Capsicum species (commonly known as peppers) are susceptible to a range of pathogens, including bacteria, fungi, viruses, and nematodes. The following diseases are documented in horticultural and plant pathology references.
Bacterial Diseases
- Bacterial leaf spot (Xanthomonas campestris pv. vesicatoria) – Causes small, water‑soaked lesions that become necrotic; can spread by rain splash and contaminated tools.
- Bacterial wilt (Ralstonia solanacearum) – Leads to sudden wilting, vascular discoloration, and plant death; soil‑borne and moves through water.
- Bacterial soft rot (Pectobacterium spp.) – Results in mushy, water‑logged tissue, especially in fruit and stems.
Fungal Diseases
- Powdery mildew (Leveillula taurica and Erysiphe spp.) – White, powdery growth on leaves and stems; reduces photosynthesis.
- Downy mildew (Peronospora capsici) – Yellowing of lower leaf surfaces with a gray‑green fuzzy growth on the underside.
- Anthracnose (Colletotrichum spp.) – Dark, sunken lesions on fruit, stems, and leaves; can cause fruit rot.
- Phytophthora blight (Phytophthora capsici) – Water‑soaked lesions on stems, fruits, and leaves; rapid collapse of seedlings.
- Fusarium wilt (Fusarium oxysporum f. sp. capsici) – Yellowing and wilting of foliage, vascular discoloration, and reduced yield.
- Alternaria leaf spot (Alternaria spp.) – Small, dark brown to black lesions with concentric rings on leaves.
- Botrytis gray mold (Botrytis cinerea) – Gray, fuzzy growth on fruit, particularly in humid conditions; leads to rot.
- Rhizoctonia root rot (Rhizoctonia solani) – Damping‑off of seedlings and rotting of roots; soil‑borne.
Viral Diseases
- Pepper mild mottle virus (PMMoV) – Mosaic patterns, leaf distortion, and stunted growth.
- Tobacco mosaic virus (TMV) – Mosaic discoloration, leaf curling, and reduced vigor.
- Cucumber mosaic virus (CMV) – Yellow mosaic and necrotic spots; transmitted by aphids.
- Pepper veinal mottle virus (PVMV) – Vein clearing and mottling of leaves.
- Tomato spotted wilt virus (TSWV) – Necrotic lesions, wilting, and bronzing of leaves.
Nematode and Other Pests
- Root‑knot nematode (Meloidogyne spp.) – Galls on roots, leading to wilting, stunted growth, and yield loss.
- Lesion nematode (Pratylenchus spp.) – Necrotic lesions on roots; reduces nutrient uptake.
Management Overview Effective control typically combines cultural practices (crop rotation, sanitation, resistant varieties), biological agents (beneficial microbes), and chemical options (fungicides, bactericides) where permitted. Integrated Pest Management (IPM) strategies are recommended to minimize pathogen resistance and environmental impact.
