Research
Hemerocallis gall midge
Biology
Observations have been made on the biology of the hemerocallis gall midge, Contarinia quinquenotata. This tiny fly lays its eggs in the developing flower buds of day lilies (Hemerocallis species and cultivars). Small white maggots develop inside the buds, causing them to be abnormally swollen but failing to open (left and centre in picture). An infested bud can contain several hundred larvae, which may be the progeny of more than one midge. When fully fed, the larvae are 2-3mm long and they drop down into the soil where they overwinter as pupae.
There is one generation a year, with damage to the flower buds occurring between mid-May to early July. Cultivars that flower after that period escape damage. Using the extensive Hemerocallis collection at RHS Garden Wisley, a list has been compiled of late-flowering cultivars that partly or wholly miss the egg-laying period of the gall midge. A selection of these cultivars, which have also received the Award of Garden Merit, include the following. The full list is available to RHS members by sending an SAE to the Members’ Advisory Service, RHS Garden Wisley, Woking, Surrey GU23 6QB.
- Red flowers: 'Chief Sarcoxie', 'Missenden’, ‘Red Precious’
- Orange flowers: 'Burning Daylight', 'Tetrina's Daughter' and the species Hemerocallis lilioasphodelus
- Yellow flowers: 'Cartwheels’, ‘Corky’, ‘Green Flutter’, 'Lemon Bells', 'Marion Vaughn', 'Nova’, 'Whichford'
- Pink flowers: ‘Neyron Rose’, 'Pink Damask', 'Stoke Poges'
Distribution
The gall midge occurs commonly in Europe but was not found in Britain until 1989, when samples of galled flower buds were brought from a private garden at Weybridge, Surrey, to the RHS Members’ Advisory Service at Wisley Garden. Since then the spread of this pest has been tracked through enquiries made to the RHS advisory service and other sources. It is now widely distributed in England, particularly in southeast England and East Anglia. For a map click here