Stigmatomycosis
Encyclopedia
The term Stigmatomycosis is the general name for a fungal disease that occurs in a number of crops, such as cotton
, soybean
, pecan
, pomegranate
, citrus
, and pistachio
. It has been reported on pistachio in Greece
, Iran
, Russia
, and is frequently a problem in California pistachio orchards severely infested by hemipteran
insects. In a 1989 survey in California
, fruit with stigmatomycosis were found in 90% of samples collected from late June to mid-September and from all growing areas.
. Kernels with stigmatomycosis can be 1) small, dark green and partially developed with a brown funiculus
, 2) well-developed, dark green and rancid, or 3) full-sized but abnormal, being white or light yellow and jelly-like, with a lobbed appearance. In contrast, symptoms of kernel necrosis
, which is caused by large hemipterans
, are dry, punky, brown areas in the kernel. Sometimes, kernel necrosis and stigmatomycosis symptoms can be present in the same fruit.
Ashbya gossypii
, Eremothecium coryli (syn. Nematospora coryli), and Aureobasidium pullulans
. All of them belong to the phylum of ascomycetes
insects of the stinkbug families Pentatomidae
and Coreidae
. Hemipterans are common pests in pistachio
orchards, and up to ten species have been found in California
pistachio orchards. Three common stinkbug pests, Thyanta pallidovirens (Western red-shouldered stinkbug), Chlorochroa uhleri, Chlorochroa ligata, and a leaffooted bug, Leptoglossus clypealis (Coreidae), experimentally transmitted E. coryli, which caused typical symptoms of stigmatomycosis in pistachio kernels
. Symptoms first appear in late June after pistachio shells have hardened, but the disease becomes frequent in July through September, a period that coincides with kernel development. Smaller hemipterans, such as Lygus
and Calocoris
, may carry but not transmit the pathogens because they are unable to puncture the firm fruit pericarp after the second part of May. Stigmatomycosis and kernel necrosis
are worse in orchards irrigated by sprinklers
than in those irrigated by drip, microjets, or flood. This suggests either greater humidity requirements for infection, more activity of hemipterans in sprinkler-irrigated orchards, or more abundant pathogen propagules.
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, soybean
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
, pecan
Pecan
The pecan , Carya illinoinensis, is a species of hickory, native to south-central North America, in Mexico from Coahuila south to Jalisco and Veracruz, in the United States from southern Iowa, Illinois, Missouri, and Indiana east to western Kentucky, southwestern Ohio, North Carolina, South...
, pomegranate
Pomegranate
The pomegranate , Punica granatum, is a fruit-bearing deciduous shrub or small tree growing between five and eight meters tall.Native to the area of modern day Iran, the pomegranate has been cultivated in the Caucasus since ancient times. From there it spread to Asian areas such as the Caucasus as...
, citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
, and pistachio
Pistachio
The pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia , which now can also be found in regions of Syria, Lebanon, Turkey, Greece, Kyrgyzstan, Turkmenistan, India, Pakistan, Egypt, Sicily and possibly Afghanistan , as well as in the United States,...
. It has been reported on pistachio in Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
, Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, and is frequently a problem in California pistachio orchards severely infested by hemipteran
Hemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
insects. In a 1989 survey in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, fruit with stigmatomycosis were found in 90% of samples collected from late June to mid-September and from all growing areas.
Symptoms
Stigmatomycosis is characterized by a wet, smelly, rancid, slimy kernelSeed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
. Kernels with stigmatomycosis can be 1) small, dark green and partially developed with a brown funiculus
Funiculus
The cerebrospinal fibers consist of numerous nerve fibers collected together and enclosed in membranous sheaths. A small bundle of fibers, enclosed in a tubular sheath, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are...
, 2) well-developed, dark green and rancid, or 3) full-sized but abnormal, being white or light yellow and jelly-like, with a lobbed appearance. In contrast, symptoms of kernel necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
, which is caused by large hemipterans
Hemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
, are dry, punky, brown areas in the kernel. Sometimes, kernel necrosis and stigmatomycosis symptoms can be present in the same fruit.
Causal Organisms
Stigmatomycosis is caused by the filamentous fungiMold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
Ashbya gossypii
Ashbya gossypii
Ashbya gossypii is a filamentous fungus or mold closely related to yeast, but growing exclusively in a filamentous way. It was originally isolated from cotton as a pathogen causing stigmatomycosis by Ashby and Novell in 1926...
, Eremothecium coryli (syn. Nematospora coryli), and Aureobasidium pullulans
Aureobasidium pullulans
Aureobasidium pullulans is a ubiquitous yeast-like fungus that can be found in different environments . It is well known as a naturally occurring epiphyte or endophyte of a wide range of plant species without causing any symptoms of disease.A...
. All of them belong to the phylum of ascomycetes
Disease Cycle and Epidemiology
The fungi causing stigmatomycosis are associated with hemipteranHemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
insects of the stinkbug families Pentatomidae
Pentatomidae
Pentatomidae, Greek pente meaning five and tomos meaning section, is a family of insects belonging to order hemiptera that includes some of the stink bugs and shield bugs. Their antennae are 5-segmented, which gives the family its scientific name. Their bodies are usually shield-shaped...
and Coreidae
Coreidae
Coreidae are a large family of predominantly herbivorous insects that belong in the hemipteran suborder Heteroptera. There are more than 1,800 species in over 250 genera. They vary in size from 7 to 45 mm, making the larger species some of the biggest heteropterans. The body shape of coreids...
. Hemipterans are common pests in pistachio
Pistachio
The pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia , which now can also be found in regions of Syria, Lebanon, Turkey, Greece, Kyrgyzstan, Turkmenistan, India, Pakistan, Egypt, Sicily and possibly Afghanistan , as well as in the United States,...
orchards, and up to ten species have been found in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
pistachio orchards. Three common stinkbug pests, Thyanta pallidovirens (Western red-shouldered stinkbug), Chlorochroa uhleri, Chlorochroa ligata, and a leaffooted bug, Leptoglossus clypealis (Coreidae), experimentally transmitted E. coryli, which caused typical symptoms of stigmatomycosis in pistachio kernels
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
. Symptoms first appear in late June after pistachio shells have hardened, but the disease becomes frequent in July through September, a period that coincides with kernel development. Smaller hemipterans, such as Lygus
Lygus
The genus Lygus includes over 40 species of plant-feeding insects in the family Miridae. At one time, nearly 200 species were classified as genus Lygus, but most of those have since been reclassified into new or existing genera. The term lygus bug is used for any member of genus Lygus. The more...
and Calocoris
Calocoris
Calocoris is a genus of true bugs in the Miridae family.*Calocoris affinis*Calocoris alpestris*Calocoris angustatus*Calocoris aragonus*Calocoris barberi*Calocoris braunsi*Calocoris dohertyi*Calocoris fasciativentris...
, may carry but not transmit the pathogens because they are unable to puncture the firm fruit pericarp after the second part of May. Stigmatomycosis and kernel necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
are worse in orchards irrigated by sprinklers
Irrigation sprinkler
Irrigation sprinklers are sprinklers used on farms, golf courses, and yards, to provide water to vegetation and plants in the event of drought. They may also be used for recreation, as a cooling system, or to keep down the amount of airborne dust....
than in those irrigated by drip, microjets, or flood. This suggests either greater humidity requirements for infection, more activity of hemipterans in sprinkler-irrigated orchards, or more abundant pathogen propagules.