A new plant scourge is spreading across the country from Wales to Eastern England and has been reportedly found on the Hertfordshire/Essex border. Aquilegia Downy Mildew is a disfiguring, ultimately fatal fungal disease for which home gardeners have no known effective chemical control. The most prudent course of action is to familiarise yourself with the visible symptoms and destroy any plants as soon as those symptoms appear. The disease spreads via sporangia which shed spores onto nearby plants, so if diseased plants are ignored then others are rapidly infected. Aquilegia Downy Mildew is not caught from downy mildew on other species of plants; the DNA is unique.
Symptoms include lighter, yellowy patches on the leaves; straight-edged shapes which are delineated by leaf veins, distinctly unlike those of intentionally variegated leaves. Growth is weak, leaves brown off and stems may become distorted. Flower buds are likely to be ‘blasted’. There can also be secondary damage due to grazing slugs & snails, drawn in by the nutritious fungal material. The toxins in Aquilegias normally repel gastropods so this is something to look out for.
As Aquilegias are present in so many British gardens, there is a real danger that this disease may become endemic. For further information, visit the website at Touchwood Plants Nursery where National Collection holder Carrie Thomas has been liaising with the RHS to monitor the disease and raise awareness: http://www.touchwoodplants.co.uk
Images taken from an article on the national HPS site on the same topic, click to view.