Content
Although thuja, regardless of the variety, is famous for its resistance to harmful environmental factors and infections, it can still occasionally be susceptible to certain diseases. Therefore, all connoisseurs of this plant need to have an idea not only of its agricultural technology, but also to study thuja diseases and their treatment in as much detail as possible.
Signs of pests and diseases in thuja
Thuja is widely considered an unpretentious plant, the care of which does not require excessive effort, and this is true. 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 event of a disease or pest attack. Often, the following signs help to understand that something is wrong with a plant.
- slowing down the growth of shrubs;
- change in needle color to black, brown or yellow;
- drying of the tips of young thuja shoots;
- increased needle drop;
- 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 change in its pigmentation;
- the appearance of new growths or unusual plaque on the branches and crown;
- increase in the number of caterpillars on thuja.
If a plant exhibits 2 or more symptoms, it is worth monitoring its condition for 5 - 7 days, paying particular attention to recommendations for caring for thuja. If the negative changes do not subside within the allotted time, 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 shrub. Below are descriptions of the most common diseases and pests of thuja with photos.
The main diseases of thuja: how to identify and how to treat
Among the main diseases to which thujas are susceptible, the most prominent are those caused by the activity of various fungi. These diseases are quite easy to track even in the early stages, since infected plants clearly show negative external changes. The main difficulty lies in diagnosing a particular disease, since often their symptoms can be very similar. Therefore, it is especially important to comprehensively study thuja diseases in order to promptly select the appropriate treatment.
Late blight
Late blight is considered one of the most dangerous fungal diseases that can occur in thuja. This disease is accompanied by the destruction of the top layer of the root, which is why the crown of the plant subsequently acquires an unhealthy gray tint, and the trunk softens, becomes covered with plaque and acquires a distinct putrid odor.
As a rule, the cause of this disease in thuja is insufficiently good drainage and subsequent stagnation of moisture in the soil. To avoid the development of 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 will have to be completely changed, otherwise the disease will affect other plants planted in this place.
Fusarium
Unlike the previous disease, fusarium, or tracheomycosis wilt, is not so dangerous for thujas if you start treating the plant 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 become brown, and the fungus gradually grows into the underground parts of the thuja, blocking the supply of nutritional compounds. As a result, the above-ground parts of the plant first dry out, and the needles turn yellow, then turn red and, ultimately, die.
During the treatment of this disease, thuja should be treated with antifungal drugs, for example, a 0.2% solution of Fundazol.
Brown shoots
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 bush.
The signs of this disease are quite easy to notice. The shoots of infected thuja begin to turn yellow, and the color change occurs from the top of the branches, most often in early spring. In later stages of the disease, yellowness covers the entire shoot and it falls off.
Regular feeding of thuja and adding lime mixtures to the soil can help as a treatment. In the period from July to October, it will not be amiss to treat the plant with a 2% solution of Fundazol at intervals of 1 time every 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 quickly as possible so that the plants do not lose too many needles during the course of the disease. It is believed that a disease such as rust occurs due to lack of nutrition, as well as in too dry or humid weather. During the process of infection, the thuja needles begin to darken, acquiring a copper tint, after which they fall off. Treatment of this disease consists of timely treatment of plants with HOM, at the rate of 40 g per 10 liters of liquid, as well as removal of the affected parts of the thuja. Fundazol fights rust on thuja no less effectively if you treat it with a solution of 20 g of the substance diluted in 10 liters of water.
Schutte
A disease such as Schutte also affects mainly the needles of young thuja. Already in early spring it turns yellow and takes on an unaesthetic appearance due to the dense gray-black mycelium that glues the plant scales together.You can cope with such a disease by regularly thinning the crown, spraying the plant with copper sulfate and Bordeaux mixture in spring and autumn.
Tinder fungus
The tinder fungus is capable of infecting a plant, penetrating its structure through broken branches and injuries. The thuja affected by the disease becomes overgrown with characteristic dense growths, while quickly drying out and turning yellow. In order for the plant to retain its decorative properties, do not delay treatment. All fungal growths and yellowed parts should be cut off, and broken parts and scratches should be cleaned and treated with a resin-based garden varnish. It will also be useful to treat thuja with Bordeaux mixture in spring and autumn.
Root rot
Another disease of thuja roots is root rot. It is characterized by the following symptoms:
- peeling of bark at the base of branches;
- fading of thuja shoots and changing their color to brown or dirty yellow;
- the appearance of white spots on wood;
- inhibition of plant growth.
There is no treatment for root rot as such, but it is possible to prevent the disease if you treat the plants with powerful fungicides, for example, a 0.2-solution of Rovral Flo 255 SC.
Gray mold
Gray mold spoils the appearance of thujas. This fungal disease appears if the plant does not receive good care. In this case, gray spots can be observed on the needles, which turn brown over time, after which the shoots die. In the advanced stages of the disease, there is nothing left to do but burn the affected plants.To prevent fungus, it is worth treating healthy thujas with the fungicide Biosept 33 SL or Teldor 500 SC. If necessary, the procedure can be repeated.
The most common pests of thuja
In addition to diseases, some pests also pose a danger to thujas. All of them can be divided into three groups:
- sucking pests;
- mining pests;
- xylophages, or stem pests.
Although the nature of the damage to these insects differs, most of them are affected by the same substances. However, there are still some features in the fight against them, and therefore they should be taken into account when selecting treatment.
Weevils
Excessively acidic soils can lead to the appearance of stem pests on the thuja - weevils, which are equally dangerous in both the larval and mature stages. 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 thuja branches and shedding of scales. The treatment in this situation is spraying the thuja with insecticides and, if necessary, liming the soil under the thuja.
Thuja fox moth
The digitalis moth is considered a leaf-mining insect. Externally, an adult specimen 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 tunnels into the needles of the thuja, which is why it turns yellow and the growth of the bush slows down. The activity of such larvae is easy to detect by the holes on the scaly leaves. It is difficult to completely get rid of these pests, but it is possible if you treat infected thujas twice with Karbofos, Kinmiks or Decis.
Thuja leaf miner
Another leaf-mining pest of the thuja bears the self-explanatory name of the thuja leaf-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 against the background of the bark. These pests are most active during May-June, when moth caterpillars begin to feed heavily 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 help destroy mining pests. The first treatment of thuja should be carried out in the spring, before the moth caterpillars move to new shoots, and the second - at the end of summer.
Thuja aphid
Thuja pests such as thuja aphids, which can be seen in the photo, can significantly spoil the appearance of thuja. These small grayish insects draw sap from 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 in the fall until the trunk is exposed.
It is possible to cope with thuja pests if you treat the plant with insecticides, for example, Fufanon from May to June, with repeated treatment of thuja in the summer in the later stages of infection. In addition, it is advisable to wash the infected areas with a soapy mixture, covering the ground so that the soap does not reach the roots of the thuja. Such procedures should be done regularly once every 7-10 days for a month. In this case, it is necessary to ensure that the solution does not come into contact with the roots of the thuja.
Thuja false scale
The thuja false scale insect 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 scale insect is a sucking pest. A plant affected by this insect becomes covered with yellow ulcers, which quickly spread over the entire surface of the bark. A long absence of treatment can result in the death of the thuja, and therefore it is necessary to treat the plant with medications at the first alarm signals. As a rule, Actellik, Karbofos, Antio are used for this, and connoisseurs of folk remedies use 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 scale insect
The juniper scale insect looks like the false scale insect in size and body color, but has one significant difference - its shell is attached to the body so tightly that it cannot be separated. It is believed that scale insects cause much less harm in comparison with the above-mentioned insects, but in large numbers they cause problems, up to the complete drying out of the thuja. This pest can be eliminated using the same methods as the false scale insect.
Thuja and juniper pine beetle
Thuja and juniper pine beetles cause a lot of trouble for gardeners.They are classified as stem pests that gnaw tunnels in the thuja bark and feed on the wood. Most often, they settle on plants that are not cared for carefully enough, however, pests can enter the area with recently purchased seedlings, so when purchasing thujas, you should carefully inspect them. The best treatment against pine beetle infestation is treatment with insecticidal compounds. And if you additionally treat thuja with Bordeaux mixture, its resistance to pests will increase significantly.
Spider mite
Spider mites often prefer thujas, which grow where there is insufficiently moist soil and dry air. This pest multiplies surprisingly quickly, entangling thujas with cobwebs during its life. Treating the bush with acaricides, as well as infusions of garlic or dandelions will help repel harmful arachnids.
How to treat thuja in the spring for prevention
As you know, treatment is much more difficult than preventing 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 the plants and increase their immunity. To do this, it is advisable in the spring to treat thujas against diseases and pests using HOM, spraying them with a solution made up of 40 g of the drug per 10 liters of water. If there is a risk of damage to the root system by fungus or infections that are in the soil, you can treat the tree trunk circle with 0.2% Fundazol once a season.
Instead of HOM, gardeners often use Bordeaux mixture. This mixture is very popular due to its effectiveness and versatility. Thujas are also sprayed with this liquid. This happens in the spring, when new needles actively begin to grow. The optimal amount of product is 10 l/100 m².
In addition to using the above-mentioned means, systematic inspection of the plant for damage and adherence to agricultural practices, which include, among other things, careful sanitary pruning, will help maintain the health of the thuja.
Conclusion
Having studied the main diseases of thuja and their treatment, there is no need to be afraid that if the plant’s health suddenly deteriorates, 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 favorite thujas from almost any ailment.
