Glossary

A group of fungi that may consist of one cell or have filaments (hyphae) with few or no cross walls and that reproduce sexually by union of two sex cells.

Change from a normal flower to leafy structures. Characteristic of certain phytoplasma infections.

A disease produced by some unfavorable physical or environmental factors (e.g., light, temperature, water, soil nutrients, chemical, physical or mechanical injury).

Microorganisms found in phloem tissue that resemble mycoplasmas in all respects except that they cannot be grown on artificial nutrient media (yet). Formerly known as mycoplasmalike organism (MLO).

Injurious to plants.

A naked, multinucleate, vegetative (fungal) body capable of amoeboid motion.

Having several to many disease cycles in a growing season (contrasts with monocyclic).

The existence of several asexual spore stages in the life cycle of an organism.

The first infection of a plant, usually in the spring by an overwintering sexual pathogen propagule.

lnoculum, usually from an overwintering source, that initiates disease in the field, as opposed to inoculum that spreads disease during the season.

The part of an organism that may be spread so as to reproduce the organism.

A chemical applied to a plant surface in advance of the pathogen to prevent infection.

A mass of fungal hyphae and host tissue.

A local elevation of the epidermis that may rupture to expose the causal agent (e.g., rust, smut, white rust, etc.).

The asexual, globose or flask­shaped fruiting body of fungi that produces conidia.

Regulation forbidding sale or shipment of plants or plant parts, usually to prevent disease, insect, nematode, or weed invasion of an area.

A strain of a pathogen characterized by the limitation of its host range to certain species and varieties of plants.

The sum of the qualities of the host and causal agent that retard the activities of the causal agent.

Intercellular thallus branch that absorbs food and provides anchorage.

An aggregation of hyphae into a cordlike or rootlike strand.

The microenvironment in the soil, immediately around roots.

A single-celled animal and human disease- causing organism with a partial cell wall that has not been grown in culture.

Symptom of a disease characterized by yellowish or dead (necrotic) rings with green tissue inside them, as in certain virus diseases.

To remove and destroy undesired individual plants from a planting on the basis of disease infection, not being true-to-type, insect infestation, or other reason.

A disease symptom characterized by short, bunchy growth habit due to shortened internodes and no comparable reduction in leaf size.

Softening, discoloration, and often disintegration of succulent plant tissue as a result of fungal or bacterial infection.

Wrinkled, roughened.

Yellowish-brown or reddish-brown scar tissue (cork) on the surface of fruit.

Destroying all infested and infected plant parts; decontamination of tools, equipment, containers, work space, and hands.

An organism that derives its nourishment from dead organic matter.

Crustlike disease lesion.

A necrotic condition in which tissue is usually bleached and has the appearance of having been exposed to high temperatures.

A small, compact, hardened mass of hyphae that may bear fruiting bodies. Can help fungus survive adverse environments.

"Burning" of plant tissue from infection, lack or excess of some nutrient, sunburn, or other weather conditions.

Infection resulting from the spread of infectious material produced after a primary infection.

Nematodes that tunnel partially into roots, their heads entering to establish permanent feeding sites while their bodies remain outside. The nematode does not move after this. (Examples: citrus nematode, Tylenchulus semipenetrans.)

Nematode that tunnel into the roots, establishing permanent feeding sites from which they do not move. They may protrude from roots as they grow. (Examples: root-knot, Meloidogyne spp.; and cyst nematodes, Heterodera spp.)

To decline with maturity or age, often hastened by stress from environment or disease.

The curved, apical portion of a blighted stem typical from bacterial infections.

Disease symptom characterized by the dropping out of small, round fragments of leaves, making them look as if riddled by shot.