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Although thuja, regardless of the variety, is famous for its resistance to harmful environmental factors and infections, it can still occasionally be subject to certain diseases. Therefore, all connoisseurs of this plant need to have an idea not only about its agricultural technology, but also study thuja diseases and their treatment in as much detail as possible.
Signs of pests and diseases in thuja
Thuja is universally considered an unpretentious plant, the care of which does not require excessive effort, and this is indeed the case. However, a careless attitude towards this shrub quickly makes itself felt. Violations committed during cultivation affect both the decorative qualities of the thuja and the state of its growth. This is also true in the case of a disease or pest attack. Often the following signs help to understand that something is wrong with the plant.
- slowing down the growth of shrubs;
- changing the color of the needles to black, brown or yellow;
- drying out of the tips of young shoots of thuja;
- increased falling of needles;
- delamination of the bark of the trunk and branches;
- deformation of thuja shoots;
- the appearance of light or dark spots on scaly leaves;
- softening of the trunk or changes in its pigmentation;
- the appearance of neoplasms or unusual plaque on the branches and crown;
- an increase in the number of tracks on the thuja.
If a plant has 2 or more symptoms, it is worth monitoring its condition for 5 - 7 days, paying especially a lot of recommendations for caring for thuja. If, within the allotted time, negative changes do not subside, most likely, the health of the thuja has been attacked by fungal organisms or insects. In this case, you should try to determine the cause of the deterioration in the health of the bush. Below are descriptions of the most common diseases and pests of thuja with a photo.
The main diseases of thuja: how to determine and how to process
Among the main diseases that thuja are susceptible to, the most prominent are the ailments caused by the activity of various fungi. These diseases are easy enough to track even in the early stages, since negative external changes are clearly manifested in infected plants. The main difficulty lies in the diagnosis of a particular disease, since often their symptoms can be very similar. Therefore, it is especially important to comprehensively study thuja diseases in order to select the appropriate treatment in a timely manner.
Phytophthora
Phytophthora is one of the most dangerous fungal diseases that can occur in thuja. This disease is accompanied by the destruction of the upper layer of the root, due to which subsequently the crown of the plant acquires an unhealthy gray tint, and the trunk softens, becomes covered with a bloom and acquires a distinct putrid odor.
As a rule, the cause of this disease in thuja is insufficient drainage and the subsequent stagnation of moisture in the soil.In order to avoid the development of a pathogenic fungus, thuja must be treated with fungicides. If the disease has already begun to spread through the root system of the plant, then its treatment will be useless. Such a thuja will have to be destroyed, and the soil under it must be completely changed, otherwise the disease will affect other plants planted in this place.
Fusarium
Unlike the previous disease, fusarium, or tracheomycotic wilting, is not so dangerous for thuja, if the plant is treated in time. In most cases, fusarium is provoked by a lack of lighting or prolonged waterlogging of the soil under the thuja. With this disease, the roots acquire a brown color, and the fungus gradually grows into the underground parts of the thuja, blocking the supply of nutrient compounds. As a result, the aboveground parts of the plant first dry out, and the needles turn yellow, then turn red and, in the end, die off.
During the treatment of this disease, thuja should be treated with antifungal drugs, for example, 0.2% Fundazole solution.
Brown shoots
The symptoms of such a common thuja disease as brown shoots are often ignored by gardeners. But the lack of treatment can not only negatively affect the appearance of the plant, but also completely destroy the shrub.
The symptoms of this disease are fairly easy to spot. The shoots of the infected thuja begin to turn yellow, and the color change occurs from the upper part of the branches, most often in early spring. In the later stages of the disease, yellowness covers the entire shoot, and it falls off.
As a treatment, regular feeding of thuja and the introduction of lime mixtures into the soil can help. In the period from July to October, it will not be superfluous to treat the plant with a 2% solution of Fundazole with an interval of 1 time in 2 weeks.
Rust
Rust most often affects the crown of thujas, as can be seen in the photo, and therefore it is worth starting their treatment as soon as possible so that the plants do not lose too much needles during the course of the disease. It is believed that a disease such as rust occurs when there is a lack of nutrition, as well as in too dry or wet weather. In the process of infection, the thuja needles begin to darken, acquiring a copper tint, after which they fall off. The treatment of this disease consists in the timely treatment of plants with HOM, at the rate of 40 g per 10 l of liquid, as well as the removal of the affected parts of the thuja. Fundazol fights no less effectively with rust on thuja if it is treated with a solution of 20 g of a substance diluted in 10 liters of water.
Schütte
A disease such as schütte also affects mainly the needles of a young thuja. Already in early spring, it turns yellow and takes on an unaesthetic appearance due to the dense gray-black mycelium, which sticks together plant scales. You can cope with such a disease by regularly thinning the crown, spraying the plant with copper sulfate and Bordeaux liquid in spring and autumn.
Tinder fungus
The tinder fungus is able to infect a plant, penetrating into its structure through fractures and injuries of branches. The thuja affected by the disease grows overgrown with characteristic dense growths, while quickly drying out and turning yellow. In order for the plant to retain its decorative effect, you should not postpone treatment. All mushroom growths and yellowed parts should be cut off, and scraps and scratches should be cleaned and treated with a resin-based garden varnish. It will also be useful to carry out the spring and autumn processing of thuja with Bordeaux liquid.
Root rot
Another disease of thuja roots is root rot. It is characterized by the following symptoms:
- peeling off the bark at the base of the branches;
- tarnishing of thuja shoots and changing their color to brown or dirty yellow;
- the appearance of white spots on wood;
- inhibition of plant growth.
As such, there is no cure for root rot, but it is possible to prevent the disease if plants are treated with powerful fungicides, for example, a 0.2-solution of Rovral Flo 255 SC.
Gray mold
The appearance of thuja is very spoiled by gray mold. This fungal disease occurs when the plant is not well cared for. At the same time, gray spots can be observed on the needles, which turn brown over time, after which the shoots die off. In the advanced stages of the disease, there is no choice but to burn the affected plants. For the prevention of fungus, it is worth treating healthy thuja with the fungicide Biosept 33 SL or Teldor 500 SC. The procedure can be repeated if necessary.
The most common pests of thuja
In addition to diseases, some pests are also dangerous to thujas. All of them can be roughly divided into three groups:
- sucking pests;
- mining pests;
- xylophages, or stem pests.
Although the nature of the damage of these insects is different, most of them are affected by the same substances. Nevertheless, there are still some peculiarities in the fight against them, and therefore they should be taken into account when choosing a treatment.
Weevils
Excessively acidic soils can lead to the appearance of stem pests on thuja - weevils, which are equally dangerous in both the larval and mature stages. The adults of these insects eat the bark of young shoots, while the larvae damage the roots of the plant. The activity of such pests provokes browning of the ends of the branches in thuja and shedding of scales. The treatment in this situation is spraying the thuja with insecticides and, if necessary, liming the soil under the thuja.
Thuvaya signet moth
The signet moth is considered a mining insect. Outwardly, an adult individual of this pest looks like a small butterfly with a wingspan of up to 2 cm. It has a smooth or slightly scaly head with antennae and large round eyes. The narrow body and dark wings are decorated with patterns of white spots and stripes.
Like all butterflies, adult insects do not pose a direct threat to plant health. The caterpillars of these pests, on the other hand, eat through the tunnels in the thuja needles, which causes it to turn yellow, and the growth of the shrub slows down. The activity of such larvae can be easily detected by the holes in the scaly leaves. It is difficult to completely get rid of these pests, but it is possible if the infected thuja are treated with Karbofos, Kinmiks or Decis 2 times.
Thuya miner moth
Another thuja mining pest is called the thuja mining moth. Adult insects reach a length of 5 mm and have a silvery-brown color with brown stripes, which allows them to successfully camouflage themselves against the background of the bark. These pests are most active during May-June, when moth caterpillars begin to feed intensively before pupating. They damage the internal structure of the needles, which ultimately leads to deformation of the shoots and the appearance of yellowness in the crown.
Various insecticides will contribute to the destruction of mining pests. The first processing of thuja should be carried out in the spring, until the caterpillars of the moth have moved to new shoots, and the second at the end of summer.
Thuvaya aphid
Thuja pests such as thuja aphids, which can be seen in the photo, can very significantly spoil the appearance of thuja. These small grayish insects draw juice from the shoots at the age of 2 - 3 years, which, together with their enviable fertility and colonial lifestyle, makes them very dangerous for weakened plants.
Deprived of nutrients, the needles turn brown during the summer, and die off in the fall until the trunk is bare.
It is possible to cope with thuja pests if the plant is treated with insecticides, for example, Fufanon, from May to June, with re-treatment of thuja in the summer at the later stages of infection. In addition, it is advisable to wash the infected areas with a soapy composition, covering the ground so that the soap does not reach the roots of the thuja. Such procedures should be done regularly once every 7 to 10 days during a month. In this case, it is necessary to ensure that the solution does not come into contact with the roots of the thuja.
Thuya false shield
Thuvaya false shield is a miniature insect up to 3.5 mm in length. It has a slightly convex spherical body of yellow-brown color. Like the thuja aphid, the false shield is a sucking pest. The plant affected by this insect becomes covered with yellow sores, which quickly spread over the entire surface of the bark. A long absence of treatment can result in the death of thuja, and therefore it is necessary to treat the plant with drugs already at the first alarm signals. As a rule, Actellik, Karbofos, Antio are used for this, and connoisseurs of folk remedies - a soap-alcohol solution mixed at the rate of 15 g of soap and 10 ml of denatured alcohol per 1 liter of water.
Juniper scabbard
The juniper scabbard outwardly resembles a false shield in size and body color, but it has one significant difference - its carapace is attached to the body so tightly that it cannot be separated. It is believed that the scale insect does much less harm in comparison with the above-named insects, however, in large quantities and they cause problems, up to the complete drying of the thuja. You can eliminate this pest in the same ways as a false shield.
Thuja and juniper bark beetle
A lot of trouble for gardeners is delivered by thuja and juniper bark beetles. They are ranked among the trunk pests that gnaw tunnels in the bark of the thuja and feed on wood. Most often, they settle on plants that are not cared for carefully enough, however, pests can get on the site with newly acquired seedlings, so when buying thuja, you should carefully examine them. The best treatment against the invasion of bark beetles will be treatment with insecticidal compositions. And if you additionally process the thuja with Bordeaux liquid, the resistance to pests will increase significantly.
Spider mite
Spider mites often take a liking to thuja, which grow where there is insufficiently moist soil and dry air. This pest multiplies surprisingly quickly, entangling thuja with cobwebs in the course of its life. Treatment of the shrub with acaricides, as well as infusions of garlic or dandelions, will help to ward off harmful arachnids.
How to treat thuja in spring for prevention
As you know, it is much more difficult to deal with treatment than to prevent the development of the disease, and therefore you should not wait for the appearance of unwanted symptoms. It is better to take preventive measures that will protect plants and increase their immunity. To do this, it is advisable to treat thuja from diseases and pests in the spring with the help of HOM, spraying them with a solution made up at the rate of 40 g of the drug per 10 l of water. If there is a risk of damage to the root system by a fungus or infections that are in the soil, you can treat the trunk circle with 0.2% Fundazole once a season.
Instead of HOM, gardeners often use Bordeaux liquid. This mixture is very popular due to its effectiveness and versatility. Thuja is also sprayed with this liquid. This happens in the spring, when new needles begin to grow actively. The optimal amount of the product is 10 l / 100 m².
In addition to using the above means, systematic inspections of the plant for lesions and adherence to agricultural techniques, which includes, among other things, careful sanitary pruning, will help maintain the health of thuja.
Conclusion
Having studied the main diseases of thuja and their treatment, you can not be afraid that with a sudden deterioration in the health of the plant, precious time will be lost. Knowing all the nuances and symptoms of diseases, even people with minimal experience in caring for infected crops will be able to save their beloved thuja from almost any ailment.
