Survivability of didymo and development of the “Check Clean Dry” method Cathy Kilroy Amy Lagerstedt Karen Robinson

Topics 1.Review of results of survival studies 2.Trials on felt-soled waders 3.Current “Check Clean Dry” recommendations

Initial findings 1a. Decon. study 2005 Effective decontaminants included: 2% Household bleach 5% Detergents 5% Nappy cleaner Desiccation: complete mortality when moisture content less than ~83% First “Check Clean Dry” in October 05

Days since start of trial Proportion of cells viable 5 °C 12 °C 20 °C 28 °C medium light, colonies kept immersed Laboratory trials 1b. Survival study 2006

Survival study 2006 (cont.) Heat: 40 °C, no survival after 20 min pH: good survival in pH range of NZ freshwaters No survival in extreme pH (~1 or >11) Salinity:seawater, no survival after 4 h 50% s/w, low survival, 1-20 d 10% s/w, good survival Freezing:no survival if frozen solid

Multiple potential decontamination products tested: Results of 2005 decon. trials confirmed Commercial products more effective than single constituents Survival study 2006 (cont.)

2. Trials on felt-soled waders Laboratory trial comparing survival of didymo on: felt soles, gumboots, leather boot uppers, neoprene waders

Trials on felt-soled waders (cont.) All exposed to didymo Returned to lab. (5 hours) All items scrubbed, rinsed (cell retrieval 1) Rinse water checked for didymo cells All items left for 36 h at 5-17 °C Scrubbed, rinsed again (cell retrieval 2) Rinse water checked for didymo cells

Trials on felt-soled waders (cont.) Results 1. After cell retrieval 1, many live cells in all items except gumboots (a few live cells) 2. After cell retrieval 2 …

Trials on felt-soled waders (cont.) …after 36 hours “drying”

Trials on felt-soled waders (cont.) Container of dyed decon. solution Waterproof sticky tape Felt sole pieces, soaked Cut Undyed = untreated interior, even after 20 mins immersion Removed from dye after 1 and 20 min Do decon. products work?

Trials on felt-soled waders (cont.) Do decon. products work? Cut Dye penetrated only to about one third the distance of soaking What about spraying?

Trials on felt-soled waders (cont.) Effective decon. methods Heat (hot water) (e.g., must be held at 45 °C for at least 40 minutes) Freezing (must be frozen solid) Combine heat and decon. products

3. Updated “Check Clean Dry” Separate methods for non- absorbent and absorbent items Drying is effective, but items must be completely dry Combination of heat with drying and decon. products increases effectiveness.

Thanks Funding: MAF Biosecurity New Zealand Support, advice: Christina Vieglais, MAF Biosecurity Advice on products / chemicals: Scott Belanger, Procter and Gamble, USA; John Clayton, Chris Hickey, Max Gibbs, Stu Pickmere and George Payne (all of NIWA) Lab facilities: Donna Sutherland Field collections: Meredith Wilson, Amy’s mum, Karen’s father. Donation of felt-soled wading boots: The Fisherman’s Loft (Christchurch) Reviews: Christina Vieglais, Frances Velvin (MAF Biosecurity New Zealand), Max Bothwell (Environment Canada; didymo TAG), Scott Belanger, Sue Clearwater (NIWA)