Introduction and control of carrot root knot nematode

Carrot (carrot), alias carrot, clove radish, gourd gold, also known as carrot, red vegetable head, yellow radish, etc., is an umbrella-shaped biennial herb with fleshy roots as vegetables to eat. Carrots contain 1.67-12.1 mg carotene per 100 grams of fresh weight, which is 5-7 times higher than that of tomatoes. After eating, carrots are digested and decomposed into vitamin A, which can prevent night blindness and respiratory diseases. Can be fried, cooked, eaten raw, pickled, pickled, etc., resistant to storage. It is distributed all over the world, and it is cultivated in both the south and north of China, and its output accounts for the second place in root vegetables. Anti-cancer, known as underground "little ginseng".

Requirements for growing environment of carrots

Temperature: temperature carrot is a semi-cold-tolerant vegetable, the temperature requirements of vegetative growth period and reproductive growth period are different. The seeds germinated at 4-6 ℃, began to grow at 8 ℃, and emerged after 10 days at 18-20 ℃. The seedlings can endure the low temperature of-3 ~-4 ℃ for a short time, and can also grow normally under the high temperature of more than 27 ℃. The optimum temperature for carrot germination period is 20: 25 ℃, the optimum temperature for leaf growth is 20: 25 ℃ in daytime and 15: 18 ℃ at night, and the suitable temperature for fleshy root expansion is 20: 22 ℃ and stop growing below 3 ℃. The root of carrot can be planted when the soil temperature reaches 8: 10 ℃. The suitable temperature for carrot flowering, pollination and seed setting is 22: 28 ℃ in daytime and 15: 20 ℃ at night. If the daytime temperature exceeds 35 ℃, it can not pollinate and bear seeds.

Lighting: light carrots are light-loving, long-day plants, especially in the vegetative growth period, which need more than medium intensity of light.

Moisture: keep the soil moist when sowing to promote seed germination and emergence neatly. In the seedling stage and the peak leaf growth stage, dry and wet, it is necessary not only to ensure the normal growth of the aboveground, but also to increase the air permeability of the soil to promote the good development of straight roots. Fleshy root expansion period is the period of the most water demand, to achieve uniform watering to meet the needs of fleshy root expansion, but also to prevent root cracking caused by drastic changes in irrigation. Carrots are generally stopped watering 10-15 days before the fleshy root is harvested to reduce cracking and facilitate storage and transportation.

Soil: carrot like sandy loam and loam with deep layer, loose soil, good drainage and high porosity. In the viscous and heavy soil with poor permeability, the fleshy root is light in color, has many whisker roots, is prone to tumor, and is of poor quality; in low-lying areas with poor drainage, the fleshy root is easy to break, often causing decay and increasing forked roots. Carrots have a wide range of adaptation to soil acidity and alkalinity. Carrots can grow well in soils with pH of 5 to 8, but grow poorly in soils with pH below 5.

Introduction and control of root-knot nematode disease of carrot

What is carrot root-knot nematode disease?

It's called peanut root-knot nematode. Among them, the northern root-knot nematode (Melotidogyen hapla Chitwood) distributes north of the isotherm with an average temperature of 26.7 ℃ in July. The perineal pattern of the northern root-knot nematode larva is composed of smooth stripes, nearly round, some patterns extending to one or both sides, common scratches near the tail, and the larva has a blunt and divided tail.

Diagnosis of carrot root-knot nematode disease:

To harm the underground roots. The aboveground leaves of the diseased plants were yellow, the outer leaves of the plants were laterally elongated, and the growth was weak. Dig out the fleshy root, it can be seen that there are many inflated semicircular tumors scattered on the straight root, the upper half of the tumor is more, at first white, then brown, hardened. There are nodular and irregular nodules on the fibrous root, or some clusters form a ball. The main root of the victim often bifurcates into different roots. The most pathogenic nematodes are southern root-knot nematode and northern root-knot nematode, and can also be mixed with peanut root-knot nematode. The pathogenic nematode is male and female heteromorphic, the male adult is linear, the tail is slightly round, colorless and transparent. In addition to the short head and neck, the female adult is enlarged nearly spherical, pear-shaped, milky white, and the perineal area is near the end of the pudenda. a special ring is formed on the cuticular membrane, which is called perineal pattern, which is an important basis for species differentiation. Larvae are finely linear. The eggs of female adults are laid in the oocysts formed by colloid secreted by the vagina, laying 300 eggs and 500 eggs per female. The females are mostly buried in the host tissue.

Incidence regularity of carrot root-knot nematode disease:

The pathogen nematode overwinters in the soil as eggs with diseased remains, or as larvae in the soil, or as larvae and female adults in the host. In the following year, the overwintering eggs hatched the second instar larvae, and the overwintering second instar larvae resumed their activity, moved and gathered the tip of the host root, invaded from the young root tip, then migrated inward and upward, settled and fed in the root cell elongation area until they developed into adults. At the same time, the secretory fluid was injected into the oral needle to stimulate the proliferation and enlargement of the host cells near the feeding point. Several multinucleated giant cells are formed around the head of the larva, which are used as nutrition cells to transfer the nutrients in the invaded roots and feed the nematodes, and cause nodules in the diseased roots, commonly known as root knots. Most of the nematodes live and move in the soil layer of 5 cm and 30 cm. It takes about 25 to 30 days to complete a generation, and it can produce 4 to 5 generations a year. Except for nematodes (second instar infected larvae) in soil, nematodes can migrate for a short distance and can be transmitted mainly by diseased soil, diseased seedlings and irrigation water. The nematodes began to move in the soil above 10: 15 ℃, and the optimum temperature for growth and development was 25: 30 ℃. Too dry and too wet soil is disadvantageous to nematodes, and soil moisture is suitable for vegetable growth, so it is suitable for nematode activity. It is suitable for pH 4-8, and the sandy soil with good permeability is beneficial to the survival activity of nematodes, so the damage of nematodes in sandy soil is often more serious than that in clay.

Control methods of carrot root-knot nematode disease:

The main results are as follows: 1) seedlings should be raised in disease-free soil. Cultivate disease-free and strong seedlings. The diseased seedlings were strictly removed when planting.

2) the seriously diseased plots should be rotated with grain crops or Sabina vulgaris for 2-3 years, and the effect of flood-drought rotation is better. Planting disease-resistant vegetables such as scallions, garlic, leeks and peppers in seriously diseased fields can significantly reduce the number of nematodes in the soil and reduce the damage of the next crop.

3) during the conditional summer leisure period, ploughing and drying the field, ploughing once every 7-10 days, 2-3 times in a row, can kill surface nematodes. It can also flood the diseased field for 1 month and kill most of the surface nematodes.

4) Pesticide control, 50% special powder can be used to prepare medicine soil according to 2.3-3.8kg per 1000 square meters and 303.5kg of fine soil, sprinkle it in the sowing ditch, and then sow and cover the soil. At the time of sowing or planting, 10% limanku granules can also be applied, 5 kg per 667 square meters.

5) sporadic disease, the root of the diseased plant can be irrigated at the initial stage of the disease, 50% phoxim EC 1500 times, or 80% dichlorvos EC 1500 times, each plant 250ml. Generally, watering before administration can improve the efficacy.