Wheat yellow rust ("Puccinia striiformis" f.sp. "tritici"), also known as stripe rust, is one of the three wheat rust diseases principally found in wheat grown in cooler environments. Such locations are generally associated with northern latitudes or cooler seasons.

As R.P. Singh, J. Huerta-Espino, and A.P. Roelfs say in their (undated) comprehensive review of literature on the wheat rusts for UN FAO:

"Although Gadd first described stripe rust of wheat in 1777, it was not until 1896 that Eriksson and Henning (1896) showed that stripe rust resulted from a separate pathogen, which they named P. glumarum. In 1953, Hylander et al. (1953) revived the name P. striiformis."

Leaf rust is a fungal disease of barley caused by "Puccinia hordei". It is also known as brown rust and it is the most important rust disease on barley.

Pustules of leaf rust are small and circular, producing a mass of orange-brown powdery spores. They appear on the leaf sheaths and predominantly on the upper leaf surfaces. Heavily infected leaves die prematurely.

The affected fruit have dark spots, about ½ cm diameter, which occur on the skin and/or in the flesh The cells in the spots are dead (necrotic), and turn brown-black.

Sooty blotch and flyspeck (SBFS) or apple summer disease is a plant disease caused by a complex of saprophytic fungi which colonize the epicuticular wax layer of apple ("Malus" x "domestica" Borkh.). It is found worldwide in regions with moist growing seasons.

The symptoms of little cherry disease in sweet and sour cherries varies greatly depending on cultivar, with respect to both the range and the severity of symptoms; some cultivars show signs of tolerance.

In infected trees of the commercially important cultivar Lambert, the fruit develops normally until about ten days before harvest, when maturation stops. At picking time, the cherries are 1/2–2/3 of the regular size, dull in color, with an angular pointed shape. The sugar and acid levels of the cherries are severely impacted, resulting in tasteless fruits, lacking both sweetness and flavor. Other cultivars show symptoms similar to those in Lambert, but usually less severe and more varied. Typically, dark-fruited cultivars show more severe fruit symptoms than cultivars with red or yellow fruit. The ability to recover is also dependent on cultivar, with some able to return to fruit sizes and coloring comparable to uninfected trees. The taste, however, never recovers.

Some sweet cherry cultivars display foliage symptoms, with the fruit crop less hidden by the canopy, and leaf symptoms, varying from a slight marginal up-curl of the leaves to marked reddening of leaf surfaces. The general vigor of infected trees may be impaired, though this is not always apparent. Diagnosis of the disease can be assisted by RT-PCR assays.

Other "Prunus" species may act as symptomless or tolerant carriers of the disease; especially cultivars of Japanese flowering cherry ("Prunus serrulata") have been implicated as such.

Sooty blotch and flyspeck is a descriptive term for a condition of darkly pigmented blemishes and smudges caused by a number of different fungi affecting fruit including apples, pear, persimmon, banana, papaya, and several other cultivated tree and vine crops. The greenish black coating resembling soot or flyspeck-like dots grow into irregular stains and blotches during the summer or growing season. They can grow into each other and may cover the entire fruit surface. Frequently blotches run down in a track resembling tears (German: "Regenfleckenkrankheit"). The blotches can be removed by vigorous rubbing or be scratched off revealing a normal peel. Symptoms can be seen particularly well when apples are light or green colored. Late varieties are more susceptible, because the disease builds over a longer growing period.

Laminated root rot also known as yellow ring rot is caused by the fungal pathogen "Phellinus weirii". Laminated root rot is one of the most damaging root disease amongst conifers in northwestern America and true firs, Douglas-fir, Mountain hemlock, and Western hemlock are highly susceptible to infection with "P. weirii". A few species of plants such as Western white pine and Lodgepole pine are tolerant to the pathogen while Ponderosa pine is resistant to it. Only hardwoods are known to be immune to the pathogen.

Bitter pit is a disorder in apple fruits, now believed to be induced by calcium deficiency. It occurs less commonly in pears.

The disease was probably first reported in Germany where it was known as "Stippen". It was also known as "Baldwin spot" and "blotchy cork" in North America. The name "bitter pit" was first used by Cobb in Australia in 1895. The disease has been shown as non-pathological and is now known as a disorder. When it occurs on the tree, it is known as "tree pit"; it may also occur in storage, when it is known as "storage pit".

The disease can infect trees as young as 6 years-old, and infects trees throughout their lifespan. Diagnostic symptoms include crown yellowing and thinning, a distress crop of cones, red brown stained outer heartwood, and laminate decay (decay that separates along annual rings). The disease tends to occur in patches due to a primarily short range spread mechansism. Infected or decayed roots break close to the root collar forming “root balls.” Laminated root rot is frequently detected during ground survey when canopy openings and standing dead and fallen trees are observed. Signs of laminated root rot include the setal hyphae (tiny hairlike hyphae) between sheets of decomposing wood and also buff-colored mycelium on the outside of the roots.

Apple scab is a disease of "Malus" trees, such as apple trees, caused by the ascomycete fungus "Venturia inaequalis". The disease manifests as dull black or grey-brown lesions on the surface of tree leaves, buds or fruits. Lesions may also appear less frequently on the woody tissues of the tree. Fruits and the undersides of leaves are especially susceptible. The disease rarely kills its host, but can significantly reduce fruit yields and fruit quality. Affected fruits are less marketable due to the presence of the black fungal lesions.

The symptoms of Cherry X disease vary greatly depending on the host. On cherry hosts symptoms can usually first be seen on the fruits, causing them to be smaller in size with a leathery skin. Pale fruit is common at harvest time. It is common for symptoms to first be seen in a single branch. The branch may lose its older leaves, and the leaves tend to be smaller with a bronzed complexion.

The rootstock that the cherry is grafted onto can play a significant role in the disease symptoms seen. Rootstocks of Mahaleb cherry exhibit different symptoms from stocks of Colt, Mazzard, or Stockton Morello. When the scion is grafted onto Mahaleb, symptoms consistent with Phytophthora root rot can be seen. To distinguish between root rot and x-disease the wood under the bark at the graft union should be examined. If it is x-disease the wood at the union will have grooves and pits this causes a browning of the phloem and shows the cells in decline. This rapid decline is caused by the rootstock cells near the graft union dying in large quantities. Foliage begins to turn yellow and the curl upward and inward toward the leaf midrib. Trees infected with Mahaleb rootstock die by late summer or early the following year.

When Cherries are grafted onto Colt, Mazzard, or Stockton Morello rootstocks, there is a different range of symptoms. Affected leaves are smaller than normal and the foliage may be sparse. Dieback of shoot tips is common as the disease progresses. Fruit on branches are smaller, lighter, pointed, low sugar content, poor flavor, and a bitter taste.

Peaches are the next most common economic fruit host of the X-disease. Symptoms can be seen after about two months single branches will begin to show symptoms of their individual leaves. These leaves curl up and inward with irregular yellow to reddish-purple spots. These spots can drop out leaving “shotholes”. Leaves that are affected by the disease will fall prematurely. After 2–3 years the entire tree will show symptoms.

The occurrence of Burrknot is quite common among rootstock, often found on apple tree M ( Malling ) and MM ( Malling-Merton ) rootstocks. At onset it begins to look like a smooth orange bulge growing from the stem or a branch, later, during one to three years, multiple adventitious roots begin to form.

When located on the roots, it is considered to be not very dangerous, but it makes it easier for diseases to infect the tree, and leaves it more susceptible to insects. When many burrknots are present on various location in the tree, it can make the tree unproductive.

Burrknot is a tree disorder, which is caused by formation of adventitious root primordia. Although previously classified as disease, is now classified as a disorder, as it is no longer believed to be pathogenic.

Velvet disease (also called gold-dust, rust and coral disease) is a fish disease caused by dinoflagellate parasites of the genus "Piscinoodinium", specifically "Amyloodinium" in marine fish, and "Oodinium" in freshwater fish. The disease gives infected organisms a dusty, brownish-gold color. The disease occurs most commonly in tropical fish, and to a lesser extent, marine aquaria.

Physiological plant disorders are caused by non-pathological conditions such as poor light, adverse weather, water-logging, phytotoxic compounds or a lack of nutrients, and affect the functioning of the plant system. Physiological disorders are distinguished from plant diseases caused by pathogens, such as a virus or fungus. While the symptoms of physiological disorders may appear disease-like, they can usually be prevented by altering environmental conditions. However, once a plant shows symptoms of a physiological disorder it is likely that that season’s growth or yield will be reduced.

Citrus Black Spot is a fungal disease caused by Guignardia citricarpa. This Ascomycete fungus affects citrus plants throughout subtropical climates, causing a reduction in both fruit quantity and quality. Symptoms include both fruit and leaf lesions, the latter being critical to inter-tree dispersal. Strict regulation and management is necessary to control this disease since there are currently no citrus varieties that are resistant.

Little cherry disease or LChD, sometimes referred to as little cherry, K & S little cherry or sour cherry decline, is a viral infectious disease that affects cherry trees, most notably sweet cherries ("Prunus avium") and sour cherries ("Prunus cerasus").

Little cherry disease should not be confused with cherry buckskin disease, which is caused by Phytoplasma.

Note that both diseases are among the diseases referred to as cherry decline.

Verticillium wilt is a wilt disease of over 350 species of eudicot plants caused by six species of Verticillium genus, "V. dahliae", "V. albo-atrum", "V. longisporum", V. nubilum, V. theobromae and

V. tricorpus. (See, for example, Barbara, D.J. & Clewes, E. (2003). "Plant pathogenic Verticillium species: how many of them are there?" Molecular Plant Pathology 4(4).297-305. Blackwell Publishing.) Many economically important plants are susceptible including cotton, tomatoes, potatoes, oilseed rape, eggplants, peppers and ornamentals, as well as others in natural vegetation communities. Many eudicot species and cultivars are resistant to the disease and all monocots, gymnosperms and ferns are immune.

Symptoms are superficially similar to "Fusarium" wilts. There is no chemical control for the disease but crop rotation, the use of resistant varieties and deep plowing may be useful in reducing the spread and impact of the disease.

The single-celled parasite's life cycle can be divided into three major phases. First, as a tomont, the parasite rests at the water's floor and divides into as many as 256 tomites. Second, these juvenile, motile tomites swim about in search of a fish host, meanwhile using photosynthesis to grow, and to fuel their search. Finally, the adolescent tomite finds and enters the slime coat of a host fish, dissolving and consuming the host's cells, and needing only three days to reach full maturity before detaching to become a tomont once more.

Cherry X disease also known as Cherry Buckskin disease is caused by a plant pathogenic phytoplasma. Phytoplasma's are obligate parasites of plants and insects. They are specialized bacteria, characterized by their lack of a cell wall, often transmitted through insects, and are responsible for large losses in crops, fruit trees, and ornamentals. The phytoplasma causing Cherry X disease has a fairly limited host range mostly of stone fruit trees. Hosts of the pathogen include sweet/sour cherries, choke cherry, peaches, nectarines, almonds, clover, and dandelion. Most commonly the pathogen is introduced into economical fruit orchards from wild choke cherry and herbaceous weed hosts. The pathogen is vectored by mountain and cherry leafhoppers. The mountain leafhopper vectors the pathogen from wild hosts to cherry orchards but does not feed on the other hosts. The cherry leafhopper which feeds on the infected cherry trees then becomes the next vector that transmits from cherry orchards to peach, nectarine, and other economic crops. Control of Cherry X disease is limited to controlling the spread, vectors, and weed hosts of the pathogen. Once the pathogen has infected a tree it is fatal and removal is necessary to stop it from becoming a reservoir for vectors.

Potassium deficiency, also known as potash deficiency, is a plant disorder that is most common on light, sandy soils, because potassium ions (K) are highly soluble and will easily leach from soils without colloids. Potassium deficiency is also common in chalky or peaty soils with a low clay content. It is also found on heavy clays with a poor structure.

Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. It is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are:

- Late blight of potato, caused by the water mold "Phytophthora infestans" (Mont.) de Bary, the disease which led to the Great Irish Famine

- Southern corn leaf blight, caused by the fungus "Cochliobolus heterostrophus" (Drechs.) Drechs, anamorph "Bipolaris maydis" (Nisikado & Miyake) Shoemaker, incited a severe loss of corn in the United States in 1970.

- Chestnut blight, caused by the fungus "Cryphonectria parasitica" (Murrill) Barr, has nearly completely eradicated mature American chestnuts in North America.

- Fire blight of pome fruits, caused by the bacterium "Erwinia amylovora" (Burrill) Winslow "et al.", is the most severe disease of pear and also is found in apple and raspberry, among others.

- Bacterial leaf blight of rice, caused by the bacterium "Xanthomonas oryzae" (Uyeda & Ishiyama) Dowson.

- Early blight of potato and tomato, caused by species of the ubiquitous fungal genus "Alternaria"

- Leaf blight of the grasses

On leaf tissue, symptoms of blight are the initial appearance of lesions which rapidly engulf surrounding tissue. However, leaf spot may, in advanced stages, expand to kill entire areas of leaf tissue and thus exhibit blight symptoms.

Blights are often named after their causative agent, for example Colletotrichum blight is named after the fungi "Colletotrichum capsici", and Phytophthora blight is named after the water mold "Phytophthora parasitica".

False melanose lesions are characterized by many small, tan, slightly raised lesions. The lesions are much smaller than the hard spot variety with an average diameter of less than 1 mm (.04 in).

They are found on unripe fruit and are difficult to observe later in the season. Unlike hard spot lesions, no pycnidia are present.