Diagnosing weevils in lupins and field peas
Weevils are beetles with long snouts that can rarely damage lupins in high rainfall areas. Species include:
Vegetable weevil is more common in high rainfall areas, often next to trees or bush.
Desiantha (also known as Spotted vegetable weevil) is widespread.
Small lucerne weevil and Fullers rose weevil mainly occur on the south coast.
What to look for
- Areas of chewed and lopped lupin seedlings.
- Damage from vegetable weevil is usually worst next to paddock edges and bush areas, or parts of the paddock that had capeweed in the previous year.
- Chewed cotyledons, leaves, petioles and hypocotyl.
- The hypocotyl may be severed causing rapid death.
- Weevils are generally grey and often hard to find.
- Vegetable weevil is about 10 mm long with two short white stripes at an angle on each side of its abdomen.
- Desiantha weevil is about 5 mm long, dark coloured and sometimes has grey flecks on its back.
- Small lucerne weevil is about 5 mm long, light grey in colour with a white stripe on each side.
- Fuller’s rose weevil is about 8-10 mm long but has yellow stripes on its side and back.
What else could it be
Vegetable beetles, cutworms, brown pasture loopers, pasture day moth, European earwigs, snails and slugs
|Can cause similar seedling damage||Pests have a different appearance|
Where did it come from?
- With the exception of vegetable weevil, the weevils are flightless and remain in the paddock during their life cycle. Adults eat broadleaf crops and a range of broadleaf weeds, particularly capeweed. Adults emerge from the soil in spring to early summer and survive by hiding in soil litter, under stones, plants or clods. Eggs are laid into the surface of the soil and hatch when there is sufficient moisture for plant germination. Desiantha larvae feed on grass, and cereal seedlings.
- Vegetable weevils rarely fly but adults rest in the soil in bush or paddock edges during summer. They are attracted to any paddock that has capeweed present, and after capeweed germination move into the paddock to feed and lay eggs. The eggs hatch into green larvae in early winter that feed on the plants on which they hatched. The adult weevils also move into the edges of paddocks soon after crop emergence to feed.
- An insecticide border spray at crop emergence will help to control vegetable weevil before it moves into the crop. Paddock boundaries should be checked every few days until the crop has four to five true leaves.
- Desiantha, small lucerne and Fuller’s rose weevil are not controlled by border sprays as they tend not to migrate out of paddocks.
- Paddocks that had desiantha weevil larvae damage cereals in the year before will have desiantha weevil adults present in the current year
- Weevil numbers in crop can be reduced by controlling plant hosts eg capeweed before the canola is sown.
- Spray 'green break' summer weeds.
How can it be monitored?
- Check paddock boundaries every few days for vegetable weevil incursion until the crop has four to five true leaves.