What are fleas on cabbage? - briefly
They are tiny jumping beetles of the genus Phyllotreta that feed on cabbage and related Brassica leaves, creating characteristic shot‑hole damage. Both adults and larvae damage foliage and roots, leading to reduced plant vigor and yield.
What are fleas on cabbage? - in detail
Cabbage flea beetles are small, jumping insects belonging to the family Chrysomelidae, genus Phyllotreta. Adults measure 1.5–3 mm, possess dark, convex bodies and enlarged hind femora that enable rapid leaping. Their antennae are short, and the elytra are typically black or dark brown with a metallic sheen. Larvae are soil‑dwelling, white, legless grubs that feed on root hairs.
Feeding damage appears as tiny, circular pits on leaf surfaces. Adults scrape the epidermis, removing chlorophyll and creating a stippled appearance that can coalesce into larger necrotic zones under heavy infestation. Larvae weaken plants by consuming fine roots, reducing water and nutrient uptake and predisposing crops to secondary pathogens.
The life cycle proceeds as follows:
- Overwintering adults emerge in early spring and seek host plants.
- Mating occurs shortly after emergence; females lay clusters of 5–30 eggs on leaf undersides.
- Eggs hatch within 4–7 days; larvae feed in the soil for 2–3 weeks.
- Pupation takes place in the soil, lasting 5–10 days.
- New adults emerge, completing the cycle. Multiple generations may develop during a warm growing season.
Environmental factors influencing population dynamics include temperature, moisture, and the presence of cruciferous hosts. Warm, dry conditions accelerate development, while heavy rainfall can suppress adult activity but favor larval survival.
Management strategies focus on cultural, biological, and chemical controls:
- Crop rotation with non‑cruciferous species reduces host availability.
- Early‑season sowing and the use of row covers limit adult colonization.
- Beneficial insects such as lady beetles and predatory nematodes can suppress larval numbers.
- Selective insecticides (e.g., pyrethroids or neonicotinoids) applied at the seedling stage target adults before extensive damage occurs; resistance management requires rotating active ingredients.
Monitoring involves visual inspection for characteristic leaf pits and the use of yellow sticky traps to capture adult beetles. Thresholds for intervention typically range from 5 beetles per plant to 10 % leaf area showing stippling, depending on crop value and growth stage.