Hi I just planted cedar trees at my backyard they are the emerald cedar trees, I water them daily with a sprinkle for about 90 mins, after 10 days I am seeing that the outer leaves are beginning to turn brown from the outside. I also noticed some cobwebs and small spiders on the branches. The tree usually gets 6 to 8 hours of direct sunlight. Please let me know what should I do. Thanks
How disappointing to have your newly planted Emerald Cedar, Thuja occidentalis “Emerald Green”, developing brown outer branches. The cobwebs and small spiders suggest that mites are the culprit. Spruce spider mites, Oligonychus ununguis, and red spider mites feed on the needles of arborvitae causing them to turn gray or brown. They can be detected by the webs that they spin over the branches. Their piercing-sucking mouthparts enable them to suck the juice from the foliage.
Light infestations can be taken care of by spraying plants with a forceful stream of water including the underside of the foliage. Do this every day for three days. If mites continue to be a problem, spray with insecticidal soap every three to five days for two weeks in order to interrupt the cycle of eggs hatching. It is advisable to spray the soil as well as the plant.
Good cultural practices include planting in full sun or at least partial shade, and providing plenty of moisture during the growing season. Concentrate on watering the roots with a deep watering once a week . You should not be watering daily. Apply a mulch of compost or other organic material to help retain moisture as well as feeding the plant but keep the mulch several inches away from the trunk.
We wish you well in eliminating the mites.