peach gummosis

Gummy disease of peach tree is a common disease in peach trees at present, and the incidence is serious, especially in peach orchards with extensive management and weak tree vigor. The incidence rate can reach more than 90%. The disease seriously weakens tree vigor, affects yield and quality, and causes dead branches and dead trees, threatening the production and development of peach trees. It is also a disease that fruit growers scratch their heads most.

I. Causes of disease. There are two causes of peach gummosis: one is non-infectious pathogen, such as gummosis caused by mechanical injury, pest injury, frost injury, freezing injury and other wounds, or gummosis caused by extensive management, excessive pruning, excessive fruit, improper fertilization, soil viscosity and other physiological disorders. The other is an infectious pathogen, caused by fungi, sexual stage belongs to Ascomycetes subphylum, asexual stage belongs to Semi-fungi subphylum.

II. Symptoms and pathogenesis

1. Non-infective exudation mainly occurs on the trunk and large branches, and when it is serious, the twigs can also be infected. At the initial stage, the diseased part is slightly swollen, and then secretes translucent and soft gum. After rain, the gum flows heavily, and then it becomes brown in contact with the air and becomes crystal soft gum block. After drying, it becomes reddish brown to dark brown hard gum block. With the increase of gum flow, the cortex and xylem of the diseased part gradually turn brown and rot (but no pathogen is produced). As a result, the tree is getting weaker and weaker, serious cases cause dead trees, heavy diseases in rainy season, heavy diseases in older trees, and light diseases in young trees.

Any wound caused by insect injury, disease injury, frostbite, hail injury, sunburn, etc. can cause non-infectious peach gum disease (no pathogenic bacteria); In addition, due to heavy soil viscosity, poor drainage, excessive or insufficient irrigation caused by tree physiological dysfunction to form gum flow, is caused by fungi infected peach gum disease, its asexual generation of spores spread by wind and rain, from the wound and lateral bud invasion, a year has two peak incidence, namely late May to early June and early August to early September.

2. The infective gummy mainly damages the branches and also infects the fruits. The pathogen invades the new shoots of peach trees in the current year, and the new shoots produce tumor-like protruding disease spots centered on the dermatome, but they do not shed gum. In May of the next year, the tumor skin cracks and overflows colloidal liquid, which is colorless and translucent viscous substance, and then becomes a dark brown hard mass. The diseased part is depressed into round or irregular patches, and small black spots are scattered on it. Perennial branches are infected with disease, resulting in blister-like bulge, and the diseased parts can exude brown glue, which can lead to ulcers and even death of branches. The peach fruit is infected with brown rot, dense with small particles, and white lumps flow out when wet.

The infectious gummosis overwinters in the diseased branches by mycelium and conidia, and spreads with wind from late March to mid April of the next year. It mainly invades through wounds, but also through dermatomes and lateral buds. Especially in rainy days, a large number of pathogens overflow from the diseased part, flow down along the branches or splash on the new shoots, invade from the skin holes and wounds, and become the main source of the first infection of the new shoots. The activity of latent pathogens in the branches is related to temperature. When the temperature is about 15℃, the diseased part can exude glue, and with the increase of temperature, the number of glue points in the tree body increases, and the disease is aggravated. There are two peaks of infection gummosis in a year, the first one is from early May to early June, the second one is from early August to early September, and the infection is no longer harmful. The most favorable time for the invasion of the pathogen is after the cortical cells of the branches gradually become cork and the leather holes are formed. Therefore, it is better to prevent this disease in the growth period of new shoots.

Third, the soil is bad, such as too viscous and acidic. Poor drainage, excessive accumulation of water on the ground. In addition, extensive management, excessive results, but also caused tree weakness and so on can cause gummosis.

IV. Comprehensive control measures. According to the above symptoms and disease occurrence rules, agricultural control and artificial control should be given priority to in production practice, and chemical control should be supplemented. Chemical control should mainly control the two peak periods of spore scattering and spore invasion. Specific measures are as follows.

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

More organic fertilizer, phosphorus and potassium fertilizer should be applied to the diseased trees, and nitrogen fertilizer should be controlled in the middle and late stages. Reasonable pruning, reasonable load, coordination of growth and fruit contradictions, to maintain a stable tree potential. Drain well in rainy season to reduce the humidity of peach orchards. Timely summer shearing, improve ventilation and light transmission conditions, at the same time control other pests, especially peach tree branches pests, reduce pest wounds and mechanical wounds.

2. Eliminate overwintering bacteria: clean the garden from the coldest December to January, scrape off the glue hard block and the rotten cortex and wood at the lower part, concentrate them and burn them, then spray 5°Be stone sulfur mixture for disinfection, and then paint the trunk and branches white to eliminate overwintering bacteria and eggs. At the same time, it can prevent freezing injury and sunburn.

3. Before peach trees germinate, spray 5°Be sulfur mixture on the trees to kill active bacteria.

4. Quicklime powder control method: In recent years, quicklime powder has been used to control the gum flow of peach, apricot, plum and other fruit trees, and the effect is very good, and the cure rate is 100%. The specific method is: apply quicklime powder to the glue flow, 5-7 days after application, all stop the glue flow, symptoms disappear, no longer relapse. The optimum period of powdering is the end of March when sap begins to flow, which is the initial period of gum flow. The number of trees is small and the range of gum flow is small, which is convenient for control and reduces the consumption of tree nutrients. Later found with the launch of human powder control, rainy days to control the best, at this time the bark outflow of glue viscosity, easy to get lime powder. Gum flow serious fruit trees or aging trees with a knife to scrape dry gum and old warped skin, exposed tender skin, powder coating effect is better. This method is simple and effective.

5. Timely spraying in growing season: late March to mid-April is the period when infectious gummy disease pops out conidia, which can be combined with other diseases, such as spraying 1500 times methyl thiophanate or 1000 times multi-effect spirit, fruit disease spirit, etc. From early May to early June and from early August to early September are the two peak periods of infectious gummosis. On the eve of each peak period, spray 1000 times of liquid bacteria poisoning or bacteria toxin cleaning, bacteria killing, etc. once every 7-10 days, alternately spray 2-3 times continuously to eliminate the disease in bud state, and reduce the spraying frequency as much as possible according to the disease condition. spray a mixture of 4 - 5 degree of stone and sulfur of Baume once before bud expansion stage, spray a solution of 1000 times of 50% carbendazim once every half month for 4 time from leaf expansion stage in April.

6. To prevent and control peach gum disease, it is necessary to spray timely to prevent diseases and insect pests and white trunk coating to avoid freezing injury, sunburn and mechanical trauma.

7. You can also scrape off the diseased tissue of the glue flow site first, and then apply 43% Dashengfu diluted to 30-60 times to the wound with cotton swab or toothbrush, usually 2-3 times in spring and autumn, and the disease can be cured after 1-2 years of prevention.