Brevicoryne brassicae Linn., commonly known as the cabbage aphid, belongs to the order Hemiptera and the family Aphididae. These small, soft-bodied insects are typically found on cruciferous vegetables such as cabbage, broccoli, and cauliflower. They are primarily distributed in the northwestern regions of China, including parts of Inner Mongolia and the northeastern provinces. In recent years, their occurrence has also been reported in eastern China, indicating a possible expansion of their range.
The damage caused by B. brassicae is significant. Both adult and nymph stages feed on the leaves, stems, and seed pods of host plants, sucking sap and causing yellowing, curling, and wilting of foliage. Their feeding activity also results in the secretion of honeydew, which promotes the growth of sooty mold and can lead to further plant decline. Infestations may also cause stunted growth, twisted stems, and deformed seed pods, ultimately reducing both yield and quality. More importantly, these aphids act as vectors for various viral diseases, and the damage from virus transmission is often more severe than the direct feeding damage.
In terms of morphology, B. brassicae has a short, oval body with a waxy coating that helps protect it from environmental stress. The adults are usually pale green or yellowish, with a distinct black cornicle (a pair of tube-like structures on the abdomen). Unlike some other aphid species, B. brassicae does not have a woody overwintering host, making it highly dependent on agricultural crops for survival.
Habitat preferences include warm and dry conditions, with optimal temperatures ranging between 18°C and 25°C and relative humidity below 75%. Winged forms, known as alates, play a key role in dispersal, and an increase in their proportion within the population often signals an impending outbreak. These aphids are strongly attracted to yellow and orange colors, followed by green, and they show less attraction to silver-gray. Reflective mulches, such as silver-colored plastic films, can be used to repel them from crops.
There are over 70 natural enemies of B. brassicae, including ladybugs, lacewings, parasitic wasps, and predatory mites. Among these, certain species like the green lacewing and hoverfly larvae are particularly effective in controlling aphid populations. Biological control methods are especially valuable in integrated pest management systems.
For control, several strategies can be employed:
1. **Physical Control**: Yellow or yellow sticky traps can be used to monitor and reduce aphid populations. Reflective mulches, such as silver-gray plastic, can also be laid between crop rows to deter aphids from settling.
2. **Chemical Control**: Insecticides such as 50% imidacloprid wettable powder diluted at 3000 times, 4.5% emulsifiable concentrate of cypermethrin diluted at 3000 times, or 50% acephate wettable powder diluted at 2000 times can be applied to manage infestations effectively.
Early detection and timely intervention are crucial in managing B. brassicae infestations and minimizing crop losses. Combining cultural, biological, and chemical control methods provides the most sustainable and effective approach.
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