What is the best medicine to treat citrus ulcer?

What people often call citrus ulcer actually refers to citrus canker, which is an ulcer disease that occurs on plants. The main cause of the disease is bacterial infection. Scars will appear on the surface of citrus fruits with this disease, and in severe cases, they will rot. Therefore, the commercial value of citrus fruits will be greatly reduced, which will cause huge economic losses to fruit farmers. So what medicine should be used to treat this disease?

What is the best medicine to treat citrus ulcer?

Citrus canker is a bacterial disease. The optimal growth temperature of the pathogen is 25-35℃. The pathogen is spread through rain, insects, seedlings, scions and fruits, and invades the host through the stomata, lenticels or wounds. The incubation period during the growing season is 3-10 days.

Environmental and climatic conditions and variety are two important factors affecting the severity of ulcers. If the conditions are hot, humid and rainy, it is very conducive to the occurrence of ulcers, especially after storms and typhoons. Some fruit trees that are managed with too much nitrogen fertilizer or too little fertilizer will have too many branches and may become seriously ill.

There are differences in susceptibility to disease among citrus varieties. Generally, oranges, grapefruits and lemons are most susceptible to the disease, followed by tangerines. Among tangerines, some varieties are susceptible to the disease (such as Sihui oranges), while Fu oranges, Nanfeng mandarin oranges and kumquats are highly resistant to the disease.

In addition, young trees are more susceptible to diseases than adult trees because they have more shoots than adult trees, which facilitates the invasion of pathogens. Ulcer pathogens generally only invade young tissues at a certain stage of development. New shoots and mature shoots are rarely infected because the very young stomata (the invasion pathway for the pathogen) have not yet formed, and the stomata of mature shoots will age and close, making invasion difficult.

Leaf miners cause cankers

When preventing and treating ulcers, if you want to achieve good prevention results, you must do several things not to do.

1. Don’t wait until the disease occurs before taking preventive measures

In spring, when the new shoots have emerged but have not yet developed into large leaves and 2/3 of the flowers have fallen, that is, when the tender leaves and young fruits have not yet formed stomata, it is the best time to use the medicine. That is, the summer and autumn shoots should be sprayed for the first time 7-10 days after sprouting, and then apply the medicine once every 15 days or so until the new shoots are mature. Generally, the medicine is used 2-3 times.

The use of medicine is most effective in the early stages of the disease. Waiting until the damage occurs on a large scale will lead to fruit settling, which will directly damage the commercial value of the fruit.

2. Don’t mix pesticides randomly

Inorganic copper is effective in preventing and treating canker disease and has no resistance. However, if it is combined with other pesticides, it can easily cause phytotoxicity and stimulate a massive outbreak of red spider mites. In addition, inorganic copper is not systemic. For diseases such as canker, after causing damage, it will remain in the gaps between the mesophyll cells and fruit cells of citrus and will not be able to completely kill the pathogens.

According to Teacher Denghuo’s summary, the mixing method is as follows:

a. The combination of inorganic copper and bacterial systemic drugs significantly enhances the efficacy

b. The combination of bacterial systemic drugs and fungal protective drugs significantly enhances the efficacy

c. The combination of bacterial and fungal systemic drugs significantly enhances the efficacy

Avoid copper preparations + copper preparations, inorganic copper + other metal ion pesticides, and do not use inorganic copper preparations monotonously for a long time.

3. Don’t ignore the diseased leaves you cut off

Prune diseased branches, leaves and fruits promptly and burn them in a concentrated manner. Especially, do a good job of cleaning the garden in winter, collect fallen leaves, fruits and dead branches and burn them. After pruning off the branches and leaves of a diseased tree, disinfect the pruning shears with alcohol in time. In addition, use Bordeaux mixture or lime sulfur mixture to clean the garden and sterilize and disinfect.

Regarding pruning, you should also cut off crossed branches, overlapping branches, and branches that droop down to the ground to ensure ventilation and light transmission, which is beneficial for spraying pesticides.