What are the symptoms of navel orange and citrus canker? What are the prevention and control methods? How do you match pesticides?

High temperature and rain, high humidity and high temperature, this kind of weather is very conducive to the occurrence of navel orange and citrus canker, which mainly harms navel orange tender shoots, tender leaves and young fruits. What are the prevention and control methods of navel orange and citrus canker? How do you match pesticides?

Symptoms of peptic ulcer

Canker is a disease caused by bacterial infection, which can damage the leaves, fruits and shoots of navel orange. at the initial stage of the disease, it is yellow or yellow-green water-stained spots, and after expansion, it forms a sunken spot in the middle of a near-circular uplift, surrounded by yellow halo, causing a large number of fallen leaves, fruit, withered shoots and so on. Seriously affect the yield and quality of fruit trees.

Leaf damage

Yellow or dark yellow-green needle-sized oily spots began to appear on the back of the leaves, and gradually raised on both sides of the leaves at the same time, becoming nearly round and beige spots.

Soon, the central part of the disease was ruptured, the bulge was more prominent, the surface was rough, lignified, grayish-white or grayish-brown crater-like, the disease was mostly round, often with wheel or spiral lines, surrounded by a yellow or yellowish-green halo ring, and there was often a brown glazed edge next to the halo ring.

Sometimes several disease spots connect with each other to form irregular large disease spots, and in the later stage, the center of the disease spot is sunken into a crater-like crack.

Shoot damage

The characteristics of the disease spot are basically similar to the disease spot of the leaf, and begin to appear oil-stained dots, dark green or wax yellow, and become grayish brown and Lignification after expansion, which is more prominent than the disease spot on the leaf.

The disease spot is sunken in the middle, such as a crater-like crack, but there is no yellow halo ring, which causes leaves to fall off and branches to die, especially in summer.

Fruit damage

The disease spot on the fruit is also similar to that on the leaf, but the disease spot is larger. The degree of Lignification is more serious and more solid than that of leaves, and the crater-like cracking in the center of the spot is also more obvious. some citrus varieties have dark brown glazed edges at the boundary between the diseased and healthy parts.

Due to different varieties, the width and width of the glaze edge are different. The disease spot is limited to the pericarp, and when it is serious, it will cause early fruit drop.

II. Occurrence conditions

1. Climatic conditions

High temperature and heavy rain (May-September every year) is a necessary condition for the epidemic of the disease. The disease can occur when the temperature is above 15 ℃, but the most suitable temperature is 20 ℃ 36 ℃ and 25 ℃ 30 ℃. Rain Water is the main vector of pathogen transmission, therefore, when the temperature is suitable, the rainfall and rainy days are positively correlated with the prevalence of the disease, and the rainfall also affects the size of the disease spot, generally in the spring shoot period, the temperature is low, the rainfall is less, the disease spot is smaller; the summer shoot and autumn shoot are high temperature and rainy, and the disease spot is larger.

2. Growth period

Generally speaking, ulcer pathogen only invades the young tissue at a certain stage of development, and does not infect or rarely infect the young shoots, leaves, young fruits just after blossom, and mature tissues. Because the stomata of the very young tissue have not yet formed, the bacteria cannot invade. While in the mature tissue, most of the original stomata are aging, the interstitial space is very small or closed, and it is difficult for bacteria to invade.

3. Cultivation and management

Unreasonable fertilization can prolong the shoot shooting period, a large number of shoots, a large number and delayed maturation, which is conducive to bacterial infection; partial application of nitrogen fertilizer will promote the disease, while the application of potassium fertilizer can reduce the disease. If the diseased branches are not pruned in winter, the disease will be aggravated the next year, and the disease can be significantly reduced by removing summer shoots and controlling autumn shoots. Where leaf miner, malignant leaf worm, butterfly and other pests are serious in orchards, ulcers often occur seriously.

4. Tree age

Seedlings and young trees are more susceptible to disease, and the older the tree is, the lighter the disease is. Because there are many lower and autumn shoots of seedlings and young trees, and the number of shoots is more, it is beneficial for bacteria to invade.

III. Prevention and control measures

1. Clear the garden and pick leaves

Clear the garden in winter, collect fallen leaves, fallen fruits and dead branches, and burn them. Pruning is combined with pruning in early spring to remove disease and insect branches, diseased leaves, overgrown branches, weak branches and so on, so as to reduce the source of disease infection. Remove the diseased leaves from the seedling stage, especially after the wind and rain, cut off the seriously diseased branches.

2. Fertilizer and water management

Reasonable fertilizer and water management, cultivate neat spring and autumn shoots, and control summer shoot growth. At the same time, the control of leaf miner should be done in time in each shoot period.

3. Scientific selection of drugs

Main medicament: 100kg water, 0.5kg copper sulfate, 1jin ammonium carbonate, 1jin lime preparation method: first dissolve copper sulfate, mix into 90% copper sulfate solution, then add ammonium bicarbonate aqueous solution, then dissolve the lime with 10% water and remove the slag (preferably lump ash). Finally, the mixture of ammonium bicarbonate and copper sulfate is washed slowly into the lime water solution from low to high.

4. Usage

The prepared cupric ammonium lime mixture is sprayed directly without dilution. If there are aphids, it can be sprayed with 1000 times of abamectin, which causes slight damage to tender leaves and shoots, but does not affect the growth of shoots, and can be used boldly. It does not pollute the fruit, and there is pollution at the beginning, but it can be washed away with Rain Water.