Life cycle and identification of pygmy beetle in sugar beet
The pygmy beetle, or pygmy mangold beetle, causes damage to sugar beet seedlings, which can lead to seedling collapse, especially in close rotations. Beetle bites can also lead to further damage from parasitic fungi.
Risk factors in sugar beet
- Seedlings are most sensitive to damage from adults in fields in which beet is grown in close rotation, or where crops are infested early from adjacent fields with beet the previous year
- Beetle bites on the root and hypocotyl may allow invasion by parasitic fungi
Pygmy beetle identification
Scientific name: Atomaria linearis
Adults are small, elongate beetles of 2 mm in length.
Bites on the root and hypocotyl cause small black pits. Cotyledons and leaves may also be eaten, leaving irregular-shaped holes. Severe damage can destroy the vascular tissue, causing the seedling to collapse.
Beetle life cycle
Adults overwinter in the soil and survive on beet crowns left after harvest.
- Spring: Adults move to the soil surface and fly on warm, still days (from May onwards) to colonise new beet fields
- Dry weather: Beetles move deep into the soil
- Humid weather: Beetles move to the soil surface and feed on the hypocotyl and leaves
Eggs are laid in late spring and summer.
Larvae feed on roots of well-grown plants, causing little damage.
Non-chemical and chemical control
Rotation is usually the most effective control. Damage after the six true leaf stage is rarely of economic significance.