Plant Disease Agents: Fungi, Bacteria, Viruses & Nematodes

Parasitic agents of plant disease include:

Fungi

Most common pathogens; cause leaf spots, wilts, rots. Examples: Botrytis cinerea (gray mold), Fusarium oxysporum (wilt), Phytophthora infestans (late blight), Rhizoctonia solani (damping-off).

Bacteria

Single-celled; cause blights, wilts, rots. Examples: Agrobacterium tumefaciens (crown gall), Erwinia amylovora (fire blight), Pseudomonas syringae (leaf spot).

Viruses

Acellular; replicate inside host cells. Cause mosaics, yellowing, stunting. Examples: Cucumber mosaic virus, Tobacco mosaic virus, Tomato spotted wilt virus.

Nematodes

Microscopic roundworms in soil. Cause root knots, lesions, stunting. Examples: Meloidogyne incognita (root-knot), Pratylenchus penetrans (lesion), Xiphinema index (dagger).