Plant disease symptoms

description and causes examples

prenecrotic symptom expression that precedes the death of cells or the disintegration of tissues

water-soaking a water-soaked, translucent condition of tissues caused by water moving from host cells into intercellular spaces late blight lesions on potato and tomato leaves; bacterial soft rot of fleshy vegetables

wilting temporary or permanent drooping of leaves, shoots, or entire plants from lack of water bacterial wilt of cucumber; Fusarium wilt of tomato

abnormal coloration yellowing, reddening, bronzing, or purpling in localized areas of leaves where chlorophyll has been destroyed; may be due to a variety of causes cabbage and aster yellows; halo blight of beans; potassium or phosphorus deficiency

the presence of two or more colours in leaves and flowers due to a genetic abnormality is called variegation; viral infection results in "flower breaking" tulip mosaic

necrotic localized or general death of cells or disintegration of tissues

blast sudden blighting or death of young buds, flowers, or young fruit; failure to produce fruit or seeds Botrytis blight of peony buds; oat blast

bleeding flow of sap, often discoloured, from a split crotch, branch stub, or other wound; usually accompanied by an odour of fermentation bleeding canker of beech, dogwood, and maple

blight sudden or total discoloration and killing of large numbers of blossoms, leaves, shoots, or limbs or the entire plant; usually young tissues are attacked; the disease name is often coupled with the name of the host and the part attacked—blossom blight, twig blight, tip blight fire blight of pome fruits; Diplodia or Sphaeropsis tip blight of conifers

canker a definite, dead, often sunken or swollen and cracked area on a stem, limb, trunk, tuber, or root surrounded by living tissues anthracnose of sycamore and brambles; Nectria canker of hardwoods; fire blight of pome fruits

damping-off decay of seed in soil, rapid death of germinating seedlings before emergence, or emerged seedlings suddenly wilting, toppling over, and dying from rot at or near the soil line preemergence damping-off and postemergence damping-off; both are common in seedbeds

dieback progressive browning and death of shoots, branches, and roots starting at the tips winter injury; wet soil; excess soil nutrients; girdling cankers; stem or root rots; nematodes

firing drying and dying of leaves nitrogen or potassium deficiency in corn; Verticillium wilt of eggplant

fleck a small, white to translucent spot or lesion visible through a leaf ozone injury to many plants; necrotic fleck of lily

mummification final stage in certain fruit rots, in which the dried, shriveled, and wrinkled fruit is called a "mummy" brown rot of stone fruits; black rot of apple

net necrosis an irregular crisscrossing of dark brown to black lines giving a netted appearance in potato tubers of plants with virus leaf roll

pitting small dead areas within fleshy or woody tissue that appears healthy externally; definite sunken grooves or pits are formed virus stem-pitting in apple and peach trunks; stony pit of pear fruit

rot decomposition and putrefaction of cells, later of tissues and organs; the rot may be dry, firm, watery, or mushy and is characterized by such names as hard rot, soft rot, dry rot, black rot, and white rot bacterial soft rot; berry rot; bud rot; bulb rot

scald blanching of young fruit, foliage, and shoot tissue; generally superficial sunscald; apple and pear scald

scorch sudden death and "burning" of large, indefinite areas in leaves and fruit toxicity from pesticides and air pollutants; drought; wind; lack or excess of some nutrient

shot hole dead spotting of leaves with diseased tissue dropping out, leaving small holes bacterial spot; Coryneum blight of peach

spot a definite, localized, round to regular lesion, often with a border of a different colour, characterized as to location (leaf spot, fruit spot) and colour (brown spot, black spot); if numerous or if spots enlarge and merge, a large irregular blotch or blight may develop gray leaf spot of tomato; black spot of rose; tar spot of maple

staghead an advanced form of dieback applied to a tree in which large branches in the upper crown are killed oak wilt on bur oak; dwarf mistletoe on Douglas fir; Armillaria root rot of oak

streak narrow, elongated, somewhat superficial necrotic lesions, with irregular margins, on stems or leaf veins virus streak of pea, raspberry, and tomato; Stewart's wilt of sweet corn

stripe narrow, elongated, parallel, necrotic lesions especially in leaf diseases of cereals and grasses Helminthosporium stripe of barley; Scolecotrichum brown stripe of forage grasses

hypoplastic the underdevelopment of plant cells, tissues, or organs

abortion halting development of an organ after partial differentiation ergot of rye and other grasses

chlorosis yellowing or whitening of normal green tissue due to partial or complete failure of chlorophyll to develop strawberry and aster yellows; genetic variegation in corn; iron deficiency of azalea

stunting or dwarfing the underdevelopment of the plant or some of its organs dahlia stunt or mosaic; curly top of beans; little-leaf disease of pines

rosetting shortening of internodes of shoots and branches, producing a bunchy growth habit peach and lily rosette

hyperplastic or hypertrophic an overdevelopment or overgrowth of plant cells, tissues, or organs; hyperplastic has come to mean an increase in number of cells, hypertrophic an increase in cell size

abscission or cast early dropping of leaves, flowers, or small fruits; usually associated with premature formation of an abscission (separation) cell layer black spot of rose; early blight of tomato; apple scab

callus overgrowth of tissues, often at margins of a canker or wound Nectria canker of hardwoods; stem pitting of peach

curl distortion and crinkling of leaves or shoots resulting from unequal cell growth of opposite sides or in certain tissues tobacco and tomato mosaic; leaf roll of potato; peach leaf curl

epinasty downward or outward curling and bending of a leaf or petiole 2,4-D injury to broadleaf plants; Fusarium wilt of tomato

fasciation, or witches'-broom a distortion that results in a dense, bushy overgrowth of thin, flattened, and sometimes curved shoots, flowers, fruit, and roots at a common point; usually due to adventitious (abnormally located) development of organs witches'-broom of hackberry; hairy root of apple; leaf gall or fasciation of geranium (see also Rosetting under Hypoplastic in this table)

metamorphosis or transformation development of more or less normal tissues or organs in an abnormal location crazy-top of corn and sorghum; formation of aerial potato tubers

proliferation continued development of an organ after it would normally stop growing adventitious shoots in China aster and chrysanthemum from aster yellows mycoplasma

russeting usually a brownish, superficial roughening or corking of the epidermis of leaves, fruit, tubers, or other organs; often due to suberization (cork development) of cells following injury spray or weather injury to apples; sweet potato scurf

scab roughened to crustlike, more or less circular, slightly raised or sunken lesions on the surface of leaves, stems, fruit, or tubers apple, peach, and cucumber scab; common scab of potato

gall, knot, or tumefaction formation of local, fleshy to woody outgrowths or swellings; the outgrowth is often composed of unorganized cells crown gall; black knot of plum; Fusiform gall rust of pine; nematode galls