Algae and the Diseases They Cause
Algae, particularly parasitic algae, can cause several plant diseases. While many algae are harmless, certain types are parasitic and can lead to significant damage to crops and other plants. Below are some examples of parasitic algae and the diseases they cause:
- Cephaleuros (Genus of Parasitic Algae)
Overview: Cephaleuros is a genus of parasitic green algae that infects plants by living beneath the leaf cuticle. It is found in tropical and subtropical regions, and it infects over 400 plant species.
Key Species: Cephaleuros virescens, Cephaleuros parasiticus
Diseases Caused:
- Red Rust Disease: Caused by C. virescens, it affects tea (Camellia sinensis), mango, and other plants. The disease is characterized by reddish-brown lesions on the leaves, which reduce the plant’s ability to photosynthesize, leading to leaf drop and stunted growth.
- Coffee Rust: Cephaleuros parasiticus is also known to cause rust-like symptoms on coffee plants, leading to reduced yields.
Hosts:
- Tea
- Coffee
- Mango
- Hibiscus
- Orchids
- Euphorbia
- Citrus
Symptoms:
- Reddish or yellowish spots on leaves
- Premature leaf drop
- Reduced photosynthetic ability
- Prototheca (Genus of Algae)
Overview: Prototheca is a genus of non-photosynthetic, parasitic algae that infects plants and animals. It has been reported to cause diseases in a wide range of hosts, including humans and livestock.
Key Species: Prototheca wickerhamii, Prototheca zopfii
Diseases Caused: Protothecosis: This is a disease primarily affecting animals, but it can also infect plants. It is known to affect various crops and ornamental plants, leading to symptoms like chlorosis (yellowing of leaves) and wilting. In humans and animals, it can lead to systemic infections.
Hosts:
- Various agricultural plants (e.g., ornamental plants)
- Dairy cattle (for human infections)
- Occasionally affects human skin and eyes
Symptoms:
- Chlorosis
- Leaf curling
- Wilting
- Necrosis
- Cladophora (Genus of Green Algae)
Overview: Cladophora is a genus of green algae that typically grows in freshwater environments, though some species can become parasitic on aquatic plants.
Diseases Caused:
- Algal Overgrowth and Eutrophication: While Cladophora is not strictly a parasitic algae, its overgrowth can lead to eutrophication in water bodies, where it competes with aquatic plants for nutrients and light. This reduces the growth of native plants and disrupts aquatic ecosystems.
Hosts: Aquatic plants, Freshwater ecosystems
Symptoms:
- Excessive algae growth on aquatic plants
- Oxygen depletion in water bodies
- Decline in aquatic plant growth due to competition for nutrients
- Anabaena (Genus of Cyanobacteria, Often Considered Blue-Green Algae)
Overview: Anabaena is a genus of nitrogen-fixing cyanobacteria (often called blue-green algae), which can form harmful blooms in freshwater environments, leading to the formation of toxins.
Diseases Caused:
- Blue-Green Algae Blooms: Anabaena can form blooms in lakes and ponds, releasing toxins that can affect plant and animal health. These blooms can lead to the death of aquatic plants and the contamination of water supplies.
Hosts:
- Aquatic plants
- Fish
- Livestock (through water contamination)
Symptoms:
- Reduced oxygen levels in water
- Death of aquatic plants due to competition for light and nutrients
- Toxin buildup affecting animals that drink contaminated water
- Saprolegnia (Genus of Water Molds)
Overview: Although not true algae, Saprolegnia belongs to a group of organisms often grouped with algae due to their similar appearance. These water molds affect fish and aquatic plants.
Diseases Caused: Water Mold Infection (Saprolegniasis): This affects fish and occasionally aquatic plants, causing the formation of cotton-like growths on infected tissues.
Hosts:
- Fish (mainly freshwater)
- Occasionally aquatic plants
Symptoms:
- Cotton-like growths on the surface of fish and plants
- Tissue rot and decay
- Death of infected fish
- Chlamydomonas (Genus of Green Algae)
Overview: Chlamydomonas is a genus of green algae that can sometimes parasitize plants, although it is mostly known for its free-living forms in water.
Diseases Caused: Root Rot in Aquatic Plants: Some species of Chlamydomonas can cause root rot in submerged aquatic plants by overgrowing and blocking nutrient uptake.
Hosts:
- Aquatic plants
Symptoms:
- Decay of roots
- Stunted plant growth
- Yellowing of leaves
