Loss of Turgor Pressure (decrease in water pressure within plant cell walls)
Causes: abiotic factors, bacteria, fungi, nematodes, insects
Examples: Ralstonia solanacearum, Verticillium dahliae, Bursaphelenchus xylophilus
Enations (scaly leaflike structures that lack a vascular system)
Causes: viruses
Examples: Cherry raspberry leaf virus, Pea enation mosaic virus
Stunting (dwarfing or loss of vigor)
Causes: viruses, phytoplasma, fungi, nematodes
Examples: Rhizoctonia, Strawberry lethal yellows
Witches’ Broom (dense clustering of abnormally small twigs)
Causes: phytoplasma, fungi, insects, mites
Examples: Ash yellows phytoplasma, Sphaerotheca sp.
Galls (abnormal growths)
Causes: fungi, nematodes, mites
Examples: Gymnosporangium sabinae, Meloidogyne spp.
Fruit and Seed Deformation (malformed fruit or seeds)
Causes: abiotic factors, viruses, bacteria, fungi, nematodes, insects
Examples: Catfacing tomatoes, Little cherry disease, Spiroplasma citri, Thrips palmi
Tumors (aggregates of cells that have multiplied excessively)
Causes: viruses, bacteria
Examples: Agrobacterium tumefaciens, Cryphonectria parasitica
Gummosis (oozing of sap from wounds/cankers on fruit trees)
Causes: abiotic factors, bacteria, fungi, insects, injury to the cutting sites
Examples: Pseudomonas syringa, Colletotrichum gloeosporioides
Rot (decay)
Causes: bacteria, fungi
Examples: Arruina carotovora, Ralstonia solanacearum, Phomopsis obscurans, Botrytis cinerea
Necrosis (death of cells or tissues)
Causes: abiotic factors, viruses, bacteria, fungi, nematodes, insects
Examples: Xanthomonas axonopodis, Fusarium oxysporum, Milbe Tetranychus cinnabarinus
For more information about plant diseases read:
A Brief Introduction to Plant Diseases