What are the natural enemies of red spider mites and the most effective methods to eliminate them?
Red spider mite, also known as cotton red spider mite, commonly called big spider, big dragon, sand dragon, etc., scientific name spider mite, widely distributed, omnivorous, mainly damaging various vegetable crops, garden flowers and trees, citrus fruit trees, etc. So what are the natural enemies of red spider mites? What are the most effective methods to eliminate them? According to netizens, red spider mites are not invincible; they often die at the mouths of green lacewings (Chrysopa sinica), mite-eating ladybugs, and predatory mites.
Red spider mites belong to the superfamily Tetranychoidea. They are relatively small, with adults about 0.2~1 mm long, round or oblong in shape, mostly red or dark red. According to the biological habits of red spider mites, agricultural, physical, and chemical control measures can be applied.
Natural Enemy Control
In the early stage of red spider mite occurrence, natural enemies are used to control the population, and predatory mites are released from flowering to fruit growth stage.
Before releasing predatory mites, try to reduce the number of red spider mites as much as possible. Use cyflumetofen for pest control. 5~10 days after application, release predatory mites at a beneficial-to-pest ratio of 1:10 to 1:30.
One predatory mite can prey on 300~500 red spider mites in its lifetime, and also feeds on pest mite eggs, effectively controlling red spider mite damage.
Flower Plant Control
In the process of cultivating flowers, red spider mites are common destroyers. Those affected include Chinese rose, Milan (Aglaia odorata), jasmine, kumquat, crabapple, osmanthus, finger citron, and other flowers. This pest is very small, less than 1 mm, round or oval, orange-yellow or reddish-brown. Because of its small size it is difficult to find; once damage is discovered, the flowers are often already quite severely affected. This pest damages plants by inserting its mouthparts into leaves to suck sap, destroying chlorophyll, causing leaves to show grayish-yellow spots or patches, turn orange-yellow, fall off, or even drop completely.
To control red spider mite damage, pay attention to observation at ordinary times. When abnormal leaf color is found, carefully check the leaf undersides. If only a few leaves are affected, remove the infested leaves. If many leaves are affected, spray pesticide as early as possible. Commonly used pesticides include propargite, dicofol, dimethoate, huachongjing, and fenvalerate. For home flower growing, prepare a flower sprayer. In 400 mL of water, add 4 drops of propargite, fenvalerate, or huachongjing (equivalent to a 2000-fold dilution); or add 8 drops of dicofol or dimethoate (equivalent to a 1000-fold dilution). After adding the pesticide, shake well and spray immediately. Spraying should be uniform and thorough, especially the leaf undersides. When spraying, it is best to move potted flowers outdoors. If spraying indoors, do not go near food or utensils. After each use, pour out the excess liquid and rinse the sprayer clean with water.
Citrus Control
Citrus red spider mite is one of the most important pests in citrus cultivation. If not controlled in time, it often causes heavy leaf drop in citrus trees, weakening tree vigor and damaging fruit peel, seriously affecting marketability. Therefore, controlling citrus red spider mite well is the primary task in citrus production. Based on practical research, it is believed that good red spider mite control should start from the following aspects.
1. Agricultural measures: apply chemical fertilizers reasonably, reasonably match the ratio of nitrogen, phosphorus, and potassium, and avoid excessive nitrogen fertilizer. Excessive nitrogen causes excessive growth of branches and leaves, frequent new shoot emergence, and provides an ideal breeding place for red spider mites. Orchards with excessive nitrogen often have severe red spider mite outbreaks. Do a good job of winter orchard cleaning and pruning to make the tree body well-ventilated and well-lit, reduce pest sources, and facilitate pesticide coverage!
2. Biological control: red spider mites have many natural enemies in nature, such as predatory mites, ladybugs, bud branch mold fungi, and other natural enemies and microorganisms. Advocating sod culture provides a living environment for natural enemies and avoids the use of broad-spectrum pesticides and fungicides. In production, if broad-spectrum pyrethroid pesticides are sprayed, the natural enemies of red spider mites are killed, and red spider mites will develop rapidly. The same is true for fungicides, such as copper agents and sulfur agents; during disease control, they also kill the red spider mite natural enemy Hirsutella thompsonii. If red spider mites average 3 adults per leaf, predatory mites can be released. Amblyseius huae is available on the market. Hang one box of about 1000 mites per tree. Within 30 days, the red spider mite population decreases by more than 95 percent.
3. Chemical control: do a good job of orchard inspection at ordinary times, and do a good job of winter orchard cleaning. Preventing red spider mites by winter orchard cleaning is the first step. Mineral oils with high safety such as Lvying and Disichong can be selected for orchard cleaning. Mineral oil at 200—300 times can be mixed with 2.0 abamectin at 3000 times, or propargite (fenbutatin oxide) at 1500 times, to improve and enhance the insecticidal effect. Lime sulfur mixture and acaricidal scale-insect mite agents can also be selected, but their insecticidal power is not very ideal and they are highly corrosive to spraying equipment. Next, do a good job of early spring control. Early spring is an important control period for red spider mites throughout the year. At this time, because the temperature is low, the activity of many temperature-sensitive acaricides is not ideal, such as propargite, azocyclotin, mono- and bis-amitraz. At the same time, other pests also occur. For pesticides, physically acting high-quality mineral oil at 200—300 times plus 2000 times fenpropathrin can be selected, or flufenzine at 5000 times, cyflumetofen at 1500—2000 times, and for high pest density, mix in manwei at 5000 times. If early control was not done well, there will be a peak when spring shoots mature. In production, pay attention to selecting suitable pesticides for control. Finally, in autumn, before and after releasing autumn shoots, red spider mites must be controlled once; otherwise, the pest mites will damage autumn shoots and fruit!
Why are red spider mites difficult to control?
1. Red spider mites are not insects, so many insecticides are ineffective against them.
2. It is difficult for one red spider mite pesticide to cover all four forms of red spider mites at the same time.
Red spider mites have a high reproductive rate and frequent generations. On a single leaf, eggs, larvae, nymphs, and adults may exist at the same time. There is no acaricide that is highly effective and fast-acting against all four forms at the same time.
3. Red spider mites are small and relatively hidden, making full coverage during spraying difficult; after the pesticide effect wears off, they easily rebound.
4. Environmental and management mode factors
In greenhouse production areas, pests and diseases have many generations, and prevention requires high-frequency use of insecticides. Some vegetable gardens must also use copper preparations to prevent canker disease. The natural enemies of pest mites are killed, and the large-scale application of pesticides also gives mites extremely high resistance, so management difficulty is higher.
5. Practitioners have not mastered the relevant techniques
Difficulty one: hiding on the leaf undersides
Red spider mites are very small and can only be seen by careful observation. They also like to hide on the leaf undersides to suck sap. By the time symptoms appear on the upper leaf surface, the situation is often already relatively serious.
Difficulty two: spinning silk and forming cocoons
Large numbers of red spider mites spinning silk and forming cocoons can defend against pesticides and adverse environments. This is also one of the reasons red spider mites are difficult to eradicate.
Difficulty three: strong pesticide resistance
Long-term single use of a small number of acaricide varieties causes pest mites to develop tolerance or increased resistance.
Difficulty four: safety issues
The peak occurrence period of red spider mites coincides with the flowering and fruit-setting period of fruit trees, so spraying must also take into account safety for flowers and fruit, bees, and humans.