Basil, also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a tender plant, and is used in cuisines worldwide. In Western cuisine, the generic term "basil" refers to the variety also known as sweet basil or Genovese basil. Basil is native to tropical regions from Central Africa to Southeast Asia. In temperate climates basil is treated as an annual plant, however, basil can be grown as a short-lived perennial or biennial in warmer horticultural zones with tropical or Mediterranean climates.
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as the signs of the causal pathogen are quite distinctive. Infected plants display white powdery spots on the leaves and stems. This mycelial layer may quickly spread to cover all of the leaves. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.
White onion or Allium cepa are a cultivar of dry onion which have a distinct light and mild flavour profile. Much like red onions, they have a high sugar and low sulphur content, and thus have a relatively short shelf life. White onions are used in a variety of dishes, such as those of Mexican and European origin. Their uses in dishes often relate to their mild nature, they are often included in dishes to provide a light, fresh and sour taste to dishes and are often added uncooked to dishes such as salads.
Peronosporaceae are a family of water moulds that contains 21 genera, comprising more than 600 species. Most of them are called downy mildews.
Hyaloperonospora brassicae, in the family Peronosporaceae, is a plant pathogen. It causes downy mildew of species of Brassica, Raphanus, Sinapis and probably other genera within the Brassicaceae. In the past, the cause of downy mildew in any plant in the family Brassicaceae was considered to be a single species Peronospora parasitica. However, this has recently been shown to be a complex of species with narrower host ranges, now classified in the genus Hyaloperonospora, for example Hyaloperonospora parasitica on the weed Capsella bursa-pastoris. From the perspective of plant pathology, Hyaloperonospora brassicae is now the name of the most important pathogen in this complex, attacking the major agricultural and horticultural Brassica species. Other significant Brassicaceous hosts are attacked by different species in the complex, e.g. horseradish by Hyaloperonospora cochleariae, wallflower by Hyaloperonospora cheiranthi.
Hyaloperonospora parasitica is an oomycete from the family Peronosporaceae. It has been considered for a long time to cause downy mildew of a variety of species within the Brassicaceae, on which the disease can cause economically important damage by killing seedlings or affecting the quality of produce intended for freezing. Hyaloperonospora parasitica causes downy mildew on a wide range of many different plants. It belongs to the Kingdom Chromista, the phylum Oomycota, and the family Peronosporaceae. The former name for H. parasitica was Peronospora parasitica until it was reclassified and put in the genus Hyaloperonospora. It is an especially vicious disease on crops of the family Brassicaceae. It is most famous for being a model pathogen of Arabidopsis thaliana which is a model organism used for experimental purposes. Accordingly, the former Hyaloperonospora parasitica has been split into a large number of species. For instance, the taxonomically correct name of the parasite of the well-known model organism Arabidopsis thaliana is Hyaloperonospora arabidopsidis, not H. parasitica, whereas the pathogen of Brassica has to be called Hyaloperonospora brassicae.
Pythium ultimum is a plant pathogen. It causes damping off and root rot diseases of hundreds of diverse plant hosts including corn, soybean, potato, wheat, fir, and many ornamental species. P. ultimum belongs to the peronosporalean lineage of oomycetes, along with other important plant pathogens such as Phytophthora spp. and many genera of downy mildews. P. ultimum is a frequent inhabitant of fields, freshwater ponds, and decomposing vegetation in most areas of the world. Contributing to the widespread distribution and persistence of P. ultimum is its ability to grow saprotrophically in soil and plant residue. This trait is also exhibited by most Pythium spp. but not by the related Phytophthora spp., which can only colonize living plant hosts.
Peronospora sparsa is an oomycete plant pathogen that causes downy mildew in berry producing plants; especially in the genus's Rubus and Rosa. Downy mildew plant pathogens are often host specific and cause problems in cloudberries, blackberries, boysenberries, strawberries, and arctic bramble. Since they are host specific, Peronospora sparsa will not cause downy mildew in grapes because a different plant pathogen causes downy mildew in grapes; Plasmopara viticola. Although it depends on the cultivar, symptoms do not normally start until later stages of disease and can look different on different plants. The most common symptoms include red lesions in the veins of leaves, with dry and deformed berries.
Sclerophthora macrospora is a protist plant pathogen of the class Oomycota. It causes downy mildew on a vast number of cereal crops including oats, rice, maize, and wheat as well as varieties of turf grass. The common names of the diseases associated with Sclerophthora macrospora include "crazy top disease" on maize and yellow tuft disease on turf grass. The disease is present all over the world, but it is especially persistent in Europe.
Peronospora farinosa is a species name that has been widely applied to downy mildew on leaves of wild and cultivated Amaranthaceae: Amaranthus, Atriplex, Bassia, Beta, Chenopodium, Halimione, Salsola, Spinacia, etc. However, the species name has been taxonomically rejected as the original description contained reference to multiple species and could not unequivocally be attributed to a species of Peronospora. In the past, some of the species on important crop plants have been given names as formae speciales, notably f.sp. betae on sugar beet and f.sp. spinaciae on spinach. However, phylogentic reconstructions have revealed that these "forms" of Peronospora on different genera and their subdivisions, are distinct species, most of which already have previously published scientific names. Such host specialization possibly also exists with respect to the various wild amaranthaceous species given as hosts of P. farinosa.
Peronospora manshurica is a plant pathogen. It is a widespread disease on the leaves of soybeans and other crop plants. The fungi is commonly referred to as downy mildew, "leafspot", or "leaf-spot".
Plasmopara halstedii is a plant pathogen infecting sunflowers. The species is one of many pathogens commonly referred to as downy mildew. P. halstedii originated in North America.
Plasmopara viticola, the causal agent of grapevine downy mildew, is a heterothallic oomycete that overwinters as oospores in leaf litter and soil. In the spring, oospores germinate to produce macrosporangia, which under wet condition release zoospores. Zoospores are splashed by rain into the canopy, where they swim to and infect through stomata. After 7–10 days, yellow lesions appear on foliage. During favorable weather the lesions sporulate and new secondary infections occur.
Pseudoperonospora cannabina is a plant pathogen that causes downy mildew, which is a fungal-like disease caused by an oomycete.
Pseudoperonospora humuli is a plant pathogen that causes downy mildew on hops.
Pseudoperonospora cubensis is a species of water mould known for causing downy mildew on cucurbits such as cantaloupe, cucumber, pumpkin, squash and watermelon. This water mould is an important pathogen of all these crops, especially in areas with high humidity and rainfall, such as the eastern United States. In most years the disease is an annual, late-season problem on squash and pumpkin in the eastern and central United States, however, since 2004 it has become one of the most important diseases in cucumber production. Considered a highly destructive foliar disease of cucurbits, successful breeding in the mid-twentieth century provided adequate control of downy mildew in cucumber without the use of fungicides. The resurgence in virulence has caused growers great concern and substantial economic losses, while downy mildew in other cucurbit crops continues to be a yearly hindrance.
Peronospora is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamental plants. There are 19 genera that produce downy mildew, and Peronospora has been placed alongside Pseudoperonospora in the group of downy mildews with coloured conidia. Peronospora has far more species than any other genus of the downy mildews. However, many species have been moved from this genus to be reclassified to other or new genera. Among these was the most famous Peronospora species, formerly known as Peronospora parasitica, and now known as Hyaloperonospora parasitica. Now, the Peronospora species of most importance is likely the Peronospora tabacina. Peronospora tabacina causes blue mold on tobacco plants and can severely reduce yields of this economically important crop to the point where it has been classified as a bioweapon.
This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United States.
Peronospora destructor is a plant pathogen. It causes downy mildew on leaves of cultivated and wild Allium. Allium cepa is most often affected, while Allium schoenoprasum (chives) and Allium porrum (leek) are only occasionally affected.
Peronospora belbahrii, common name basil downy mildew, is a pathogenic water mold that affects basil species. Rapidly spread by windborn spores, the pathogen was first discovered in Italy in 2003. In 2007 it was detected in Florida and by 2008 had already spread to outdoor and greenhouse basil crops in the United States and Canada. Infections are untreatable and usually lead to complete crop loss, although multiple mildew-resistant cultivars have been developed and are now available for commercial and home growers. Leaves from affected plants are unmarketable due to their unappetizing appearance, but remain safe for human consumption.
