An abiotic disorder. Can be caused by hydrogen fluoride or ozone.

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A polyetic, polycyclic disease.

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A common polycyclic disease caused by Puccinia asparagi. Affects all aboveground parts of the host. Affects asparagus and occurs wherever asparagus is grown. Symptoms are dark brown to red pustules on stems and needles, which release rust coloured uredospores throughout the summer. Black protruding lesions form during dry periods, producing teliospores. Management strategies include removing infested crop prior to spear emergence, destroying wild or volunteer asparagus, planting away from established plantings, cleaning fields after harvest by cutting spears below the soil level, planting rows in direction of prevailing winds, using tolerant varieties, and fungicides.

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"Self house"

Monoecius rust

A rust that completes its life cycle on a single host. Includes Puccinia asparagi.

Club fungi

Produce basidiospores. Includes rust fungi and fleshy fungi including mushrooms, puffballs, and bracket fungi.

A stagnant, dark layer of anaerobic organic matter in the soil just below a layer of turf. Visible in the sand profile, and has a rotting egg smell. Hydrogen sulphides are produced from anaerobic decomposition, and react with iron to form a black precipitate. Leads to yellowing of leaves and thinning of turf. Caused by heavy thatch, compaction, poor drainage and excess water, and heavy use of the field.

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An abiotic disorder.

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A disease caused by Gymnosporangium juniperi-virginianae. Affects apples, and cedar is the alternate host.

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Reddish-brown, raised and elongated galls form on twigs and small branches. A circular dimple-like depression appears, resembling the surface of a golf ball. In the spring, small chestnut-brown structures protrude from the dimples which expand in wet weather into an orange mass of telial horns. Galls take two years to produce spores, and can remain on the host for several years.

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Orange-yellow spots develop on the upper surface of leaves, fruit, petioles, and new twigs. Spots have black pimple-like pycnia. Later, orange spots, the aecia, appear directly below these spots with tiny projections.

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A disease caused by Gymnosporangium clavipes.

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Yellowing

A symptom of a nutritional deficiency. Occurs on the entire leaf, or in veins.

Berberis vulgaris

The aecial host of wheat stem rust. It was brought to North America by early settlers from Europe. A source of primary inoculum of wheat stem rust in the spring, and the pathogen reproduces asexually, allowing it to hybridize and form new races. In 1918, a federal program to eradicate it began. Eradication delays disease onset by 10 days, reduces initial inoculum level, decreases the number of pathogenic races, and stabilizes pathogenic races. It is listed as a noxious weed, and is destroyed wherever possible.

A heteroecious disease caused by Puccinia sorghi. Red-brown pustules appear on any shoot part, mostly on leaves. The telial host is corn, and the aecial host is wood sorrel (Oxalis sp.). It is of minor economic importance, byt spring storms can cause early-season infections; it is favoured by high humidity and cool evening temperatures. Symptoms are yellow flecks or spots on leaves that develop into small, brick-red pustules that break the leaf surface and eventually turn black. The pustules release spores. Leaf yellowing occurs around the lesions and dead, brown areas develop. In severe cases the leaf can die. Management strategies include tillage, crop rotation, resistant varieties, and foliar fungicides. Inbred corn, sweet corn, and specialty hybrids have higher susceptibility.

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A disease caused by Puccinia coronata. Orange pustules burst through the surface, producing uredospores. Some areas produce black teliospores.

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A stem holoparasite or hemiparasitic flowering plant. A noxious weed. It has spaghetti-like stems, with leaves reduced to small scales. Light yellow in colour, with minimal chlorophyll content. Stems develop suckers that enter the host. Causes physical damage to the host, reducing nutrients and water, weakening it. Shades the crop, decreases yield, increases harvesting costs, and can vector diseases. Elevated levels in fodder can be toxic to horses and cattle, causing liver damage and diarrhea.

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Cultural practices include removal of dead and damaged branches. Pesticides may be used for the tree and beetles. Partial resistance may be found from genetic crosses between American and Asian elm species. Biological control using Verticillium dahlia, and ELMguard. Exclusion using quarantine and trenches between trees.

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Arceuthobium sp.

One of the most economically damaging mistletoes. Very specific, affecting only conifers. Smaller than true mistletoes.

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Peridermium harknessii

An endocyclic, autoecious rust pathogen that causes western gall rust of pine. Spores infect the branches of pine in May and June, and produce galls the next summer. Produces growth regulators in the vasculature of the host, stimulating formation of galls and witches' broom. Galls produce spores after one year, and can continue to do so for several years.

"Different house"

A rust that requires two alternate hosts to complete its life cycle. Includes Puccinia graminis and Gymnosporangium juniperi-virginianae.

There is a latent period of a few days to several weeks. Bright yellow or orange spots form on the upper leaf surface, or on the stems or calyx. Reddish-brown pustules form on the lower leaf surface beneath lesions. Lesions turn grey in high humidity, and produce basidiospores. Eventually spots turn brown and drop out. Lower leaves are affected first. Severely infected plants may shrivel and fall.

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Ghost plant

An endoparasitic flowering plant.

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Berberis thumbergii

A species of barberry which is not susceptible to wheat stem rust, and can be grown in Canada as an ornamental plant.

Pueraria sp.

Japanese arrowroot

A legume in the family Fabaceae. A structural parasite that is a climbing, coiling, and trailing perennial vine. It is the alternate host for soybean rust. Native to eastern Asia, southeastern Asia, and some Pacific islands. It edible, but often sprayed with herbicides. Introduced to the USA in 1876 as an ornamental bush. It was used to stop eriosion in the 1930s, and people were paid to sow it into topsoil. It spread at a rate of 150,000 acres annually, and now the estimate is 2,500 acres annually.

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May be eradicated by burning the shoot prior to harvest, to prevent tuber infection. Raised beds may be used to reduce tuber infection.

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Not a serious disease unless the crop is grown in monoculture.

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An abiotic injury.

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Woody galls develop in the spring. After two years, the galls form horn-like projections which are telia. During wet weather the telia swell and become orange and gelatinous, and produce basidiospores.

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Bright yellow-orange spots form on leaves which have dark, dot-like pycnia on the upper surface. Spots turn red around the margins in early summer. The underside of the lesions turn brown and swell and blister. Lantern-shaped aecia form in the late summer on blisters on the lower surface, and produce aeciospores.

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A nutritional deficiency.

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A parasitic flowering plant.

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"Plant toxic"

Mulches have some risk of phytotoxicity.

A disease caused by Erysiphe cichoracearum.

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Spermatia

Produced by macrocyclic and demicyclic rust fungi. Formed in the pycnia. Not technically a spore; it is a gamete and cannot infect a host. It fuses with receptive hyphae of a compatible mating type to become dikaryotic hyphae that form aecia.

A disease which has high incidence in overwatered plants.

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Corpse flower

A holoparasitic, endoparasitic flowering plant. Causes little damage to its host. Found in rainforests in southeast Asia. Embedded inside the host for most of its life, except for flowering. Lacks chlorophyll and has no leaves, stems, or true roots. Only the flower is visible on the surface, up to 1 m in diameter. Can only grow on the Tetrastigma vine. Germination and haustoria penetration require damaged vines. The flowers smell like rotting flesh, and flowering lasts 5 - 7 days. Buds are produced near host tendrils, or "roots", 9 - 12 months after flowering. The seeds are sticky and attach to animals to disperse. The smallest member of this genus, 9.73 cm in diameter, was discovered in the Philippines, and may be critically endangered.

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An abiotic disorder caused by salt. Salt damage usually follows a pattern, such as where a snowbank was.

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Asian soybean rust

A serious, heteroecious disease caused by Phakopsora pachyrhizi. Initial inoculum is carried on the wind from the USA. First occurred in Japan in 1902. It spread to South America in 2001, then to North America in 2004. Affects soybeans (Glycine max), Glycine soja, Pachyrhizus erosus, Pueraria lobate (kudzu), Vigna unguiculata, legume species including kidney bean, and clover. Resistant soybean varieties are not yet available.

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A disease caused by Puccinia graminis.

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Wheat stem rust

A heteroecious, macrocyclic disease caused by Puccinia graminis f.sp. tritici. There was an outbreak in 1916, causing loss of 200 million bushels of wheat, and increases in wheat and flour prices. In Canada, the main source of primary inoculum is uredospores blown northward on the Puccinia Pathway.

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Pilostyles thurberi

An epiparasitic flowering plant.

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Orobranche sp.

A holoparasitic flowering plant.

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Mistletoe which is larger and less damaging than dwarf mistletoe. Has many hosts, including oak and pear. It is green and photosynthesizes more. It includes the traditional Christmas mistletoe.

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Pine-pine gall rust

A disease caused by Endocronartium harknessii. Affects two- and three-needled Pinus species, including hard pine, spruce, jack, ponderosa, lodgepole, Scots, and mugo pines. Found in northern and eastern North America. Symptoms are globose, woody galls on stems and branches that can grow for many years. Galls erupt in the spring with bright orange spores. Galls can weaken the stems, resulting in wind breakage. Symptoms can also include witches' broom and girdling of the stem with cankers associated with galls. Affects trees of all ages, and can lead to death in young trees. Can make up to 10% of nursery pines or Christmas trees unsalable. Management strategies include removing galls and/or felling infected trees before sporulation in the spring, a single application fo maneb at the beginning of sporulation, use of disease-free stock, and use of resistant varieties.

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An abiotic injury.

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Striga sp.

A hemiparasitic flowering plant. Affects rice and corn. Causes economic losses from 40 - 100% in Africa and Asia. Most damage is below-ground until it is too late. Symptoms include yellowing of veins and foliage, leaf withering and death, and decreased growth, fruiting, and yield. Seeds germinate close to host roots. There is a three-week window to detect the weed and take action. The tiny seeds (0.4 mm) require an after-ripening period, waiting for correct temperature (20 - 35ºC) and moisture conditions. One plant can produce over 500,000 seeds, which remain viable in the soil for several years, at temperatures as low as -15ºC. The seeds may be dispersed by water, wind, animals, or humans. After germination, haustoria form underground with host roots, and alter the host by increasing root formation. It grows a shoot and emerges from the soil to produce chlorophyll and photosynthesize, flower, and produce seeds. Management is difficult, because host and parasite share a vascular system: sanitation hand removal, crop rotation, biocontrol, herbicides (expensive), burrying flowers, and biological control such as Fusarium sp. Resistant crop varieties usually have decreased production of germination stimulants in the roots.

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Rhinanthus minor

A hemiparasitic flowering plant.

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