Polychagotarsonemus latus Banks, also known as Hemitarsonemus latus Banks, is commonly referred to as the "tea mite" or "tea red spider." It belongs to the class Arachnida, order Tetranychidae, and is a polyphagous pest that affects a wide range of host plants, including tea, chili peppers, and various vegetables. This mite is particularly destructive to tea crops, causing significant damage to leaves, stems, and fruit.
The symptoms of infestation include oily, yellowish-brown spots on the back of leaves, with the leaf edges curling downward. Infested leaves often stand upright, while young stems turn brown and may eventually die. Severe infestations lead to stunted growth, twig dieback, and bald patches on the plant. The stalks and fruit tips become yellow-brown, lose their luster, and the fruits may stop growing, becoming hard and unmarketable.
Morphologically, the female mite measures approximately 0.21 mm in length, has an oval shape, and ranges from pale yellow to orange-yellow. It has five pairs of short legs and four pairs of slender legs. The male is smaller, about 0.18 mm long, with a hexagonal body shape and a pointed end. Both sexes are translucent. The eggs are elliptical, around 0.1 mm long, colorless and transparent, with 5–6 rows of white nodules on the surface. Nymphs are elliptical, pale green, and have three distinct abdominal segments. They are tapered at both ends, with one pair of bristles and three pairs of legs. Juveniles tend to remain stationary, often surrounded by shed skins.
In terms of life habits, this species completes one generation within 7–10 days at temperatures between 20–30°C. In tropical and greenhouse environments, it can reproduce year-round, though its reproductive activity decreases in winter. The mites are primarily sexual, but parthenogenesis is also possible. Unhatched eggs usually result in male offspring. Eggs are laid sparsely on the backs of young leaves and in fruit depressions. Both adults and nymphs prefer tender leaves, stems, and flower parts. The optimal temperature for their development is 16–23°C, with relative humidity between 80–90%. High temperatures and heavy rainfall can reduce population levels.
For prevention and control, regular field inspections are essential. Early detection during the flowering stage of chili plants is crucial. Spraying should be done every 10–14 days, with a total of three applications. Focus on the upper leaves, especially the undersides of tender leaves, young stems, flowers, and fruit. Recommended pesticides include 1.8% spinosad (such as avermectin, efford) diluted at 3000 times, with a 7–10 day interval. 20% compound liuyangmycin EC at 1000 times, with a 7-day interval. Also effective are 57% kete EC at 800 times, 48% lethben EC at 1500 times, and 20% oleolacil WP at 1000 times. Always follow label instructions and observe safety intervals to ensure effective and safe application.
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