Incidence regularity and control techniques of iron skin disease of jujube

Jujube iron skin disease, also known as fruit shrinkage disease, black rot, commonly known as fog scald, fog Liaotou, dry waist, black waist, iron coke, fire and so on, is a serious fruit disease of jujube. Since the early 1980s, the disease has become more and more serious. It begins before and after coloring, the disease is fast and concentrated, and it often breaks out. Many jujube producing areas, such as Hebei, Henan, Shandong, Shanxi, Inner Mongolia, Guangxi, Sichuan and so on, have occurred. In general years, the disease caused a yield loss of 20% to 50%, and in severe years, the loss reached 70%, 80%, or even no harvest.

I. harmful symptoms of iron skin disease

The disease began to show symptoms in the white ripening stage of the fruit, and at the initial stage, a water-immersed yellow-brown irregular spot appeared in the middle of the jujube fruit to the shoulder, the spot continued to expand, and developed to the longitudinal depth of the pulp, the flesh of the diseased part became yellow-brown and the taste became bitter. The fruit is easy to fall off after the disease and loses its edible value. The disease occurs rapidly from mid-late August to early September, often showing sudden and fulminant symptoms, especially in the 5 days after rain or fog between the white ripening stage and the ripening stage of the fruit, the disease suddenly aggravated and the rate of diseased fruit increased rapidly.

II. The pathogen of iron skin disease

As early as the late 1970s, the iron skin disease of jujube was reported in newspapers and periodicals. Han Jinsheng (1979) inferred that the disease was caused by physiological deficiency or virus. Chen Yijin et al (1989) considered that the pathogen of the disease was a new species of the genus Erwinia of Enterobacteriaceae, while qu Jianxu and Shen Ruixiang considered it to be Streptomyces verticillata and Xanthomonas oryzae. Zheng Xiaolian et al. (1995) put forward three kinds of weak parasitic fungi and one kind of bacteria.

Peng Shiqi, Kang Shaolan and Mao Yongmin (1996) collected diseased fruits with typical jujube ironing symptoms from Wangdu, Hejian, Xinle, Fuping and Zanhuang of Hebei Province and Xinzheng of Henan Province for three consecutive years from 1993 to 1995. Through the mass isolation of many batches for many years (the total number of fruit blocks was 6358), it was found that there were mainly three kinds of fungi in the diseased fruit: Alternariaalternata (Fr.) Keissler; destroyed PhomadestructivaPlowr;, Clostridium, a fungus Fusicoccumsp. Among them, Phomasp. The largest number. Only one kind of fungus was isolated from a jujube fruit, and the above three fungi or any two of them could be isolated at the same time. The separation results of the standard samples collected in different years are not exactly the same. No Fusicoccumsp., was detected in the jujube collected from Hejian and Xinle in 1993, but Fusicoccumsp was detected in the standard sample collected in 1995. The detection rates were 34.09% (Hejian woman jujube) and 30.91% (Xin Le Po jujube). The separation results of different varieties were also different. The frequencies of three kinds of fungi isolated from Wangdu, Xinle and Hejian jujube areas were basically the same, among which Alternariasp. And Phomasp. Higher frequency, Fusicoccumsp. The frequency is lower, while Zanhuang jujube and Henan gray jujube are on the contrary, Fusicoccumsp. The frequency of occurrence was significantly higher than that of the other two fungi. According to Koch's method, the pathogen of jujube iron skin disease was confirmed to be the above three kinds of fungi, which could be infected alone, or caused by any pairwise infection or mixed infection of three kinds of bacteria.

Third, the incidence regularity of iron skin disease

1. Overwintering place

The overwintering sites of the pathogens of iron skin disease are 1-and 2-year-old branches and perennial jujube branches, jujube strands, bark, falling fruit, hanging, fallen leaves and so on. The results showed that the pathogens could survive through the winter in these tissues and became a large number of sources of primary infection in the growing season.

two。 Infection period

The three pathogenic fungi of jujube iron skin disease not only infected fruits, but also infected jujube leaves, flowers and jujube branches, but showed no symptoms on jujube leaves, flowers and jujube stems. The time of the first isolation of three kinds of fungi from jujube leaf, jujube stem, jujube flower and jujube fruit was different. Alternariaalternata (Fr.) Keissler; was isolated for the first time in young leaves in late April, in jujube flowers in late May and in young fruits in mid-July. PhomadestructivaPlowr; was isolated for the first time in jujube fruits only in early August. The infection of the three pathogens to jujube hanging branches, jujube leaves, jujube flowers and jujube fruits had no obvious peak.

The results showed that iron skin disease was a single infection disease and there was no further infection.

3. Control techniques of iron skin disease of jujube

The main results are as follows: (1) do a good job of orchard hygiene in autumn and winter to clean up fallen leaves, fruit and hanging, burn them centrally, and scrape the bark in early spring to reduce the source of primary infection.

(2) scrape the bark in early spring and burn it centrally.

(3) after scraping the bark, spray 3Mel 5 Baumedushi sulfur mixture before sprouting.

(4) starting from the middle and late June, mancozeb and other broad-spectrum fungicides were sprayed every 10 miles every 15 days.