What are the control methods for the main pest mites of Sichuan cherry blossoms?

In the Mianyang area of Sichuan, the mites harmful to cherry blossoms are mainly the European red mite (Panonychus ulmi), the hawthorn spider mite (Tetranychus viennensis), and others. The larvae, nymphs and adult mites suck the leaf sap; the damaged leaves develop many small chlorotic spots, and in severe cases the leaves turn pale and scorch, which not only affects plant growth and flowering but also affects photosynthesis.

Morphological characteristics

The female adult of the European red mite is 0.45 mm long and 0.29 mm wide, round, with a raised back, dark red; the male adult is 0.3 mm long. Summer eggs are orange-red, winter eggs dark red.

The female adult of the hawthorn spider mite is 0.49 mm long and 0.32 mm wide, oval, brown; the male adult is 0.33 mm long and 0.18 mm wide. The eggs are spherical, orange-red, and those laid later are orange-yellow or yellow-white.

Occurrence pattern

The European red mite has about 10 generations a year and overwinters as eggs on the branches. In late April to early May of the following year, the overwintering eggs begin to hatch, and after about 2 weeks the adult mites flare up; in June to July the generations overlap and reproduce rapidly, which is the peak period of damage. After August they begin to lay overwintering eggs, continuing until early October.

Hawthorn spider mite: about 10 generations a year; it overwinters as several to dozens of fertilized female adults in hidden places such as bark crevices, under dead branches and fallen leaves, and in the surface soil layer. When the tree buds swell the following year, they emerge from overwintering; in mid-April, after feeding, the females become full and lay eggs; the first-generation eggs hatch in early May; from the second generation on the generations overlap; overwintering female adults appear in September, and by late November all have entered the overwintering state.

Control methods

Before bud break, spray 20% ovotran (mite-egg ester) wettable powder at 800 times dilution, or 5-6% anthracene oil emulsion, or 5% heavy diesel oil emulsion, to kill the overwintering eggs.

When the tree buds swell (mid to late March), spray lime sulfur mixture at 0.5-1 degree Baume, or 4% omethoate emulsifiable concentrate at 1000 times dilution, to control the newly hatched larvae and the female adults emerging from overwintering.

From late May to early June, use the biological acaricide liuyangmycin (20% compound preparation) at 1000-2000 times dilution, or 20% ovotran wettable powder at 800-1000 times dilution, to control the first-generation newly hatched larvae, nymphs and female adults that have not yet laid eggs.

When there is a major outbreak in June to July, spray 73% propargite emulsifiable concentrate at 4000 times dilution, or 40% saomanjing emulsifiable concentrate at 4000 times dilution, or 20% pyridaben wettable powder at 2000-3000 times dilution. Generally spray once every 10 days, using them alternately, for 3-4 consecutive times. When spraying, the middle and lower parts of the plant and the undersides of the leaves must be thoroughly and evenly covered. Do not spray the same pesticide continuously, to avoid resistance.

In winter, remove weeds and fallen leaves, and flooding the woodland is also possible, to eliminate overwintering sources of the pests. At the same time, pay attention to protecting and using natural enemies such as the deep-spot mite-eating ladybird (Stethorus punctillum).