Diseases of corn. Fusarium maize Fusarium maize control measures

Fusarium shoots of corn can be found literally anywhere where corn grows. The harm from it is directly dependent on the degree of infection of corn seeds - the higher their percentage, the more infected plants will be found at the stage of their germination. If the degree of infection is weak enough, crop losses can reach 15%, and with a strong defeat, this figure often reaches 40%. Under especially unfavorable conditions, in some years, up to 60-70% of the crop can be lost. This disease is especially harmful in areas with wet weather and a protracted spring - shoots in this case can begin to appear only twenty to thirty days after sowing the seeds.

A few words about the disease

On the surfaces of seedlings of germinating caryopses attacked by fusarium, one can observe a mild fungal plaque, painted in white or pink. Gradually, the sprouts begin to turn brown and die. And sometimes they die before reaching the soil surface. If the sprouts survive, then they will differ in a poorly developed root system. The leaves will begin to dry out, infected plants will lag behind in growth, and some specimens will even lie down.

As a rule, the manifestation of Fusarium corn seedlings begins at the germination stage and until the formation of two or three leaves. Sometimes Fusarium seedlings can also affect adult plants, and grains with cobs can be affected not only in the fields during the growing season, but also in case of non-compliance with the storage regime. By the way, at the storage stage, the ill-fated attack can cover absolutely any part of the cob. And if they are stored in poorly ventilated or damp rooms, characterized by high humidity, the causative agent of the infection will easily pass to the cobs that are not affected by the disease and infect them.

There is also a hidden form of Fusarium seedlings of corn. It is considered especially dangerous, since at first the infected embryos are quite viable, and after they are in the soil, the development of the mycelium begins, spreading at lightning speed to sprouts with roots, which in turn leads to rapid decay of seedlings and their death.

The causative agent of Fusarium seedlings of corn are harmful fungi of the genus Fusarium, which persist on plant debris, in soil and in seeds. The unicellular microconidia they form are usually colorless. Curved or crescent-shaped macroconidia are also colorless and are equipped with several septa. Conidial sporulation of pathogenic fungi often provokes repeated infections of corn.

The development of the disease is markedly increased by increased acidity and soil moisture, as well as low temperature at the time of seed germination. Not the last role in the development of a harmful disease is played by the depth of seed placement. If they are buried too deep, aeration conditions will be greatly worsened. If they are planted too shallow, the top soil layer dries up, contributing to the deterioration of seed germination. And if the corn crops are excessively thickened, then the seedlings will begin to be quite affected by root rot.

How to fight

It is necessary to sow corn at the optimum time and only in well-heated and thoroughly fertilized areas. Also, when growing it, it is necessary to carry out a whole range of the most important agrotechnical measures that contribute to the speedy germination of corn seeds, as well as the best development of plants.

Pre-sowing treatment of corn seeds with the preparation "Maxim XL" gives a good effect. This fungicidal protectant will help tiny seedlings germinate better.

And before being sent for storage, seed corn cobs must be thoroughly dried so that their moisture content does not exceed 16%.

Also, at present, much attention is paid to the breeding of corn hybrids resistant to Fusarium seedlings and their subsequent use.

Distributed everywhere. It appears in the field on the cob at the end of the milk or the beginning of the wax ripeness of the grain and develops before harvesting, and sometimes during storage of the crop at elevated temperatures and humidity.

Cobwebby or denser pale pink coating appears in patches on the cobs. Grains in such places become dirty-brown, easily destroyed, especially when threshing cobs.

The causative agents of the disease are imperfect fungi of the genus Fusarium Link, mainly Fusarium moniliforme Sheldon. In addition to abundant mycelium, it forms micro- and a small amount of macroconidia.

Microconidia are colorless, fusiform-ovoid, unicellular or with one septum, 4-30 × 1.5-4 μm in size, formed on the tops of conidiophores in the form of disintegrating chains or false heads. Macroconidia are colorless, styloid or slightly sickle-shaped, gradually tapering towards both ends, usually with 3-5, rarely 6-7 transverse septa, 5.4-6.0 × 4-4.5 µm in size.

Occasionally, dark blue spherical sclerotia, 80-100 microns in diameter, form on the mycelium.

Severely affected corn seeds lose their germination capacity, while seeds with a healthy germ produce weak shoots that usually die before reaching the soil surface.

The main source of infection is post-harvest maize residues and especially cob wraps, in the tissues of which there is a mycelium, which gives a new generation of conidial sporulation in the spring. Infection usually begins on cobs damaged by insects or affected by corn underwear.

Mushroom F. moniliforme does not have toxic properties, so the cobs affected by it can be fed to animals.

Corn is susceptible to diseases such as Fusarium, blister smut, seed mold, seedling rot (pytium). A description of diseases that harm corn and methods for combating these diseases are described in this article.

Fusarium. This dangerous disease of plants, both cultivated and wild, is caused by fungi of the genus Fusarium. Fusarium is manifested by the appearance of a weak coating of white or pink color on the surface of corn. The main source of Fusarium corn is seeds, soil and plant residues. The development of the disease in the plant largely depends on the infection of the seeds. Fusarium corn is the most common and widespread disease of corn and is found everywhere. Fusarium can develop on shoots of corn and on the cob.

Fusarium seedlings of corn. Enhances the development of the disease low acidity of the soil and high humidity, as well as low temperature during the germination of corn seeds. Fusarium of corn seedlings is manifested by the appearance on the surface of a germinating grain of a weak plaque of a white or pink fungus. After the appearance of seedlings of corn on the surface of the earth, the sprouts begin to turn brown and die. If a corn sprout infected with Fusarium survives and continues to grow further, then such a sprout has a poorly developed root system. Fusarium-affected corn plants are markedly retarded in growth, corn leaves dry up, and later some plants lie down.

As a measure to combat Fusarium, sowing of corn with treated seeds should be carried out. Sowing should be carried out at the optimum time and in areas well warmed by the sun. It is also necessary to carry out a complex of agrotechnical measures to some extent conducive to faster germination of corn seeds and better development of plants. For planting corn, corn hybrids that are more resistant to Fusarium can be used.

Fusarium cobs of corn. A disease appears in the form of a pale pink bloom of the fungus on the cobs of corn at the end of the milk and at the beginning of the wax maturity of the grain. With the formation of an excessive thick coating of Fusarium, the cob grains are destroyed. There can be up to 30 such grains half-destroyed by fusarium on the cob.

The source of the appearance of Fusarium are mainly seeds infected with Fusarium and post-harvest residues of corn. The marsupial stage of the fungus can form on these residues left after harvesting corn, and they are a source of infection. Susceptible to infection with Fusarium fungus and insect-damaged corn kernels.

Fusarium on the cob of corn is the most common disease of corn. Fusarium develops especially well in areas with high humidity. In such areas, about 50% of corn crops can be affected by fusarium. Fusarium cobs of corn leads to a significant reduction in the yield of corn and a noticeable deterioration in its quality. Fusarium cobs of corn continue to develop even when the cobs are stored in poor conditions: with high humidity and poor aeration.

The fungus can have a negative impact on humans and animals, causing the development of dangerous diseases, such as cancer.

Measures to combat Fusarium cobs of corn are: removal of infected and diseased corn cobs; seed dressing; carrying out autumn plowing of the field and removal of plant residues of corn; carrying out measures to combat insects damaging corn cobs; proper storage conditions for cobs and seeds of corn.

Bubble head. This disease manifests itself mainly on stalks and cobs of corn in the form of gall formation. However, under certain conditions, all parts of the plant can be affected. Infection is carried out by airborne spores. The flight of spores begins 40-45 days after the emergence of corn seedlings, and the optimum temperature for the flight of spores is a temperature of 20-30 degrees. The source of this infection is plant residues and soil. Gall formation takes about 2 weeks.

The main control measure is the choice of more resistant hybrids for sowing, as well as plowing the soil and exterminating plant residues.

Seed molding. The causative agents of this disease are mainly representatives of the genera Alternaria, Aspergillus, Penicillium, Trichothecium and some others. This maize disease often causes the death or severe inhibition of seedlings, which manifests itself in the appearance of chlorotic, yellow-green leaves of the plant. Sometimes the drying of plants from the disease can be observed in the phase of 4-5 leaves.

During the germination period, corn seeds are covered with a thick coating of mycelium of gray, green and some other colors. This disease is most pronounced during the period of sowing seeds in cold soil, when the temperature is not yet high enough for the rapid germination of corn seeds, but this temperature is already quite suitable for the development of fungi. At low temperatures, the release of microtoxins by fungi, which adversely affect the development of the plant, increases. The appearance and development of this disease is promoted by deep planting of seeds in the soil and sowing of seeds of poor quality, as well as seeds with a damaged shell.

Measures to combat the disease are reduced to sowing corn with healthy seeds at the optimal time and at the optimal depth when the soil warms up above 10 ° C.

Seedling rot (pytium). The causative agents of this disease are fungi of the genus Pythium. This disease manifests itself in the earliest stages of plant development. The symptoms of this disease are stunting of the plant in growth. This disease manifests itself even in conditions of plant growth in sufficiently moist soil. Affected plants have yellowing leaves or may die. Enhances the defeat of seedlings and cool weather. This disease can affect all crops in a crop rotation.

Sowing at the optimal time and balanced mineral nutrition of plants serve as measures to combat this disease.

Symptoms of the disease appear on the cobs with foci of pinkish or whitish mycelial plaque. One focus covers at least 50-90 grains. In the center of the hearth, the grains change color to dirty brown, become brittle and crumble easily, especially when threshed. Caryopses located closer to the center of the hearth are covered with a pink bloom. On the periphery of the affected area, the grains have a normal appearance, and external signs of infection are not detected on them. Several lesions may be present on one cob, and when they grow, most of it becomes infected.

The pathogen spreads to the involucres and the stem node.

Symptoms of the disease form on the cobs towards the end of the milky phase or towards the beginning of waxy ripeness.

Dense plaque can spread from the top of the cob to its base. In this case, the wrappers practically stick to the cob, and they can be separated only with great effort.

The pathogen can develop not only in the field before harvesting, but also during storage. In this case, there is a focal formation on the cobs of a cobweb layer or a denser coating of a pale pink hue.

The infectious onset may be present in the embryo or colorization of seeds that do not outwardly differ from healthy ones.

Sometimes there is germination in the cobs of damaged grains. This is due to the release of substances with high biological activity by fungi.

Artificial infection of corn in the phase of formation of sultans leads to the formation of cobs with varying degrees of sterility.

Seeds in which the pathogen has destroyed the embryo lose their germination and die. With a healthy embryo, sprouts appear, but they die before reaching the soil surface.

Morphology

The causative agent of the disease is fungi of the genus, most often it is Fusarium moniliform. This species is able to form abundant mycelium, microconidia and macroconidia on the cob. Marsupial stage -.

Mycelium - cobweb or denser white or pinkish.

Microconidia are spindle-ovate, unicellular or with one septum. Size 4-30x1.5-4 microns, usually 5-22x2-3.5 microns. They are formed on conidiophores in the form of false heads or disintegrating chains.

Macroconidia are awl-shaped or slightly crescent-curved, but always tapering at both ends. There are from three to seven transverse partitions, more often three to five. Size 20-90x2-4.5 microns, usually 41-63x2.7-4 microns.

Sometimes on the mycelium, the formation of dark blue spherical sclerotia is observed, the diameter of which is from 80 to 100 microns.

Asci are flask-shaped, cylindrical, flat in the upper part, contain 8 ascospores. Size 84-150x9-8 microns.

Ascospores are elongated-elliptical in shape, with one septum. Size 10-24x4-9 microns.

Biology

The infection is well preserved in post-harvest residues of plants, especially in cob wraps.

The causative agent of Fusarium cobs of corn is a soil-dwelling pathogen adapted to the saprotrophic mode of development. It is able to persist in the soil even after the decomposition of plant residues of infected plants.

Another equally important source of infection is seeds. Under natural conditions, all sources overlap, and it is almost impossible to distinguish between them.

The pathogen develops mainly in the conidial stage. The infection usually enters the cob through damage caused by caterpillars, various birds. Often, the development of fusarium is noted on cobs affected by underwear. And also in the presence of genetic damage and under ill-fitting wrappers of some hybrid varieties.

. Hemibiotrophs.

All grain crops are affected. 7-10 days after infection, an orange-pink mass of conidia forms on the affected spikelets. Fungi can overwinter with mycelium, chlamydospores, perithecia on infected plant debris, seeds. Conidia are dispersed by the wind over fairly long distances. Ascospores are stored on plant debris and are a source of infection in the next growing season.

For the last 10-15 years, Fusarium head blight has been widespread in Russia. The disease is observed in most regions where wheat is grown. Epidemics of the disease are regularly observed in years when warm and humid weather conditions occur during the heading period. Yield losses during the development of infection can reach 20-50%. The growth of fungi in affected grains leads to the accumulation of toxic metabolites (mycotoxins) that are dangerous to human and animal health.

Protective measures: alternation of grain crops and corn with a break of at least one year in the crop rotation; cultivation of varieties tolerant to the disease (highly disease-resistant varieties do not exist); seed treatment with fungicides to reduce the development of seedling rot (the event does not affect the development of fusariosis of the ear); treatment of plants with fungicides, to some extent reducing the harmfulness of the disease; incorporation of plant residues, contributing to the reduction of the disease; seed storage at less than 14% moisture to prevent pathogen growth and mycotoxin production.

Fusarium ear of rye

Fusarium ear of barley

Fusarium alfalfa

Called by species complex Fusarium, among which dominates Fusarium oxysporum. The fungus causes root rot and plant wilt. The leaves turn whitish-yellow initially on one stem, later the other stems of the bush turn yellow, and then the whole plant. The top of the stem dries up or the whole plant dries up. In a diseased plant, the main root and root collar begin to rot. Sometimes the roots look outwardly healthy, but browning of the vascular fibrous bundles is observed on the cut. Fusarium wilt is more common on 2-3 year old and older alfalfa. Aerial mycelium on potato-sucrose agar is membranous-cobweb or felt, low, pale lilac or white. Macroconidia are few. Microconidia are abundant, in false heads, cylindrical, oval, ellipsoidal, unicellular. Chlamydospores intermediate and apical, smooth, solitary and in pairs, rounded, uncolored.

The development of the disease is promoted by increased acidity and unstable water regime in the soil, as well as high temperature. On the territory of the former Soviet Union, alfalfa fusarium is registered in the Voronezh region, Rostov region, Stavropol Territory, Krasnodar Territory, the Baltic States, Ukraine (Poltava region, Kharkov region) and Uzbekistan (Tashkent). The disease can cause the death of alfalfa and lead to sparse crops. Protective measures: destruction of plant residues, compliance with the crop rotation recommended for each zone, use of resistant varieties.

Fusarium seedlings of corn

Pathogens: fungi of the genus Fusarium. The disease is ubiquitous.
Low temperature during seed germination, high humidity and acidity of the soil enhance the development of the disease. On the surface of a germinating grain, there is a slight coating of a pink or white fungus. Shortly after the emergence of corn plants on the surface, the sprout turns brown and dies. If the sprout survives, then it has a poorly developed root system, diseased plants are stunted, the leaves dry up, some plants lie down.
Protective measures: it is recommended to sow with treated seeds in well-warmed areas and at the optimum time; to carry out a complex of agrotechnical measures that contribute to faster seed germination and better plant development. Much attention is paid to the creation and use of disease-resistant hybrids.

Fusarium cobs of corn

Fusarium rice

Pathogens: some species of the genus Fusarium, in particular Fusarium graminearum Schwabe (syn.: Gibberella zeae(Schwein.) Petch).
The spots on the surface of the glumes are whitish at first, then yellow, pink or carmine. Affected grains are light, feeble, crumbling, may have a reddish color or brown spots. Stem nodes rot, blacken and collapse. The stems wither, break and the plants lie down. On the scales, sporodochia, clusters of conidia, blue-black perithecia can be seen. Perithecia also form at the nodes of affected stems. The source of the primary inoculum is the affected plant residues on which bags with ascospores, overwintered conidia and infected seeds are preserved. The fungus remains in seeds for more than 13 months. The germination of affected rice seeds is reduced by 2-3 times. The fungus produces mycotoxins that contaminate grain.
Protective measures: optimal agricultural practices, compliance with crop rotations, cultivation of relatively resistant varieties, destruction of affected plant residues, cleaning seed material from feeble seeds, dressing seeds before sowing, spraying with fungicides during the growing season.
On the territory of the former USSR, the disease is noted in the Rostov region, the Caspian region, the Krasnodar Territory, Dagestan, the Far East, Kazakhstan, Uzbekistan and Tajikistan.

Fusarium root rot of wheat

Fusarium soybean (root rot, tracheomycosis wilt)

Sunflower fusarium, sunflower root rot

Fusarium or tracheomycosis wilt of conifers

Fusarium wilt of tomatoes

Fusarium wilt of cucumber

Cucumber root rot

Tracheomycosis wilt of rhododendron

Pathogen: fungus Fusarium oxyspopum. Symptoms: the roots turn brown and rot, the fungus penetrates the vascular system of the plant and fills it, blocking the movement of nutrients. Leaves, starting from the upper parts of the shoots, gradually lose turgor, turn brown and dry. The leaves fall off along with the petioles, and a grayish-white mycelium begins to spread from the vessels of the stem along the bark. The infection persists in plant debris and infected plants.
Control measures: timely burning of dead plants along with the roots. In industrial cultivation, preventive spraying of plants and watering the root zone with a 0.2% solution