Occurrence and control of potato tuber rot nematode

Fengning and paddock counties in the north of Chengde City grow more than 40, 000 hectares of potatoes a year, produce more than 800 million kilograms of seed potatoes and commercial potatoes, and store about 120 million kilograms of potatoes in winter. it is one of the four major potato production graveyards in the country. In recent years, due to the damage of potato tuber rot nematodes, the loss of stored potatoes was 5%-7% in 1994, and that of seriously damaged potato cellars was as high as 20%-30%. According to the data retrieved at present, this nematode is widely distributed in potato growing areas of Asia, Europe, America and Africa, and has a wide range of hosts, which pose a threat to potato storage in varying degrees. After two years of work, the occurrence regularity and control measures are as follows.

1. Pathogens and harmful symptoms

1.1 the pathogen was identified as potato tuber rot nematode by microscope.

1.2 symptoms this nematode only infects the tuber of potato during its growth, and the aboveground part has no special symptoms. The initial intuitive symptom is the appearance of small white spots on potato tubers. The serious disease of tuber occurs during the storage period, and the tissue of the infected tuber is dry and granular. When the whole tuber is infected, the epidermis of the tuber becomes as thin as paper, and split, the tuber becomes dry, and the weight loss is more than 80%. And the tissues infected by nematodes are easy to be re-infected by fungi.

two。 Infection cycle

2.1There are three main ways for overwintering: ① lives widely in the soil and saprophytic life after potato harvest. ② can be parasitized on weeds and a variety of crops; ③ goes into the cellar with seed potatoes for the winter and into the fields with potato lumps in the coming year.

2.2 after the potato was colonized, the nematode entered the young potato block from the epidermis near the lenticels and bud eyes. In the early growth stage of potato, only a small number of nematodes invaded into the subcutaneous tissue of potato tuber. during the expansion and maturity of tuber, a small white spot was formed on potato tuber. a large number of nematodes existed at the junction of disease and health, and the tissue under the disease spot softened and showed granule shape. when the nematode enters the cellar with the potato block after harvest, once it enters the cellar earlier or the storage capacity is too large, a large number of respiratory heat is produced, which leads to the increase of temperature. Nematodes occur seriously, more tuber tissues are damaged, and lead to secondary infection of potato tubers caused by Penicillium, Aspergillus and other bacteria.

2.3 suitable temperature, humidity, ① temperature. This nematode can develop in the range of 5-34 ℃ and can survive in the low temperature of-28 ℃ in the field. ② humidity. The suitable relative humidity is 90%-100%. When the relative humidity is less than 40%, it basically does no harm to this nematode.

3. Prevention and cure measures

3.1 use 5% Dur granule for sowing with medicine, 4-5 kg per 667 square meters, and apply it to the field at the same time when sowing potatoes.

3.2 rotation with corn, @ # @ 245 crop rotation, broad bean, etc., can be prepared to change the ecological environment of nematode survival and play a role in reducing the population number.

3.3 after entering the cellar late, this method was adopted to release the field heat and respiration of the potato block outside the cellar to avoid the increase of temperature after entering the cellar, resulting in nematode activity and overreproduction, resulting in serious losses to the stored potato.

3.4 Ecological control of the disease

Due to the early entry into the cellar and extensive management, when nematodes occur seriously, the temperature and humidity can be reduced by increasing venting. The specific measures are as follows: keep the temperature range in the cellar within the range of 0.5 ℃, when the temperature is higher than 4 ℃, open the stomata or pit mouth, and close the vents when the temperature is lower than 0.5 ℃. In winter, the pest can be controlled in about 7 days after such repeated release during the day.