What Is Wrong With My Sierra Redwood?

Are there any localized dead (necrotic) areas on branches, trunks, or roots?

Are there any distinct browning or blighting of the scales or needles, which typically starts on the inner portions of the lower branches?

Are the buds and leaves covered with gray mold, stems are soft, may be rotted?

Are the leaves discolored, fine webbing may be present?

Are the leaves and twigs covered with small, armored insects?

Sierra redwood trees are susceptible to Botryosphaeria canker disease. Many canker diseases primarily damage plants that lack proper cultural care. Keep plants vigorous to avoid and limit these diseases. Prune dead and dying branches when they are first observed, making the cuts in healthy wood below any apparent cankers, and use good sanitation to avoid spreading canker pathogens on contaminated tools.

Cercospora needle blight, caused by a fungus Cercospora sequoiae, affects redwood after warm, wet conditions. To minimize needle blights, choose a planting site with good air circulation and avoid planting conifers too close together. Provide appropriate cultural care to encourage vigorous plant growth. When irrigating, use drip irrigation instead of overhead sprinkling and avoid irrigating in the late afternoon or evening. Generally, no other management is practical or necessary.

Gray mold on flowers and leaves, followed by rotted stems are symptoms that indicate a fungal disease - Botrytis blight. Other symptoms include brown to black spots that may appear on leaves and petals. You can only prevent Botrytis blight disease by planting flowers in areas with good air circulation. Water plants sparsely. Infected plants should be removed. Spray weekly with a copper fungicide until the disease is under control.

Spider mites are known pests of Sierra redwood. Hose off plants when symptoms first appear. A strong stream knocks mites off plants and may give control. Introduce predatory mites. For severe infestations, spray plants with insecticidal soap or pyrethrin.

Small, armored insects on leaves and twigs are armored scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

Mineral deficiencies can cause tip chlorosis or necrosis or cause foliage to discolor, fade, distort, or become spotted, sometimes in a characteristic pattern that can be recognized to identify the cause. When nutrient deficiencies occur, nitrogen and iron are the most commonly seen deficiencies. Apply only the mineral found to be deficient. Excess nutrients, on the other hand, cause symptoms like leaf tip dieback, marginal leaf chlorosis, necrosis (or burn), branch dieback, and pest problems. In this case, you should provide good drainage, and use good practices during fertilization and irrigation.