Rhizoglyphus echinopus (Fumouze et Robin), commonly known as the bulb mite, belongs to the family Acrididae. This pest becomes particularly active from May to August, causing significant damage in onion fields and has emerged as a serious threat to various crops.
Bulb mites primarily affect plants such as onions, leeks, lilies, loquats, beets, potatoes, gladiolus, Pinellia, and Fritillaria. The symptoms of infestation include yellowing leaves, stunted growth, and withering. The underground stems or bulbs become dark brown and decayed, with the mites spreading into surrounding tissues, leading to poor development above ground. Seedlings are especially vulnerable, showing withered leaves, discoloration, and even blue-tinged tissue damage. In lilies and other bulbous plants, brown spots appear on the bulbs, and the above-ground parts dry up. Some vegetables and flowers may show purple leaves after germination, which then gradually wither. It is important to differentiate these symptoms from those caused by diseases.
Morphologically, adult bulb mites are oval-shaped, measuring 0.6 to 0.9 mm in length. Their bodies are milky-white and shiny, with light red-brown legs. They have three pairs of legs as larvae, and four pairs in both nymphs and adults. Eggs are white and oval, approximately 0.2 mm long.
In terms of life habits, bulb mites attack the false stems of leeks and garlic, causing rotting. Under high humidity, they complete one generation in 17 to 27 days at temperatures between 18.3°C and 23.9°C, and as little as 9 to 13 days at 20°C to 26.7°C. Females can lay 195 eggs on average, with some reaching up to 500. When environmental conditions are unfavorable, they produce smaller, mobile forms. In Japan, they can complete over 10 generations per year. These mites prefer sandy soils and can be found in large numbers, with more than 10 individuals per root. They move through the soil and thrive in acidic conditions.
The occurrence of bulb mites follows certain patterns, often increasing in warm and humid environments. To manage this pest, several control methods are recommended:
1. During soil preparation, deep plowing and proper fertilization should be practiced. Applying 80 to 100 kg of slaked lime per acre helps neutralize the soil.
2. Implement crop rotation to avoid continuous planting of host crops, such as melons and beans.
3. Expose root crops to sunlight to reduce infestations.
4. Control the transplanting period by using insect-free seedlings and eliminating any infested ones. Before planting, dip the roots in a 20% net emulsion or 50% Nisone EC diluted 2000–3000 times for 5–10 minutes, achieving up to 90% mortality.
5. During the adult stage, chemical control can be applied using 48% Le Siben EC, 20% Ke Ke EC, 1.8% Cumulong EC, or 20% broom net EC diluted 1000–1500 times. Apply the solution directly to the base of green onions, resulting in more than 80% control effectiveness.
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