Plant Disease Management Handbook

An organism that is ordinarily saprophytic but under proper conditions may be parasitic.

Thick-walled, sexually-derived resting spore of oomycete fungi.

Image of Phytophthora cactorum with mycelium on the bottom, antheridium (male) to the left and the large round structure is the oogonium (female) which contains the product of fertilization, a thick-walled, resilient resting structured called an oospore.

Paul Reeser.

Thick-walled resting spore produced by some fungi, notably rusts and smuts, that germinates to form a basidium.

Teliospores (developed and developing) with paraphyses. Also shown are three urediniospores.

Photo by Peter R. Bristow

A fruiting body that produces asexual spores within a more or less spherical wall.

Sporangia of Phytophthora sp.

Melodie Putnam collection.

A group of fungi characterized by the pro duction of sexual spores on a clubshaped filament called the basidium.

Many mushroom producing fungi are basidiomycetes such as Armillaria.

Laura Sims, 2012.

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

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

A disease characterized by yellowing and stunting of affected parts (caused by fungi, virus, bacteria, or deficiency of essential elements).

An abnormal outgrowth from the surface of a stem or leaf.

Cherry leaves infected with certain viruses can develop enations on the underside of the leaf.

Jay W. Pscheidt, 2016.

Disease symptom characterized by nonuniform foliage coloration, with a more or less distinct intermingling of normal and light green or yellowish patches. Usually caused by a virus.

Very distinct patches of dark and light green.

Jay W. Pscheidt, 2020.