Why your arborvitaes are turning brown and how to save them

Arborvitaes are a popular choice due to their low cost and manageable growth. They don't require much attention or special treatment, and after a few years, they create a tall, dense hedge that ensures privacy. To care for arborvitaes, you should regularly water and prune them and also check if fungal diseases attack them. 

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 are 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 long, so early detection and combating the disease is crucial.

Comprehensive measures are needed to save an infected arborvitae. First, remove and destroy all diseased parts of the plant, including infected branches and roots. Then, soil conditions can be improved by loosening the soil around the arborvitae to a depth of 4-6 inches and adding compost or manure for better drainage.

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