Control methods of jujube mad disease

1. Symptoms

Jujube mad disease, also known as witches' broom disease, broom disease, fire dragon disease, is a devastating disease. Fruit growers call it "mad jujube tree" or "male jujube tree". Both aboveground and underground parts of jujube trees can be infected. The aboveground infection was mainly characterized by floral organ degeneration, bud germination and abnormal growth, resulting in clusters of branches and leaves, extension of the hanging end of jujube, bright veins, yellowing or curling of tender leaves, and occasionally ear-shaped leaves. The disease in the underground part is mainly manifested as a cluster of roots and tillers. The whole flower organ of the diseased tree was degenerated into a vegetative organ, and the flower stalk was 5-7 times longer than that of the healthy flower, showing obvious small branches, and the sepals, petals and pistils could all become leaflets. The severe disk is also degenerated, and the sepals are dark green and hypertrophic, turning into leaflets, and sometimes the axillary buds of the leaflets sprout branchlets. The petals are enlarged, wrinkled and become leaflets; the pistil remains intact, but the ovary becomes fat, thickened and columnar, and the top of some stigmas also become two leaflets. Another type is that stamens become leaflets and ovaries become short branches, but axillary buds germinate and produce short and thin new branches and leaves, which continue to grow. Diseased flowers generally can not bear fruit, only flowers with extended flower stalks can bear fruit, but most of them fall off earlier. The fruit is infected, becomes smaller and thinner, and the fruit tip is cone-shaped. Some varieties, such as Yuanling jujube, the fruit surface is uneven, the raised part appears red, the concave part appears green, showing a flower face; the internal tissue is empty and unedible. There are two types of abnormal germination of buds. One is lobular symptoms. That is, most of the positive buds on the annual developmental branches and the hidden buds on the perennial developmental branches germinated into developmental branches, and the buds on them continued to sprout branches, so the shoots sprouted step by step, until the main buds of jujube heads stopped sprouting and clustered branches were formed. Most of the fruiting mother branches of diseased trees grow into developed branches, and this kind of branches also produce tufted branchlets. The diseased branches were slender, the internodes shortened, and the leaves became smaller and yellowed. The arbuscular branches are dry but not easy to fall off in autumn. The other is mosaic symptom, which is not common, which occurs at the top of the twig, slightly smaller than the healthy branch, with yellow and green spots on the leaf surface, sometimes the leaf vein fades into a bright vein, the leaf edge curls inward into a spoon shape, the leaf surface is uneven, sometimes yellowing, it is not easy to fall off in autumn. After the underground part was infected, a large number of adventitious buds germinated and formed clumps of short crazy branches, many clumps could appear on the same lateral root, and the branches and leaves were small and yellowish green after they were unearthed; they stopped growing when they grew to about 0.3m, and then all of them scorched into a brush and died, leaving only residual branches. Finally, the cortex of the diseased root turned brown and rotted, the phloem was easy to fall off, the fruit was not harvested, or the whole plant died.

2. The regularity of the disease

2.1 the pathogen is mycoplastid. Under electron microscope, mycoplastids with different shapes and sizes of 80~720nm were observed in the leaf vein sieve tube cells. Nucleic acid fibrous substances can be clearly seen in mature bacterioid particles. The pathogen can first be transported to the root of the jujube tree, and then spread from the diseased part to the whole tree after proliferation.

2.2 the route of transmission and disease conditions are transmitted by various grafting methods, such as skin grafting, bud grafting, branch grafting, root grafting and so on. In nature, leafhoppers are the transmission media of the disease, such as Chinese rhomboid leafhopper, orange belt rhombus leafhopper, concave edge rhombus leafhopper and red flash leafhopper. Once the concave edge diamond leafhopper ingested the mycoplast of jujube leprosy disease, it could carry bacteria for life and could infect many jujube trees one after another. As for the contact of soil, pollen, seeds, juices and diseased roots, the disease could not be transmitted. The direction of pathogen running in the host is consistent with that of tree nutrients, from the bottom to the top when sprouting and from top to bottom after the branches stop growing. After grafting and inoculation, the incubation period was 25 to 31 days, showing symptoms on the newly issued buds, and the incubation period was as long as 382 days. The factors affecting the incubation period were inoculation time, which could occur in the same year before the end of June; after the end of June, the inoculation showed symptoms in the flowering of the following year; the disease occurred early in the year of root inoculation, and the more the number of skin grafts, the faster the disease; in addition, it was also related to the growth of new shoots and the size of the plants inoculated, and the symptoms of seedlings were faster than that of adult plants. The occurrence of the disease is related to the topography, soil quality, management and variety of jujube orchard. The soil is dry and barren, the fertilizer and water condition is poor, the management is extensive, the diseases and insect pests are serious, the tree is weak and the disease is serious, and vice versa. The disease is rarely occurred in saline-alkali land, which may be due to the influence of saline-alkali land on the metabolism of jujube trees and the enhancement of disease resistance to jujube mad disease, or the lack of local vector insects. There are thousands of differences in susceptibility among jujube varieties. The artificial inoculation test showed that Jinsi jujube was highly susceptible, Tengxian red jujube was more resistant, and Jiaocheng vinegar jujube was immune. In addition, jujube and round jujube were highly susceptible to disease, and the whole plant died within 1-3 years after the disease, followed by long red jujube, which could last for about 5 years. Maya jujube, Changling jujube, Huiling jujube and sour bell jujube were more resistant.

3. Prevention and control methods

3.1 Quarantine. Strengthen the quarantine of the place of origin, and the vaccine of mad disease will enter the jujube area. The disease-free mother plant was selected to collect scions, cuttings and propagate root tillers. Jujube mad disease seedlings are strictly prohibited from entering the jujube area.

3.2 Disease-resistant jujube varieties and disease-resistant jujube varieties with jujube kernels were selected as rootstocks.

3.3 scion disinfection. The scion with disease can be sterilized by soaking in 1000mg/kg tetracycline hydrochloride solution for half an hour.

3.4 adopt scion, bud grafting or root division to propagate in the disease-free jujube area; cultivate disease-free seedlings; once diseased seedlings are found in the nursery, they should be pulled out immediately.

3.5 eradicate diseased trees and prevent infection. Timely and thorough planing of diseased trees, early elimination of the infection center; when plucking diseased trees, the big roots should be cleaned together to avoid germination. Diseased trees, branches or roots removed should be burned in time.

3.6 strengthen the management of jujube garden. Increase the application of organic fertilizer and alkaline fertilizer. Jujube needs to increase water and fertilizer during sprouting, flowering, fruit setting and fast-growing stage, combined with spraying 300 times urea solution twice for extra-root topdressing. It can improve soil physical and chemical properties, improve soil fertility and enhance tree potential.

3.7 Control of field transmission medium insects. From May to September, spray 50% parathion EC + 50% dimethoate EC 250 times each or 50% dimethoate EC + fenvalerate 250 times each, spray strict canopy and surrounding weeds to control disease vectors.

3.8 girdling of the trunk. Because of the directionality of bacteria transmission in the trunk, this method is effective. The method is as follows: before the sap flows in spring, ring peeling is carried out in the middle and lower part of the main trunk of jujube tree to widen 0.3~0.5cm.

3.9 instilling medicine to kill the disease. From April to August, 2 holes were drilled on the same side of the diseased branch, reaching to the xylem. 50g peppermint water, 100g keel powder and 50g turquoise were ground into fine powder, mixed and poured into the hole with a paper tube, 3G per hole, then nailed with wood wedges, sealed with mud, killed the disease and cured the disease.

3.10 remove the spirit of madness. Before sprouting in spring, make a ring-shaped groove at the base of the trunk, which is as deep as half of the phloem. Fill the trough with liquid medicine, wrap it tightly with plastic film and apply it for the second time every one month. The effect of 20cm on tree diameter was better when it was applied at 40cm with 8g and 16g at 40cm.