Hygiene measures can greatly reduce the risk of resting spores contaminating soil, from where they can infect subsequent plantings of Aquilegia. Affected plants should be disposed of as soon as possible. Do not compost them. Ideally burn them or bury them deeper than 50cm (20in). Although the spores should not survive the commercial composting used for council green waste collections, it is best to deal with contaminated material within the garden.
Because of the risk of soil contamination, rest affected areas from Aquilegia for at least a year (some species of Peronospora affecting other plants produce resting spores that can survive for several years but this information is unclear for Aquilegia downy mildew).
Where infected plants have been grown in containers, replace the compost (bury contaminated compost, ideally in a vegetable plot) and wash using a garden disinfectant, as directed by the manufacturer, to cleanse the container if you intend to grow Aquilegia in it again the following year.
It is not yet known if Aquilegia downy mildew can be seed-borne. The full host range of the disease is not yet known, but downy mildews usually only affect a limited range of plant species.
Seek assurances from suppliers that plants offered are disease-free. Growing from seed is a lower risk source of plants than buying plants from sources that are unable to offer suitable assurances.
No resistant cultivars (varieties) of Aquilegia are currently available. It is known that the disease can also affect the related plant Semiaquilegia, although it has not yet been found on this plant in the UK. However, where the disease has been found on Semiaquilegia (for example, in Asia), plants affected by the disease were visually almost indistinguishable from healthy plants, so perhaps they could be considered for use in areas affected by the disease, where it may prove difficult to grow Aquilegia successfully.
Do not use excessive amounts of nitrogen rich fertiliser, which can lead to soft susceptible growth. Avoid crowded plantings where air movement is limited.
There are no fungicides available to gardeners for the control of this disease.