Blight: Sudden and severe withering and/or killing of leaves, flowers, shoots, fruit, or the entire plant. Young growing organ is prone to blight attack. According to parts of the plant affected, it can be defined as bud blight, leaf or needle blight, tip blight, shoot blight, twig blight, flower blight, etc.

Bleached: White to straw-colored areas on leaves, fruits or other parts of plants.

Bleeding: Sap flow from a wound due to mechanical injury or infection. It usually occurs on mature trees.

Blotch: A irregular and usually superficial necrotic area on a leaf, shoot, stem, or fruit.

Bunt: The contents of the wheat grains are replaced with odorous smut spores. It is a disease on wheat caused by the fungus Tilletia.

Canker: A necrotic, localized, often sunken lesion on a stem, branch, or twig of a plant. Cankers are usually surrounded by living tissues. However, a canker may girdle a stem, a branch, or a twig, causing death of an entire tree, a branch, or a twig.

Chlorosis: Loss of green color or yellowing of normally green tissue due to virus infection or nutrient deficiency that usually cause chlorophyll destruction or failure of chlorophyll formation. Some other factors such as nematode parasitizing, environmental stress or mechanical injury also cause chlorosis.

Cyst: A dead adult females of the nematodes Heterodera or Globodera. At the end of growing season, cysts can be seen on roots as a distinct characteristic of cyst nematode infection.

Damping-off: Seedlings suddenly wilt and fall over on the ground due to the decay of stem tissue near the soil line caused by some soil-borne fungal pathogens.

Dieback: Progressive death of shoots, branches, or roots generally starting from the tip. Dieback my be due to cankers, stem or root rots, insect borers, nematodes, nutrient deficiency or environmental stresses.

Downy mildew: Appearance of  fungal structure (mycelium, sporangiophores, and spores) as a downy drowth on the lower side of host leaves. The fungi belong to oomycete family Peronosporaceae.

Dwarfing: The significantly less development of a plant or plant organs than its normal potential, generally shown as short or small plants. May be caused by pathogens or certain environmental stresses.

Enation: Abnormal outgrowth of host tissue or eruption from a plant surface caused by infection of some viruses. Literally it means "small leaf".

Gall: An abnormal swelling or tumor-like outgrowth on leaves, stems, roots, or other parts of plants. It is produced by host plant cells as the result of attack by a fungus, bacterium nematode, insect, mite, or other agent.

Leaf spot: A localized, necrotic lesion on a leaf.

Mildew: Appearance of mycelium and spores of the fungus as a whitish growth on the host surface.

Mold: The presence and extensive growth of fungal mycelium and/or spores on surfaces of plant tissue or other materials.

Mosaic: Variegated patterns of dark and light green to yellow on leaves. It is caused by disarrangement or unequal development of the chlorophyll content due to some viral infection.

Necrosis: Localized dead and discolored tissue on leaves, stems, fruit, or roots.

Ringspot: A circular area of chlorosis or necrosis with green tissue inside the circle, usually caused by plant viruses.

Rot: The softening, discoloration, and often disintegration of plant tissue by enzymes produced by fungal or bacterial infection. Rots may be classified into hard rot, soft rot, dry rot, wet rot, black rot, brown rot, white rot.

Root-knot: Round to irregular galls on the roots, caused by Meloidogyne species.

Scab: A roughened, crust-like area on the surface of a plant organ. Most common scab diseases are apple scab, cherry scab, citrus scab, and potato scab, etc.

Scorch: Burning appearance of leaf margins as a result of infection or environmental stresses.

Shot-hole: Small holes on leaf generated by shaking off dead tissue inside necrotic spots.

Slime flux: Fermented sap exuded through a limb or trunk wound; a thick liquid from the stem or branches of trees made up of , or having a connection with yeasts, other fungi or bacteria. It is also called "wet wood".

Slime molds: The presence and growth of primitive organisms of the Acrasiomycota, Dictyosteliomycota, and Myxomycota on low growing plants, lawns, strawberry beds, seedbeds, rotting logs, tree trunks, sidewalks, or organic mulches, etc.

Smut: Dark brown or black, dusty to greasy masses of teliospores of a smut fungus that generally accumulate in black, powdery sori.

Spot: A definite, localized, necrotic area on a leaf, stem, flower, or fruit, etc. There are many different types of spot.

Stubby root: Excessive branching of roots caused by infection of the nematode Trichodorus.

Tumor: Uncontrolled overgrowth of tissue on any parts of plants.

Wilt: Appearance of lack of rigidity or dropping of leaves and flowers due to inadequate water supply, excessive transpiration, or infections of vascular tissue by certain fungi or bacteria, which interrupts the normal uptake and distribution of water by a plant.

Witches' broom: Broom-like growth or massed proliferation caused by the dense clustering of branches of woody plants.

Yellows: Turning a normal color to yellow on affected plant parts, usually leaves. It may be caused by pathogens, nutrient deficiency, or environmental stresses.