Sphaeropsis blight, also known as Diplodia tip blight, is a widespread disease caused by an opportunistic fungal pathogen, Diplodia sapinea. It is found in “both hemispheres between the latitudes 30° and 50° north and south". The diseases symptoms include: damping off and collar rot of seedlings, stem canker, rood disease, and, most commonly, shoot blight. These symptoms have caused significant economic loss to nurseries and pine plantations. In a nursery in the north-central United States, losses of 35% have been reported. Shoot blight and eventual die back can cause a reduction of marketable volume in timber by 63%. Infection of terminal shoots can result in dead-top which significantly limits the usable length of the tree trunk. The presence of the pathogen in concert with severe weather conditions can lead to extreme loss. Following a severe hailstorm in South Africa, nearly 5,000 acres of pine plantation were infected with Diplodia tip blight. It was necessary to prematurely harvest large swaths of the plantations resulting in a loss of 45%. Areas that were not harvested prematurely still suffered an average timber loss of 11%.
Phytophthora sojae is an oomycete and a soil-borne plant pathogen that causes stem and root rot of soybean. This is a prevalent disease in most soybean growing regions, and a major cause of crop loss. In wet conditions the pathogen produces zoospores that move in water and are attracted to soybean roots. Zoospores can attach to roots, germinate, and infect the plant tissues. Diseased roots develop lesions that may spread up the stem and eventually kill the entire plant. Phytophthora sojae also produces oospores that can remain dormant in the soil over the winter, or longer, and germinate when conditions are favourable. Oospores may also be spread by animals or machinery.
Alternaria alternata is a fungus which has been recorded causing leaf spot and other diseases on over 380 host species of plant. It is an opportunistic pathogen on numerous hosts causing leaf spots, rots and blights on many plant parts.
Leptosphaeria coniothyrium is a plant pathogen. It can be found across the world.
Alternaria triticina is a fungal plant pathogen that causes leaf blight on wheat. A. triticina is responsible for the largest leaf blight issue in wheat and also causes disease in other major cereal grain crops. It was first identified in India in 1962 and still causes significant yield loss to wheat crops on the Indian subcontinent. The disease is caused by a fungal pathogen and causes necrotic leaf lesions and in severe cases shriveled.
Gibberella zeae, also known by the name of its anamorph Fusarium graminearum, is a fungal plant pathogen which causes fusarium head blight, a devastating disease on wheat and barley. The pathogen is responsible for billions of dollars in economic losses worldwide each year. Infection causes shifts in the amino acid composition of wheat, resulting in shriveled kernels and contaminating the remaining grain with mycotoxins, mainly deoxynivalenol, which inhibits protein biosynthesis; and zearalenone, an estrogenic mycotoxin. These toxins cause vomiting, liver damage, and reproductive defects in livestock, and are harmful to humans through contaminated food. Despite great efforts to find resistance genes against F. graminearum, no completely resistant variety is currently available. Research on the biology of F. graminearum is directed towards gaining insight into more details about the infection process and reveal weak spots in the life cycle of this pathogen to develop fungicides that can protect wheat from scab infection.
Botryosphaeria ribis is a fungal plant pathogen that infects many trees causing cankers, dieback and death.
Diaporthe helianthi is a fungal pathogen that causes Phomopsis stem canker of sunflowers. In sunflowers, Phomopsis helianthi is the causative agent behind stem canker. Its primary symptom is the production of large canker lesions on the stems of sunflower plants. These lesions can eventually lead to lodging and plant death. This disease has been shown to be particularly devastating in southern and eastern regions of Europe, although it can also be found in the United States and Australia. While cultural control practices are the primary method of controlling for Stem Canker, there have been a few resistant cultivars developed in regions of Europe where the disease is most severe.
Ascochyta is a genus of ascomycete fungi, containing several species that are pathogenic to plants, particularly cereal crops. The taxonomy of this genus is still incomplete. The genus was first described in 1830 by Marie-Anne Libert, who regarded the spores as minute asci and the cell contents as spherical spores. Numerous revisions to the members of the genus and its description were made for the next several years. Species that are plant pathogenic on cereals include, A. hordei, A. graminea, A. sorghi, A. tritici. Symptoms are usually elliptical spots that are initially chlorotic and later become a necrotic brown. Management includes fungicide applications and sanitation of diseased plant tissue debris.
Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides.
Phomopsis obscurans is a common fungus found in strawberry plants, which causes the disease of leaf blight. Common symptoms caused by the pathogen begin as small circular reddish-purple spots and enlarge to form V-shaped lesions that follow the vasculature of the plant’s leaves. Although the fungus infects leaves early in the growing season when the plants are beginning to develop, leaf blight symptoms are most apparent on older plants towards the end of the growing season. The disease can weaken strawberry plants through the destruction of foliage, which results in reduced yields. In years highly favorable for disease development, leaf blight can ultimately lead to the death of the strawberry plants. A favorable environment for the growth and development of the Phomopsis obscurans pathogen is that of high temperature, high inoculum density, a long period of exposure to moisture, and immature host tissue. In the case of disease management, a conjunction of cultural practices is the most effective way of reducing the infection.
Ascochyta pisi is a fungal plant pathogen that causes ascochyta blight on pea, causing lesions of stems, leaves, and pods. These same symptoms can also be caused by Ascochyta pinodes, and the two fungi are not easily distinguishable.
Didymella bryoniae, syn. Mycosphaerella melonis, is an ascomycete fungal plant pathogen that causes Gummy stem blight on the family Cucurbitaceae [1-3]. The anamorph/asexual stage for this fungus is called Phoma cucurbitacearum[2]. This pathogen commonly affects the foliage and stems of plants from the family Cucurbitaceae, which includes cantaloupe, cucumber, muskmelon and watermelon plants [1,3,8]. When this pathogen infects the fruit of cucurbits it is called black rot [2].
Diaporthe phaseolorum var. caulivora is a fungal plant pathogen which infects soybean, causing soybean stem canker.
A pycnidium is an asexual fruiting body produced by mitosporic fungi in the form order Sphaeropsidales. It is often spherical or inversely pearshaped (obpyriform) and its internal cavity is lined with conidiophores. When ripe, an opening generally appears at the top, through which the pycnidiospores escape.
Raspberry spur blight is caused by the fungus Didymella applanata. This plant pathogen is more problematic on red raspberries (Rubus idaeus) than on black or purple raspberries. The fungus infects the leaves first and then spreads to the cane. It causes necrotic spots on the cane near the base of the petiole attachment. Raspberry spur blight can cause a significant reduction in yield, fruit blight, premature leaf drop, and weak bud and cane growth. The magnitude of damage is not clearly understood in the United States, however, studies from Scotland suggest damage to the cane itself is limited. The disease has minor economic impacts by reducing leaves in the summer or killing buds. Major economic damage occurs if the disease manages to kill the entire cane. In the United States, this disease is found in Oregon and Washington.
Ascochyta blights occur throughout the world and can be of significant economic importance. Three fungi contribute to the ascochyta blight disease complex of pea. Ascochyta pinodes causes Mycosphaerella blight. Ascochyta pinodella causes Ascochyta foot rot, and Ascochyta pisi causes Ascochyta blight and pod spot. Of the three fungi, Ascochyta pinodes is of the most importance. These diseases are conducive under wet and humid conditions and can cause a yield loss of up to fifty percent if left uncontrolled. The best method to control ascochyta blights of pea is to reduce the amount of primary inoculum through sanitation, crop-rotation, and altering the sowing date. Other methods—chemical control, biological control, and development of resistant varieties—may also be used to effectively control ascochyta diseases.
Phomopsisblight of juniper is a foliar disease discovered in 1917 caused by the fungal pathogen Phomopsis juniperovora. The fungus infects new growth of juniper trees or shrubs, i.e. the seedlings or young shoots of mature trees. Infection begins with the germination of asexual conidia, borne from pycnidia, on susceptible tissue, the mycelia gradually move inwards down the branch, and into the main stem. Management strategies mainly include removing and destroying diseased tissue and limiting the presence of moisture on plants. Junipers become resistant to infection as they mature and the young yellow shoots turn dark green. Preventive strategies include planting only resistant varieties and spraying new growth with fungicide until plants have matured.
Gummy Stem Blight is a cucurbit-rot disease caused by the fungal plant pathogen Didymella bryoniae . Gummy Stem Blight can affect a host at any stage of growth in its development and affects all parts of the host including leaves, stems and fruits. Symptoms generally consist of circular dark tan lesions that blight the leaf, water soaked leaves, stem cankers, and gummy brown ooze that exudes from cankers, giving it the name Gummy Stem Blight. Gummy Stem Blight reduces yields of edible cucurbits by devastating the vines and leaves and rotting the fruits. There are various methods to control Gummy Stem Blight, including use of treated seed, crop rotation, using preventative fungicides, eradication of diseased material, and deep plowing previous debris.
Alternaria Black Spot of Canola or grey leaf spot is an ascomycete fungal disease caused by a group of pathogens including: Alternaria brassicae, A. alternata and A. raphani. This pathogen is characterized by dark, sunken lesions of various size on all parts of the plant, including the leaves, stem, and pods. Its primary economic host is canola. In its early stages it only affects the plants slightly by reducing photosynthesis, however as the plant matures it can cause damage to the seeds and more, reducing oil yield as well.
