Common diseases occurring in many hosts. Symptoms are foliar spots, damping off, stem rots, and fruit rots.

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Castanea dentata

Was one of the three most prevalent trees in North America. Highly susceptible to chestnut blight. Due to chestnut blight, it is now an endangered species in Canada. It is being bred with Asian chestnut to produce resistance.

Spermatium

The male gametangia. Its nucleus passes into the ascogonium to form the dikaryon, in the producion of an ascus.

"Carbuncle disease"

A term coined in 1886 to refer to diseases characterized by a dark, sunken lesion. Common on the foliage of many plants, from deciduous trees to grasses. Each fungus is host specific. Includes several species of Colletotrichum. Penetrates hosts with an appressorium. There are often acervuli on the leaf surface.

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plural: Apothecia

An ascocarp. An open, cup or saucer-shaped structure where asci are exposed. Looks like an "upside down" mushroom. Found in white mould.

plural: Appressoria

A structure which forms from the germ tube during penetration. Forms at the junction between two host cells. After it forms, the spore dies. Uses enzymes to dissolve the cuticle and push it aside, forming a crater-shaped hole into which it presses itself. The cuticle glues it to the surface of the host. Produces a penetration peg.

Sac fungi

True fungi

A group of fungi classified by sexual structures. Produce ascospores in sacs; in ascocarps. May produce conidia with simple conidiophores or pycnidia. Septate mycelia.

Light, olive-coloured irregular spots on the lower surface of sepals and young leaves; mycelia grow beneath the epidermis. Lesions become darker and develop a velvety surface, then they become black and raised. Lesions can develop on the upper surface of older leaves. Infected fruit develop circular, velvety, olive-green lesions, which become darker and scabby. The fruit is misshapen, cracked, and drops prematurely.

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plural: Asci

A structure which produces ascospores. Found in ascocarps. An ascogonium fuses with an antheridium, producing a dikaryotic ascogenous hyphae. Nuclei fuse, producing a zygote. The crozier hook helps maintain dikaryotic state. Meiosis produces four haploid nuclei, which each undergo mitosis and walls form to produce eight haploid ascospores. There may be pressure in teh ascus which can shoot ascospores up to a metre away. After ascospores are ejected, the ascus can undergo another round of division to produce eight more ascospores.

Anamorph

Imperfect stage

The mitosporic, asexual stage of a fungi.

A disease caused by Rhynchosporium secalis.

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Anthracnose of bean

A disease caused by Colletotrichum lindemuthianum. Almost worldwide distribution. There was an oubreak in Canada in 1976 due to introduction of new races.

Poor seed germination, poor seedling vigour, and low yields. Seeds have low quality rating due to brown-black blemishes and sunken lesions. Seedlings of infected seeds have dark brown-black lesions on cotyledons and stems. Cotyledons senesce prematurely, and plant growth is stunted. Lesions may girdle the stem, killing the seedling. Time from infection of a healthy plant to symptoms is 4 - 9 days, depending on coniditions and host variety and age. Linear, dark, brick-red to black lesions form on veins on the undersides of leaves, and discolouration spreads to the upper side. Small, red-brown to black blemishes and circular, reddish brown lesions form on pods, which turn grey and become surrounded by a circular red-brown to black border. Severely infected pods may shrivel; these pods have infected seeds. Pink masses of spores may form on lesions in humid conditions.

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A disease. The pathogen forms a structure over the stomata of the host.

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"Two coats"

An ascus with two walls. Consists of a thin brittle outer wall, and a thick elastic inner wall. When spores are ready, the outer shell splits open and the inner wall takes up water, building up pressure that eventually shoots spores up to a metre away. Found only in pseudothecia.

A common disease, caused by Botrytis cinerea. Affects cherries. Symptoms are similar to brown rot. Causes fruit rot problems in the field and post-harvest in stone and pome fruits.

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Blossom blight, twig blight, twig canker, and brown fruit rot.

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Septoria brown spot

A disease caused by Septoria glycines. Not to be confused with bacterial leaf blight. Found in all soybean fields in Kentucky. Causes yield losses up to 15% in favourable conditions. Often plants can recover from early season infections with no permanent damage.

Small, 1/4 inch, irregular red-brown spots on both sides of unifoliate leaves 2 - 3 weeks after planting. Spots occur on trifoliate leaves later in the season, starting on the lower leaves and spreading upwards. Spots may coalesce to form black-brown irregular bltoches. Leaves yellow and drop.

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A disease caused by Cercospora carotae and Alternaria dauci.

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A disease caused by Colletotrichum acutatum.

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A leaf blight disease of celery caused by Cercospora apii. An important disease of celery, causing yield reduction.

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plural = Chasmothecia

Cleistothecium

An ascocarp. A closed structure with hyphal appendages, and one or more asci. Dark coloured with melanin for UV protection. Can survive teh winter. Found in powdery mildew.

A disease caused by Cryphonectria parasitica. Affects American chestnut. Introduced to the USA in 1904. Symptoms include cankers, with no foliar symptoms. Infected branches and stems die quickly. May be managed with hypovirulent strains of the parasite applied to cankers, to contain spread of the disease.

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Also known by its sexual stage, Glomerella cingulate.

A fungal pathogen that causes bean anthracnose. There are several races. Conidia are produced in acervuli with dark setae.

Deuteromycota

Asexual fungi

Imperfect fungi

An artificial grouping of organisms, because they are difficult to classify. The asexual stages of ascomycetes or basidiomycetes, but the sexual stages are absent or rare. Description is based on conidia or mycelial characteristics. Produces conidia and chlamydospores. Conidia are formed in pycnidia, acervuli, sporodochia, and synnema. Not all produce conidia. May produce sclerotia. Cause diseases including leaf spots, blights, fruit rots, anthracnoses, stem rots, root rots, and vascular wilts.

(n+n)

Containing paired, unfused, haploid nuclei. Dikaryotic hyphae are produced on the same mycelium that produces conidia. The nucleus of the antheridium passes into the ascogonium, but there is no fusion of the nuclei.

A disease caused by Agrostis stolonifera. Can be managed with Civitas + Harmonizer activated defense treatment.

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Vascular bundles turn brown. There are beetle galleries in the bark. Death of the elm tree; the tree dies standing and must be removed.

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Symptoms occur on the stem, foliage, and tubers. Lesions on tubers are sunken and irregular, often surrounded by a raised purple border. Tuber tissue beneath the lesion is leathery or corky with brown discolouration. Tuber lesions are dry.

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Symptoms occur on fruit, stem, and foliage. In young seedlings lesions may girdle the stem, leading to collar rot. Lesions on fruit can reach considerable size, and appear leathery and sunken, and may have concentric rings. Infected fruit often drop prematurely. Can result in reduced fruit size and number. Can reduce yields 9 - 52%.

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Time from infection to symptoms depends on conditions and host age and cultivar; usually within 5 - 7 days. Black-brown lesions, 1 - 2 mm in diameter enlarge and are often surrounded by a yellow halo. Lesions greater than 100 nm in diameter often become target spot lesions. Lesions on stems are often sunken and lens-shaped with a light centre with concentric rings.

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Forecasting Alternaria solani on Tomatoes

A method for timing fungicide control of early blight of tomato. Developed by Madden, Pennypacker, and MacNab, and was further modified by Pitbaldo to make TOMcast.

plural: Forma speciales

A fungal parasite or pathogen that is adapted to a specific plant host species. Have few or no morphological differences from each other. Analogous to pathovars of bacteria.

Impaired seed germination.

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Gametes

Sexual cells produced for dikaryon formation. Includes antheridia and ascogonia.

Germ tube

A structure that emerges from the spore during pre-penetration. Multiple germ tubes may form to increase the pathogen's chances. May produce an appressorium, or release enzymes to aid in penetration. It can find stomata by sensing gas gradeints, and can find wounds by sensing exudates such as polysaccharides.

Light pink to red mould grows down the ear. Cobs become spongy. Husks are bleached and cling to kernels. Perithecia may be visible as black spots. Impaired seed germination.

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A leaf spotting disease caused by Stagonospora nodorum.

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A disease caused by Magnaporthe grisea.

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plural: Haustoria

A feeding structure produced by fungi which punches into the epidermal cells of the host. Produced by powdery mildwe and late blight of potato. Haustoria have a wide variety of shapes.

(n+n)

Containing unfused nuclei from two or more genetically different cells.

Priming

A type of activated defense. When the cell recieves the signal, it arms its defenses against pathogens. Specific attack; defenses act specifically against the pathogen. Resistance activators include Civitas, Harmonizer, and butanediol.

A leaf spotting disease caused by Septoria sp. and Stagonospora sp.

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A disease. Plants that emerge from disease seeds are infected directly. Spores produced on infected plants can spread, causing additional infections. Favoured by high relative humidity, and temperatures around 20ºC. The disease moves up the plant and the head and kernels can become infected.

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A disease caused by Sclerotinia sclerotiorum.

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A leaf spotting disease. Severely infected leaves may die. The disease moves up the plant, and the head can become infected. Has two forms: net form and spot form.

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The more common form of net blotch. Caused by Pyrenophora teres f.sp. teres. Starts as tiny green or brown spots, which enlarge into narrow brown blotches with a cross-hatched apperance. Often tissue surrounding the lesion becomes yellow.

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A disease caused by Taphrina deformans. Affects hosts in the Prunus genus: peaches and almonds. Symptoms include discolouration and curling of leaves, later developing whitish bloom which is naked asci. Germination of conidia requires a minimum of 3 mm of rainfall followed by at least 12 days where conidia remain damp and temperatures are below 19ºC. Conidia germinate to produce hyphae which have intercellular growth during the 9 - 33 day incubation period. When symptoms develop, asci are produced at nighttime.

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A disease caused by Cladosporium paeonia.

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plural: Perithecia

An ascocarp. A flask-shaped structure with an ostiole at the tip. Forms beneath the surface of bark. Has perithecial walls, and unitunicate asci. Found in Dutch elm disease.

Also known by its asexual stage, Oidium sp.

Formly known as Sphaerotheca pannosa. An ascomycetes pathogen which causes powdery mildew of rose. Produces chasmothecia and conidia.

A disease caused by several genera of ascomycetes pathogens. Pathogens are host-specific biotrophs. Hosts include wheat, barley, cucurbits, grape, strawberry, rose, lilac, apple, and oak. Produce conidia, as well as ascospores formed in chasmothecia. Genera of pathogens are distinguished by the number of asci in the chasmothecium and morphology of its hyphal appendages. Mycelia grow on the surface of the plant, never invading host tissue. Nutrients are absorbed by haustoria.

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A disease caused by Blumeria graminis f.sp. hordei.

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A disease caused by Unicula necator. Symptoms include patches of white-gray powdery mycelial growth. Chasmothecia may appear as tiny dark specks in the mycelia. Symptoms are most common on the upper surface of leaves, young shoots and stems, buds, flowers, and young fruit.

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A disease caused by Podosphaera pannosa. Symptoms include patches of white-grey powdery mycelial growth. Chasmothecia may be visible as dark specks in the mycelia.

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A disease caused by Blumeria graminis f.sp. tritici.

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plural: Pseudothecia

An ascocarp. A cavity within a mass of hyphal tissue, usually a black stroma, in which asci are located. Similar to a perithecium, but asci are bitunicate. Found in apple scab.

"Quiet" infection

Latent infection

The host is infected with a pathogen, but there are no symptoms.

A disease caused by Sclerotinia sclerotiorum.

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A disease caused by Sclerotinia sclerotiorum. Affects sunflowers.

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plural: Sclerotia

A small, compact mass of pigmented mycelia that facilitates long-term survival of deuteromycetes fungi in the soil. May become detached and remain dormant until favourable growth conditions return. Composed of a thick, dense shell with thick and dark cells, and a core of thin colourless cells. Rich in oils, and has very little water. Can survive in dry conditions for several years. Germinates in favourable conditions to form fruiting bodies or mycelium with conidia.

A leaf blight of celery caused by Septoria apiicola. An important disease of celery, causing yield reduction. Affects mature celery plants, causing damage to leaves and reducing marketability of stalks. Infection is dependent on duration of leaf wetness, and favourable air temperatures (10 - 30ºC). Chlorotic spots on outer leaves become brown-red, and may coalesce to form large necrotic areas. Stalks may have brown lesions. Pycnidia form within lesions, giving them a speckled appearance, and may release conidia in cirrhi.

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Teleomorph

Perfect stage

The meiosporic, sexual stage of a fungi.

A leaf spotting disease caused by Cochliobus sativus.

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The less common form of net blotch. Caused by Pyrenophora teres f.sp. maculata.

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Induction

A type of activated defense. When the cell receives the signal, it prepares for defense against the pathogen. General attack; defenses act randomly. Resistance activators include phosphites, Actigard, Harmonizer, and silicon.

A leaf spotting disease caused by Pyrenophora tritici-repentis. Infection requires six hours of continuous leaf wetness, and disease development is greatest at 20 - 28ºC; it is a summer disease. Symptoms initially include small dark spots on lower leaves, then oval tan spots, 5 - 15 mm, form on veins, sometimes with a yellow halo. No pycnidia form on lesions.

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Bull's eye lesion

Characteristic lesions of early blight, with concentric circular rings of alternating bands of light and dark. Rings develop due to successive periods of conidia production that occur every night. May form on leaves, fruit, or stems.

"One coat"

An ascus with one wall. Found in perithecia.

Also known by its sexual stage, Spilocaea pomi.

An ascomycetes pathogen which causes ascomycetes apple scab. Overwinters in a pseudothecium in dead leaves; ascosporse mature as weather becomes favourable. Conidia have two cells, unequal in size.

A disease that occurs worldwide. Caused by Verticillium albo-atrum and V. dahliae. Affects over 200 species: vegetables, field crops, and trees. Most important in temperate regions. Favours warm, moist soils. Conidia enter young, actively growing plant roots directly, or through wounds. Pathogen enters the vascualr system xylem elements, resulting in plugging and vascualr wilt. Sapwood may appear brown.

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White rot

A monocyclic disease caused by Sclerotinia sclerotiorum.

Managed by trimming the canopy to limit moisture.

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Tan-brown lesiosn with fluffy white mycelium. Black sclerotia form in the mycelia and in the stem. Stem rot; foliage above lesiosn wilts and dies.

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