As a vibrant Black-eyed Susan (Rudbeckia spp.), I stand tall in the summer sun, my golden petals radiating warmth. But my life is not without its challenges. From my roots to my flower heads, I am constantly under threat from various pests and diseases that seek to diminish my vitality. Here is a detailed account of my most common adversaries and the treatments that can help me thrive.
My broad leaves are my solar panels, and when fungi attack them, my entire energy production is compromised. The most frequent issues I face are powdery mildew and leaf spot diseases. Powdery mildew appears as a white, powdery coating on my leaf surfaces, often due to humid conditions with poor air circulation. It’s unsightly but rarely fatal. More concerning are the various leaf spot fungi, which cause dark brown or black spots that can cause my leaves to yellow, wilt, and drop prematurely, severely weakening me.
Treatment from My Perspective: The best help involves cultural practices. Please ensure I am spaced adequately from my plant neighbors to allow breezes to flow through my leaves, reducing humidity. When watering, aim the water at my base rather than sprinkling my foliage, as wet leaves are a fungal paradise. If an infection is severe, you may apply a fungicide, but I prefer organic options like neem oil or a baking soda solution. Most importantly, in the fall, please clear away all my fallen, diseased leaves to prevent the fungi from overwintering and attacking me again next spring.
Aphids and spider mites are tiny but relentless enemies. They pierce my tender stems and the undersides of my leaves to suck out my nutrient-rich sap. This stunts my growth, causes my leaves to curl and distort, and leaves behind a sticky residue called honeydew. This honeydew can attract ants and lead to the growth of sooty mold, which further blocks sunlight from my leaves. I often feel a general weakness when these pests are present in large numbers.
Treatment from My Perspective: A strong spray of water from a garden hose can often dislodge these soft-bodied pests. Introducing or encouraging beneficial insects, like ladybugs and lacewings, is a strategy I wholeheartedly support, as they are natural predators. For heavier infestations, insecticidal soaps or horticultural oils are effective treatments that are gentle on the environment. Please be sure to spray the undersides of my leaves where these pests love to hide.
While I don’t mind sharing a few leaves, caterpillars and slugs can cause significant damage. The Rudbeckia beetle, a small black beetle, and its larvae are particularly fond of my foliage, chewing irregular holes and sometimes skeletonizing my leaves. Slugs leave a tell-tale slimy trail and create large, ragged holes, especially in damp, shady conditions. Severe defoliation can prevent me from photosynthesizing effectively and may reduce or prevent my flowering.
Treatment from My Perspective: For larger pests like beetles and caterpillars, the simplest method is to hand-pick them off my leaves and dispose of them. For slugs, you can set up traps using shallow dishes of beer sunk into the soil near my base; they are attracted to it and will drown. Creating a barrier of diatomaceous earth or crushed eggshells around my stem can also deter slugs, as the sharp edges are unpleasant for them to crawl over.
One of my most insidious enemies isn't an insect or a fungus, but another plant: dodder. Dodder is a parasitic vine that lacks chlorophyll. Its seeds germinate in the soil and then it grows until it attaches to a host plant—like me. It inserts haustoria (sucking structures) into my stem to steal my water and nutrients. I become weak, stunted, and yellowed, and if not freed, I can be killed.
Treatment from My Perspective: This requires immediate and careful action. The only reliable method is to physically remove the dodder vines from me before they set seed. You must carefully unwind the pale, string-like vines and dispose of them in the trash, not the compost. It’s crucial to remove all parts of the vine, as any piece left attached can re-grow. In severe cases, it may be necessary to remove and destroy an entire infected plant to save its neighbors.
