Garden rhododendron: planting and care in the open field. What to do with rhododendrons if the upper shoots turn yellow after winter
Plants known as rhododendrons are unique shrubs. Azaleas and rhododendrons bloom in May and June, so they are the best choice for people who expect beautiful and impressive flowers at the beginning of summer. Rhododendrons are evergreen shrubs, while azaleas shed their leaves in autumn. They also vary in height and appearance colors that are exceptionally good.
Rhododendron - is a species of shrubs belonging to the heather family ( Ericaceae). In the natural environment plants of the genus Rhododendron found mainly in the mountain forests of Asia and North and Central America. They inhabit places with high humidity. Azaleas have soft, slightly hairy leaves that fall off in the winter, making them more frost hardy. The "correct" azaleas are evergreen, and in winter they cannot tolerate the influence of cold, drying winds.
Both species plant the ground between April and mid-September. They are bought in containers. Before we make a decision on a particular purchase, it is worth checking if the substrate in the container is sufficiently moist. If it turns out to be too dry, it may mean that the plant has dead roots because they do not have enough moisture. You also need to carefully examine the leaves and shoots. They should be free from discoloration, spots, cavities, or other worrying changes that may indicate rhododendron disease.
Planting a rhododendron
In general, rhododendrons will thrive best in areas of the country where winters are relatively mild and wet. In the garden itself, rhododendrons will be comfortable in partial shade or a shady place that is protected from the wind. The best position is near the water, where the humidity is high. In turn, azaleas are planted in a well-lit or slightly shaded area.
Rhododendrons need an acidic substrate and fertile soil.
Unfortunately, this soil is not often found in gardens, so it must be properly prepared before planting. In a hole 50 cm deep and about 1 meter wide, pour 10 to 20 centimeters of drainage in the form of gravel or mulch. Then a layer of peat mixture, composted bark and compost in equal proportions. After planting shrubs upper layer the substrate is additionally mulched with a five-centimeter layer of bark. This will ensure sufficient soil moisture and minimize the development of weeds.
well-prepared soil and proper fit will create ideal starting conditions for the growth of rhododendrons.
We plant correctly
- 1. In a healthy seedling, thin white roots penetrate the earthen ball. For their further normal development, loose soil enriched with peat is necessary.
- 2. Before planting, submerge the root ball in water and keep it there until bubbling stops.
- 3. The planting hole should be 2 times wider than the root ball of the plant. Loosen the soil in the planting hole with garden forks.
- 4. To fill it, a mixture of garden soil with peat (50% each) or a special soil for rhododendrons is suitable.
- 5. Important: do not plant rhododendrons too deep. The upper part of the coma should be at the level of the soil surface.
- 6. Mulch the soil around the plant with a layer of 1 to 3-5 cm. Use for this purpose compost from bark or pine needles aged for at least six months, as well as well-rotted oak or beech leaves.
- 7. After planting, fertilize the plants. The ideal top dressing is a mixture of horn shavings and mineral fertilizers or special fertilizers for rhododendrons. Spread the fertilizer evenly over the surface of the earth and water the seedling well. If you plant a plant in the fall, do not feed it, but wait until spring with this.
- 8. Water the rhododendron thoroughly, but do not overdo it (so that there is no moisture stagnation).
Watering is important not only after planting, but also in the following months, until root system the bush will not be strengthened. Rhododendron planted in dry places should be watered more often. Watering is also necessary after each fertilization.
Substrates, fertilizers and mulch
For health and abundant flowering rhododendrons need loose, humus-rich soil. You can improve your garden's clay or calcareous soil by adding peat and humus to it. Special soils for rhododendrons or peat substrates are ideal. Remember that fertilizers must meet all the needs of rhododendrons. Fertilizers vary in quality, so we advise you to buy products from well-known manufacturers. But as a mulch, it is good to use pine bark.
Lime is no longer scary
Limestone gardeners can now grow rhododendrons too. As a result of many years of work, breeders managed to obtain a rootstock that is tolerant to lime (INCARHO rhododendrons). Many popular varieties of rhododendrons are grafted onto this stock. True, they are not entirely immune to lime, but show a certain tolerance for it. Experts recommend these varieties for gardens with soils with a pH of 5.5 to 7.0.
Outdoor rhododendron care
The soil under the rhododendrons can not be dug up, so as not to damage the roots. Loosening with a thin hoe is allowed. However, weeds must be removed regularly before they reach large sizes, since removing large weeds can also damage the small roots of rhododendron.
Rhododendrons need to be fed with special preparations that can be purchased at garden stores. Nutrient delivery should occur in spring and early summer. However, be careful not to extend this period as the plants will not have time to prepare for winter.
Fertilizers for growth and abundant flowering
Rhododendrons growing near deciduous trees do not need additional fertilizer, its function is performed by the foliage that falls every year. However, in most gardens, rhododendrons still need regular fertilizing with mineral fertilizers, especially if the bushes are still young.
- The first time to fertilize rhododendrons is best in April-May, when the plants are actively growing.
- The second - more important - feeding is done after the flowering of rhododendrons, when new shoots appear on the plants (usually in June-July).
Indicative figures: for a plant with a height and width of 40 cm, about 15-20 g (half a tablespoon) of fertilizers are required in spring and summer, for a plant with a height of 150 cm, respectively, 80-100 g.
Do not use liquid fertilizers, it is better to take granular, long-acting or specially formulated fertilizers for rhododendrons.
Careful rhododendron care also includes an annual pH test of the substrate. If necessary, we also mulch the substrate with a mixture of bark and acid peat.
After the rhododendron fades, it begins the process of seed formation. Gently pinch off the buds as soon as they wilt. Thanks to this, the plant will not waste energy on seed maturation, but will save energy for the formation of new shoots and flowers next year. In addition, rhododendron bushes take on a more well-groomed appearance.
pruning
Can you prune rhododendrons?
It is better not to prune at all - rhododendrons look more picturesque over the years It is better not to cut them at all - rhododendrons look more picturesque over the years. If you have to cut too much tall bush, then it will soon give new shoots even on old lignified branches (see photo). Note, however, that these slow-growing shrubs will take several years to grow back to their original height.
In the spring, dried and frozen shoots should be cut. Young plants can also be stimulated at this time by lightly pruning them. Old bushes that have lost a lot of lower leaves and look ugly should be rejuvenated by cutting out all shoots, even thick ones. After pruning the branches in a few weeks, many young branches will grow from the dormant buds. If you're unsure if a bush is strong enough to withstand such a drastic cut, you can rejuvenate half of the bush in the spring and the rest next year.
Shelter from frost and wind
Hanging leaves are not a sign of frost damage. Rhododendrons grow well in temperate climates with warm winters and high humidity. In such conditions, even in the cold season, metabolism occurs in their evergreen leaves. But cold winters Central Europe not quite suitable for rhododendrons - on sunny days, the process of photosynthesis begins in the leaves, and the roots cannot absorb enough water from the frozen soil for metabolism, and the leaves begin to dry out. Therefore, for rhododendrons, the winter sun at sub-zero temperature more dangerous than the frost itself.
For sensitive varieties and standard plants it is advisable to use shelters that create shade. They protect plants from the wind and, by creating shade, prevent dehydration of the leaves. Such shelters are best made from breathable materials, such as agrofibre, otherwise mold may appear under them. Dehydration is especially dangerous for container rhododendrons, so they should be watered abundantly in winter.
Rhododendrons growing in the shade, for example under the crowns of trees, usually do not need to be covered for the winter.
Hanging leaves are not a sign of frost damage, but the plant's natural reaction to it. The tent will protect from the wind, cold and winter sun, which can dry the leaves during frost on the ground. In standard plants, both the crown and the trunk should be covered for the winter.
Small "LEGS" under the tubs and pots will ensure that excess water drains.
Optimal watering
Rainwater is ideal for irrigation, as it does not contain lime.
Rhododendrons prefer evenly moist soil. They are equally sensitive to both drying and waterlogging. When watering, you need to know when to stop: a large amount of water washes out nutrients and leads to rotting of the roots, with insufficient watering, the bushes wither and dry out. If the leaves drop during the day from the heat, then this is normal, the plants usually recover overnight. For irrigation, it is better to use rainwater, which, unlike tap water, does not contain lime. A layer of mulch prevents water from evaporating and retains moisture in the soil. The same function is performed ground cover plants creating a favorable microclimate. For dry soil, computer-controlled drip irrigation is suitable, evenly moistening the soil.
Important: evergreen rhododendrons should be watered in winter.
Reproduction by layering
After flowering has ended, lightly cut the bark of a branch close to the ground under the whorl of leaves. Bend the branch so that it can be placed with the cut down into the hole filled with humus to a depth of 5 cm. Gently fix the branch with a hook and make a support. The next spring, rooted cuttings can be separated with a shovel and transplanted to a permanent place in the garden. After planting, do not forget to water the young plant well.
Caring for rhododendron after flowering
- 1. Removing faded flowers
Removing faded flowers is necessary condition for rhododendrons to form new flower buds and leaves next season. Faded inflorescences are removed in summer, when rhododendrons finish their flowering period, leaving new leaf buds underneath. It is better to cut off the inflorescences manually (not with scissors). Thanks to this treatment, the seed production process is not carried out, and nutrients can be used by the plant for growth, development and creation of new buds. You can also cut dead, dry shoots.
- 2. Removing fallen flowers and leaves
It is necessary to carefully remove fallen flowers and leaves from under the bush. Especially if they are affected by lesions, they must be removed and burned. The litter will rot, providing nutrients for the development of fungal diseases.
- 3. Fertilizing rhododendrons after flowering
Rhododendron after flowering feels a lack of nutrients that were used in the flowering process. In summer and autumn, phosphorus-potassium fertilizer should be used. During this period, plants do not need much nitrogen. Mineral fertilizers- potassium sulfate and superphosphate or available ready-made fertilizers for rhododendrons, containing all the necessary ingredients that also affect soil acidification. In addition, foliar fertilizers are used that contain trace elements such as iron and magnesium, which affect the intense color of the leaves. Fertilizers should be applied no more than the recommended doses.
Providing nutrients will allow the rhododendrons to set up many new flower buds.
- 4. Watering rhododendrons after flowering
With excess water, plants are exposed to fungal diseases. However, if there is a drought, big amount sunlight and hot weather, which often happens in the summer months, after the flowering of the rhododendron, the bushes must be watered. In particular, plants that grow in light and permeable soils require watering. In other periods, rainfall water is sufficient and most healthy for plants. Plants need more water before winter. With big frosts, they will no longer be able to collect it, and this is necessary for the proper development of the leaves. In the absence of water, the leaves wilt and turn brown. Therefore, rhododendrons should be watered abundantly just before the onset of frost.
- 5. Shelter of rhododendrons for the winter
Most varieties of rhododendrons are resistant to frost, even down to -30 ° C. Some varieties are less frost resistant (down to -20 ° C). The best cover for winter is snow, but it is not always present. It is advisable to cover young rhododendrons planted in the current year. you can use fir branches, straw mats or agrofibre. Young and older shrubs are well mulched for the winter with pine bark, which additionally acidifies the soil. Freezing of the soil and loss of water is less. Roots are less vulnerable to frost damage. Rhododendrons that will survive the winter in good condition, will bloom again in a year.
Diseases and pests of rhododendron
Why do rhododendrons get sick? Rhododendrons have fairly high cultivation requirements and our climate is not conducive to these plants.
Rhododendrons can be affected by different types of fungi. As a result, the leaves turn brown at the edges or at the tips, dry out and eventually fall off. In addition, shapeless heels often appear on the leaves. With the help of fungicides, these symptoms can be removed, but the cause of their appearance - the unfavorable living conditions of the plant - will remain. Sometimes just good feeding leads to the recovery of rhododendrons. Also control the acidity of the soil.
Kidney death
Brown buds with black down indicate fungal infection. Such kidneys should be removed.
Unfortunately, a common disease of rhododendrons is the death of the kidneys. It is caused by a fungus carried by rhododendron cicadas. Buds affected by the fungus turn brown and fall off. It is impossible to destroy the fungus, but, fortunately, it does not spread to other parts of the plant. Cut off and destroy the affected kidneys.
To check if there are insects on the rhododendron, a yellow sticky paper (photo) attached to a plant branch will help.
To prevent damage to the kidneys by the fungus, you must first fight the cicadas: inspect the rhododendron, usually these insects sit on the back of the leaves.
It is best to destroy cicadas in the early morning, when the insects are still inactive. Treat the leaves with an insecticide: you need to spray the plants immediately after the appearance of cicadas in mid-May, if necessary, repeat the procedure after 2 weeks.
Green-yellow cicadas about one centimeter long sit mainly on the underside of the leaves. Small dots on the leaves are traces of their vital activity - give out the presence of "uninvited guests".
Wasting, chlorosis
With chlorosis (exhaustion), the leaves of the rhododendron turn yellow, while the veins remain green. This disease occurs most often due to insufficiently acidic or very dense soil that does not allow air to pass through.
Most often, chlorosis begins a few years after planting, when the roots extend beyond the planting hole and enter the calcareous soil. Remedy: Move the plant to a more suitable location or acidify the soil underneath by lowering the pH.
frost
Even if the rhododendrons survived low temperature relatively good in winter, they are sensitive to late spring frosts. A light frost in May can severely damage the young leaves and flower buds of the plant that have already appeared. If new shoots come out of the spare buds, the plant will not die, but it is better to remove the darkened branches of the rhododendron.
Ravenous Weevil
Weevil is a dangerous pest Semicircular eroded places on the sides of the leaves are a sign of the appearance of a pest.
More dangerous than the beetles themselves are their larvae, which eat the roots of shrubs. They are yellowish white in color with a brown head.
If the lower old leaves of rhododendrons have turned completely yellow (unlike those affected by chlorosis) and are gradually falling off, the plant is most likely lacking nitrogen. It is one of the main plant nutrients, and flowering rhododendrons especially need it. Help: immediately apply complex fertilizers to the soil. And best of all, feed the bushes every spring with horn shavings - this will prevent a lack of nitrogen.
It would seem that, suitable conditions for plant development and proper care guarantee success. However, the enemy does not sleep and sometimes he manages to surprise us unexpectedly. Plants that are less resistant and prone to disease are susceptible to the spread of pests. One of these is the rhododendron. The different specific conditions required for the growth of a shrub are a big challenge for a gardener, especially when it comes to pest control. Let's figure out how to defeat rhododendron diseases.
Causes
If the soil for rhododendrons is devoid of any nutrients, the leaves of the plant become discolored. Potassium deficiency signals brown spots along the edges of the leaves And yellowing of tissues. Brown or reddish spots indicate a small amount of boron in the soil. Iron deficiency appears yellowing of the tissues between the veins. When the soil of rhododendrons is overloaded with nutrients, it appears on the leaves chlorosis caused primarily by excess lime in the soil. The leaf blades become yellowish, white or light green, the veins remain dark green. Chlorosis is treated by spraying rhododendron with iron chelate. Use a multi-component fertilizer to strengthen plants. Supporters of homemade methods are advised to add chopped tree bark to the base, natural fertilizers or untreated peat.
Yellowing leaves
Yellowing of the leaves can be a sign of incorrect soil pH in the garden, when planting rhododendrons, you need to take care of the correct pH. Research can be done independently using Helling pH meter can be bought at a garden store. If the soil is not acidic enough, a rhododendron fertilizer can be applied to acidify the substrate. You can mix the substrate with acidic peat. If the soil reaction is alkaline or neutral, it is imperative to apply acidic fertilizer for rhododendrons.
The rhododendron withers and dies also because of physiological drought, occurs when the plant is not able to replenish stocks from frozen soil. Rhododendron loses water through evaporation on sunny days. Physiological drought is especially dangerous for plants with big leaves. To prevent or minimize symptoms, it is worth planting a rhododendron in a calm place where the sun only gently warms up during the midday hours. Better in a place among conifers near the wall of the building. winter rhododendron shade with agrofibre to reduce exposure to direct sunlight. A thick layer of mulch around the plant limits evaporation.
Fungal and bacterial diseases
Rhododendron is especially prone to fungal diseases. The development of the fungus is facilitated by a violation of the rules of care, the presence of various pests on the plant. A sign of the disease is the darkening of the leaves and buds. Fruiting bodies of the fungus appear in the form of black spots on the affected plants. Treatment of the disease begins immediately when the first symptoms appear. Cut diseased parts off and apply a suitable fungicide.
Regular presence light or dark brown spots on the leaves may indicate fungal disease – leaf spot, the affected rhododendron withers. Leaf spot is caused by fungi and bacteria. Infected leaves dry up and fall off. The fight against spotting is the use of fungicides. Infected leaves should be burned.
A common fungal disease that attacks rhododendron is gray rot, caused by fungi that spread in a humid environment. Mealy appears on leaves, shoots and flowers, gray-white bloom, as a result, the rhododendron turns brown and dies. Gray rot is destroyed by chemicals, sprayed with rhododendron infusion of nettle or horsetail decoction. Infected parts should be quickly removed and burned.
Rhododendron under attack rust And flour beetle. Rust is caused by fungal spores that are rusty in color. The leaves become covered with brown or reddish-red spots and the rhododendron slowly dies. Infected parts are removed, the plant is sprayed with chemicals. Flour beetle contributes to the development of fungal diseases in the garden. Causes a fungus that covers plants with mealy, initially white, then gray-brown bloom. The affected rhododendron withers and dies. The plant must be sprayed with a fungicidal drug, you can use a garlic-based drug.
late blight
Dangerous consequences are brought by diseases of rhododendrons, which have their origin in the soil. Diseases of rhododendrons caused in the soil by fungi are sometimes called withering. These include phytophthora root rot, leaves on infected roots light brown, rapidly darkening spots. The diseased plant withers, completely or partially, the leaves curl, become light green or grayish in color, the infected rhododendron stops growing. Action must be taken immediately, step by step. Sick specimens are removed and burned, not forgetting to disinfect the tools after each action, the plant is sprayed with a fungicide.
Pests
A common pest of rhododendron - furrowed weevil, the presence is easy to notice, characteristic U-shaped passages appear on the leaves. Symptoms of an insect attack are yellowing of the plant and the appearance of visible holes on the leaves. It is difficult to find the weevil, the insect hunts at night, during the day it hides in the soil under the trees. Weevil attacks plants in May-June. The females lay their eggs in the soil, and the eggs hatch into larvae that damage the roots. The larvae overwinter in the upper layers of the soil, between the roots of plants. In the spring, they gnaw the root neck, eating small roots. In May, the larvae pupate and turn into adults.
On initial stage attacks on a plant, you can catch weevils using a plate with a twig, which are left overnight. Chemical control should be carried out in the evening by spraying the plants with an insecticide. The procedure is repeated every seven to eight days. You need to defeat the pests before they have time to lay their eggs, destroying the larvae is much more difficult. Females can lay thousands of eggs, which will hatch into white larvae with brown heads. You can spray the plants with a solution of tansy. Weevils are also food for moles, millipedes, birds, centipedes and spiders.
Diseases caused by pests
The stubborn destroyer of the rhododendron is rhododendron leafhopper.
Symptoms of the presence of leafhoppers are individual punctures on the leaves, as well as a white molt on the plant. Insect females lay their eggs in September in the buds of the plant; from May to June, yellowish, inactive larvae develop under the underside of the leaves. In July and August, adults feed on the leaves, about a centimeter in length and quite mobile. If the pest is frightened away, it will quickly jump to other leaves. The leafhopper is green, with clear orange elongated pigment spots on the sides. Insects, sucking the juices from the plant, make small damage to the leaves, due to their mobility. spread fungal diseases, leads to the death of flower buds. A plant with symptoms of a disease caused by the presence of rhododendron leafhopper is treated by spraying with an insecticide. Spraying is repeated after ten to fourteen days.
Rhododendron - a delicacy for rhododendron bug, a small winged insect, up to four millimeters in length. The adult specimen has a flat body and transparent wings, the larvae are yellow and small. Large and small individuals feed on leaf sap from inside. A sign of the presence of a pest is yellowish spots on top of the leaves, in the lower part - dark excrement. Affected leaves fall off over time. Fallen leaves must be collected and burned. Bushes are sprayed with insecticide in May-June, when the time of hatching of the larvae is approaching.
It is necessary to conduct an active fight against pests and diseases of rhododendrons at the first symptoms, we use chemical methods of control. Chemical plant protection products are called: in the fight against fungal and bacterial diseases(fungicides), weed control (herbicides) and insect control (insecticides). When spraying a plant with a chemical agent, the indicated doses must be observed, the dosage should not be exceeded. Spraying is carried out in calm weather, best in the evening, so as not to kill beneficial insects. Spraying is not done in the burning sun and during or before rain. Before performing the procedure, it is necessary to check how long the period that must elapse between the application of the chemical protection product and the moment of harvest after the complete decontamination of the product is. For the prevention of diseases of shrubs, plant nutrition helps.
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, in more susceptible to disease and pest attack 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 liquid. 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 the vascular system of the plant 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, growths and 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 the correct irrigation regime.
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 collar.
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. 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-like growths on young leaves of evergreen rhododendrons (Rhododendron maximum L., Rhododendron catawbiense Michx.) and deciduous rhododendrons in their natural places of growth.
Exobasidium burtii forms characteristic spots on the leaves, which at first are small, round, and later, increasing in size, acquire an indefinite shape. 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 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. 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. Small brown spots appear on the leaves irregular shape with a thin brown border. Spots are often scattered around the edges leaf blade which turns yellow and dries out prematurely. Gray sporulation pads form on the spots. 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.
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 of 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: fungus 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, flower buds are not normally laid. 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 at normal air humidity 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 of the lower tiers are more affected. 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 helps. Bordeaux mixture.
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.
Common 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. From late summer until the following spring, overwintering females are 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 the 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 hibernate in the upper soil layer 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. It 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. In recent years, drugs from the group of neonicotinoids have become increasingly widespread.
Whitefly rhododendron, or white rhododendron fly (Dialeurodes chittendeni)
IN 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.
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 much high level soil moisture.
- Insufficient percentage of soil acidity, which contributes to the weakening of the root system.
- Planting a plant in areas where it is constantly Sun rays, contributing to burns of sheet 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 flaw necessary elements for vigorous plant growth.
- 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 are formed on the root and root neck, which acquire over time dark color and solid form.
- 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 can spread 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 declines sharply 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, it is necessary to remove the affected leaves and branches at the initial stage. 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. IN spring period on the reverse side of the 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, for prevention and for therapeutic purposes, the bush can be sprayed with Bordeaux mixture 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.
The main signs: the stems and leaves are covered with dark spots of a burgundy hue, sometimes they turn purple. Then the root system begins to rot, the plant slows down in growth, and general state 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 as follows:
- All parts of the plant are infected.
- It is characterized by the appearance of spots of dark brown or brown shades. After some time, they dry out, the top layer begins to crack.
- In wet rainy weather, the affected areas are covered with a grayish, heavily 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. Spots of a dark brown shade of irregular shape appear on them. 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 yellowing of the foliage or a white coating with spores on the inside.
Here is an incomplete list of diseases that affect rhododendron. Only proper care, prevention and timely Taken measures help keep the plant healthy and blooming.
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, mealybug, weevils, scale insects, rhododendra 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
- It is necessary to carefully examine the planting material upon purchase, 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.
