Plant Pathology: Midterm + Lab Quiz 5

Abiotic
Nonliving, or caused by a nonliving agent.
Acervulus
A sub-epidermal, saucer-shaped asexual fruiting body producing conidia on short conidiophores.
Adsorbents
A control method for mycotoxins. Controls insects and microbes.
Aflasafe
A biocontrol method for Aspergillus flavus used in Africa.
Aflatoxin

A. flavus toxin”

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An important mycotoxin produced by Aspergillus flavus and A. parasiticus. It can cause anorexia, specific visceral haemorrhage, embryo toxicity, vomiting, reproductive problems, anemia, immunosuppression, jaundice, liver cancer, and death. Through histopathology, it was found that the most common symptoms include fatty liver, necrosis of the liver, and hyperplasia of the bile duct. It decreases the activity of various enzymes requried for digestion of carbohydrates, protein, fat, and nucleic acids. Pre- and post-harvest contamination of cereals, figs, oilseeds, nuts, tobacco, corn, and other commodities is common. There must be < 0.5 ?g in milk for human consumption. There are four main types which fluoresce blue or green under UV light: B1, B2, G1, and G2.

Aflatoxin B1
The major type of aflatoxin. It is regulated in the USA at 20 ?g/kg in agricultural products for human food. A carcinogen, one of the most potent liver cancer-inducing agents known. In India 106 people died in 1974 from contaminated corn. The toxin is excreted in urine within 96 hours in animals. It has synergistic interaction when combined with ochratoxin A.
Agriculture and Agri-Food Canada
Have developed guidelines for DON intake in livestock. The limit for cattle and horses is 1 ppm, and for beef cattle, sheep, and poulty 5 ppm.
Albert Hofmann
Accidentally created LSD in 1943 from ergot alkaloid precursors. He absorbed a small amount through his fingertips and discovered its hallucinogenic properties.
Albugo candida
A chromista pathogen which causes white rust. Produces zoospores.
Alphascan
A machine which removes ergot from grain. It sorts seeds by colour, separating infected seeds from healthy.
Alternaria solani
A deuteromycetes pathogen which causes early blight. Conidia have long tails.
Anamorph
The imperfect, asexual stage of a fungus.
Antheridium
The male sex cell which can fertilize an ascogonium to form an ascus.
Anthracnose

A disease that appears as black, sunken lesions on leaf, stem, or fruit, caused by fungi that produce asexual spores in an acervulus.

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Apothecium
An open cup- or saucer-shaped ascocarp. Ascospors form in a dense layer on the concave surface. Occurs in ascomycetes including cup fungi, which typically produce sclerotia or pseudothecia, out of which the apothecium germinates.
Apple scab
A polycyclic disease caused by Venturia inaequalis. Occurs every year in eastern Canada. Causes losses from fruit infections, affecting fruit quality and storability, or from defoliation and loss of tree vigour and winter survival. Occurs everywhere that apples are grown, especially in North America and Western Europe.
Apple scab conditions
Favours cool, wet conditions in the spring. As temperatures increase, less time of continual leaf wetness is needed for spores to germinate. Occurs in relatively cool, humid climates.
Apple scab dissemination
Ascospores are ejected from pseudothecia in rain or heavy dew, and dispersed by wind and rain. Conidia form on lesions and are dispersed by wind and rain.
Apple scab hosts
Affects apples and ornamental crab apples.
Apple scab infection
Primary infections are caused by ascospores, when trees break bud dormancy in the spring and there is green tissue. Secondary infections are caused by conidia throughout the season.
Apple scab management
Often based on repeated curative fungicide applications; high cost, and can lead to resistance in the pathogen. Fungicides may have protectant, pre-symptomatic, or post-symptomatic activity. Use tolerant cultivars. Prune for improved aeration and spray coverage. Do not over-fertilize. Irrigate in dry periods. Burn, mow, till, or apply urea to the leaf litter; this can reduce ascospores as much as 95%. A Degree Days Celsius model is used to predict apple scab.
Apple scab survival
Venturia inaequalis overwinters in pseudothecia on dead leaves which form in September and mature in May.
Apple scab symptoms

Young leaves and fruits are more susceptible. Pale, irregular, small scab lesions form on leaves or flowers, which become circular and olive-coloured with a velvety texture that is conidiophores. The fungus forms a solid layer between the cuticle and epidermal cells. Severely infected leaves or flowers may drop. Lesions of early fruit infections may crack and lead to fruit drop. Lesions of late fruit infections are black, circular, and very small, appearing in storage. Can cause small, misshapen fruits, and weakening of next year’s fruit buds. The tree rarely dies.

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Appressorium
The swollen tip of hyphae or germ tube that facilitates attachment and penetration of the host by a fungus.
Ascocarp
Structures of ascomycetes in which asci are produced. Includes chasmothecia, perithecia, apothecia, and pseudothecia.
Ascogenous hyphae
Hyphae produced when an ascogonium is fertilized by an antheridium or spermatium. Has two nuclei: one female and one male. The tip of each hyphae develops into an ascus.
Ascogonium
The female sex cell of ascomycetes which is fertilized by an antheridium or spermatium to form ascogenous hyphae.
Ascomycetes

Sac fungi

A large group of fungi which have ascocarps. Ascospores are produced by sexual fertilization between an antheridium and an ascogonium, which develops into an ascus.

Ascospore
A sexually produced spore borne in an ascus. Vary in size, shape, and colour.
Ascus
A structure that produces ascospores. Forms from ascogenous hyphae produced when the ascogonium is fertilized by an antheridium or a spermatium. The two nuclei fuse to form a zygote. Meiosis occurs, followed by a mitotic division and free-cell formation to produce eight ascospores. The crozier hook maintains dikaryotic state in the ascus initial, so it may repeat the process. Most asci can shoot spores away with hydraulic pressure, up to several centimetres.
Aspergillus flavus
A mould fungus. Many strains produce aflatoxins when temperature is 15 – 37?C with high humidity or grain moisture. A common contaminant in agriculture; it can be prevalent in fields. Some nontoxic strains have numerous valuable applications such as production of proteases used in baking, pharmaceuticals, and animal feed.
Aspergillus parasiticus
Many strains produce aflatoxin.
Aspergillus sp.
A soft rot of apples. Produces patulin. Often found in apples during wet growing seasons.
Aster yellows

A disease caused by Candidatus Phytoplasma asteris. A potentially polycyclic disease. Spread by leafhoppers. Symptoms include leaf proliferation.

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Ataxia
Lack of muscle coordination. Can be caused by ergot alkaloid.
Bacillus subtilis
May be used as a biological control for powdery mildew of rose. Includes Serenade ®.
Bacteria
Single-celled prokaryotes. There are approximately 1,600 known species, 100 of which cause plant diseases. Have a single circular DNA strand floating freely in cytoplasm, and many have additional plasmids. Have 70S or 80S ribosomes. Lack most internal structures found in eukaryotes, but have a cell wall that is rigid but does not contain cellulose. Exist as single cells or in clusters. Reproduce asexually by binary fission, with generation times as short as 20 minutes. Lack distinctive morphological features, and are classified based on stains, cell walls, physiology, and DNA sequences. Groups of bacteria based on shape include: coccus, coccobacillus, vibrio, bacillus, spirillum, and spirochete.
Bean anthracnose

A diasease caused by Colletotrichum lindemuthianum.

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Beetle gallery
A characteristic sign of elm bark beetle and a symptom of Dutch elm disease. The female beetle bores into the bark of a dead or dying elm tree and creates a tunnel into which she lays her eggs. The eggs hatch, creating tunnels perpendicular to the mother’s tunnel. Ophiostoma sp. survives in the tunnels created by the larvae, and conidia may be deposited on beetles as they leave the tree.
Biological contorl
Total or partial inhibition or destruction of pathogen populations by other organisms.
Biotroph
An organism that can live and multiply only on another living organism.
Bitunicate asci

“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.

Blumeria graminis
Used to be known as Erysiphe graminis. An ascomycetes pathogen that causes powdery mildew of cereals.
Bordeaux mixture
Invented in 1885 by Pierre Millardet. A mixture of CuSO4 and lime. Deters passersby from eating grapes; it is visible and bitter-tasting.
Brown rot
A polycyclic disease caused by Monilinia fructicola. Globally distributed.
Brown rot dissemination
Conidia produced in mummies are dispersed during wet weather.
Brown rot hosts
Affects stone fruits.
Brown rot survival
Overwinters in mummies or mummyberries.
Brown rot symptoms

Can have a latent infection, and symptoms do not appear until fruits are mature. There is blossom blight, or brown rot of fruit.

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Canadian Grain Commission

Allows only very low levels of fusarium-damaged kernels in feed grains, and none in malting barley. Reported that an aggressive strain of Fusarium graminearum is moving westward through the prairie provinces.

The threshold of ergot levels are based on type and class of grain:

No. 1 grain = 0.01 – 0.05

No. 2 grain = 0.02 – 0.06

No. 3 grain = 0.04 – 0.33

Candidatus Phytoplasma asteris
A prokaryotic mollicute pathogen which causes aster yellows.
Canker
A necrotic, often sunken lesion on a stem, branch, or twig of a plant.
Canned asparagus
Up to 10% can harbour asparagus beetles or egg sacs.
Canned pineapple
Can be packed with up to 20% of mouldy pineapple.
Cellulose
A polysaccharide composed of hundreds of glucose molecules linked in a chain and found in plant cell walls.
Chasmothecium

plural: Chasmothecia

Cleistotheicum

A closed spherical ascocarp structure with hyphal appendages, and one or more asci. Dark coloued with melanin for UV protection. Can survive the winter. Found in powdery mildews.

Cheese
It is one of the foods that is highest in mycotoxins. It acquires mycotoxins via direct contamination or from the milk that it is made from. No food poisoning cases have been reported.
Chitin
A complex, N-containing carbohydrate, derived from N-acetyl-D-glucosamine, forming the hard outer shell of insects, crustaceans, arthropods, fungi, and some algae.
Chlamydospore
A thick-walled asexual spore formed by the modification of a cell of a fungus hyphae.
Chocolate
Can contain up to 60 insect fragments per 100 g.
Christine Johanna Buisman
A Dutch scientist who identified Dutch elm disease in Ohio in 1930.
Cinnamon
Can carry up to 1 mg of animal excrement per pound.
Claviceps sp.
Some species produce ergot alkaloids in their sclerotia.
Clubroot of crucifer

A disease caused by Plasmodiophora brassicae. Controlled with bait crops.

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Colletotrichum lindemuthianum
A deuteromycetes pathogen which causes bean anthracnose. Has races. Produces conidia in acervuli.
Conidia
Non-motile, asexual spores of deuteromycetes, ascomycetes, and basidiomycetes. Have a wide variety of shapes, sizes, and colours. Produced by conidiophores. Includes pycnidio spores. Take less energy to produce than ascospores.
Conidiophore
A specialized hyphae on which one or more conidia are produced.
Convulsive ergotism
A type of ergotism that causes convulsions, hallucinations, and burning and freezing sensation.
Crown gall

A disease caused by Rhizobacterium radiobacter.

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Crozier hook
A structure in a developing ascus which maintains the dikaryotic state of the ascus, so it may produce ascospores another time. Some ascomycota lack them.
Damping-off
Destruction of seedlings near the soil line, resulting in seedlings falling over onto the ground.
Degree-days (DD)

Used to calculate ascospore maturation of Venturia inaequalis. 50 – 400 DD in base 5?C is the highest risk time for ascospore ejection. Growers can obtain site-specific forecast of ascospore maturity and discharge.

DD = ((Tmax + Tmin) / 2) – Tbase

Deoxynivalenol (DON)

Vomitoxin

An important mycotoxin produed by Gibberella zeae, with optimal production at 24?C. It can be found in grain affected by gibberella ear rot or fusarium head blight, common in corn, barley, wheat, and oats. Contamination mostly occurs in the field. It has synergistic interactions when combined with T-2 toxin. One of the least toxic mycotoxins, but in high amounts in combination with nivalenol, it can cause feed refusal and vomiting in pigs and cattle. Chickens are not as sensitive. Agriculture and Agri-Food Canada have guidelines for DON intake in livestock. It affects the baking quality of wheat and the malting and brewing qualities of malt barley. It can be detected with laboratory tests.

Deuteromycetes

Imperfect fungus

Mitosporic fungus

Fungus that is not known to produce sexual spores.

DONcast ®
A tool for wheat producers which provides a means of predicting DON concentration at wheat harvest. Uses forecasted and historical weather data. Allows producers to make informed management decisions about fungicide applications for reducing DON concentrations in grains. Helps strategize which fields should be harvested first, and provides a warning of DON concentrations toward better or alternative market destinations before harvest.
Downy mildew

A plant disease in which sporangiophores are spores of a fungus appear as downy growth on the lower surface of leaves and stems, fruit, etc., caused by fungi in the family Peronosporaceae.

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Dutch elm disease (DED)
A polycyclic disease caused by Ophiostoma species including O. ulmi and O. novo-ulmi. First identified in the Netherlands in 1921. Has been found in Europe, North America, and Asia.
Dutch elm disease conditions
Production of conidia occurs at 20?C. Production of perithecia occurs at 8 – 10?C.
Dutch elm disease dissemination
Sticky conidia or ascospores in sticky drops are vectored on elm bark beetles. An elm tree can get the disease from root grafts with infected trees within 7 metres. The disease can be spread on pruning equipment; this is common.
Dutch elm disease hosts
Affects many species of elm, including Ulmus americana. Asian elm species are less susceptible, and have been used in breeding programs to develop resistance.
Dutch elm disease management
Avoid monoculture of elm. Remove all dying or dead branches, trees, and cut wood, and burn, chip, or burry it. Break root grafts between adjacent elm trees. Diligent inspection of elms is required. Preventative fungicides can be injected into the tree, but this is expensive. Clean pruning equipment with 10% solution of bleach. Biocontrol. Insecticides are not effective.
Dutch elm disease survival
Ophiostoma sp. overwinter as mycelia and synnemata in the bark and outer wood of dying or recently dead elm trees.
Dutch elm disease symptoms

Symptoms are similar to verticillium wilt. Discontinuous brown discolouration in the outer layer of wood below the bark. There are beetle galleries in the bark. Infection causes cease of sap flow, causing foliar symptoms: yellowing and wilting of the leaves, which turn brown, curl, and drop. Symptoms can spread throughout the crown, and the tree can die in a year. Trees infected in the spring die faster.

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Early blight

A disease caused by Alternaria solani. Symptoms include bull’s eye lesions. Controlled using TOMcast and DSVs.

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Elm bark beetle
A vector of Dutch elm disease. Sticky conidia and ascospores stick to the beetle and they carry them to other elm trees. The female bores in the bark of a dead or dying elm tree and creates a beetle gallery. Beetles with conidia on them can spread the disease to elm trees that it feeds on. Includes European elm bark beetle (Scolytus multistriatus) and native elm bark beetle (Hylurgopinus rifipes).
Equine leukoencephalomalacia (ELEM)
A fatal disease in horses caused by funnmonisins. Symptoms include blindness, drowsiness, liquefaction of brain tissue, and esophageal cancer.
Ergot

A plant disease that produces ergot alkaloids. It can occur in wheat (red, hard white, soft white, and durum), rye, oats, barley, and triticale. The amount that is allowed in grains is regulated by the Canadian Grain Commission, based on the type and class of grain. Grains with ergot can be removed with an Alphascan or by soaking seeds in saltwater; infected seeds float.

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Ergot alkaloids
An important mycotoxin. Produced in the sclerotia of Claviceps species as a toxic mixture of alkaloids. Associated with animal and human diseases, including ergotism, suppression of lactation, ataxia, and death. It stops blood flow. Has some beneficial properties: it was used in 1583 in small doses to produce uterine contractions for childbirth, in 1824 it was used to control postpartum hemorrhage, and in 1920 it alleviated migraine headaches. There are four main groups: claviceps, ergopeptides, lysergic acids, and lysergic acid amides.
Ergotism

St. Anthony’s fire

A disease caused by ergot alkaloids, produced in ergot of rye. Outbreaks have been reported since 857 AD. Modern methods of grain cleaning have almost eliminated it as a human disease. Includes gangrenous ergotism and convulsive ergotism.

Erwinia amylovora
A prokaryotic pathogen that causes fireblight.
Fireblight

A polycyclic disease caused by Erwinia amylovora. Affects Rosaceae plants, especially apples. Sings include bacterial exudate. Symptoms include shepherd’s crook and cankers.

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Flagellum

Cilium

A whip-like structure projecting form a bacterium or zoospore, functioning as an organ of locomotion.

Forma specialis (f.sp.)
Analogous to pathovar. Strains of fungal pathogens that have few differences, but are adapted to specific hosts.
Free-cell formation
The process by which each nucleus in an ascus develops into a separate ascospore.
Fumonisins
An important mycotoxin. Produced by Fusarium species. In animals it causes decreased performance, immunosuppression, neurotoxicity, hepatotoxicity, nephrotoxicity, porcine pulmonary edema, carcinogenicity, and equine leukoencephalomalacia. Can cause esophageal cancer and liver and kidney problems.
Fusarium-damaged kernels (FDK)

Tombstone kernels

Grain kernels which are damaged by Fusarium sp. Shrivelled, lightweight, white-pink. They can be lost during harvest or seed cleaning due to their light weight, and can lower seed grade. You can get 10x decrease in number by adjusting the fan in the combine. Most apparent in wheat, and less apparent in hulled barley. They contain mycotoxins including fumonisins and DON. Have reduced germination and seedling vigour, and produce infected plants that lead to the spread of Fusarium graminearum.

Percentage of FDK acceptable depends on type and class of grain:

No. 1 grain = 0.25%

No. 2 grain = 1.0%

No. 3 grain = 2.0%

Fusarium graminearum
The asexual stage of Gibberella zeae. Causes fusarium head blight. Produce mycotoxins including zearalenone, DON, and nivalenol. Conidia are sickle-shaped, 35 – 62 ?m.
Fusarium head blight (FHB)

Scab

Fusarium ear rot

A disease caused by several Fusarium species including F. graminearum. Its range includes the Canadian Prairies. The first outbreak was in Manitoba in 1993. Causes reduction in yield, grade, and end-use qualitiy, restricts crop rotations, and has expensive control measures. There can be contamination with fumonisins. Epidemics occur every 4 – 6 years. Epidemics occured in 1989 and 1996.

Fusarium head blight conidtions
Sporulation and infections occur in warm, wet conditions during flowering. A 12 hour period of precipitation or high humidity, 16 – 30?C, is needed for germination, with an optimum for Fusarium graminearum at 25 – 28?C.
Fusarium head blight dissemination
Spores of Fusarium graminearum are spread by wind and rain-splash.
Fusarium head blight hosts
Affects wheat, barley, oats, rye, corn, triticale, canary seed, and some forage grasses.
Fusarium head blight infection
Most likely to occur in July when florets are open and the host is susceptible. A spore comes into contact with a floret, and the pathogen enters through wounds inflicted by hail, birds, or insects.
Fusarium head blight management
Plant clean, vigorous seed. Rotate with non-susceptible hosts for 1 – 2 year. Avoid seeding into wheat, barley, or corn stubble, or adjacent to fields that had fusarium head blight. Control grassy weeds. Chop and till residue. Use resistant crops. Adjust combine air velocity to blow out fusarium damaged kernels, and do this do not plant cereals for two years afterwards. Preventative foliar fungicides early in flowering. Seed treatments limit seedling blight but does not stop secondary infections.
Fusarium head blight survival
Fusarium graminearum overwinters as spores or mycelia in fusarium damaged kernels and crop debris. Can survive in roots of pulses and oilseeds.
Fusarium head blight symptoms

In humid coniditions symptoms can occur within 3 days of infection. The head is green, but water-soaked brown spots appear at the base of glumes, after which glumes become bleached. In humid weather, white-pink-orange spores form on the base of glumes or over the infected head. In early infections, production of fusarium-damaged kernels can occur on a few spikelets or the entire head.

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Fusarium sp.
A fungus that produces fumonisins. Affects corn, wheat, and other cereals, in field or in storage. It does not produce fumonisins if moisture is below 19%. Avoided by harvesting when seed moisture is below 18%, and reducing harvest speed to separate damaged kernels, and turning up the fan speed on the combine to blow out damaged kernels.
Gall
A swelling or overgrowth produced on a plant as a result of infection by certain pathogens.
Gangrenous ergotism
A type of ergotism that causes a burning and freezing sensation and, if severe, gangrene.
Gastroenteritis
A stomach illness in livestock which can be caused by mycotoxins.
Gibberella ear rot

Head blight of maize

Scab of maize

Ear rot of maize

Red ear rot

Pink ear rot

Cobweb disease

Stalk rot

Pink mould

Graminearum ear rot

A disease caused by Gibberella zeae. Not to be confused with pinking of white maize. Common in maize production areas worldwide. Causes direct losses and produce mycotoxins in storage. Epidemics occur every year.

Gibberella ear rot hosts
Can affect oats, soybean, barley, lupins, tobacco, rice, pearl millet, millet, rye, sorghum, wheat, maize, cotton, medic, common bean, pea, nightshade, clover, and broad bean. Crops are being bred for resistance to primary infection, subsequent colonization, developing kernels, and reduced accumulation of mycotoxin and yield tolerance: these are all multi-trait genes, making it harder to breed. Transgenic breeding has been done with antibodies of DON from bacterial enzymes that degrade the mycotoxin.
Gibberella ear rot infection
Only young ears are susceptible. The pathogen infects silks and grows into the ear during grain fill.
Gibberella ear rot management
Tillage, burning, or removal of residue to reduce overwintering. Staggering planting of crops and variety maturity so not all crops flower at once. Fungicide sprays based on weather (reduces incidence by 50 – 60%). Rotate with non-susceptible crops to reduce inoculum. Use resistant hybrids that have good husk coverage.
Gibberella ear rot survival
Gibberella zeae overwinters in plant debris.
Gibberella ear rot symptoms

Pink-red mould appears at the tip of the ear. In early infection, the mould tighly adheres together the cob, husk, and silks. Infection can reach the base of the ear in wet conditions. Blue-black specks which are perithecia may develop on husks and ear shanks.

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Gibberella zeae
Also known by its asexual stage, Fusarium graminearum. An ascomycetes pathogen that causes gibberella ear rot. Produces mycotoxins including T-2 toxin, zearalenone, and DON. Produces genetic recombination, and sexual spores are capable of dispersing greater distance than asexual spores. Ascospores are produced in a perithecium, 150 – 350 ?m in diameter; tens of thousands may be produced by one ear of corn.
Haustorium
A simple or branched projection of hyphae into host cells that acts as an absorbing organ. Form from branches of mycelia of powdery mildew.
Hypertrophy
A plant overgrowth due to abnormal cell enlargement.
Incubation period
The period of time between penetration of a host by a pathogen and the first appearance of symptoms in the host.
Inoculum
The pathogen or its parts that can cause infection. The portion of individual pathogens that are brought into contact with the host.
Irradiation
A control method for mycotoxins. Controls insects and microbes.
Laminitis
A disease of livestock that is caused by a mycotoxin. A part in the hoof swells, and causes pain and the animal has a characteristic leaned-back stance. Can affect horses and cattle.
Late blight of potato

A polycyclic disease caused by Phytophthora infestans. Caused the Irish potato famine.

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Latent infection

Quiescent infection

Symptoms of brown rot do not appear until fruits mature. Makes it difficult to control the disease, since the fungus is deep within host tissues.

Lysergic acid diethylamide (LSD)
An illegal drug that was accidentally created by Albert Hofmann in 1943 from precursors in ergot alkaloids.
Maraschino cherries
Up to 5% can legally contain maggots.
Marie Beatrice Schwartz
A Dutch scientist who first identified the causal agent of Dutch elm disease.
Mollicute

“Soft skin”

Gram-positive bacteria which lack a cell wall. The smallest and simplest self-replicating prokaryotes. 0.3 – 0.5 ?m in size. Vary in shape. Reproduce asexually by binary fission. Resistant to antibiotics including penicillin which target cell wall formation. Usually have a smaller genome than other bacteria. Include spiroplasmas and phytoplasmas.

Monilina fructicola
An ascomycetes pathogen which causes brown rot. Mycelia of the pathogen remain alive in tissues during latent infection. Can complete an infection cycle in a week. Produce ascospores in an apothecium.
Monoculture
When plants of the same species are grown in close proximity with few other types of plants present. People create them for aesthetic or production reasons. They are susceptible to disease outbreaks.
Mummy
Desiccated, shriveled remains of fruits affected by brown rot from previous seasons. Brown rot survives in mummies. Those which fall in the spring produce more conidia than those that fall in the fall. Mummies are often buried, but apothecia can form in some mummies 1 – 3 years after burial.
Monocyclic
Having one cycle per season.
Mycotoxicology
The study of mycotoxins.
Mycotoxicose
An animal disease caused by a mycotoxin. Symptoms in humans can include food poisoning, vomiting, nausea, anorexia, appeptite suppression, protein synthesis inhibition, headache, abdominal pain, chills, convulsions, precocious pubertal changes, breast enlargement in boys, jaundice, and carcinoma of the liver. In livestock it can cause gastroenteritis, intestinal hemorrhages, impaired rumen funciton, diarrhea, ketosis, irregular heats, low conception raites, ovarian cysts, embryonic loss, milk contamination, decreased milk production, mastitis, decreased feed intake, lower milk production, decreased feed efficiency, and laminitis. Severity of symptoms depends on type of mycotoxin, exposure concentration and duration, organs affected, other compounds, type of fungus, interactions with microbes, and the species, health status, and age of the animal.
Mycotoxin
The term was coined in 1963 when Turkey X disease occured in England. Fungal metabolites which cause lowered performance, sickness, or death in humans or animals. They are typically ingested in contaminated food, but also by skin and respiration, causing mycotoxicoses. Compounds with low molecualr weight, not visible by eye. There are 300 – 400 known mycotoxins, and approximately a dozen regularly receive attention as threats to human or animal health; they are a huge impact on safety, health, and economics. Most are not destroyed in milling, food processing, cooking, baking, malting, ethanol production, freezing, or the digestive system. Not all moulds produce mycotoxins; production is limited to a small number of speices including ascomycetes when under conducive temperatures and moisture conditions. Production of a certain mycotoxin is often limited to one species or strain, and many of these species are naturally present in the soil and crops. One species may produce several mycotoxins. They are secondary metabolites, produced to suppress competition, or to discourage insects, microbes, nematodes, or animals (including humans) from eating the fungus. Cause $5 billion of losses annually in North America. Can be managed by controlling moisture and temperatures in fields, cleaning equipment, crop rotation, genetic resistance, fungicides, biological control, insect control, biocontrols, mould inhibitors, drying, refrigeration, irradiation, absorbents, avoiding mixing old grain with new grain, and separation.
Mycotoxin contamination
Food is generally contaminated with mycotoxins during warm temperatures and high moisture. It can occur prior to harvest, or during harvest, storage, transportation, or processing. Often several moulds producing mycotoxins can be present in one feed mix.
Naked asci
Asci that do not form in an ascocarp. Occurs in yeasts and leaf curl fungi.
Necrotroph
A microorganism feeding only on dead organic tissues.
Nivalenol
A mycotoxin produced by Fusarium graminearum. It can be found in grain affected by fusarium head blight. In high amounts in combination with DON, it can cause feed refusal and vomiting in pigs and cattle. Chickens are not as sensitive.
Obligate parasite
A parasite that in nature can grow and multiply on or in living organisms.
Ochratoxin A
An important mycotoxin discovered in the 1960s. Produced by Penicillium verrucosum. A nephrotoxin that causes kidney damage in pigs and humans. A neurotoxin, and can contribute to neurological diseases including Alzheimer’s. Causes liver necrosis, immunosuppression, and carcinogenic effects. It is linked to testicular cancer. It affects mostly poultry, causing reduced weight gain, weak egg shells, and kidney disease. It is carried through the food chain, and can be transferred by milk, blood, and meat. It has synergistic interactions when combined with aflatoxin B1.
Oomycete

Water mould

A fungus-like chromista that produces oospores.

Oospore
A sexual spore produced by the union of two morphologically different gametangia: oogonium and antheridium.
Ophiostoma novo-ulmi
An ascomycetes pathogen that causes Dutch elm disease. A more aggressive pathogen than O. ulmi, replacing it in the 20th century. It killed many elms that had survived the Duth elm disease epidemic in the 1900s, and has devastated elms in Europe and North America since the late 1960s. Spread into Ontario and Manitoba, but Alberta has not yet been infected due to quarantine measures.
Ophiostoma sp.
An ascomycetes pathogen which causes Dutch elm disease. Parasites when the tree is living, and saprophytes when the tree is dead. Mycelia are creamy white with haploid nuclei. Conidia are small, white, oval, and formed in conidiophores in xylem vessels and carried in xylem flow to spread throughout the tree. Sticky conidia are produced on synnemata in beetle galleries, sticking to beetle vectors. Have long-necked perithecia that form in bark singly or in groups. Ascospores are discharged and accumulate in sticky drops disseminated by elm bark beetle vectors. Produce enzymes that degrade plant cell walls and lead to formation of tyloses.
Ophiostoma ulmi
An ascomycetes pathogen which caused the relatively mild, original Dutch elm disease epidemic in Europe and North America in the mid-1900s. Introduced to North America in 1920 in elm logs.
Oregano
Can legally contain up to 1,250 insect fragments per 10 g.
Ostiole
The opening or pore in a perithecium.
Parasite
An organism living in or on another living organism, and obtains its food from the latter.
Pathogen
An entity that can incite disease.
Pathovar
In bacteria, a subspecies or group of strains that can infect only plants within a certain genus or species.
Patulin
An important mycotoxin. Produced by Aspergillus sp. and Penicillium sp. soft rots. It is relatively resistant to short heat treatment such as pasteurization, particularly in acidic pH. Found in apple juice and apple-related products. In an apple, it is distributed only 1 cm around the damaged area; it can sometimes  be cut out. In grapes, plums, cherries, and berries it cannot be cut out. The threshold limit is 50 ?g/kg.
Peach leaf curl

A disease caused by Taphrina deformans. Symptoms include curling of the leaves.

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Peanut butter
Can contain one rodent hair per 100 g.
Penicillium citreoviride
A fungus which produces the mycotoxins that cause yellow rice disease.
Penicillium sp.
A soft rot of apples. Produces patulin. Often found in apples during wet growing seasons.
Penicillium verrucosum
A fungus which produces ochratoxin A. Contamination usually occurs with moisture around 14% in wheat, corn, soybeans, oats, barley, coffee, beans, or grapes. There are no visual symptoms of contamination.
Perithecium
A closed globular or flask-shaped ascocarp of the Pyrenomycetes. Has an ostiole.
Phytophthora infestans
A partially biotrophic chromista pathogen which causes late blight of potato. Produces oospores, sporangia, and zoospores.
Phytoplasma
Mollicutes that infect plants and cannot be grown in culture.
Pierre Millardet
Invented Bordeaux mixture in 1885 when he noticed grape vines near the road has less powdery mildew.
Pinking

A physiolgoical disease in corn that causes naturally white kernels to turn pink. Can be confused with gibberella ear rot.

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Plasmodium
A naked, slimy mass of protoplasm containing numerous nuclei.
Plasmodiophora brassicae
A biotrophic chromista pathogen which causes clubroot of crucifer. Not a slime mould. Produces resting spores that make zoospores. Its feeding structure is a plasmodium root rot.
Polycyclic
Completes many life or disease cycles in one year.
Post-symptomatic activity

Curative activity

Fungicides used for apple scab to prevent or inhibit further production of conidia when applied to sporulating scab lesions. Includes Flint.

Potential ascospore dose (PAD)
A method of estimating the quantity of ascospores of Venturia inaequalis, based on sampling of leaves in the fall.
Powdery mildew

Among the most common, widespread, and easily recognizable plant diseases. Affects over 9,000 species including rose, grape, and grasses. Obligate biotrophic, polycyclic pathogens that grow on living host tissue and are host-specific. White mycelia grow on the plant surface, absorbing nutrients through haustoria. Mycelia seem powdery when conidia appear. Conidia can germinate in dry conditions. Chasmothecia may form later in development, white at first, but turn yellow-brown then black. Susceptibility is the greatest in succulent tissue, 15 – 24?C, and humid.

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Powdery mildew of cereals

A disease cauesd by Blumeria graminis.

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Powdery mildew of grape

A disease caused by Unicula necator. Downy mycelia form on the leaf surface with haustoria.

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Powdery mildew of rose
A disease caused primarily by Sphaerotheca pannosa var. rosae. Occurs wherever roses are grown. Affects greenhouse and outdoor plants.
Powdery mildew of rose conditions
Powdery mildew epidemics can occur during warm (27?C), dry (40 – 70%) weather when nights are cool (16?C) and damp (90 – 99%), most commonly in the late summer or fall. The spore can germinate at 5 – 25?C, with an optimum at 22?C and relative humidity 23 – 99%, with little free moisture.
Powdery mildew of rose dissemination
The conidia of Sphaerotheca pannosa var. rosae are vectored on the wind, splashing water, or on insects, mites, or snails. The ascospores are vectored by wind or rain splash.
Powdery mildew of rose hosts
Affects nearly all species and cultivars of rose, as well as climbers, small-flowered ramblers, floribundas, polyanthas, hybrid tea roses, and grandifloras. In some cultivars the pathogen is unable to produce chasmothecia.
Powdery mildew of rose infection
The conidia or the ascospores of Sphaerotheca pannosa var. rosae land on the leaf and initiate a new disease cycle. Both spore types produce an appressorium and penetration peg, which form a globose haustorium that allows the fungus to grow a mycelium that produces additional haustoria.
Powdery mildew of rose management
Use diseae-free plants and resistant cultivars. Prune plants in the fall and spring, and burn the trimmings to reduce overwintering. Grow in good soil, not near any larger plants. Use a low planting density. Do not work in fields when wet. Do not over-fertilize. Irrigate thoroughly in a way that does not wet the foliage. Protects plants during the winter. Destroy any wild roses in the area. Fungicide application on all parts of the plant, with a detergent or surfactant in the tank mix to improve its stick to mycelia and conidiophores. Vaporised sulfur or dust is a good control in greenhouses, but is risky because burned sulfur can be toxic to rose leaves. Defense-activating compounds such as Actigard. Biolgoical control using Bacillus subtilis.
Powdery mildew of rose survival
Overwinters as mycelia in dormant buds, or as chasmothecia embedded in mealy or felt-like mycelia on stems, thorns, or leaf litter.
Powdery mildew of rose symptoms

New shoots are dwarfed, distorted, and have white-grey mildew growth. There is lowered photosynthetic efficiency resulting in reduced plant growth, susceptibility to injury, and reduced quality as a cut flower. Irregular, light green-red, slightly raised blister areas appear on the upper surface of young or old leaves, which develop into powdery white growth which is myeclia, conidiophores, and spores. Young leaves can become severely infected: leaves curl, are covered with powdery, mealy, or felt-like patches of mycelia that turn red-purple then yellow and dry, causing leaf drop. Old leaves are more resistant. It can cause complete defoliation. Mycelia can be found on buds, stems, thorns, peduncles, sepals, and petals. Petals may become discoloured, dwarfed, and the flower may fail to open, or die prematurely. Death of the whole plant is rare.

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Pre-symptomatic activity

Afer infection activity

Fungicides used for apple scab within a specified period to prevent scab lesion development once the infection has occurred. Includes demethylation inhibitors.

Prokaryote
A microorganism whose genetic material is not organized into a membrane-bound nucleus. Includes bacteria and mollicutes.
Protectant activity
Fungicides used for apple scab that inactivate and/or kill fungal spores to prevent infection. Includes Captan.
Pseudothecium

Astrostroma

The ascocarp of the Loculoascomycetes in which asci are formed directly in cavities within a stroma of mycelium. Resembles a perithecium, but there is no wall surrounding the central region of the ascocarp. It forms as a stroma within one or more locules, which asci form. Asci are bitunicate.

Pycnidium
An asexual, spherical, or flask-shaped fruiting body lined inside with conidiophores and producing conidia.
Race
A genetically and often geographically distinct mating group within a species; also a group of pathogens that infect a given set of plant varieties.
Resting spore
A sexual or other thick-walled spore of a fungus that is resistant to extremes in temperature and moisture and which often germinates only after a period of time from its formation.
Rhizobacterium radiobacter
A prokaryotic pathogen which causes crown gall. Uses T-DNA and a Ti plasmid to induce plant transformation and production of opines.
Saprophyte
An organism that uses dead organic material for food.
Sclerotinia sclerotiorum
An ascomycetes pathogen which causes white mould. Produces sclerotia which overwinter and produce apothecia. The sclerotia do not produce any mycotoxins. Does not produce conidia.
Sclerotium
A compact mass of hyphae with or without host tissue, usually darkened rind, and capable of surviving under unfavourable environmental conditions.
Secondary metabolite
Chemicals with no direct role in major metabolic pathways. Include mycotoxins.
Separation
A control method for mycotoxins. Mechanical sorting or screening, washing or floatation, or blowing of seed.
Septate
Having cross walls.
Septoria brown spot

A disease caused by Septoria tritici. Symptoms include tan spots with black pycnidia.

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Septoria tritici
An ascomycetes pathogen which causes septoria brown spot. Produces conidia in pycnidia.
Sign
The pathogen or its parts or products seen on a host plant.
Slime mould

Formerly fungi, now protozoa of the class Myxomycetes, also superficial diseases caused by these pseudofungi on low-lying plants.

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Society to Prevent Dutch Elm Disease (STOPDED)
A non-profit organization whose mandate is to preserve and protect elm trees in Alberta from Dutch elm disease. Alberta has the highest number of unaffected elm trees in the world. Members across the province take active roles in prevention of the spread of Dutch elm disease.
Spermatium
A male sex spore which can fertilize an ascogonium to form an ascus.
Sphaerotheca pannosa var. rosae
An ascomycetes pathogen which causes powdery mildwe of rose. Mycelia develop on the surface of the host, with haustoria feeding structures. Can overwinter as mycelia in dormant buds, and in the spring it infects the shoot and produces conidia. Conidia are barrel-shaped and produced in simple conidiophores, and they can survive 5 – 48 hours, less with higher temperature and moisture. It can complete a disease cycle in 72 hours. At the end of the season it produces chasmothecia in severely infected plants, or in leaf litter. Chasmothecia overwinter and discharge a single ascus in the spring.
Spilocaea pomi
The asexual stage of Venturia inaequalis. Conidia are 16 x 8 ?mm, formed on short conidiophores.
Spiroplasma
Pleomorphic, wall-less microorganisms present in the phloem of diseased plants; often helical in culture and thought to be some kind of mycoplasma or mollicute.
Sporangium
A container or case of asexual spores. In some cases it functions as a single spore.
Sporodochium
A fruiting structure consisting of a cluster of conidiophores woven together on a mass of hyphae.
Stroma
A compact mycelial structure on or in which fructifications are usually found. Produce asci.
Symptom
The external and inner reactions or alterations of a plant as a result of a disease.
Synergistic interaction
With some mycotoxins, combined toxicity is greater than individual toxicity levels added together. It makes feed more toxic than might be predicted. Synergistic interactions include aflatoxin B1 + ochratoxin A, and T-2 toxin + DON.
Synnema

plural: Synnemata

A structure in which conidiophores may grow. Conidiophores are fused at the base, and conidia form at the apex or side. Looks like a bundle of wheat. Includes coremia.

T-2 toxin
A mycotoxin produced by Gibberella zeae in the northern hemisphere. It can be found in grain affected by gibberella ear rot. Has synergistic interaction when combined with DON.
Tapharina deformans
An ascomycetes pathogen which causes peach leaf curl.
Teleomorph
The sexual, perfect stage in fungi.
Tomato paste
Can contain up to 45% mould.
Transfer DNA (T-DNA)
DNA in the Ti plasmid of Rhizobiaum radiobacter. It moves into host DNA, and causes cell division and uncontrolled growth in the host plant. It codes for production of cytokinins, indoleacetic acids, and opines.
Turkey X disease
A disease that killed 100,000 turkeys in 1962. It was originally believed to be caused by a virus, until it was linked to peanut meal that was imported from Brazil, contaminated with aflatoxin. This incident lead to coinage of the word “mycotoxin”.
Tyloses
Overgrowths of parenchyma cells that block xylem flow. Hormonal balances created by Ophiostoma sp. can lead to formation of tyloses. This causes wilting symptoms of Dutch elm disease.
Unicula necator
A biotrophic ascomycetes pathogen which causes powdery mildew of grape. Mycelia form on the leaf surface. Feeding structures are haustoria.
Venturia inaequalis
Also known by its asexual stage, Spilocaea pomi. An ascomycetes fungus that causes apple scab. Ascospores are ejected from pseudothecia during rain events or heavy dew. Ascospores have two cells of unequal size, 11 – 15 ?m long. Pseudothecia are 90 – 150 ?m in diameter. Produces conidia on simple conidioiphores.
Venturia inaequalis

A disease which has symptoms similar to Dutch elm disease: causes wilt.

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White mould

White rot

A monocyclic disease caused by Sclerotinia sclerotiorum. Causes losses across the USA, especially in central and western New York.

White mould conditions
Sclerotia need 10 days of soil moisture for germination. Ascospores need 48 hours of continuous leaf wetness for infection of blossoms, and 16 – 24 hours for infection of stems, leaves, or pods.
White mould dissemination
Ascospores are sticky, and disperse by wind when ejected from asci.
White mould hosts
Affects over 400 species in 64 families, including vegetable and fruit crops, dandelions, wild clover, hedgerows, and trees. Includes wheat, beans, soybeans, cabbage, lettuce, carrot, and potato.
White mould infection
Infection is most likely to occur 1 – 2 weeks after peak bloom. Ascospores germinate on blossoms when there is a film of water, and colonizes leaves, stems, and pod tissues. Fallen infected petals can adhere to other plant parts, causing infection.
White mould management
Use a low planting density to increase aeration, and avoid planting near woods. Benomyl fungicide foliar applications when 70 – 80% of plants have opened first bloom. Use resistant varieties. Plant rows in the direction of prevailing winds. Seed treatments. Zero tillage. Use crops with persistent residues, such as wheat.
White mould survival
Sclerotinia sclerotriorum overwinters as sclerotia in the soil, and produces apothecia in the spring that shoot asospores 1 – 3 inches.
White mould symptoms

Symptoms appear about a week after full bloom. Pale, water-soaked lesions on leaves enlarge and have white cottony growth that can produce sclerotia. Severely infected leaves yellow and drop. Fleshy tissues may have watery soft rot.

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White rust

A polycyclic disease caused by Albugo candida. Symptoms include white rust-like pustules.

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Witches’ broom
Broom-like growth or massed proliferation caused by the dense clustering of branches of woody plants.
Yellow rice disease
A disease reported in Japan in 1891, causing paralysis of the central nervous system in dogs and other animals. Caused by mycotoxins of Penicillium citreoviride.
Zearalenone (ZEA)
A mycotoxin produced by Gibberella zeae. It can be found in grain affected by gibberella ear rot or fusarium head blight. It is estrogenic and can cause reduced conception rates, vaginal prolapse, and abortion. Cattle are not as sensitive, and chickens are the least sensitive.
Zoosporangium
A sporangium which contains or produces zoospores.
Zoospore
A spore bearing flagella, capable of moving in water.