Glossary

Excrement of an insect, usually mixed with plant debris.

Damage by freezing or below freezing temperatures when plants are actively growing. See also winter injury.

Any of various complex, spore-bearing fungal structures.

Vapor-active chemical used in the gaseous phase to kill or inhibit the growth of microorganisms or other pests.

A major group of fungi for which no sexual production of spores is known.

An agent that inhibits or kills fungi.

A chemical or physical agent that prevents fungi from developing but does not kill them.

A single- or many-celled, naked or covered, irregular or filamentous organism, usually with a chitinous cell wall. Lacking chlorophyll and incapable of manufacturing its own food, it gets nutrition from dead or living plant or animal matter.

Outgrowth or swelling of unorganized plant cells produced as a result of attack by bacteria, fungi, or other organisms.

To begin growth of a seed or spore.

Large, usually multinucleate cells formed by abnormal cell fusions or failure of proper cell wall formation following growth and nuclear division. Associated with nematode feeding.

To circle and cut through; to destroy vascular tissue, as in a canker or knife cut that encircles the stem.

A negative (or positive) reaction to the standard Gram's stain for bacteria.

A crop plowed under while still green and growing to improve the soil; sometimes used to enhance populations of antagonistic microorganisms for biological control.

A chemical substance produced in one part of an organism and transported in minute quantities to induce a growth response in another part, such as auxins, cytokinins, and gibberellins. Some fungicides induce a growth-regulation response when applied to plants.

A pathologic condition in stone fruits characterized by excessive formation of gums exuding from buds, twigs, branches, or trunks.

The exudation of watery, sticky liquid from hydathodes, especially along leaf margins.

The chromosome number of the gametophytic generation or phase or having a single complete set of chromosomes.

A modified mycelial branch that grows into a plant cell, makes intimate contact with the protoplast, and absorbs food. Also used for parasitic plants.

Requiring two or more unrelated hosts for completing the life cycle of a rust.

Producing fusing gametes on separate and distinct mycelia.

Producing fusing gametes on the same mycelium.

The plant on or in which a parasite lives and from which it obtains its food.

Clear, translucent.

An epidermal leaf structure specialized for secretion or exudation of water; leaf opening at terminus of vein.

The abnormal increase in the number of cells without their enlargement.

The abnormal increase in the size of cells, causing abnormal development of an organ or tissue.

A single filament of a fungus mycelium.

The underdevelopment of cells, tissues, or organs.

A relationship between a plant and a causal agent in which the plant does not become diseased.

A structure developed within a plant cell as a result of infection by a virus, often useful in identifying the virus.

Time between infection by a pathogen and appearance of symptoms.

Determining presence of disease in a plant by removing buds or other parts for inoculation of a susceptible indicator plant that exhibits specific symptoms of a transmissible disease.

Process in which a pathogen enters, invades, or penetrates and establishes a parasitic relationship with a host plant.

Presence in numbers (e.g., of insects, mites, or nematodes). Do not confuse with "infection," a term that applies only to living, diseased plants or animals.

Pathogen or pathogen part (e.g., spores, mycelium) that infects plants.

Between the cells.

Between (leaf) veins.

Within the cells.

Ability of an otherwise susceptible variety of plant to escape infection because of the way it grows (e.g., early-maturing plants escape late-season diseases).