I noticed it after the heavy snows we had in Redmond this November. But when you can see brown spots where the leaf tissue hasn't fallen away yet, you know that it's a fungal problem not an insect problem. Previous. Phyllosticta leaf blotch can be managed in landscape settings. Brown leaf edges or entire leaves that have turned crispy are winter damage, usually from a combination of the ground being frozen (the plant can’t absorb water that is being lost through the leaves), sunburn from direct sun or sunlight being reflected off snow, or wind burn. Inspect the leaves weekly, particularly in warmer months. Cercospora leaf spot) Circular to irregular brown spots up to 1/2 inch in diameter form on leaves, especially lower leaves. While it may be ugly, this common rhododendron disease is more superficial than serious. How to Prune Lower Branches of a Rhododendron, Organic Treatment for Apple Tree Diseases, Gardening Know How: Azalea Insect Problems – Lace Bug Damage To Azaleas, Gardenia: Hardiest Azaleas and Rhododendrons, Clemson Cooperative Extension: Azalea & Rhododendron Diseases, Rhododendron Horticulture Society: Rhododendron Diseases, The American Rhododendron Society: Plant Culture and Care, My Gardenia's Leaves Are Turning Yellow & the Buds Are Falling Off, How to Get Rid of Fungus on a Rhododendron's Leaves. This kind of damage is most likely due to unfavorable environmental and weather conditions. This disease, caused by the fungus Glomerella cingulata, results in rounded spots on the leaves. During Summer, it is recommended that you check plants under eaves where rainfall may not penetrate even on the wettest days. Some ... Rhododendron leaf-miner (Fig. Severe infections can cause defoliation of the shrubs. Rhododendrons and azaleas are some of the most popular spring-flowering shrubs in the landscape, and healthy plants can give years of pleasure. The main cause of unsightly foliage or a lack of flowers is fungi. The two primary reasons that rhododendron leaves turn brown are cold weather and rhododendron wilt. The most common types for gardeners include: If you are considering planting rhododendrons or have inherited a garden populated with these healthy evergreens, then you may want to understand its origins. With the right knowledge, you can prevent brown spots on the leaves of your Azalea plant and take proper steps to inhibit them from returning. Most of the plant is OK -- the diseased leaves appear on the ends of some branches, but not others. Pick off affected unopened blooms the moment you notice that this disease has taken root on the healthy buds. Apply fungicides specifically formulated for brown spots on rhododendrons to help kill the fungus and prevent its spread. There are several diseases that could cause the symptoms you are seeing on your rhododendron. Many diseases and other problems can be prevented by following the recommended cultural practices for proper planting and care. Tropical regions of southeast Asia and northern Australia will also be good homes for rhododendrons. For about 11 months of the year, rhododendrons show us only their evergreen leaves. If the plant looks wilted yet is getting plenty of water, then it may be suffering from water mold. To control the damage that can be done to rhododendron leaves by the insects that immigrate to your garden, you need to control the population of these pesky invaders. What is Causing Rhododendron Leaves to Brown and Curl? Phyllosticta leaf spot is a fungal disease that causes small dots of yellowish-tan to brownish spots on the rhododendrons leaf surfaces. More information on successfully growing azaleas and rhododendrons is available in the fact sheets HGIC 1059, Azalea Care; HGIC 1058, Azalea Planting; and … Placing a layer of mulch or compost 2-3 inches thick under your rhododendron … Get in close and investigate the plant. This includes balancing the soil condition at the proper pH range and adding fertilizers, mulch and adequate watering. Fungus Leaf Spot Symptoms: Spots are irregular in size and color (Fig. During mild and wet weather in the spring, new infections are initiated. Brown spots on rhododendron leaves may not be a sign of disease. Bud blast is spread by the rhododendron leafhopper. See the picture and the leaves are browning on the edges. Now the leaves are turning a rust color, curling upward, and falling off. The spots are typically outlined by a dark brown edge. Understand that chemical controls are mostly ineffective once symptoms appear in the landscape. 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