Brown spots on Gerbera daisy leaves are often caused by fungal infections. Common fungal pathogens include Alternaria, Cercospora, and Botrytis cinerea. These fungi thrive in humid conditions and can spread rapidly if the plant's foliage remains wet for extended periods. The spots may appear circular or irregular, with a dark brown or black center and a yellow halo. Fungal spores can be transmitted through water splashes, contaminated tools, or infected soil.
Bacterial infections, such as those caused by Pseudomonas or Xanthomonas, can also lead to brown spots. These spots often appear water-soaked initially, later turning brown or black with a yellow margin. Bacteria enter the plant through wounds or natural openings, spreading in warm, moist environments. Overhead watering or poor air circulation exacerbates the problem, as bacteria thrive in stagnant moisture.
Gerbera daisies are sensitive to environmental stressors, which can manifest as brown spots on leaves. Excessive sunlight (sunscald), extreme temperatures, or inconsistent watering can damage leaf tissues. For example, water stress—either drought or overwatering—can cause cell death, leading to brown, necrotic spots. Similarly, high salinity in soil or water can burn leaf edges, creating brown patches.
Nutrient imbalances, particularly deficiencies in potassium, calcium, or magnesium, can result in brown spotting. Potassium deficiency often causes brown edges and tips, while calcium deficiency leads to distorted growth and necrotic spots. Magnesium deficiency manifests as interveinal chlorosis (yellowing between veins) with brown spots developing as the condition worsens. Proper fertilization and soil testing can help prevent these issues.
Certain pests, such as spider mites, thrips, or aphids, can cause brown spots by feeding on Gerbera daisy leaves. Their piercing-sucking mouthparts damage plant cells, leading to stippling, yellowing, and eventually brown necrotic areas. Heavy infestations weaken the plant, making it more susceptible to secondary infections. Regular inspection and pest control measures are essential to mitigate damage.
Exposure to herbicides, pesticides, or foliar fertilizers at incorrect concentrations can cause chemical burns, resulting in brown spots. Physical damage from rough handling, hail, or abrasive winds can also create wounds that turn brown as the tissue dies. Always follow product instructions and handle plants gently to avoid such injuries.
Though less common, viral infections like Tomato spotted wilt virus (TSWV) or Impatiens necrotic spot virus (INSV) can cause brown or necrotic spots on Gerbera daisy leaves. These viruses are often transmitted by thrips and may also cause stunted growth, ring spots, or mosaic patterns. Infected plants should be removed to prevent spread.
Waterlogged soil due to poor drainage can lead to root rot, which indirectly causes brown spots on leaves. Oxygen-deprived roots cannot absorb nutrients efficiently, leading to foliar symptoms like browning and wilting. Ensure well-draining soil and avoid overwatering to maintain healthy root systems.
