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Survivability of didymo and development of the “Check Clean Dry” method

Survivability of didymo and development of the “Check Clean Dry” method. Survivability of didymo and development of the “Check Clean Dry” method. Cathy Kilroy Amy Lagerstedt Karen Robinson. Topics. Review of results of survival studies Trials on felt-soled waders

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Survivability of didymo and development of the “Check Clean Dry” method

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

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

  3. 1a. Decon. study 2005 Initial findings 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

  4. 5 °C 12 °C Proportion of cells viable 20 °C 28 °C Days since start of trial medium light, colonies kept immersed 1b. Survival study 2006 Laboratory trials

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

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

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

  8. 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

  9. 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 …

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

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

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

  13. 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

  14. 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.

  15. 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)

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