John Scrace

John diagnoses the causes of member’s plant problems from their plant samples and online enquiries

What do you do?

My main area of work is diagnosing the causes of member’s plant problems – by examining photographs or plant samples by eye or under the microscope, backed up by scientific techniques such as humid incubation chambers, agar cultures, serological tests or DNA analysis.
I also carry out research into potential new diseases and lecture on plant health to students studying for the RHS Diploma in Horticultural Practice.

“Every day, when I start work, there’s the possibility of finding something new to the UK, or even to science. Unfortunately for gardeners, it’s usually a plant disease.”

Why is your team’s research important?

The health of plants – growing in our gardens and in nature – has probably never been under such a threat as now.
From the current problems with ash dieback, to the huge potential consequences should Xylella arrive in the UK, gardeners need to be aware of the threats. My job is to help them understand the risks and what they can do to combat them, not only in response to new threats but also existing common diseases that still have an impact on their individual gardens.


I am proud that I help RHS members with their gardening problems on a daily basis. It’s always satisfying receiving letters and emails thanking me for my help. It’s also great if I have played a small role when one of my students decides that they want to pursue a career in the plant sciences.


  • Newbery F, Scrace J, Beal L. (2021) Fungi on Rudbeckia in gardens. Field Mycology 22 (2) pp41–43
  • Vazquez-Iglesias I, Scrace J, McGreig S, Pufal H, Robinson R, Clover GRG, Adams IP, Boonham N, Fox A. (2020) First report of rose spring dwarf-associated virus in Rosa spp. In United Kingdom. New Disease Reports, 42, 13
  • Newbery F, Robinson RJ, Beal E, Scrace J. (2020) First record of Septoria rudbeckiae on Rudbeckia in the United Kingdom. New Disease Reports, 42, 2
  • Newbery F, Beal E, Scrace J. (2019) First record of Alternaria thunbergiae on Thunbergia alata in Europe. New Disease Reports, 39, 14
  • Beal E, Waghorn I, Scrace J, Henricot B. (2018) First report of Phytophthora tentaculata affecting Santolina in the UK. New Disease Reports, 37, 8
  • Robinson RJ, Könyves K, Scrace J. (2017) First record of the fungus Blumeriella kerriae in the UK. New Disease Reports, 35, 34
  • Beal E, Denton J, Denton GJ, Scrace J. (2016) First report of Verticillium dahliae causing wilt in Impatiens New Guinea Group hybrids. New Disease Reports, 33, 18
  • Scrace J, Denton J, Clover G. (2015) Potyviruses and tobraviruses infecting ornamental Allium species in the United Kingdom. New Disease Reports, 32, 13
  • Henricot B, Scrace J, Spooner B. (2013) First record of smut caused by Entyloma eschscholziae on California poppy in the United Kingdom. New Disease Reports, 28, 10

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.