Pea and bean weevil (Sitona lineatus)
These small (c. 5mm long) grey-brown devils nibble tell-tale U-shaped notches around young leaves. They overwinter as adults and come out eating in the spring. Eggs are laid in late spring and early summer - the larvae (white with brown heads; 5mm long) eat the roots, particularly the nitrogen-fixing nodules. When the adults emerge from the brown pupae, they will seek out other plants if there are no tender young seedlings to attack. They are only really serious in young plants unless there is a secondary infection.
- U-shaped notches around the edges of young leaves
Prevention & control
- Good crop rotation
- Prevent adults getting to the crop with insect mesh
- Earlier sowings are more susceptible so avoid them in areas where these weevils are a problem.
- Pick any weevils you can find off by hand - but they're hard to spot
- Keep plants growing strongly so they can cope with the attack
- In serious cases, derris root powder is effective