Common Plum Tree Pests and Diseases and Key Points of Control Techniques

The plum tree is one of the more common fruit trees in everyday life, especially in the past, when peach trees and plum trees were grown in almost every household. Plum trees are relatively susceptible to pest and disease attacks during their growth. Today we mainly introduce the details of common plum tree pests and diseases and key points of control techniques.

I. What are the common pests and diseases of plum trees?

1. Plum fruit borer

The plum fruit borer is a pest of the family Olethreutidae, order Lepidoptera (more common in areas between 40 and 50 degrees north latitude). It is the most serious pest damaging plum fruit, with a damage rate as high as 80% to 90%. Affected fruit often exudes teardrop-shaped gum at the bore hole, cannot continue to develop normally, and gradually turns purplish red and drops off. Because its tunnel is filled with red frass, it is also vividly called "red bean paste filling".

2. Red spider mite

The red spider mites harming plum trees are mainly adults and nymphs of the hawthorn red spider mite. They suck the sap of leaves and newly sprouting buds, causing the new buds to fail to continue sprouting. After leaves are severely damaged, the whole leaf turns scorched yellow and drops off. In outbreak years, most leaves drop in July and August, sometimes causing a second flowering. Severely affected plum trees not only fail to ripen fruit that year, but also greatly affect flower bud formation that year and the yield of the following year.

3. Bacterial shot hole disease

On the skin of diseased fruit, this disease first produces water-soaked small spots centered on the lenticels. When they expand to 2 mm, the center of the lesion turns brown, eventually forming a nearly round, dark purple lesion with a water-soaked halo at the edge, slightly sunken in the middle, hardened and rough on the surface, and showing irregular cracks, reaching about 35 mm. When humidity is high, yellow ooze may appear on the diseased part, and diseased fruit drops early. High temperature and high humidity favor infection by the pathogen and worsen the disease. Orchards with weak tree vigor, poor drainage and ventilation, or excessive nitrogen fertilizer application have more severe incidence.

II. Introduction to the key points of control techniques for common plum tree pests and diseases

1. Key points of control techniques for the plum fruit borer

The key periods for this pest are the peak adult stage and peak egg-laying stage of each generation and the period when the first-generation mature larvae enter the soil. Spray 0.8% solution of 90% trichlorfon, 1% solution of 50% malathion, or 50% dichlorvos. Before the physiological fruit drop of plum trees, apply 1% to 1.5% solution of 50% phoxim once to the soil under the canopy. At the end of flowering (95% of flowers fallen), when young fruit is the size of a wheat grain, spray the first treatment; dichlorvos, deltamethrin, fenvalerate, or lambda-cyhalothrin may all be used, spraying once every 7 to 10 days. From the perspective of integrated control, biological agents such as Beauveria bassiana may also be used to treat the soil under the canopy. After autumn, fallen fruit should be swept up thoroughly to reduce the source of insects the following year.

2. Control techniques for red spider mite

According to the living habits of red spider mites, in field management, rational intercropping should be carried out, the tree disk should be deeply turned or the tree disk should be earthed up in time, pruning should be rational, and fertilization and irrigation should be appropriate. Traditional methods may also be used for control, such as spraying garlic juice or mixing washing powder with lime sulfur mixture. At the same time, natural enemies should be protected so as to give play to their natural control of pests.

3. Control techniques for bacterial shot hole disease

Strengthen integrated orchard management and increase the application of organic fertilizer to improve the disease resistance of the tree.

For orchards with heavy clay soil and a high groundwater table, attention should be paid to improving the soil and drainage; select and plant disease-resistant varieties, carry out rational shaping and pruning, and create good conditions for ventilation and light penetration.

In winter, cut off diseased branches; in early spring, scrape off the lesions on branches and trunks and apply 25 to 30 degree lime sulfur mixture to the wounds to reduce the source of initial infection.

Chemical control: spray amobam, agricultural streptomycin, xinzhiromycin, and thiram at conventional use concentrations, and appropriately increase the number of chemical control applications during the fruit growth period.