Occurrence regularity and control measures of fruit shrinkage disease of jujube

Jujube fruit shrinking disease, also known as jujube iron skin disease, jujube black rot disease, jujube dry waist shrinking disease, jujube wilting fruit disease, fog copying, fog head falling, fog blanching, iron coke and so on, was officially reported in China in the late 1970s, and its harm is becoming more and more serious. it has become a destructive disease in jujube production. In recent years, the disease is becoming more and more serious in jujube producing areas in Shanxi Province, which has become an important factor affecting jujube yield and commodity quality. However, at present, there are different reports on the pathogen and control rules of the disease, and no effective prevention and control methods have been found in production. After years of investigation and research in more than 10 jujube orchards in Taigu County, Shanxi Province, this paper preliminarily obtains the occurrence law of jujube fruit shrinkage disease, and summarizes the control measures suitable for the actual production in Shanxi Province according to the jujube tree management practice in recent years.

I. the occurrence regularity of jujube fruit shrinkage disease.

1. Pathogen

There are many opinions about the pathogen of jujube fruit shrinking disease in jujube producing areas. One is that it may be caused by physiological deficiency or virus, and it is reported that it is caused by Rhizoctonia solani. Liu Yuanrong and others reported that it was caused by a kind of bacteria called Owensi jujube. It is denied that lack of elements can lead to fruit shrinkage disease. Qu Jianxu et al identified the pathogen as Xanthomonas spp., in addition, a kind of Eucalyptus was isolated. Zheng Xiaolian and other experiments showed that the pathogens of fruit shrinkage disease included three kinds of weak parasitic fungi and one kind of bacteria, and the typical symptoms could be produced by inoculation alone or mixed inoculation of four kinds of bacteria. Among them, the report of group small hole shell fungus was consistent with that of qu Jianxu, but qu Jianxu's experiment showed that fruit shrinkage disease was caused by group small hole shell bacteria alone. Kang Shaolan et al reported that the pathogen of fruit shrinkage disease was three kinds of fungi: Alternaria, Streptomyces and Clostridium, and pointed out that these three fungi could infect jujube fruit alone or mixed. Up to now, there is still a lot of controversy about the pathogen of fruit shrinkage disease. Six species of fungi and one kind of bacteria have been publicly reported.

two。 Characteristics of the disease

The disease mainly harms the fruit of jujube, causing fruit rot and early shedding. The injured fruit first appeared a yellowish halo in the shoulder or carcass, the edge was clear, gradually enlarged into a concave irregular light yellow spot, and then the pericarp showed water-soaked, tear-soaked, needle-like round brown spots; the flesh changed from light green to yellow, soft and atrophied, and the exocarp was dark red and dull; the healthy fruit stalk was green, the diseased fruit stalk was brown or dark brown, and the diseased fruit stalk formed delamination and early fall in advance. The diseased fruit is small, wrinkled and thin; the diseased tissue is spongy necrotic, bitter and unedible; the fruit is easy to fall off after the disease, and the bigger the diseased fruit is, the easier it is to fall off; the incidence of the same plant is higher than that of small fruit.

Intuitively, the course of fruit shrinkage disease can be divided into five periods: halo, water stain, coloring, atrophy and shedding, but the shedding period is very different. most of the diseased fruits are in the waterlogging stage in the early stage, fall off in the semi-red period in the middle stage, and fall off at the end of the atrophy period in the later stage.

3. Morbidity regularity

Jujube fruit shrinkage disease can invade at flowering stage, showing a latent state, and the disease spot began to appear in late July, but the disease began in mid-late August. Generally, from jujube pedicel depression turning red (red circle stage) to red turning red at 1 red ring stage (coloring period), jujube flesh sugar content was more than 18%, hydrogen ion concentration was 1000~3163nmol/L (pH 5.5-6), and the temperature was 23-26 ℃, the peak period of the disease occurred. During this period, the disease often breaks out if it is rainy or rainy at night, sunny and foggy during the day. The accumulated temperature of the activity is high, the rainfall is large, and the peak of the disease is advanced, otherwise it is postponed. That is to say, the peak period of the disease occurs sooner or later in different years, which is related to the climatic factors and fruit growth in that year. The severity of the disease is closely related to jujube fruit development period, tree age, branch age and tree potential, meteorological factors, site conditions, insect pests, cultivation conditions and varieties.

The germs mainly invade through the wound. According to field observation, except for the effect of wind and rain and natural friction caused by wound disease. During the peak period, the density of piercing aspirator insects was positively correlated with the disease index, which was mainly caused by stab sucking pests such as leafhopper, bugs, shell insects and heart-eating insects. Partial application of nitrogen fertilizer, dense branches and leaves, poor ventilation of intercropping jujube orchard, induced the occurrence of pests, increased the vector of disease, and the disease was more serious.

The pathogen of fruit shrinkage disease not only infected jujube fruit, but also infected jujube leaves, flowers and jujube hanging, but did not show any symptoms on jujube leaves, flowers and jujube hanging. The overwintering sites of pathogens are old bark, all kinds of branches, falling fruit, hanging and leaves.

II. Prevention and control measures of jujube fruit shrinkage disease

1. Select disease-resistant varieties

According to the local climate and soil conditions, the selection of suitable disease-resistant varieties of jujube is the prerequisite for the prevention and control of jujube fruit shrinkage disease.

two。 Strengthen the management of jujube garden and tree body to improve the disease resistance of tree body

Doing well the comprehensive management of jujube orchard is the fundamental measure to prevent and reduce the occurrence and spread of jujube fruit shrinkage disease. The effective measures are as follows: (1) scrape the old bark in early spring, thoroughly clean up the fallen leaves, fruit and hanging in autumn and winter, and burn them centrally to reduce the source of the disease. (2) strengthen soil fertilizer and water management, reasonable shaping and pruning, improve ventilation and light transmission conditions, enhance tree potential, improve tree disease resistance, strengthen ditch drainage and reduce soil and air temperature. (3) No intercropping of tall stalk crops and crops with the same diseases and insect pests as jujube trees. Covering or growing grass in jujube orchard can also reduce the occurrence of jujube fruit shrinking disease. (4) re-apply organic fertilizer, improve soil structure, increase phosphorus, potassium, calcium and boron fertilizer, properly control nitrogen fertilizer, achieve formula fertilization, reasonably supply nutrients, promote the coordination of water and fertilizer, enhance tree potential and improve disease resistance.

3. Control of disease-transmitting insects

In the early stage (April to July), methamidophos, cypermethrin, omethoate, cypermethrin, methotrexate, cypermethrin, omethoate, cypermethrin, cypermethrin and other insecticides were sprayed in the early stage (April to July).

4. Chemical control

Adopt early spring jujube orchard to scrape the bark, remove the diseased body, spray 5 Baomedu stone sulfur mixture: reasonable pruning to make the tree ventilated and transparent; 0.5% borax is sprayed once in the leaf expansion stage, early flowering stage and full flowering stage of jujube trees. In general, the medicine can be sprayed for the first time at the end of July or early August, once every 7 to 10 days. 15-20 days before jujube fruit harvest is the key period of control, the control agents are streptomycin 70~140U/mL or kanamycin 140U/mL, 75% Baiyinqing wettable powder 600x. In the application of fungicides, insecticides such as 2000 times disinfectant, red and high chlorine can be added to control insects.

The following two specific methods can be used to spray:

(1) spray 68.75% Yibao granule 1500 times and Bordeaux liquid once in the young fruit stage before the onset of jujube fruit shrinkage disease in July, enter the disease period in August, and use 0.76% Wanxing EC 3000 times. Mix some insecticides into the above solution.

(2) in the middle and later stage of fruit growth, 10% high water dispersible granule was used, 72% sulfuric acid agricultural streptomycin crystal powder 5000 times liquid and 2.5% diazepam EC 1000 times solution spray.