RHS Cardiff show on the lookout for pests

The Royal Horticultural Society will be calling on Welsh gardeners to plot pests when they hold their annual show in the parklands of Cardiff Castle April 16-18 (www.rhs.org.uk/cardiff)

The RHS is currently conducting a nationwide survey to plot the spread of four of the UK’s most troublesome, non-native, invasive garden pests, and will be in Cardiff later this month to ask Welsh gardeners to get involved, as there is little information about the spread of these pests and their impact on the environment in Wales.

RHS Cardiff show
The RHS Show Cardiff is a co-production with Cardiff Council and features the best of the spring blooms from nurseries across the UK, with ideas and inspiration for the growing season ahead.

The RHS survey aims to record the distribution of four species of garden pests, and determine their rate of expansion across the UK, providing valuable research data for RHS scientists. The four pests under investigation are:

Lily beetle (Lilioceris lilii) – the third most troublesome pest in the UK in 2009.* Lily beetle adults and larvae defoliate lilies and fritillaries. It became established in Surrey in the late 1930s and until the 1980s remained confined to South East England. Over the past two decades the beetle has spread rapidly and is now found throughout much of England, with more scattered records in Wales, Ireland and Scotland.

Rosemary beetle (Chrysolina americana) – The Rosemary beetle was first reported outdoors in Surrey in 1994. It is now common in parts of England, with scattered reports from the rest of the UK and Ireland. The adults and their grey grubs defoliate rosemary, lavender and some other related plants.

Berberis sawfly (Arge berberidis) – The caterpillar-like larvae of Berberis sawfly defoliate some Berberis, especially Berberis thunbergii, and Mahonia species and hybrids. This insect was first reported from Essex in 2000, and has spread rapidly across much of England although it’s not yet known to be in Wales.

Hemerocallis gall midge (Contarinia quinquenotata) – Hemerocallis gall midge was first reported in Surrey in 1989. It has spread throughout England and into parts of Wales and Scotland. Larvae of the 2mm long midge develop within the flower buds, causing them to become abnormally squat and swollen.  Damaged flower buds dry up and fail to open.

Andrew Halstead, RHS Principal Entomologist, says: “Wales is an under-recorded area of Britain and the support of Welsh gardeners is vital for us to get a true understanding of the distribution of these pests.”

“Adult Berberis sawflies start emerging in late April and both adult rosemary beetles and lily beetles should be visible on sunny days throughout that month. Hemerocallis gall midge is a tiny fly that is likely to be missed by most people, but the abnormally swollen flower buds are easy to spot, although not until late May to early July.”

Gardeners can find out more about the survey and submit their records at www.rhs.org.uk/science/plant-pests.

In addition to RHS expertise on hand, the Cardiff event features show gardens created by the finest Welsh horticultural talent, the ever-popular schools wheelbarrow competition supported by Legal & General, and numerous plants and accessories for sale. There are nature trails, street entertainers and live music throughout the weekend. The beautiful parklands site also contains a Craft Village and a taste of Welsh produce in the Café Quarter.