Root-knot nematode disease is widely distributed in cucumber production areas. It not only affects the normal growth and development of cucumber, but also can aggravate the occurrence of diseases such as wilt disease, and has always been a disease headache for vegetable farmers.
In Chengde area, with the continuous increase of the vegetable cultivation area and planting period of solar greenhouses and cold sheds, the occurrence of cucumber root knot nematode disease is increasing year by year. According to survey data from the Crop Protection Station of Chengde County in 2013-2014, cucumber root-knot nematode disease occurs in greenhouses in Liugou Township and Liyao Township of the county, especially in old sheds for many years, and the mortality rate in greenhouses is generally 11 %-28%. The author combines many years of first-line practical experience and two consecutive years of related experiments on cucumber root-knot nematode disease, and talked about the occurrence and prevention and control of cucumber root-knot nematode disease for the reference of farmers.
First, the symptoms
The disease occurs only in the roots, with lateral roots and fibrous roots most vulnerable, and generally no obvious symptoms on the ground. After the roots are damaged, they can form tumors of different sizes. The early roots of the nodule are white and smooth, turning yellowish-brown to dark brown, with rough or even cracked surfaces, and decayed when severe. No appearance of nodules, necropsy, can be seen inside the white pear-shaped body slightly larger than the needle, pathogenic female nematode body, but also a standard for the diagnosis of this disease. The above-ground parts of the diseased plants are not obvious in the early stages. As the root damage is aggravated, their performance is yellowing of the leaves, and the lack of water and fertilizer are wilting, the growth is slow, the plants are weak, and the nectar is unhealthy. In severe cases, the plants are stunted. Even all fields die. In addition, after the infection with root-knot nematodes, the resistance of cucumber itself to other diseases is also significantly reduced.
Second, the pathogen
Cucumber root knot nematode disease is caused by the infection of the nematode Gangsiodes nematode. Observed by a magnifying glass, the pathogenic nematodes are male and female, the larvae are slender and worm-like, and the female adults are parasitized in the roots, inflated in a pear-shaped or spherical shape, the tip is pointed, milky, and the size is 0.44-1.59 mm and 0.26-0.81 mm. The anatomical root knot or Nodules are visible to the naked eye. The male adults were linear, colorless and transparent, with slightly rounded tails. The size was 1-1.5 mm and 0.03-0.04 mm. They lived mainly in the soil. Root knot nematodes are most suitable for development at soil temperatures of 25°C to 30°C and soil water holding capacity of about 40%.
Third, the transmission route
Root-knot nematodes live in the soil with 2nd-instar larvae or eggs. With the help of rainwater and irrigation water, they invade young roots until they become adults and become internal parasitic nematodes. At the same time as they feed, they secrete irritants that stimulate the growth and proliferation of root cells and form root knots or nodules. The primary sources of infestation are diseased soil, diseased seedlings, and irrigation water. The long-distance invasion and spread rely on flowing water, wind, diseased seeds, sick soil, agricultural machinery, and various agricultural operations.
Fourth, the factors that affect the incidence
1. Relationship between soil and topography and pathogenesis. Root-knot nematodes are aerobic, and all soil moisture, clay soil, structural compaction, etc. are not conducive to root-knot nematode activity, so the incidence is lighter. On the other hand, sandy soils with high dry terrain, loose structure, and low salinity, which are neutral responses, are suitable for the activity of root-knot nematodes and are therefore of severe disease severity.
2. The relationship between farming system and disease. The incidence of disease in continuous cropping, the longer the continuous cropping, the more serious the victimization. If the diseased area is soaked for 4 months, the nematodes in the soil will all die.
3. The relationship between temperature and humidity and onset. The suitable propagation temperature of root-knot nematode is 25°C-30°C. Less than 5°C or higher than 40°C, the activity is less. In 55°C condition, it can be lethal for 10 minutes. In general, the soil moisture conditions suitable for growing vegetables are also suitable for root-knot nematodes, and the suitable humidity is 40%-70%.
4. The relationship between ploughing and disease. Root-knot nematodes are mostly distributed 20 cm below the soil surface, especially within 3-9 cm. Because the activity of pathogenic nematodes is not strong, and the deeper the soil is, the worse the permeability is, it is not suitable for the life of pathogenic nematodes. If the surface soil is deep turned, a large number of insects will be turned from the upper layer to the bottom layer, which will not only eliminate part of the overwintered insect resources, but also loosen the surface soil after ploughing and drying after the ploughing. This will adversely affect the nematode activity and reduce the insect source.
V. Prevention methods
In accordance with the plant protection policy of "prevention first, prevention and control combined," the comprehensive prevention and control of cucumber root-knot nematode disease should be followed in accordance with the principle of "giving priority to agricultural control and supplemented by chemical control."
1. Rotation. Rational rotation can reduce the amount of soil nematode, reduce the incidence of disease, if you can implement 2-3 years of rotation, the effect is more significant. It is best to rotate with grass crops because root crop nematode disease does not occur in grass crops. Disease-free soil nursery and deep-turning soil can also effectively control the occurrence and development of root-knot nematode disease.
2. Strengthen field management. Dispose of the diseased plants thoroughly, concentrate burned or buried deeply, and reduce the number of insects. Rational fertilization and irrigation can delay the symptoms of the disease or reduce the loss. Deep plowing before sowing, through the deep plowing and deep turning, the nematodes distributed in the topsoil turn to the depth of the soil. The application of organic fertilizer can increase the developed strength and toughness of the root system and increase the resistance and patience of the plant.
3. Flooded insecticide. Irrigation of severe diseased fields caused nematodes to suffocate and suffocate, with a water depth of 10-15 cm for 4 months.
4. Soil disinfection. It is mainly used for seedbeds, with 1.8% avermectin EC or granules. The pesticide is applied to soil 15-25cm deep from the topsoil 2-3 weeks before sowing. Keep moist before application, and apply soil after compaction to achieve the purpose of fumigation and insecticide.
5. Medication Irrigation. Cucumber growth during the initial symptoms when 1.8% avermectin EC or Le Siben EC diluted to 1000-1500 times the water irrigation control, can also be used 50% phoxim EC 1500 times Irrigation root.
6. High temperature insecticide. The soil temperature of 5 cm deep in the soil reaches 60°C-70°C during the day, and the ground temperature at a depth of 10 cm reaches 30°C-40°C, which effectively kills various insect nematodes. Generally after the irrigation in July-August, use plastic film to lay on the ground and compact it, and keep it for 10-15 days to achieve insecticidal effect.
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