrysomyxa rhododendri D. C. Most often found on small-leaved species and species from the Osmothamnus subgenus - Rhododendron parvifolium, Rhododendron adamsii, Rhododendron dauricum L., Rhododendron ferrugineum L., Rhododendron kotschyi, and others.
Symptoms: in autumn, yellow, red or brown dust-like swellings - sporangia appear on the underside of the leaves of affected plants. Severely infected plants shed their leaves prematurely. In spring, dark red pads are visible on the leaves - the winter form of the fungus.
Control measures: Affected leaves are collected and burned. Sick plants are sprayed with copper-containing preparations. In the early stages of this disease, spraying plants with Bordeaux liquid helps.
Mosaic of rhododendron
The causative agent is the Rhododendron mosaic virus. Symptoms are described by different authors with slight differences.
1. Small mosaics appear on the leaves. yellow spots and swelling. Plants are stunted and bloom poorly. The leaves turn yellow, but they retain patches in the form of alternating green and brown spots.
2. Leaves become rough, calloused and ugly. Calluses are usually normal Green colour, and the rest of the leaf becomes greenish-yellow. The light part of the leaf blade is much thinner than in places where there are calluses. Venation on calluses is less noticeable.
Control measures: pruning of leaves and branches, culling of heavily affected plants. Mosaic virus is carried by aphids, bedbugs and other insects.
Pests
Furrowed weevil (Otiorrhynchus sulcatus)
Adults are black, 8-10 mm long, not flying, with an elongated head extended forward, at the end of which there are mouthparts. Elytra with deep punctate beards. The larvae are white, with a brown head, legless, curved, up to 12 mm long. The larvae live from 2 to 12 months, then pupate, and after 20 days the pupa turns into an adult beetle. Females live 5-12 months, laying 100 to 1000 eggs in their lifetime. Eggs are laid in groups in the soil, where after 2-3 weeks the larvae emerge from them and immediately start feeding.
The nature of the lesion. Along the edges of the leaves, characteristic eaten away areas are observed. If the damage is inflicted by larvae living in the soil, then the plant suddenly withers and dies.
Control measures: spraying with decis, splender, actellik, or spark.
Ordinary spider mite(Tetranychus urticae)
Almost invisible, since its dimensions are 0.25-0.43 mm. At the larval stage of development, they are transparent, colored from light green to greenish brown in color with two distinct, large dark spots on the sides, which are formed by transparent blind sacs of the midgut. With late summer until the next spring, wintering females are colored from orange-red to bright red. In contrast to the six-legged first larval phase, all adult ticks have 8 legs.
Damaged leaves turn yellow, deform, turn brown and dry. Up to 10 generations of ticks develop during the growing season.
Control measures: spraying plants with fitoverm, fufanon, karbofos, actellik, or colloidal sulfur.
Acacia false shield
Acacia false scale, or acacia scale, or hazel scale, or acacia scale insect (Parthenolecanium corni). It is currently ubiquitous. In the north, the range reaches Leningrad region. Sexual dimorphism is pronounced. The body length of females is from 3 to 6.5 mm, width - 2.4 mm, height - 4 mm. There are no wings. Body oval or broadly oval, sometimes almost round, no segmentation. The shape, color and size of the body of the female vary depending on the species. fodder plant. Young females with a delicate, not very convex body, more oval in shape, light brown, with two black stripes and longitudinal black stripes extending from them. Dead - shiny, painted in dark yellow, brown or dark brown. The body length of males is 1.4-1.6 mm. The body is thin, elongated, with a clear segmentation into the chest, head and abdomen. The head is black with three pairs of simple eyes. Abdomen and thorax red-brown, covered with white waxy coating. Ten-segmented antennae and legs are yellow. At the top of the abdomen there are two caudal filaments, 2-2.5 times longer than the body size. Larvae of the first age (tramps) are 0.36 mm long. The body is flat, elongated-oval, slightly narrowed towards the posterior end. The color of the covers is cream or light yellow. In the second age, the larvae of heterosexual individuals differ from each other in body shape. The nymphal stage of development is observed only in male larvae. Nymphs are dark brown in color, have well-developed rudiments of wings, legs and proboscis. Reproduction in acacia false scales is often parthenogenetic, sometimes bisexual in the south. The larvae hibernate. In the northern part of the range, one generation develops per year, in the southern part - two or three.
Insects pierce the bark of the plant with their proboscis and attach tightly to the branches. Damaged plants weaken, lose their decorative effect and gradually dry out.
Control measures: timely spraying of plants with organophosphorus compounds, neonicotinoids, pyrethroids, fitoverm, fufanon, karbofos, actellik.
Thrips tobacco (Thrips tabaci)
In Russia, it is ubiquitous. Polyphagous, damages about 400 plant species in open and closed ground. The coloration of the female is variable, from light yellow to brown, often more or less yellow, sometimes strongly darkened. Body length 0.8-1.0 mm. The male is smaller and lighter, the chest is bright yellow. Body length 0.7-0.75 mm. The larva, 0.8-0.9 mm long, is very mobile, two pairs of wings are surrounded by a fringe of cilia, the body color is variable - from yellow to almost black. Adults overwinter in top layer soil at a depth of 5-7 cm or in plant debris. They emerge after wintering in the first half of April, feed and lay eggs at first on weeds. One female during her life (20-25 days) lays about 100 eggs in the leaf tissue, and their fertility largely depends on the type of host plant. Then the females fly to cultivated vegetation. Is a distributor of viruses. On rhododendrons, buds are damaged, which, if severely damaged, do not open, turn yellow and fall off.
Control measures: timely spraying of plants with organophosphorus compounds, neonicotinoids, pyrethroids, fitoverm, fufanon, karbofos, actellik, actara.
Rhododendron mite or American azalea bug (Stephanitis rhododendri)
It occurs on the Katevbinsky rhododendron, Smirnov's, Ungern's rhododendron and other species and varieties that have felt pubescence on the underside of the leaf.
Adult size is about 3.6 mm. Wings are colorless, reticulate with a sheen. Bedbug larvae reach a length of 0.7 to 2.2 mm, they do not fly, they are yellow in color with dark spots and hairy outgrowths from the sides.
Symptoms: the leaves turn yellow, and black spots appear in their lower part, resembling resin. Damage contributes to curling and drying of the leaves. The bug appears in summer, spreads along with peat and pine needles along with the substrate.
With minor damage, you can collect pests by hand. In addition, in late May - early June, plants should be sprayed with nicotine and soap, or a flavored pyrethrum extract. In case of severe damage, pruning of shoots is recommended.
Greenhouse whitefly (Trialeurodes vaporariorum)
Tropical species. Introduced to all continents. It is noted near greenhouse plants, where the pest persists all year round. The greenhouse whitefly is known as a carrier of many viral infections.
Signs of damage: small white insects are visible on the underside of the leaves. The body of the adult is light yellow, the wings are white, without spots. The size of the female is 1.1 mm, the male is 0.9 mm. In GBS, it is quite often noted on large-leaved rhododendrons (Caucasian, Pontic). To combat the greenhouse whitefly, pesticides are chosen that are of little danger to pollinating insects and entomophages. AT last years neonicotinoids are becoming more and more popular.
Whitefly rhododendron, or white rhododendron fly (Dialeurodes chittendeni)
AT GBS 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. For preventive purposes, it is recommended to spray adult flies with nicotine dust during the summer. Affected leaves should be cut off and burned.
gastropods
Leaves, buds and young shoots of rhododendrons damage Helix snails and slugs. Control measures: manual collection of molluscs, use of molluscicides.
crows
In GBS in early spring, the facts of pecking of the buds of rhododendrons by crows were noted, Smirnov's rhododendron most often suffers.