Combating Phytophthora: Save your arborvitaes from browning

Arborvitaes are popular garden shrubs that often turn brown despite their charm and ease of cultivation. Why does this happen? We provide tips on how to save the plants when they start to lose their green colour.

Arborvitaes are a popular choice due to their low cost and ease of growing. They do not require much attention or special treatments, and after a few years, they create a tall, dense hedge that ensures privacy. To care for arborvitaes, you should not only regularly water and prune them but also check if they are being attacked by fungal diseases.

One of the most dangerous diseases that threaten arborvitaes is Phytophthora. This disease most commonly attacks arborvitaes in August due to high temperatures and high humidity caused by heavy rain or excessive watering.

Phytophthora in arborvitaes initially manifests as browning and drying needles, starting from the lower parts and moving upward. The disease weakens the plant, stunts its growth, and causes root rot. Characteristic symptoms include brown spots on the roots and at the base of the trunk. In severe cases, the entire arborvitae can die.

When you see that arborvitaes are infected, immediately take appropriate steps. Phytophthora can spread to other plants with similar needs, such as rhododendrons or spruces. The pathogen can survive in the soil for a long time, so early detection and combating the disease is crucial.

To save an infected arborvitae, comprehensive measures are needed. First, you should remove and destroy all diseased parts of the plant, including infected branches and roots. Then, you should improve soil conditions by loosening the soil around the arborvitae to a depth of 10-15 cm and adding compost or manure for better drainage.

It is worth using mulch made of pine bark or sawdust. Natural plant protection agents, such as extracts from garlic, grapefruit, nettle, or field horsetail, will be helpful in the fight against the disease. Biofungicides containing Bacillus subtilis can also be effective. Fertilization correction is also important - you should limit the use of nitrogen fertilizers in favour of potassium-phosphorus fertilizers, especially in the second half of the summer. These comprehensive actions can help in combating the disease and strengthening the plant.