Join the RHS today and support our charitable work
Free personalised gardening advice
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Free entry to RHS members at selected times »
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Join the RHS today and support our charity
The western conifer seed bug, Leptoglossus occidentalis is a large brown bug native to North America which has become established in Britain since 2007. It feeds on pines but causes no noticeable damage to garden trees.
Western conifer seed bug
The western conifer seed bug Leptoglossus occidentalis, is a large reddish-brown squashbug that can reach 2cm (¾in) in length. There is a white zigzag line across the centre of its wings and it has leaf-like expansions on its hind legs. It feeds on the sap of pines, and some other conifers, especially the seed cones. The bug is native to North America and was first reported in Europe (Italy) in the late 1990s, it reached Britain in 2007 and is becoming widespread in England and Wales.
The adult insects can fly and they are attracted at night to bright lights. They also have a tendency to seek shelter in buildings as the weather turns cooler in the autumn.
Western conifer seed bug feeds on the sap of pines, Pinus and some other conifers, especially from the seed cones. It can affect the viability of seeds but it is unlikely to affect the health or growth of garden plants. The bug can affect seed production and so it may become a problem for nurseries and the natural regeneration of coniferous woodland.
Western conifer seed bug is unlikely to affect the health and vigour of garden trees and so control measures in the home garden are not necessary.
You can report sightings of this bug in Britain here.
Western conifer seed bug overwinters as adults in sheltered places such as under bark and in buildings.
In spring the adults emerge and females lay up to 80 eggs on the foliage of conifers. After two weeks the eggs hatch and the nymphs feed on needs and tender cones. There are five stages of development (nymphal instars) and they become adults in mid to late summer. Larger nymphs and adults feed almost exclusively on developing seeds and cones.
British bugs information on western conifer seed bug
British bugs reporting form for Western conifer seed bug
Conifers: brown patches
Green shield bugs
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.