Detailed Explanation of the Occurrence and Control Methods of Peach Tree Gummosis

Peach tree gummosis is a disease commonly occurring on peach trees today, and its incidence is severe. Especially in peach orchards with extensive management and weakened tree vigor, the rate of affected plants can reach over 90%. This disease severely weakens tree vigor, affects yield and quality, and in severe cases leads to dead branches and dead trees, threatening the production and development of peach trees. It is also one of the most troublesome diseases for fruit growers.

I. Causes of the disease. There are two causes of peach gummosis: one is non-infectious pathogens, such as gummosis caused by wounds from mechanical injury, insect and disease damage, frost injury, freezing injury, etc., or gummosis caused by physiological disorders of the tree body due to extensive management, excessive pruning, excessive fruiting, improper fertilization, heavy clay soil, etc. The other is infectious pathogens caused by fungi; the sexual stage belongs to Ascomycota, and the asexual stage belongs to Deuteromycota.

II. Symptoms and Occurrence Patterns

1. Non-infectious gummosis mainly occurs on the trunk and large branches, and in severe cases small branches can also be affected. In the early stage, the diseased part swells slightly, then secretes translucent, soft gum. Gum flow is heavy after rain, and then it turns brown upon contact with air, becoming crystal-clear soft gum blocks. Later it dries and becomes hard gum blocks ranging from reddish-brown to tea-brown. As the amount of gum flow increases, the cortex and xylem of the diseased part gradually turn brown and rot (but no pathogens are produced). This causes tree vigor to become weaker and weaker, and in severe cases causes tree death. The disease is severe in the rainy season, severe in older trees, and mild in young trees.

2. Infectious gummosis mainly harms branches and trunks, and also infects fruit. The pathogen invades the current-year new shoots of peach trees, producing tumor-like raised lesions centered on lenticels on the new shoots, but no gum flows. In May of the following year, the tumor skin cracks and exudes a gum-like liquid, which is a colorless, translucent viscous substance, later becoming a tea-brown hard block. The diseased part sinks into round or irregular patches, scattered with small black dots. When perennial branches and trunks are infected, water-soaked bulges form, and brown gum liquid can seep from the diseased parts, which can cause branch and trunk cankers or even death. Infected peach fruit develops brown rot, densely covered with small granular spots, and in humid conditions exudes white block-like material.

Infectious gummosis overwinters in diseased branches as mycelium and pycnidia. From late March to mid-April of the following year, conidia are released and spread by wind, mainly invading through wounds, and can also invade through lenticels and lateral buds. Especially on rainy days, large amounts of pathogens overflow from diseased parts, flow down along branches and trunks or splash onto new shoots, invading through lenticels and wounds, becoming the main inoculum source for initial infection of new shoots. The activity of latent pathogens in branches and trunks is related to temperature. When the temperature is around 15°C, gum liquid can seep from the diseased part. As the temperature rises, the number of gum flow points on the tree increases and the disease worsens. Infectious gummosis has two disease peaks in one year: the first from early May to early June, and the second from early August to early September. After that, it no longer causes infection damage. The most favorable time for pathogen invasion is when the cortical cells of the branches gradually become suberized and lenticels have formed. Therefore, preventing this disease is best done during the new shoot growth period.

III. Integrated Control Measures. Based on the above symptoms and occurrence patterns, in actual production, the control of this disease should focus mainly on agricultural control and manual control, with chemical control as a supplement. Chemical control mainly controls spore dispersal and the two peak periods of spore invasion and disease occurrence. Specific measures are as follows.

1. Strengthen cultivation management, enhance tree vigor, and improve the disease resistance of peach trees.

Apply more organic fertilizer to diseased trees, appropriately increase phosphorus and potassium fertilizer, and control nitrogen fertilizer in the middle and late stages. Prune reasonably, manage load reasonably, coordinate the contradiction between growth and fruiting, and maintain stable tree vigor. Do a good job of drainage in the rainy season to reduce humidity in the peach orchard. Conduct timely summer pruning to improve ventilation and light conditions, and at the same time control other diseases and pests, especially branch and trunk pests of peach trees, reducing disease and pest wounds and mechanical wounds.

2. Eliminate overwintering inoculum sources: In the coldest December to January, carry out orchard cleaning and disinfection, scrape off hard gum blocks and the decayed cortex and wood below them, gather them and burn them, then spray 5°Be lime sulfur mixture for disinfection, and then whitewash the trunk and large branches to eliminate overwintering inoculum sources and insect eggs. At the same time, it can also prevent freezing injury and sunscald.

3. Before peach trees bud, spray 5°Be lime sulfur mixture on the tree body to kill active pathogens.

4. Quicklime powder control method: In recent years, quicklime powder has been used in control trials against gummosis occurring on fruit trees such as peach, apricot, and plum, with very good results and a cure rate of 100%. The specific method is: apply quicklime powder to the gum flow site. After application, all gum flow stops within 5-7 days, symptoms disappear, and there is no recurrence. The optimal period for applying the powder is when tree sap begins to flow, that is, the end of March. This is exactly the initial stage of gum flow, when the number of affected plants is small and the scope of gum flow is limited, making control easier and reducing nutrient consumption of the tree body. Afterward, as cases are found, manpower can be mobilized to apply powder for control. Control is best on cloudy and rainy days, when the gum liquid flowing from the bark is more viscous and easily adheres to the quicklime powder. For fruit trees with severe gum flow or old and declining trees, use a knife to scrape off dried gum and old rough bark, exposing tender bark, and then apply powder for a better effect. This method is simple and effective.

5. Spray pesticides at appropriate times during the growing season: From late March to mid-April is the period when infectious gummosis releases conidia. Combined with the control of other diseases, spray 1500x thiophanate-methyl or 1000x Duoxiaoling, Guobingling, etc. for prevention. From early May to early June and from early August to early September are the two peak periods of infectious gummosis. Before each peak period, spray 1000x liquid Jundusha or Junduqing, Junlimie, etc. once every 7-10 days, alternating for 2-3 consecutive sprays, to eliminate the disease in the bud. According to the condition of the disease, reduce the number of sprays as much as possible.