Many have heard of a herbaceous plant afflicting sunflower fields. Zarazikha - one of the most common parasites on the territory of our country. Large agricultural producers and summer residents have to deal with it. You can cope with a weed in different ways. In addition, there are preventive measures to ensure the purity of the fields.
The plant that litters the planting of oilseeds, is a root parasite and is part of the broomrape family. In adults, the light stem, tapering upwards, is not branched. Leaves are light green, similar to hard scales. In summer, the parasitic weed begins to bloom and forms dense panicles-inflorescences. A little later, fruits ripen, each of which contains up to 2 thousand seeds.
The danger of the grass is that it retains its ability to germinate for a long time. Ripe seeds remain viable for 10 years, and all this time they are in the soil until favorable conditions occur. The seed material of a broomrape parasite can be carried by the wind, and in addition, it is spread by people on clothes and shoes.
Summer residents and farmers should closely monitor the state of sunflower planting and begin to fight the parasitic weed as soon as it appears.
Sunflower seed: familiarity with the parasite
Sunflower contagion - a root parasite belonging to the broomrape family. The plant has a straight whitish stem, thickened at the base, without branches. Leaves on it in the form of scales. Blooms brown disproportionate flowers, collected in the inflorescence-spikelets. The fruit is a box containing up to 2000 small dark-brown seeds. Seeds are easily transferred by wind, water, human feet and tools.
Signs of plant damage
The main sign of sunflower damage by this plant will, of course, be the very presence of broomrape shoots and flowers at the base of sunflower stems. This parasite significantly reduces the fertility of the host plant, which is another sign of infection. And if the broomrape has not yet sprouted up, but has already struck the sunflower root system, this will be evident from the withering and drying look of the latter.
Plants at risk
This attack is dangerous not only for sunflowers. At risk are also such plants as tobacco, tomatoes, safflower, hemp and various weeds. All of them, too, are often victims of sunflower seed broomrape, but sunflower is still the best host plant for it.
This method involves alternating seeding of different crops in one field. That is, in the affected area after the sunflower, plant crops invulnerable to this scourge for 8–10 years before the sunflower can be sown again. During this time, the seeds of the parasite, which remained in the soil after the last sowing of sunflowers, lose their vitality, and the land becomes safe.
Agricultural practices include the following methods:
- deep plowing of the earth (with skaters),
- weeding the broomrape until we begin to ripen the seeds,
- preventing the parasite's seeds from entering the uninjured areas,
- soil moistening, because this type of pest likes dry land,
- deliberately stimulating the germination of as many seeds as possible from the ground by means of thickened sunflower sowing on contaminated areas. After that apply method 2 from our list. This frees the earth from more seeds.
Chemical control methods
Chemical methods suggest, as already stated above, the use of various herbicides that provoke the disease and the death of sunflower seed broomrape. You can buy these drugs in specialized stores and use according to the instructions. A vivid example of an effective herbicide is the water-soluble concentrate “Device Ultra”. It was developed by the Clearfield system and contains imazapir 15 g / l and imazamox 33 g / l. These substances act on the weed through the leaves and the root, causing its death. The same system has developed another equally effective herbicide, Euro-Lighting. It contains the same substances of the imidazolinone class as the “Device Ultra”, and for many years it has been successfully fighting broomrape and other weeds, ensuring a good harvest of sunflower.
There are developments (proposed by Dutch scientists at the 3rd International Symposium on Broomrape, Amsterdam, 1994) synthetic preparations of the string GR-24 on the basis of stririgol, which stimulate the germination of broomrape seeds. The preparations show high efficacy in provocation of the germination of broomrape seeds, but this method does not have mass use under production conditions due to the high cost of production of such preparations.
Since 2008, the Clearfield® production system on sunflower was registered in Russia, which allowed us to actually get crops and effectively fight all broomrape races on heavily infected fields. It is important to know that a hybrid resistant to herbicides of the chemical class of imidozalinones must be sown. An example of a herbicide for the Clearfield® Production System is a herbicide. KAPTORA.
It is desirable that the hybrid also has genetic resistance to race D, E.
Seeds are sown, and in the plant phase of 4–6 leaves (2–3 pairs of true leaves), crops are treated with herbicide KAPTORA at a dosage of 1–1.2 l / ha - this ensures the destruction of germinated seeds of broomrape and plant protection for 30 days. As a rule, crops before harvesting remain clean from broomrape and most of the annual weeds that came to the surface. It is noted that with heavy precipitation before the sunflower blooms, the sunflower root system actively grows in the upper soil layer and provokes the growth of broomrape from the seeds. However, the parasite has a minimal effect on the yield and quality of oilseeds in this case. After harvesting this hybrid, the return of sunflower to this field should be on the 5-6th year.
For the Clearfield® system, Syngenta offers sunflower hybrids NK Neoma, NC Fortima, Sanay MR, Tristanas well as high oleic hybrids SI Colombi and SI Expert.
One of the newest developments in sunflower protection is the Clearfield® Plus production system, which is a development of the Clearfield® system. It includes the Clearfield® Plus sunflower hybrids and the Euro-Lightning® Plus herbicide.
The herbicide reliably controls weeds, while the flexible rate of consumption of the drug allows you to select a solution for a specific situation in the field. Clearfield sunflower hybrids have a greater sensitivity to sulfonylureas, which makes it easier to control crop rotation in subsequent crops.
For the Clearfield® Plus system, Syngenta offers a new, mid-season, highly productive hybrid SI Bacardi KLP.
The germination of broomrape seeds can persist for many years - it has been scientifically proven that seeds germinated after 20 years of storage. Under the conditions of the soil horizon, moisture, diseases (fusarium) affect the seeds of broomrape, and seed germination may decrease, but only slightly. However, broomrape has enormous fecundity. Nowadays, a single broomrape plant can produce up to 500 thousand seeds, some of which can be stored in the soil for over 10 years.
The contagion sprouted and came out from a depth of 19 cm!
The use of different depth soil tillage and reservoir turnover in the farm leads to the "conservation" of seeds. When applying treatments in a layer of 0–15 cm, the effect on the reduction of seed germination is maximum.
It is believed that the mechanical removal of the parasite (weeding, pruning) is one of the methods of control, however, as a rule, the broomrape starts deep in the soil and before reaching the surface the parasite has time to damage the sunflower plant, until its death. It is also impossible to mechanically remove a broomrape, since with any damage to it, new shoots will grow from the remains at the root (not one, but many, like thistles, when pruning it).
Multiple broomrape shootsO. cumanafrom one nodule.
As a result of the traumatization of the nodules during the cultivation of the rows between them, multiple points of growth were laid, from which additional stalks grew, if the main shoot was threatened with death. The same phenomenon causes the defeat of Fusarium main escape. Over time, the sign of a multi-stem in a broomrape could be genetically inherited as a mutation useful for the species, and in this field there is already a certain percentage of broomrape plants capable of transmitting such a trait by inheritance.
Myth number 2. Deep plowing is an effective method to combat broomrape
Deep plowing does not help in the fight against broomrape. Broomrape seeds live longer inside the soil layers than on the soil surface. They also live longer in soils with a lower organic content. Deep plowing creates ideal conditions for the long survival of broomrape seeds.. Sooner or later, new plowing will lift them back to the upper layers of the soil, where the next infection of sunflower will occur.
Myth number 3. Mostly broomrape seeds are transferred to a new field with the help of wind
Obligate parasite, which is a broomrape, rarely migrates over long distances from heavily infected fields. In the course of development, broomrape seeds are more likely to attach to the host plant for the next year if they remain at a distance of 1-2m from the place of the previous infection. In addition, during evolution, broomrape seeds developed certain properties to avoid long-range transport. They are rather electrostatic and immediately adhere to soil particles upon contact with them. And observations on the ground showed that the broomrape seeds fall and remain within a radius of no more than 1 m from the parent plants. This leads to the appearance of foci of infection with broomrape, which increase every year and have a higher level of infection with broomrape in the middle.
Myth number 4. Immediate defeat of the field by broomrape (4th level) is possible if the seeds of broomrape are present in the seed
When using certified seeds of key global producers, such as Syngenta, this risk is excluded: seeds of first-class hybrids are produced in the fields, and often produced in countries where there is no broomrape.. When using counterfeit seeds, there is a small likelihood of broomrape seeds in the seed material. But this will never be the cause of infection of a field by a broomrape of the 4th level in the same year when its seeds hit the field. In the first year, when the broomrape seeds hit the field, only a minor infection is possible (level 1), which farmers often ignore. Only after the 3rd or 4th cycle of reproduction the broomrape can provoke the 4th level of infection, since it requires a billion seeds.
Conclusion: In order to minimize the risk of infection with a broomrape field, counterfeit seeds and seeds stored in farms should be avoided.
Myth number 5. New broomrape races appear every 10 years
New races of broomrape appear on every field, as soon as a stable hybrid is planted on it. A parasitic plant in each generation forms many new random mutations that occur when a suitable host plant appears. In the broomrape seeds collected in 1990, when only race E and genetically resistant hybrids existed, the seeds of broomrape race F were found, i.e. They have overcome the resistance of the hybrid in just 1 generation.
Conclusion: To prevent the development of new broomrape races, the use of resistant hybrids should always be accompanied by other ways of dealing with broomrape.
Myth number 6. The best way to fight broomrape is to use the latest sustainable hybrids.
This is not true. Experience shows that the broomrape is able to create new races as soon as a new stable hybrid appears on the field. In the mechanism of resistance of hybrids, under certain circumstances, malfunction may occur, leading to sporadic infections. Failures can be caused by several factors, and they are often associated with stress or the end of the vegetation cycle of plants.
When the sunflower is at the end of the ripening / wilting phase, its protective mechanism is weakened, and at this stage it is possible that it will be infected with a broomrape. This method broomrape uses to create new mutations to overcome the stability of hybrids.
Since hybrid seed companies do not use the same source of genetic resistance, it is difficult to classify new broomrape races using traditional control hybrids. New resistant hybrids should be used only when they are necessary according to the results of diagnostics of field races..
Opinion of the company "Singenta"
According to the experts of Syngenta, supported by laboratory analysis and diagnostics in the field, the best way to prevent new infections and to develop new broomrape races is a comprehensive monitoring system, which includes:
- using the necessary genetic resistance depending on the degree of infection of the fields,
- application of IMI-herbicides,
- optimal technology of cultivation of hybrids, which includes the use of provocative crops in crop rotation (corn, sorghum, etc.), the use of minimal and zero tillage, the implementation of technological cleaning equipment when it moves from the infected fields to non-infected areas.
Only by applying a scientifically based control system of broomrape for each specific field, the farmer can be confident in the high yield of sunflower from year to year.