Pea and bean weevils

Adult pea and bean weevils can cause distinctive notch-like damage to the leaf margins of young pea and broad bean plants in spring. This can be alarming but in most cases does not affect the growth of the crop.

Pea and bean weevil adult damage on broad beans

Quick facts

Common name Pea and bean weevil
Scientific name Sitona lineatus
Plants affected Broad bean and garden pea
Main cause Adult beetles eating the leaf margins
Timing April- July
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What is pea and bean weevil?

Pea and bean weevils are beetles that eat the leaf margins and shoot tips of garden peas and broad bean, causing characteristic notch-like damage.

Symptoms

The adult beetles are greyish brown and are 4-5mm long. They tend to drop to the ground when disturbed, so can be difficult to find. Their feeding activities are readily detected as the beetles eat a series of U-shaped notches around the edges of the leaves. The larvae feed unseen underground on the plants' root nodules.

The amount of leaf area lost to pea and bean weevils is generally small, even when the foliage has been extensively nibbled. Established pea and broad bean plants can generally tolerate this damage, but there may be a check in growth if small seedlings are heavily infested.

Control

Control is usually unnecessary as plants can generally tolerate damage from these insects.

Non-chemical control

Cold dry spells in spring check plant growth more than weevil activity. Covering with fleece or cloches can help plants outgrow damage. Keeping seedlings watered so they grow quickly through the more vulnerable stages. Older plants generally tolerate the leaf damage and so the weevils do not need control.

Chemical control

  • If it is necessary to use an insecticide, the seedlings can be sprayed insecticide
  • Manufactures instructions must be followed regarding maximum number of applications, spray interval and harvest interval for food plants
  • The contact pesticide pyrethrum (considered organic e.g. Bug Clear Gun for Fruit & Veg, Defenders Veg Bug Killer, ecofective Bug Killer (also contains fatty acids)) may have some effect but may need repeated applications due to its short persistence
  • The contact synthetic pyrethroids deltamethrin (e.g. Provado Ultimate Fruit & Vegetable Bug Killer) or lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) can also be used
  • Plants in flower should not be sprayed due to the danger to pollinating insects
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

Pea and bean weevil overwinters as adult beetles that hide away in leaf litter and other sheltered places. Eggs are laid during late spring in the surface layers of the soil near suitable host plants, such as broad bean and garden peas. The larvae are creamy white legless grubs with pale brown heads. They feed on the nitrogen-fixing nodules on their host plants' roots but do not usually affect the plants growth in garden and allotments. When fully fed the larvae pupate in the soil, with adult beetles emerging in late summer. There is only one generation per year.

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