Nematodes are a very harmful pest in the cultivation of vegetables in facilities. This year the occurrence of nematodes is heavier than in previous years, especially in cold sheds. This is mainly because last year's winter was warm winter and the ground temperature rose relatively quickly this spring, which created a favorable living environment for the occurrence of nematodes. In order to fundamentally control the harm caused by nematodes to vegetable cultivation, it is necessary to have a detailed understanding of the classification, occurrence characteristics, transmission routes, and control measures of nematodes, and then we can fundamentally control nematodes.
Nematodes harm the roots of cucumber plants, causing wilting to die
<h1 class= "pgc-h-arrow-right" >, the classification of nematodes that harm vegetables</h1>
There are many types of nematodes, but the nematodes that cause harm to vegetables are mainly divided into the following types:
Root-knot nematodes: it is the most harmful to vegetable cultivation and the most harmful, because the most significant feature of root-knot nematodes is the root system or tubers that harm vegetables, and the typical feature is the formation of fat deformed nodules on the roots or lateral roots of the root of the diseased plant. In general, small new roots can be born on top of the root knot, and if it is re-infected, a root-knot tumor will be formed. When the disease is mild, the plant has no obvious symptoms, while when the disease is more severe, the diseased plant is dwarfed, the fertility is poor, and wilting or dying at noon in the arid environment.
Stem nematodes: mainly harmful to tubers and strawberries, etc., stem nematodes will not appear root knots, but will directly rot, and there will be spots.
Bud nematodes: The most harmful bud nematodes are strawberries and the only aboveground nematode disease. Bud nematodes harm axillary buds and creeping stems, resulting in leaf deformities.
Among these three types of nematodes, the most serious harm to our vegetables is the root-knot nematodes, and the root-knot nematodes are divided into southern root-knot nematodes and Javan root-knot nematodes, where the southern root-knot nematodes are not regions, but the names of nematodes. In our northern vegetable cultivation, almost 90% of the root knot nematodes are southern root knot nematodes.
The leaves are yellowed and water-stained due to nematodes
<h1 class= "pgc-h-arrow-right" > second, the occurrence characteristics of nematodes</h1>
The prevention and control of any disease and insect pest, in order to fundamentally control it, must understand the characteristics of its occurrence, and the occurrence of nematodes mainly has the following characteristics:
Temperature: Temperature here refers to ground temperature. The most suitable ground temperature for nematodes is 15 to 30 ° C, in this temperature range, every 30 to 45 antenna worms can reproduce one generation, therefore, the breeding speed of nematodes is very fast. Eggs can hatch at ground temperatures of 10 to 12°C. The lethal temperature of nematodes is 55 ° C at high temperature and 5 ° C at low temperature, why mention temperature, because this is closely related to the later control.
Environment: Extreme humidity and drought in the environment will be inhibited by the activity of nematodes, which is not conducive to the survival of nematodes. Nematodes have particularly strict requirements for the living environment, not tolerant to high temperature, low temperature, nor tolerant of flooding and drought, including lack of oxygen, which are extremely detrimental to the growth of nematodes, and we can also use this feature to control nematodes.
Long survival time without a host: Nematodes can survive for 3 years before dying in the absence of a host, that is, nothing is planted in the ground, which is also an important reason why nematodes are more difficult to treat.
Nematodes live in the soil tillage layer: nematodes mainly live in the soil tillage layer of 3 to 10 cm, accounting for about 80%; there is almost nothing below 20 cm, because the soil tillage layer below 20 cm is poorly permeable, and the nematodes are difficult to survive.
Nematodes are acidic: Nematodes prefer soil with a PH value of 5 to 6.5, and it is difficult to survive when the PH exceeds 7.2. Nematodes prefer sandy loam soils rather than clay-heavy soils, and sandy loam soils are well breathable, so the rate of reproduction is fast and the heavier it occurs.
Understanding the occurrence characteristics of nematodes and control are closely related, if you want to light the occurrence of nematodes, you must artificially create an environment that is not conducive to the occurrence of nematodes.
Orange-red egg mass of root-knot nematode
<h1 class= "pgc-h-arrow-right" > third, why is it difficult to control nematodes? </h1>
The reason why nematodes are difficult to control is related to the nematodes themselves and our management factors:
Fast reproduction speed: As we mentioned earlier, nematodes can reproduce a generation in a month or so when the environment is suitable, and the breeding methods of nematodes are diverse, not only can reproduce in both sexes, but also can reproduce parthenogenesis, somewhat similar to aphids, that is to say, nematodes can also lay eggs and reproduce when there are only female insects.
Facility cultivation creates the conditions for the occurrence of nematodes: nematodes are not tolerant to high temperatures nor low temperatures, and open-field cultivation can use low temperatures to kill nematodes in winter. However, in the cultivation of facilities, nematodes can overwinter smoothly in the facilities, which creates favorable living conditions for nematodes to occur.
Lack of resistant varieties: There are very few varieties of nematode-resistant vegetables, and only a small number of vegetable rootstocks are nematode-resistant, such as tomatoes, but there are very few varieties.
Strong resistance: Vegetable farmers with many years of experience in vegetable cultivation know that in the past, the best agent for defense insects was avermectin, which could be prevented by 500 grams of a mu of land, but now an acre of land with 2 kg is useless, because nematodes have strong resistance.
Poor awareness of integrated control: For the control of nematodes, many of our vegetable farmer friends do not have integrated control programs or awareness. It is simply controlled after the occurrence of nematodes. The control of nematodes focuses on integrated control, that is, the combination of physical control and chemical control.
Females of root-knot nematodes
<h1 class = "pgc-h-arrow-right" > iv. Transmission of nematodes</h1>
80% of the transmission of nematodes is passive transmission. For example, flood irrigation when watering; the use of agricultural machinery, such as rotary cultivators, ridge lifting machines across shed transmission; another important way of transmission is the spread of seedlings, especially our vegetable farmer friends themselves seedlings, as long as there are insects in the shed, it will be cured year by year, and it will become more and more serious. Therefore, when raising seedlings, be sure to set up the nursery bowl or use plastic film to separate the nursery bowl from the ground.
< h1 class = "pgc-h-arrow-right" > five, the control of nematodes</h1>
The control of nematodes is divided into biological control, physical control and chemical control, and their advantages and disadvantages should be combined in the control of comprehensive control. Advantages and disadvantages of these three prevention and control measures:
Physical prevention: the cost is low, but it is more troublesome, and the prevention and control rate is greatly affected by the operation. Commonly used methods are high temperature shed, low temperature frozen ground, flooding.
Chemical control: the cost of prevention and treatment is high, the side effects are large, and the effect period is particularly affected by the agent.
Biological control: The cost of control is high and the impact of the soil environment is particularly large.
Nematodes cause the roots of cucumber plants to shrink
1. Biological control
Biological control is the use of some specific microorganisms to control nematodes, such as Penicillium lilace, with a part of actinomycetes or Trichoderma. In the use of biological control, the survival of bacteria is fundamental, therefore, biological control of the soil environment requirements are particularly high, to ensure that the soil is in a particularly good state, if the soil deteriorates, such as compaction, acidification, salinization is heavier, the control effect will not be very good.
2. Physical prevention and control
The methods commonly used in physical control in vegetable cultivation are mainly high temperature sheds, low temperature frozen ground and flooding.
High temperature shed: The high temperature shed is mainly aimed at greenhouse cultivation, and the core is to let the ground temperature reach more than 55 °C. Diseases, underground pests, weeds and other problems can be controlled at the same time. In the summer high temperature idle farming period, close the shed room, so that the soil temperature reaches 60 ~ 80 °C, 30 minutes can effectively kill the nematodes and microorganisms in the soil. However, the high temperature shed is not selective for microorganisms, and while killing nematodes, it will also kill beneficial microorganisms in the soil, so this method should be adopted when necessary.
Low-temperature frozen land: Low-temperature frozen land is aimed at cold shed cultivation. Root-knot nematodes are mainly distributed in the topsoil layer of 3 to 10 cm, and are deeply turned before the soil is frozen. One can turn the eggs in the topsoil into the deep layers, because the deep breathability of poor nematodes is difficult to survive; the second is to use the lethal temperature of the winter nematodes to kill the nematodes. Therefore, when turning deep, the depth of deep turning is required to reach about 24cm.
Flooding: Flooding requires that the soil be maintained for about 10 to 15cm water layer, which is generally not reached in the vegetable area in the north, and the paddy fields in the south can use this method to control nematodes, the principle is to use flooding to artificially cause an oxygen-deficient environment, so as to achieve the purpose of killing nematodes.
In addition, if the nematodes occur in a heavier shed, we must pay attention to the application of manure, can not be used as much as possible, you can use commercial organic fertilizer instead of manure or directly use straw to replace manure.
3. Chemical control
When using chemicals for chemical control, we must control the dosage of agents. At present, the main agent for the treatment of nematodes is thiazole phosphine, which will absolutely burn the roots as long as the dosage is large. Therefore, try to avoid single use. It is recommended to add additives when using thiazolidine, the recommended formula is thiazole phosphine + amino acid oligosaccharide + plant essential oil, must be washed when watering plant water, flushing when watering is large, the larger the water, the agent can be brought into the deeper soil, the better the control effect.
As long as the upper stubble vegetables have nematode damage, the lower stubble must be prevented. Therefore, in the prevention and control, the high temperature shed or low temperature frozen land should be carried out once a year, and then combined with the watering plant water to apply chemical agents, so that physical measures and chemical control combined with comprehensive control, the control of nematodes can reach more than 95%.