She said because there was no published information about downy mildew of Aquilegia, she has compiled known information onto her website to warn gardeners and help them prevent, identify and cope with infections.
Thomas said: "What is needed is early discovery and measures to control spread once it is found. It is my hope that these informative pages will help early identification, and hence slow or minimise spread. This new disease, downy mildew of Aquilegia is a very virulent disease and it is killing plants.
"The Touchwood National Plant Collections of Aquilegia have been affected and may not last into the 2015 flowering season."
Nigel Stringer (volunteer at National Botanic Garden of Wales) and the RHS Members' Advisory Service identified the pathogen for her.
Thomas said: "I now see that I had some infected plants at least one year earlier, but had no reason to believe that a sickly-looking Aquilegia plant had a virulent infection of any sort, let alone one likely to lead to the death of the plant after efficiently infecting other plants around it, as well as creating the long term issue of resistant, infective spores in the soil."
"However a kindly blind eye was the worst thing I could have done with downy mildew. I do not know if my collections will survive. I do not know if I will ever be able to easily grow aquilegias in this soil again."
Thomas is urging gardeners to email her if they have any signs of the disease so that she can build an accurate picture on her website of where it is found in the UK and worldwide. It is also important to know what treatment methods have failed, which have seemed to work, and why. Immediate removal of any plant even suspected of having the disease, may be the only effective solution.
Visit her webpages to find out what signs to look out for: http://www.touchwoodplants.co.uk/aquilegia-downy-mildew.htm