Spots on the leaves - what it is and how to fight
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Stains on plants - identify a disease or pest
From the middle of the summer, before the spotlessly clean foliage begins to become covered with various spots. Spots come in a variety of colors, large and small, round and irregular in shape, bordered and without, dropping out, merging. But their external similarity should not lead us astray.
Spots - due to illness
Most of them are caused by infections of various kinds. Specialists call such spots spotted leaves. The causative agents of spotting are most often fungi, less often bacteria and viruses. Pathogenic microorganisms develop inside the tissues of the leaf and cause discoloration and drying in the form of necroses of various forms and colors.
Mushroom and bacterial infections persist in plant debris and infected parts of plants - for example, in the bark of shoots, in wintering leaves (incense). Viral - in infected plants, seeds and is transmitted by sucking pests, for example trip-selves. aphids.
Some varieties and species of plants are resistant to spotting, while others, on the contrary, are highly susceptible. So if you get a plant whose leaves are already “stained”, you must be prepared for the fact that such spots will be present constantly. And over time, the varieties may be overdone, and then on each plant the spots will appear already in a complex way.
Reference by topic: Rust of pears (orange spots on leaves and outgrowths)
Mushroom infection it is present on overwintered leaves, petioles, and shoots and is manifested during vegetation on physiologically old leaves of the lower and middle tiers. Viral and often bacterial appears on young leaves of the upper tier. Spotting is often called by the name of the pathogen fungus - for example, septorious, askohitoenaya, pestalocium, etc., and by the color of the spots - black, ocher, white.
Manifestation spotting we notice from mid-summer to late autumn, but infection of young leaves begins long before that, almost from the beginning of regrowth. Spores from plant debris and from infected bark of shoots re-infect young blossoming leaves, mycelium develops within tissues, and as tissues die out one or another spotting. Spots on the leaves are already dead (necrotic) tissue sites. In them, over time, the point fruit bodies of the wintering stage of the fungus (pycnidia) are formed.
Moreover, the disease does not just disfigure the species of the plant, the stronger it is, the more abundant the premature fall of the leaves, and accordingly, the lower winter hardiness. All biochemical processes take place in the leaves, and without them young shoots become ripe and often freeze.
If on different plants the patches have the same name, for example, septoria, this does not mean that they pass to each other. So, septorious spotting roses - this is not at all that of delphinium, cinquefoil, mahonia, spirea, phlox, etc. And the pathogen fungi will be different, and the symptoms of manifestation will vary. So, in a rose, spots on the leaves are rounded, dark brown, brightening in the center, with a dark thin rim. On the shoots, the spots are oblong.
В necrotic point pycnidia are formed.
In flox, the septoria spot is shown to be small, 1-3 mm, brown, lightening and merge into large necrosis spots.
Phallostictose spotting geraniums are manifested by large brown spots with red bordering, and phylostictic, or red-brown, leaf spotting of chestnut trees are large red-brown or ocher spots of irregular shape without bordering.
Ascortic spotting of hydrangeas - ocher spots, irregular in shape, from the edge of the leaf blade.
Pestalotsia spot of rhododendron - small brown spots of irregular shape with a thin dark border at the edges of the leaf blade. Tissues die, and on them gray mushrooms of sporulation of a mushroom develop. Strongly affected shoots of young bushes. Pestalium spotting of the rose is manifested by brown spots growing towards the middle of the leaf, a yellow stripe is visible at the border, sporulation pads develop. the leaves turn yellow prematurely.
Black spot, or Marsonin, roses - this is a multitude of rounded merging radiant spots and the sporulation of the cornea that forms on them. Black spotting, or ritism, maple - spots are first yellowish-green, later black, merging, surrounded by a yellow border. The black bacterial spotting of the delphinium is caused not by the fungus, but by the bacterium. The spots on the leaves are round, numerous, black-brown, with a convex surface and concentric zoning. On the stems they are depressed and elongated.
Hole spot, or clusterosporiosis, - spots are numerous, reddish, brightening in the center, with a blurry border. Necrotic tissues quickly fall out and holes remain. When the shoots are affected, shallow ulcers with gum form.
Viral spotting is manifested by various stains, strokes, rings, yellowing of the tissue and deformation of leaves and shoots. For example, the mosaic virus of the rheusa is manifested by small spots, chlorotic zones of irregular shape, and veining of the veins. This virus does not limit itself to one rosula, but infects many flower and berry crops. The white gladiolus mosaic can be caused by several different viruses and manifests as yellow-green spots and bands that are necrotic and acquire a bronze hue.
Gray mold may also appear as spots. The spots are small, brown, enlarging, zonal. In dry weather, the necrotic tissue cracks and falls out, forming holes, with abundant precipitation and in the autumn the spots increase and are covered with abundant smoky-gray sporulation. Over time, small brown sclerotia are formed. Almost all plants are affected.
See also: Spots on tomatoes - reasons and struggle
Mines and their inhabitants
But there are spots of a completely different kind and nature, although they look similar. On the leaves you can often find spots of elongated, rounded and even serpentine shape. They are similar to spotting, but inside are always empty, since it is not necrosis, but mines, and inside they develop and feed on the tissues of the caterpillar of small butterflies - moths.
Widely distributed chestnut moth on chestnuts, lilac mole-pestryanka on lilacs, and mines of hawthorn moth are found on many trees and bushes. Butterfly moths are very small, and to detect their presence is obtained already after the fact, it is due to the presence of mines.
Chestnut moth - red-brown butterfly, lays eggs on leaves. The caterpillars are yellowish-green, feed on the inside of the tissues and form a tan mine of round or irregular shape. Pupae overwinter in a litter of leaves. 2-3 generations develop in a year. With a large number of leaves, they are completely covered with mines and dry out prematurely.
Mole hawthorn moth - a small butterfly with narrow wings trimmed with delicate fringe. Caterpillars form rounded wide dark mines in which excrement swirling in a spiral is noticeable.
Moth-Pearly Lilac lays eggs on leaves. Caterpillars form mines on the upper side of the sheet. Mina at first light color, but gradually becomes brown and occupies most of the leaf blade. In a year, two generations are developing, the pupae are hibernating in mines.
Mole-baby thorny - a very small butterfly. The caterpillar forms a mine on the upper side of the leaf. The beginning of the mine in the form of a thin, slightly sinuous passage filled with excrement, later a large brown oval spot with translucent excrement forms.
Cherry slimy sawfly - a black shiny insect with transparent wings. Larva is a greenish-yellow pseudo-caterpillar covered with black mucus. Transparent spots appear on the leaves, on which quite large larvae (9-11 mm) are often visible. Larvae overwinter in soil; two generations develop in a year. Oblong mines also appear on maples, but they are located on the underside of the leaf and form their caterpillars of the maple mining mottled moth. While in our country it is found singly, on planting material imported from the Baltic states. But there, this mole flies for a long time.
Stains on the leaves - protective measures
As you can see, the stains on the leaves are different, and the measures of struggle against them are always different. Against patches on plants it is customary to carry out preventive and eradicating treatments with copper-containing preparations: in the spring, in the beginning of summer and with a strong spread in autumn, especially on roses.
Caterpillars of moths feed on the leaf blade, and it is impossible to get them there. The most effective is the collection and burning of leaves with pupae in early spring and the preventive spraying of plants with phosphorus-containing preparations in May or early June, during the departure of butterflies and egg-laying.
Reference by topic: Brown spots on tomatoes - how to fight?
Spots on leaves - photo
© Author: L. TREIIVAS, O. KASHTANOVA, Phytopathologists of the GBS RAS
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