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Video: Dodder Is A Dangerous Neighbor. The Plant Is A Parasite. Weed Pest. Wrestling. Photo
The genus dodil includes the parasitic flowering plants most dangerous for cultivated plants, combining great vitality with high fertility. Dodder comes from tropical America and Africa, from where it spread to the north and south, gradually adapting to new conditions and plants and distinguishing new species (up to 100 species are described). Distinguish between thin and thick-stemmed forms.
In our country, there are more than 30 types of dodil. All of them are objects of internal quarantine. The most common and harmful: Dodder field (Cuscuta campestris), Dodder clover (Cuscuta trifolii), Dodder hmelevidnaya (Cuscuta lupuliformis), Dodder linen (Cuscuta epilinum), Dodder korotkotsvetkovaya peppermint (Cuscuta breviflora), Dodder Lehmann (Cuscuta lehmaniana).
Dodders are aerial parasites, the body of which has turned into a filamentous or cord-like, curly, yellowish, greenish-yellow or reddish smooth or warty, chlorophyll-free stem with barely noticeable leaf traces in the form of scales. Plants are rootless, feed on and attach to the host plant with the help of suckers - haustoria, which are formed in places of contact with the feeding plant and deeply penetrate into its tissue. The suction of nutrients occurs due to the higher osmotic pressure of the parasite's cell sap.
The stem of the dodder is covered with numerous rather small, sessile or short-stalked flowers with a double perianth of white, pinkish or greenish color, collected in glomerular, spike-shaped or spherical inflorescences. The fruit is a capsule with four, rarely two or one spherical, oval or slightly elongated (sometimes irregularly shaped) seeds; from the inside, they are angular, covered with a hard cellular, pitted-rough shell.
Dodders parasitize on annual and perennial grasses, shrubs and trees (fodder legumes, technical, vegetable, melons, ornamental crops, vineyards, fruit trees, berries, wild herbs, shrubs and tree species). In addition to the main host plants, some species of dodilia are capable of infecting very many plants belonging to a variety of families. Only a few species are specialized for certain nutritional plants.
Sucking off water with organic and inorganic compounds dissolved in it, dodders cause metabolic disorders in host plants, weaken and retard their growth and development. Growing rapidly, the parasite covers entire areas of susceptible crops, often causing the death of affected plants. Not only the yield decreases, but also the winter hardiness of plants, the quality of products deteriorates. Grasses cut for hay, infected with dodder, dry poorly, grow moldy, lose their nutritional value, can cause diseases of animals, and sometimes even their death. Dodder also serves as a carrier of viral plant diseases.
The spread of these flowering parasites occurs mainly with the seeds of cultivated plants when they are poorly cleaned. In addition, they are carried by animals, cars, water, wind; get into fields with manure if cattle were fed plants infected with dodder; distributed with planting material, containers. The source of infection can be wild plant species and weeds infected with this parasite.
Distinctive features of different types of dodder are the morphology of the stem and flowers, as well as specialization to parasitize on certain feeding plants.
At dodder thyme thin yellowish or reddish threadlike stems branching thickness up to 1 mm, developing mainly in the lower part of the stems of the host plant, often forming a thick felt to the ground. The flowers are pink-white on very short peduncles, collected in dense spherical bunches. Abundant fruiting. Infects clover, alfalfa, vetch, beets, flax, potatoes, timothy and many weeds.
Field dodder has threadlike, pale yellow branching stems that develop in the middle and upper parts of the affected plants. The flowers are white. Abundant fruiting. It infects tobacco, makhorka, beets, clover, vetch, alfalfa, lentils, peas, soybeans, cabbage, carrots, watermelon, pumpkin, potatoes, yellow sweet clover and many weeds.
In alfalfa dodder or contiguous stems hairy-thin, yellow with a pink tinge or greenish, smooth, naked, white flowers, collected in dense glomeruli with bracts at the base. Abundant fruiting. Strongly affects alfalfa and many herbaceous plants.
Clover dodder has filiform, up to 1 mm thick, branched red stems. Before flowering, it spreads in the lower part of the stem of the feeding plant, where it forms a thick felt of branches, and only later rises higher. The flowers are pink, less often white, on very short pedicels, collected in dense spherical bunches. It parasitizes clover, alfalfa, nickel, beet, flax, potatoes and a number of weeds.
Linseed dodder has greenish-yellow, medium thickness, juicy, unbranched stems. The calyx of yellowish flowers is almost as long as the corolla. Seeds are single or double. It infects flax, camelina, clover, alfalfa, hemp, beets and other cultivated and weed plants.
European dodder is similar to thyme dodder, from which it differs in a thicker (2.5 mm) reddish stem. Her flowers are pinkish. Seeds are spherical or pear-shaped. It infects alfalfa, clover, sainfoin, hemp, beans, tobacco, hops, potatoes, lupine, vegetable seed plants, numerous weeds, as well as shrubs and trees.
Single -stemmed dodder has cord-like branched stems 2 mm thick or more. Her flowers are sessile or on short pedicels, collected in loose spike-shaped inflorescences. The corolla tube is short and does not protrude from the cup. It parasitizes grapes, trees and shrubs, can infect sunflowers, cotton plants, beets, as well as some weeds (nettle, wormwood, quinoa).
Dodder fruits (capsules) contain from 2 to 5 small seeds with a diameter of 1-3 mm, covered with a hard shell with a cellular, pitted-rough surface.
The embryo of the dodder is not differentiated into cotyledons; the root and stem are a spirally twisted thread immersed in a gelatinous proteinaceous nutrient mass.
The seeds of many types of dodder are very similar in weight, shape, and often color to the seeds of cultivated plants on which they parasitize. So, the seeds of dodder and creeping clover are so similar that they can only be distinguished upon close examination. The disguise of the seeds of a parasite under the seeds of a cultivated plant is the result of parasitic adaptation. This makes it difficult to use conventional methods of separating clover and alfalfa seeds from dodder seeds.
Seed cleaning has to be carried out on special sorting, the action of which is based on a combination of sieves and carminers with the subsequent use of special electromagnetic machines. Dodder seeds, which have a cellular surface, are mixed with magnetic powder and separated by electromagnets from the seeds of cultivated plants, in which the powder does not linger on the smooth seed coat.
Dodder seeds germinate 5-15 days after sowing. Unripe seeds swell and germinate faster than mature seeds.
When the seed swells, the spirally twisted embryo straightens, its thickened end, devoid of a cap and equipped with colorless hairs, grows into the soil and absorbs water. The opposite end of the seedling is freed from the seed coat, rises vertically and begins to rotate clockwise in search of a feeding plant.
In the initial period of development, seedlings receive nutrients from seed reserves. The sprout can "crawl" for a short distance due to the movement of nutrients from its base to the top. Such an independent existence can last 16-25 days, and there are cases when the length of the seedling reached 30 cm or more.
If the parasite does not meet a plant suitable for infection, it dies.
The attachment of the parasite to the host and its feeding are carried out with the help of haustoria, which are formed on the filamentous stem of the dodder from the side adjacent to the stem of the host plant. The substances secreted by the suction cups soften the epidermis, which facilitates the penetration of the parasite into the tissue of the feeding plant. If conditions are acceptable, the inside of the suction cup expands to form a wedge-shaped fluke.
The moss breaks the skin of the sucker, deeply enters the body of the feeding plant and is directed to its conducting beam. Having reached the wood, the central fluke cells turn into tracheids, and the phloem elements, in turn, combine with the corresponding elements of the host plant into a common system that allows the parasite to receive water and nutrients.
After the dodder adheres to the feeding plant, its connection with the soil is disrupted and it begins to live on the nutrients extracted from the host plant. In this case, the parasite develops surprisingly quickly, throwing out a huge length of yellowish or orange-tinged lashes, in the stem nodes of which lateral shoots are laid. Soon, the plants in the focus of infection are strongly entangled with long dodder stems. From one seed, a lesion with a diameter of up to 6 m2 can form. The vegetative body of the dodder has a high turgor pressure, which allows the cuttings of the shoots to not fade for several days.
Dodder seeds, due to shells with different water permeability, do not germinate at the same time, so the emergence of seedlings can be extended over several years.
Dodder control measures
In the fight against dodder, preventive measures are of great importance. Sowing is carried out with seeds cleared of dodders. They carry out approbation of crops on the vine, phytopathological examination, quarantine measures. Sowing with seeds contaminated with dodder is prohibited according to state standards.
The main source of infection of crops with dodder is the soil, in which large reserves of parasite seeds accumulate. Therefore, for sowing, they choose non-contaminated areas (according to field testing data) or clean the soil. Cleaning of the arable horizon is carried out either by planting dodder seeds to a great depth using plows with skimmers, or by stimulating their germination with subsequent destruction of seedlings by surface treatment. In areas of irrigated agriculture, seed germination is stimulated by provocative autumn and spring watering.
From the crops of alfalfa and clover, which are most often infested with dodder, the parasite spreads to other crops, primarily those that follow them in the crop rotation. Therefore, on infected fields, affected crops are excluded from crop rotation for 5-6 years.
If the dodder appears in the crops of perennial grasses (clover, alfalfa), they are mown before the beginning of flowering or seeding of the dodder. Timely cutting is especially effective against field dodders, 95% of whose stems are located at a distance not exceeding 5 cm from the soil surface, and with a low cut they are easily removed from the field along with hay.