6. Rust buds

Spruce cones are affected by rust. They are easily distinguished from healthy ones by their wide-open scales, on which the aetia of rust fungi are located in the form of orange or brown spherical containers. Rust damage sharply reduces seed yield and quality. The seeds become small and light. Cone rust is caused by two types of fungi.

Thekopsora padi Kleb from the class Teliomycetes - Teliomycetes forms inconspicuous spermogonia on the outer side of the covering scales, looking like flat crusts, and on the inner side - numerous closely crowded spherical aecia with a diameter of 1-2 mm of a dark brown color. The aeciospores that spill out of them infect the bird cherry leaves, on which first urediniospores develop, and then teliospores of the fungus. Damage to bird cherry leaves appears in the form of characteristic angular purple or brownish-crimson spots. After overwintering on fallen leaves, teliospores germinate and form basidia with basidiospores; the latter, spreading through the air, again infect the spruce cones.

Chrysomyxa pirolae Rostr from the class Pucciniomycetes also forms spermogonia and aecia on the covering scales of spruce. But unlike T.padi, in C.pirolae aecia are usually located two per scale; they are larger (3-4 mm in diameter), in the form of rounded orange subepidermal pads filled with aeciospores. When ripe, aeciospores are quickly destroyed, and the released aeciospores cover the surface of the affected cones with orange powder. Aeciospores infect the leaves of wintergreens, and the uredinio- and telio-stages of the fungus develop on wintergreens. Measures to combat spruce cone rust have not yet been developed.

Fig.3 Rust of spruce cones

Measures to combat spruce cone rust have not yet been developed. There are recommendations for the destruction of affected cones and bird cherry, an intermediate host of the fungus T.padi, in forest seed plots of spruce and in adjacent plantings.

Fig.1. Rust of broad beans: 1-affected leaves with aecia; 2-aeciospores; 3-affected leaves with uredinia; 4-urediniospores; 5-affected leaves with telopustules; 6-teliospores. Distributed everywhere. Known in England, France, Poland and others...

Bioecological features and development cycle of pathogens of broad beans

The disease is caused by the fungus Uromyces fabae. Division Basidiomycota Class Basidiomycetes Order Uredinales. All stages of pathogen development take place on broad beans. In spring, the spermogonial and aecial stages appear on the upper and lower sides of the leaves...

Molecular genetic identification of bread wheat lines from the KNIISKh collection resistant to leaf rust

Soft wheat (Triticum aestivum), the main grain crop in most countries, is widely cultivated from the northern polar regions to the southern reaches of Africa and America. Today, wheat is sown in the world on an area of ​​about 225 million hectares...

When studying the course “Protection of ornamental plants from pests and diseases” in laboratory classes, students become familiar with the ecology of pathogens and plant pests, their taxonomy and biology.

Using herbarium and collection material characterizing each group of diseases, students must study the main signs of diseases and damage to ornamental plants, accurately diagnose a particular pathological phenomenon observed in plants in order to prescribe effective health measures in accordance with the nature of the object.

Laboratory classes are conducted in subgroups. The student’s main document is his workbook, in which the necessary notes and drawings are made for each type of disease and pest being studied for each topic of study. Students work on missed laboratory classes independently using methodological instructions, a textbook and visual aids.

When studying pests and diseases of ornamental plants, collections and color tables are used. It is proposed to make entries in the workbook according to the following scheme:

Name of the disease or pest;

Russian and Latin names of malware and their systematic position;

Diagnostic signs of diseases and injuries, the nature of sporulation of fungi;

Brief information on the biology and ecology of diseases and pests.

Topic 1 Pests and diseases of fruits and seeds of ornamental plants

1.1.1 Using collections and textbooks, study and record signs of diseases and damage by insects to fruits and seeds.

1.1.2 Provide brief information on the protection of fruits and seeds from pests and diseases using the “State Catalog of Pesticides and Agrochemicals Permitted for Use on the Territory of the Russian Federation.”

Reporting form: prepared notes with completed tasks, quiz.

1.2 Diseases of fruits and seeds (according to I.G. Semenkova, E.S. Sokolova, 2003)

1.2.1 Rust of spruce cones

Spruce cone rust is caused by two fungi.

ThekopsorapadiKleb. forms inconspicuous spermogonia in the form of flat crusts on the outer side of the covering scales, and on the inner side - numerous closely crowded spherical aecia with a diameter of 1-2 mm of a dark brown color. The aeciospores that spill out of them infect the bird cherry leaves, on which first urediniospores develop, and then teliospores of the fungus. Damage to bird cherry leaves appears in the form of characteristic angular purple or brownish-crimson spots. After overwintering on fallen leaves, teliospores germinate into basidia with basidiospores; the latter again infect the spruce cones.

ChrysomyxapirolaeRostr. also forms spermogonia and aecia on the covering scales of spruce, but, unlike T.padi, in this fungus aecia are usually located two per scale; they are larger (3-4 mm in diameter), in the form of rounded orange pads filled with aeciospores. When the aecia ripen, the released aeciospores cover the surface of the affected cones with an orange powder. Aeciospores infect the leaves of wintergreens, on which the uredinio- and teliostages of the fungus develop.

1.2.2 Deformation of fruits and seeds

Deformation of alder fruits. The disease is caused by a fungus Taphrina alni- incanae (Kuhn.) Magn. It manifests itself in the deformation of seeds and the proliferation of scales, turning into ugly leaf-like formations on which bags develop. The mycelium of the pathogen overwinters in the buds, from where, after flowering of the alder tree, it passes into the female catkins.

Pests rarely attack healthy, properly planted spruce trees. The soil should be light, moist and slightly acidic. The application of fertilizers helps improve the growth of spruce trees, the development of their root system, and also protects them from diseases and pests.

It is more difficult to detect pests on coniferous trees than on deciduous trees, but measures to combat common pests - aphids, scale insects, butterfly caterpillars - are the same for all plants.

Dark coniferous species (spruce, fir, cedar pine) are very sensitive to damage; the loss of 70–80 % of needles usually leads to the death of the tree.

Several dozen species of sucking pests are known on spruce trees, including coccids (scale insects, false scale insects, mealybugs), aphids, hermes and spider mites. They suck juices from needles, shoots, branches, trunks and even roots. They are small in size and unnoticeable. They can be detected by sticky secretions that cover the surface of needles and branches, or the presence of galls.

• Yellowish spots appear on old needles, and later the needles fall off. Sitka spruce aphid- pest of prickly spruce, Serbian spruce and Sitka spruce. This is a green sucking insect measuring only 1-2 mm in size. Aphids can be detected by holding up a sheet of white paper and tapping on a branch.

Sitka spruce aphid

Control measures. Aphids are bred and grazed by ants. The solution is to prevent the spread of ants. If there are only a few aphids, regularly wash the infected areas with clean cold or soapy water (but before doing this, you need to cover the soil so that large quantities of soap do not get on the roots). The procedure must be repeated more than once with an interval of 6–10 days. Cutting off the ends of shoots with colonies of aphids significantly reduces the harmfulness of insects. This event can be combined with scheduled pruning.

• Curvature and yellowing of the needles; sticky fluffy snow-white formations are visible on the underside of the needles. At the ends of young shoots there are formed Gauls. This HERMES GREEN SPRUCE-LECH or SPUR-FIR. These “bumps” gradually grow, enlarge, and acquire a crimson color. Inside such a shortened, mutilated spruce shoot there are up to 120 pest larvae. You can see adult females on the bark of the buds, and brown or yellowish-green larvae on the needles. Hermes larvae cause bending, drying and further shedding of needles. The branches on which galls appear dry out the next year. In mid-summer, the galls crack and young aphids fly to spruce, fir or larch trees growing nearby. Hermes mainly harms spruce and prickly spruce.

Control measures. It is very simple to eradicate Hermes - remove all shoots with galls in a timely manner, and no chemicals are required. Do not plant larch and fir next to spruce. When spreading - spraying with insecticides. Insecticide aerosols do not penetrate through the fluff, so it is best to treat Hermes through the sap of the plant with systemic insecticides.

• The needles are braided with a web and due to this they stay on the tree. When there are gusts of wind, the needles fly away and the crown is exposed. Tiny caterpillars mine needles by making round holes at the base of the needles. This is how it works SPRUCE LEAF ROLLER, it harms many types of spruce trees. It can be difficult to diagnose unless you touch the needles with your hands.

Control measures. Affected shoots must be repeatedly treated with a solution of liquid soap or removed. Dry needles can be combed out with a small fan rake, polyethylene or other material laid under the tree, and the collected needles can be burned. If the pest is widespread, use systemic pesticides that penetrate the plant tissue and are transported through vessels throughout the plant.

• The needles are entangled in a thin, sparse web, covered with yellowish spots, later turning brown and crumbling. SPUR MITE and its larvae damage young plants: spiny spruce, Canadian spruce, common spruce, western thuja, juniper, biota. They do little damage to Engelmann spruce, Serbian spruce. Over the summer, the female gives 3–4 generations. The mite causes the greatest damage in hot years to trees growing on dry soils. During the growing season, mites form from four to six generations, so the degree of damage increases towards the end of summer.

Spruce spider mite

Control measures. Good care of young seedlings. Preventatively spray plants with cold water to increase humidity. When symptoms appear, spray with colloidal sulfur, infusions of dandelion or garlic. If the affected area occupies a significant area, then use acaricides.

• Browning and falling of needles, drying out of branches, shiny marks. SPUR FALSE SCALE It is not only a pest of common spruce, but also of other spruce species. Massive colonies of insects on young plantings, sucking out the juices, not only cause a general slowdown in growth, but often completely destroy the plant. branches of adult trees on which colonies of pseudoscale insects appear dry out and become deformed, their total assimilating surface decreases, and this retards growth and reduces the winter hardiness of trees. Females and larvae feed on sap on needles and shoots, secreting honeydew.

Spruce moth

Control measures. Trees growing in shaded areas and on dry soils are especially affected by spruce scale insects. Compliance with correct agricultural practices prevents pest attacks. Preventive spraying of young trees with insecticides helps. If the number is large, spraying is repeated in August - September.

• The needles of young spruce seedlings and saplings begin to dry out and crumble. Two types of juices are sucked from the thin roots of young fir trees. ROOT APHIES: spruce honeysuckle, for her spruce is an intermediate plant, and spruce root. Root aphids mainly damage seedlings and saplings.

Root aphid

Control measures. Root aphids can be destroyed only with systemic insecticides.

• The needles turn yellow and curl. Small insects with white fibrous shields on their backs appeared on the branches, protecting them from predators. These are relatives of aphids - CONIFERE BUGS. In dry years they multiply in such numbers that the branches appear to be covered with frost. These pests can also be found on fir and pine trees. Like all other sucking insects, mealybugs are the main carriers of viruses.

Coniferous Cherevtsy

Control measures. Spraying with tobacco infusion three times at weekly intervals. In case of severe damage, you should resort to “systemic” insecticides; they penetrate the sap of the treated plant and temporarily make it poisonous to pests.

Insects that eat buds and needles are called pine-eating pests. They are quite numerous and are represented by species of butterflies, sawflies and beetles.

• Young needles on the apical and lateral shoots acquire a red-brown color and do not fall off for a long time. It is first mined, and then eaten entirely by the larvae of the common SPUR SAWFLIGHT. Its larvae are very difficult to see; they are well camouflaged under pine needles. Old spruce needles are gnawed by solitary and nesting sawflies. Both of these sawflies make their homes out of cobwebs and excrement.

Control measures.

• The kidneys are eaten. If the kidney is damaged from the inside, then it is SPUR BUD SAWFLIGHT or caterpillar SPRUCE MOTH. If the kidney is damaged from the outside, then this WEevil. Damage to buds and shoots is especially dangerous for young trees.

Control measures. Dig up tree trunk circles. Destroy nests and larvae when the pest population is low. Spraying with infusions and decoctions of insecticidal plants. In case of large numbers, treat the larvae with insecticides.

• In May-July, moths fly around the spruce trees, followed by caterpillars appearing on the branches. It could be SPOTTED MOTH, a butterfly from the noctuid family. Its harmful caterpillars are brownish-gray and covered with long hair. They appear in August-September and eat the needles. They look different, but they also cause harm. MOTH DARK GRAY And CONIFEROUS MOTH. They pupate in the ground under the spruce tree.

Control measures. Food baits with fermentation additives. These baits are good because they work all summer long. Digging or loosening destroys brown pupae. Treatment of plantings with insecticidal and biological products during bud break.

Fir cones are a real delicacy for many pests. The cones are damaged by caterpillars of leaf rollers, moths, moths and the larvae of grinders, gall midges and seed eaters. Pest-damaged pine cones can be easily identified by their distortion, discoloration, and dust spilling out of the cone.

• In June-July, butterfly flights usually occur in the evenings. This CONE FIRE, whose caterpillars gnaw cones and eat seeds. A brownish mass of excrement hangs on the surface of the cones, with resin deposits in places. The cone moth inhabits the cones of common, oriental and Siberian spruce, Caucasian fir, Siberian larch, and Korean cedar pine. This is one of the main pests of coniferous seeds.

Control measures. Treatment with systemic insecticides during the hatching period of caterpillars.

Stem pests damage the bark and various layers of wood. Their larvae develop under the bark, penetrating all layers of the tree (depending on the species of the pest). Burying under the bark, bark beetles secrete odorous substances - pheromones, and new beetles flock to their smell. For example, beetles flock to the smell of the spruce bark beetle from a distance of up to 11 km! It is extremely rare that a tree infested with bark beetles can be saved, and if the beetles have infested it along the entire circumference of the trunk, then the only measure is to urgently destroy the tree before the young generation of beetles emerges from under the bark.

• Already in mid-summer the needles begin to fade, later turning yellow and falling off. Numerous small holes in the bark. Brown drill flour is poured abundantly around the entire circumference of the trunk. BARK BEETLE-TYPOGRAPHER often affects weakened spruce trees of various ages. A very dangerous pest. It destroys trees in the historical parks of Pavlovsk and Pushkin, at one time it destroyed the spruce tent in Trigorskoye and several memorial Hannibal spruces in Mikhailovskoye (Pushkin Mountains Museum-Reserve). Ubiquitous in our forests. Such trees must be removed before the young generation of the typographer finishes developing under the bark and flies out into the wild.

• Red needles on the branches of spruce and fir trees, large resin funnels in places where pests have entered the trunk. LARGE SPRUCE BEETTER- the largest of our bark beetles, up to 9 mm long. An extremely dangerous pest, very aggressive. It attacks mainly old spruce trees, but does not neglect young ones. It can also inhabit pine trees. In recent years, blue spruce trees in Peterhof have been dying from it. At the slightest sign of weakening of the tree, you need to carefully examine the trunk, and if you see drill flour, do not spare the tree, but remove it as soon as possible.

Great spruce beetle

• Beetles crawl along the trunk; they have an elongated body and mustaches characteristic of these insects, which can extend over their backs. The length of the whiskers in some species significantly exceeds the length of the beetle itself. BLACK SPRUCE BEETLES penetrate into the tree trunk and make numerous moves there. When laying eggs, longhorned beetles leave characteristic marks on the bark, as if they had pressed on the bark with a fingernail. Usually the barbel comes to us from nurseries along with infected planting material.

• In May-June, black beetles appear with a rusty-red border of the shield and yellow-brown elytra, along which there are two longitudinal stripes. It's dull-chested SPRUCE LOOKMAN. It harms spruce and also damages fir, pine and larch. The beetle settles on weakened or diseased trees. The larvae make wide passages in the wood.

Spruce Lumberjack

Control measures. At the initial stage there is a chance to save the tree. Careful treatment with protective drugs and douching of the resulting holes can kill the first beetles, preventing them from multiplying and attracting the bulk of pests to the trees. During the period when beetles emerge (June - July), the tree crowns are sprayed with contact insecticides. If you find borer, use a knife to remove the bark where it appears and scrape off the white larvae that eat the cambium. The fight against bark beetles using pheromone traps cannot be carried out in the garden plot, as the traps will attract beetles from all surrounding forest plantations. Traps are hung in the nearest forest area, as is done in forests and parks, where a dozen trees can be sacrificed to save a thousand. The main thing is not to forget to check the traps and remove any pests caught in them.

Pheromone trap

Spruce trees, like all conifers, suffer more from non-infectious diseases caused by unfavorable environmental conditions and gardeners’ mistakes during planting and care.

• Landing with strong DEEPening. In nature, the roots of spruce trees come to the surface.
• LACK OF WATER is a common cause of spruce death.
• If your Norway or Norway spruce has yellowed needles, in most cases the cause is a lack of nutrients.
• SEVERE FROSTS can damage young plantings.

• The heavy mass of SNOW leads to branches breaking.

Spruces very often suffer from FUNGAL diseases. As a rule, they do not cause the death of the tree, but can provoke premature needle shedding, which affects the appearance of the trees. Fungal diseases are provoked by dense planting, lack of light and excess moisture in the air and soil.

• The needles turn brown in May, but remain on the branches. Fungal spores form at the bottom of the needles. The neighboring needles become infected, the plants turn brown, the shoots do not overwinter well - SCHUTTE.

• In autumn, brown spots appear on young needles; in early spring, white mycelium develops on the needles. The needles darken and fall off - SNOW SCHUTTE.

• On young seedlings the needles turn brown and fall off, traces of fungal sporulation are visible - Fusarium, a disease that affects the roots, the infection penetrates through the vessels into all tissues.

• Dry top, thinning and drying out of part of the crown; in case of severe damage, mushroom caps grow on the trunk - stem and root ROT. Root rot penetrates the wood of the trunk and causes the death of the tree.

• The bark of the branches darkens, dries out, brick-colored growths or dark small pads form on it, the bark dies, and the tree dies. NECROSIS bark.

• Ulcers form on the trunks: open, with tar, with protruding mushroom bodies, or closed, in the form of numerous resin nodules - ULCERATIVE (wound) CANCER can be caused by fungi and bacteria.

• Round dusty dark brown pustules appear on the inside of the bark scales. The cones are wide open, hang for several years, the seeds do not germinate. This RUST CONES. Sometimes the shoots become bent; the disease in this form is called SPUR SPINNER. Infection occurs from bird cherry.

Control measures. Healthy planting material, timely removal of dried branches, coating of cuts with garden varnish and paint. Increasing sustainability through the use of microfertilizers and immunostimulants. Do not plant next to bird cherry. Treating the roots of seedlings with fungicides before planting. When signs of disease appear, water with fungicides at the roots. Preventive spraying in early spring with copper-containing preparations. Destruction of affected needles and branches.

Lyudmila Shcherbakova,
Candidate of Agricultural Sciences, Associate Professor of the St. Petersburg Forestry Academy, specialist in the conservation and protection of garden and park plants

Fungal disease.

Rust spruce cones are affected. They are easily distinguished from healthy ones by their wide-open scales, on which the aetia of rust fungi are located in the form of orange or brown spherical containers.

The affected cones have wide open scales, a darker color, and on their inner surface numerous dark brown spherical spores of the fungus called bird cherry tecopsora.

Rust damage sharply reduces seed yield. In addition, the seeds developing in such cones are usually puny, small, and lightweight. They have low germination. With severe development of the disease, the affected cones sometimes do not produce viable seeds at all. Therefore, you should not collect cones, even slightly affected by rust, for seeds. This disease causes harm to forestry, preventing the natural regeneration of the forest and the production of valuable seeds for artificial propagation of spruce. Spruce cone rust is caused by two species of different host fungi with a complete development cycle.

Thekopsora padi forms inconspicuous spermogonia on the outer side of the covering scales, which look like flat crusts, and on the inner side - numerous closely crowded spherical aecia with a diameter of 1-2 mm, dark brown in color. The aeciospores that spill out of them infect bird cherry leaves, on which first urediniospores develop, and then teliospores of the fungus. Damage to bird cherry leaves appears in the form of characteristic angular purple or brownish-crimson spots. After overwintering on fallen leaves, teliospores germinate and form basidia with basidiospores; the latter, spreading through the air, again infect spruce cones.

Another causative agent of cone rust has a similar development cycle - chrysomyx wintergreen.

Chrysomyxa pirolae also forms spermogonia and aecia on the covering scales of spruce. But unlike T. padi, in C. pirolae aecia are usually located two per scale; they are larger (3-4 mm in diameter), in the form of rounded orange subepidermal pads filled with aeciospores. When ripe, aeciospores are quickly destroyed, and the released aeciospores cover the surface of the affected cones with orange powder. Aeciospores infect the leaves of wintergreens, on which the uredinio- and teliostages of the fungus develop.The intermediate host of this fungus is wintergreen. Wintergreens are interesting because their leaves are green all year round. The mycelium of the fungus with autumn spores overwinters in such leaves. In the summer you can find specimens of wintergreens whose last year's leaves have dried out as a result of infection by the fungus, and on the new leaves bright orange pustules of the fungus are noticeable - the result of the current year's infection. Infected wintergreens do not form slender peduncles with snow-white flowers.

Control measures rusty spruce cones have not yet been developed. There are recommendations for the destruction of affected cones and bird cherry, an intermediate host of the fungus T. padi, in forest seed areas of spruce and in adjacent plantings;destruction of fallen pine needles; spraying spruce seedlings and young crops with 1% Bordeaux mixture.

Rust cones

Spruce cones are affected by rust. They are easily distinguished from healthy ones by their wide-open scales, on which the aetia of rust fungi are located in the form of orange or brown spherical containers. Rust damage sharply reduces seed yield and quality. The seeds become small and light. Cone rust is caused by two types of fungi.

Thekopsora padi Kleb from the class Teliomycetes - Teliomycetes forms inconspicuous spermogonia on the outer side of the covering scales, looking like flat crusts, and on the inner side - numerous closely crowded spherical aecia with a diameter of 1-2 mm of a dark brown color. The aeciospores that spill out of them infect the bird cherry leaves, on which first urediniospores develop, and then teliospores of the fungus. Damage to bird cherry leaves appears in the form of characteristic angular purple or brownish-crimson spots. After overwintering on fallen leaves, teliospores germinate and form basidia with basidiospores; the latter, spreading through the air, again infect the spruce cones.

Chrysomyxa pirolae Rostr from the class Pucciniomycetes also forms spermogonia and aecia on the covering scales of spruce. But unlike T.padi, in C.pirolae aecia are usually located two per scale; they are larger (3-4 mm in diameter), in the form of rounded orange subepidermal pads filled with aeciospores. When ripe, aeciospores are quickly destroyed, and the released aeciospores cover the surface of the affected cones with orange powder. Aeciospores infect the leaves of wintergreens, and the uredinio- and telio-stages of the fungus develop on wintergreens. Measures to combat spruce cone rust have not yet been developed.

Fig.3

Measures to combat spruce cone rust have not yet been developed. There are recommendations for the destruction of affected cones and bird cherry, an intermediate host of the fungus T.padi, in forest seed plots of spruce and in adjacent plantings.

The disease is caused by the fungus Taphrina alniincanae (Kühn) Magn from the class Archaeascomycetes. It manifests itself in the deformation of seeds and the growth of scales, turning into ugly leaf-like formations on which bags develop. The source of infection is the mycelium of the pathogen, which overwinters in the buds, from where, after flowering of the alder tree, it passes into the female catkins.

Measures to combat fruit deformation should be aimed at eliminating overwintering infections and preventing new infections. This is achieved by pruning branches on which deformation of fruits was observed, collecting and destroying affected fruits, and preventive spraying of trees with fungicides in autumn or early spring. The most commonly used is a 3% solution of iron sulfate.

Fig.4

Diseases of seedlings and seedlings

The disease is caused primarily by fungi of the genus Fusarium. Distributed almost everywhere. A characteristic feature of lodging pathogens is that their conidia germinate in the spring when the soil warms up to 6 - 8 °C, i.e. most often 2 weeks earlier than coniferous seeds, and therefore by the time seedlings appear, the mycelium is developed to such an extent that it is quite capable of infecting seedlings and seeds. Infection from diseased plants to healthy ones is transmitted in the soil through mycelium due to the close proximity of seedlings to each other.

This disease most severely affects coniferous crops, and among deciduous trees it most often affects euonymus, Norway maple and Tatarian maple.

Fig.5

Less commonly, this disease is found in crops of elm, linden, birch, poplar, ash, mulberry, white acacia, oleaster and yellow acacia. For many breeds, 4 main stages of the disease can be distinguished.

Rotting of seeds and seedlings begins to develop during seed germination; empty spaces remain in the sowing lines among the seedlings. When excavating the soil, seeds and black seedlings that have died from rotting are discovered.

Lodging of seedlings is most often observed from the second - third day of their appearance on the soil surface and up to 4 weeks of age, while the plants are not yet sufficiently lignified. The stalk near the root collar becomes wrinkled, thins out, a constriction appears in this place, and the plant falls to the ground and lies down (Fig. 1 - pictures not shown

In seedlings older than 4 weeks of age, the roots rot, but the plants no longer lie down, but dry up while standing. In this case, as in the previous stage of disease development, the seedlings are easily pulled out of the soil with the axial cylinder exposed. This sign of the disease and its focal nature are characteristic of lodging.

When the tops of seedlings wilt, the above-ground part is affected, but the root system remains healthy. The plant loses turgor, the needles become soft and have a disheveled appearance. The vascular system of seedlings turns out to be filled with fungal hyphae.

The source of infection is contaminated soil and, to a lesser extent, seeds and auxiliary materials (tire, shields, etc.). The development of lodging is favored by rainy and cool weather in May - June, deep planting of seeds, the formation of a crust on the soil surface, introducing undisinfected composts from rotting residues into the soil and using them for cover, creating thickened crops, as well as crops on heavy soil.

To prevent the spread of infectious lodging, it is necessary to stratify pine, spruce and larch seeds in the snow and treat them with microelements before sowing.

Seed stratification. Before stratification, the seeds are scattered into gauze bags of 2 - 3 kg, soaked for 1 day in water, and then dried until flowable and thoroughly etched with 80% TMTD at the rate of 4 - 5 g of the drug per 1 kg of seeds. Bags with pickled seeds are laid out in a layer of 5-6 cm and covered with snow, and the whole pile is covered with sawdust on top to prevent the snow from melting. Pine, spruce and larch seeds are stratified in this way for 1.5 - 2.0 months.

Treatment of seeds with microelements. 2 days before sowing, the seeds in bags are removed from under the snow and soaked in one of the solutions of microelements. For this purpose, use: for pine - zinc sulfate salts (0.02 percent solution), cobalt (0.05%), copper (0.03%), potassium permanganate (0.002%), a mixture of potassium permanganate, boric acid, copper sulfate, zinc and cobalt (0.002% each); for larch - zinc sulfate (0.02%), cobalt (0.03%) and sodium bicarbonate (0.12%); for spruce - cobalt sulfate (0.03%), copper (0.03%) and a mixture as for pine. Solutions of microelements are prepared immediately before their use. Seeds (in bags) are soaked at the rate of 1 kg in 2 liters of solution for 18 - 20 hours, after which they are left moist in the shade for 1 day, without spilling out of the bags, thus “simmering”, and then dried in the shade, pickled and immediately sown. Seeds stratified and treated with microelements cannot be stored.

Damping off of pine seedlings

The disease is caused by the fungi Sclerotinia graminearum Elen., and Typhula graminearum Gul., which affect only annual pine seedlings in central European Russia, Siberia and the Far East. The first mushroom belongs to marsupials, and the second to aphyllophoroid hymenomycetes.

It is characterized by the death of the top of the seedling. The first signs of the disease can be detected in pine crops under the snow, starting in the second half of March, when aerial mycelium grows and spreads to healthy plants. Immediately after the snow cover melts, the clumps of seedlings are covered with a film of cobwebby mycelium, which after a few days collapses and disappears. The affected needles are uniformly colored reddish-brown. A few days after the snow melts, sclerotia are found on the needles, in their axils, on the buds, on the stem near the bud, and sometimes inside the stem of the affected seedlings.

Sclerotia do not adhere well to plants; by the end of May, the tops of the seedlings are destroyed and fall off. The affected needles become discolored over time, as if they are fading.

Fig.6

In addition to pine, wild herbs are also susceptible to the disease: timothy, fescue, bluegrass, hedgehog, foxtail, bromegrass, wheatgrass, forget-me-not, chickweed, chickweed, cinquefoil and yarrow. These grasses infest nurseries and are a source of infection for pine crops. Sclerotia located on the soil surface and at a depth of 2 - 6 cm retain the ability

Successful germination of Sclerotinia graminearum Elen. is facilitated by warm and humid autumn, and for Typhula graminearum Gul. a warm autumn is not necessary.

To protect crops from disease, systematic weed control should be carried out, including in autumn and spring. To speed up the melting of snow, it is advisable to scatter peat chips or ash over its surface. If the disease is detected, it is necessary to carefully select and burn all infected seedlings no later than a week after the snow cover melts. Chemical measures to combat the disease have not been developed.