Yellowing and withering of thujais a common phenomenon, despite the fact that it makes plants quite resistant.The cause of yellowing and withering of thuja shootsmay be improper planting, care errors or pathogens. Whatever the reason, quick intervention is needed to save the plants. Here are3 common causes of yellowing and withering of thujaand ways to restore a nice, he althy look to these plants!
Why do thujas turn yellow and wither?
Why thujas turn yellow and witherand how to save such plants is explained by MSc.Agnieszka Lach, a graduate of the Faculty of Environmental Management and Agriculture at the University of Warmia and Mazury in Olsztyn. On a daily basis, she is professionally involved in the care and arrangement of plants. The author of many interesting tutorial articles on gardening and an expert on the gardening forum.
1. Yellowing of thuja as a result of inadequate soil and food conditions
Proper fertilization is the basic factor determining the proper coloring of thuja scales. The deficiency of basic nutrients responsible for the production of chlorophyll will cause changes in the color of trees. Thujas most often suffer from insufficient amounts of magnesium (Mg) and iron (Fe). The lack of these ingredientsmanifests itself initially with a lighter and then yellowing of the thuja shootsIn the case of magnesium deficiency, the yellowing of thuja starts from the oldest shoots, and in the case of iron - from the youngest. Nitrogen (N) deficiency, manifested by yellowing of the scales and stunted growth, is less common.
The excess of nutrients is as dangerous as the lack of nutrients. Excessive doses of mineral fertilizers disrupt the uptake of macro- and microelements and water from the ground (so-called physiological drought),which leads to yellowing and drying out of thuja in moderation, taking care not to exceed the recommended doses of fertilizers.
Nutrient deficiencies often result not only from errors in plant fertilization, but also from inadequate soil pH. Thujas require a slightly acidic substrate (pH 5.5-6.5). If the pH is too high, for example in calcium-rich soils, then iron deficiency occurs. On the other hand, when the pH is too low, the uptake of magnesium is difficult. In such cases, instead of administering consecutive doses of compound fertilizers, the soil pH should be adjusted.
Specialist thuja fertilizers, e.g.Thuja fertilizer with Target micronutrients. Remember that nitrogen fertilizers are given from April to mid-July, and nitrogen-free autumn fertilizers are used later.
2. Yellowing and withering of thuja due to inadequate watering
Thuja have high water requirements and react very badly to the drying of the substrate.Lack of water leads to the drying out of thuja shoots, and in extreme cases to the withering of whole plantsIn hot and dry summers it is necessary to irrigate, especially thuja planted in containers. The substrate should be constantly moist. It is also recommended to mulch the soil under the trees with pine bark, which reduces evaporation of water from the substrate.Remove drying shoots and water generously the dried plantThen water the plants every day in the early morning or evening. Dry plants should not be fertilized, so as not to weaken them even more.
Dieback of thuja as a result of dryness occurs very often in the early spring Thuja, which are conifers, do not have a dormant period. In winter, on frost-free days, when the temperature reaches 0 ° C, their transpiration starts. The ground is still frozen at this time, which prevents the roots from collecting water that could replenish the amount of transpiration. Strong, drying, frosty winds pose an additional threat. As a consequence, there ismass drying of thuja, often one-sidedWe can prevent this by properly preparing the plants for winter. In the fall, water the thuja (especially those grown in containers) until the first frost so that they can store as much water as possible.
It is also not allowed to flood the roots of thuja and stay in very wet soil for a long time. Most often this is a threat to thujas grown in containers and on heavy clay soils.Flooding of the root system is manifested by yellowing and browning of thujaand promotes the development of fungal diseases. That is why the containers in which we grow thujas should be equipped with holes in the bottom, through which excess water will drain.
3. Yellowing of thuja caused by fungal diseases
Thuja are rarely attacked by plant fungal diseases. However, after elimination of errors in cultivation, it is necessary to consider this possibility. The most common diseases of thuja are: phytophthora, armillary root rot and shoot dieback.
Phytophthora citricola
Phytophorosis is the most dangerous fungal disease of conifers, but it rarely attacks thymus. Symptoms of phytophorosis appear on plants in July or August. They are visible on the shoots located low above the ground.Single shoots of thuja turn gray, turn yellow, then turn brown and die.To make sure that our thuja has phytophthora, scrape the bark from the infected shoot. If it is reddish-brown in color, this indicates a fungus infection. Phytophotorosis especially attacks the western thuja (Thuja occidentalis), while some varieties of the eastern thuja (Thuja orientalis), e.g.'Aurea Nana' are completely resistant to the fungus that causes phytophthora.
Armillaria root rot (Armillaria)
It is a fungal disease caused by fungi of the genus Armillaria (Armillaria). It attacks thuja growing on plots located near forests.Infected thujas lose their natural color and shine of the scales. They become dull, turn yellow and dieAt the base of the trunk, the bark turns brown, dies and cracks lengthwise, revealing the wood. Abundant white mycelium is visible on the wood and the inside of the bark. In autumn, cap mushrooms may appear at the base of the shoot.
Shoot dieback (Phomopsis, Ascophyta, Pesalotiopspis, Sphaeropsis)
Shoot dieback is the most common disease of thuja aerial organs. As a result of the disease,yellowing of the tops of the twigs, spreading over their entire surface .
Plants heavily infested with fungi should be removed and burned.The remaining ones growing nearby are sprayed with the biological preparation Polyversum WP. In the case of phytophthora, plants should also be watered with this preparation. This natural and environmentally safe preparation allows you to effectively fight thuja diseases without the need to use chemical fungicides.
If this does not work, we can use stronger fungicides, such as Topsin M 500 SC (spraying with a 15ml solution dissolved in 10 liters of water) and Scorpion 325 SC (10ml of the agent for 3-12 liters of water). These sprays can also help in the event of noticing the first symptoms of disease, when only single branches are infected. Then we cut the diseased shoots and spray the whole plant.
In order to reduce the risk of fungal diseases, first of all, watering the roots should be avoided and the thujas should be provided with optimal development conditions. An important procedure is also the removal and destruction of all diseased parts of the plant as soon as we notice the first symptoms of infection.As a preventive measure, even he althy plants should be sprayed with the natural biopreparation Biosept Active, which stimulates growth and immunizes plants against diseases.
MSc Eng. Agnieszka Lach
