Disease Control Products for Stored Potatoes Jill Thomson and Doug Waterer Dept of Plant Sciences, University of Saskatchewan

Control of Storage Diseases Challenge - need dependable control of various diseases during storage/handling Challenge - need safe, affordable products Challenge - products must be readily applied with available equipment

Control of Storage Diseases Traditional options Mertec (TBZ) spray applied during load-in good coverage critical not effective against bacteria not effective against Late Blight extensive resistance in Dry Rot and Silver scurf $ 6.40/tonne at CDN label rate

Control of Storage Diseases Available options Dithane (Mancozeb) spray applied during load-in good coverage critical not effective against bacteria effective against Dry Rot and Silver scurf $ 11.06/tonne only registered for use on seed

Control of Storage Diseases Alternate options Purogene Oxidate Ozone

Control of Storage Diseases Purogene (Anthium) UAP Sodium chlorite + acid = Chlorine dioxide (gas) + other Cl species applied as spray to potatoes going into storage and/or added to ventilation air

Control of Storage Diseases Purogene works by oxidation reactions label indicates effective against L. blight, Silver Scurf, Dry Rot and Bacterial Soft rot inactivated by soil no residual activity repeated or continuous treatment recommended

Control of Storage Diseases Purogene - Status Researched by MSU, NDSU, Idaho, MB and AB. 5th year of Class 18 Exemption in U.S. Emergency use in Canada in 1999, 2000 and 2001 but not in 2002

Control of Storage Diseases Purogene Efficacy against Soft rot MB data some control

Control of Storage Diseases Effect of Purogene on the amount of rot found on tubers (MANITOBA) Cultivar Concentration Avg Rot per Tuber (%) Russet B. 0 23.5 50 3.8 200 1.1 400 2.2 Shepody 0 9.1 50 5.8 400 3.2 Shepody 0 1.1 50 2.4 200 0.2 400 0.3

Control of Storage Diseases Purogene vs Late Blight MB data Tubers treated immediately after inoculation some control

Control of Storage Diseases Purogene vs Rhizoctonia, Silver Scurf, Soft Rot and Dry Rot AB data Tubers sprayed at load in Tubers treated in storage (weekly) minimal control

Control of Storage Diseases Purogene - Safety mixing step requires safety equipment (ClO2 vapors) ventilate storage for 2 h prior to re-entry potatoes must be washed prior to consumption slowly corrodes copper, brass, aluminum

Control of Storage Diseases Purogene - Economics 16-32 ml/ton applied at load-in max rate of 16 ml/ton/month applied during storage humidifaction $25/L $ 2.50/ton for pre-treatment + continuous application over 5 months

Control of Storage Diseases Purogene Conclusions variable results problems getting full activation problems with inactivation by soil problems with uniformity of distribution of effective dosages problems with adding humidity to problem storages relatively safe and affordable

Control of Storage Diseases Oxidate BioSafe Hydrogen Peroxide + acetic acid applied as spray to potatoes going into storage and/or added to ventilation air

Control of Storage Diseases Oxidate works by oxidation reactions label indicates effective against L. blight, Silver Scurf, Dry Rot and Bacterial Soft rot inactivated by soil no residual activity continuous treatment recommended

Control of Storage Diseases Oxidate - Status approved in U.S. for use in wide range crops in field and storage approved as an “organic” pesticide “Emergency Use” in BC and AB in 2002 full registration anticipated for April 2003 NB has done some testing in potatoes

Control of Storage Diseases Oxidate - Efficacy

Control of Storage Diseases Oxidate - Efficacy

Control of Storage Diseases Oxidate - Efficacy

Control of Storage Diseases Oxidate - Efficacy

Control of Storage Diseases Oxidate - Safety no mixing step concentrated product is corrosive no re-entry restriction no limit to amount applied no requirement to wash prior to consumption slowly corrodes copper, brass, aluminum

Control of Storage Diseases Oxidate - Economics 1-2% solution applied to wetness at load-in 1:100 to 1:300 applied during storage humidifaction $17.78/L pre-treatment = $ 0.71-1.42/tonne 1% in humidification system = $1.78 per injection How many injections into system over 5 month period?

Control of Storage Diseases Oxidate – Conclusions potential to reduce disease levels high dosages and continuous application most effective safe and affordable need uniform delivery of effective dosages adding humidity to problem potatoes ? Impact on sprouting ??

Control of Storage Diseases Ozone various manufacturers O2 + high energy = O3 (gas) applied at high levels to potatoes going into storage and/or added to ventilation air

Control of Storage Diseases Ozone works by oxidation reactions lab studies indicates effective against range of bacteria and fungi inactivated by soil no residual activity continuous treatment recommended

Control of Storage Diseases Generator unit, outside storage

Control of Storage Diseases Monitoring equipment mounted above conveyor. Injection of O3 into conveyor system, removal of excess O3.

Control of Storage Diseases Ozone - Status well established in other food areas data for storage use is limited advantage = does not depend on water for delivery (spray or humidity)

Control of Storage Diseases Ozone – Efficacy

Control of Storage Diseases Ozone – Efficacy

Control of Storage Diseases Ozone – Efficacy O3 applied loading into storage

Control of Storage Diseases Ozone - Safety widely used to sanitize food and buildings corrosive at high concentrations exposure levels well established no limit to amount applied no requirement to wash prior to consumption

Control of Storage Diseases Ozone - Economics generators + power 500 ppm during loading 2 ppm during storage ventilation $ ?

Control of Storage Diseases Ozone - Conclusions primarily provides contact control most effective against surface problems (scurf and bacteria) ineffective against aggressive or well established infections economics ? Impact on product/facilities ?

Control of Storage Diseases Conclusions Purogene and Oxidate demonstrated to provide some control under certain conditions Ozone also shows potential Most effective against new, surface problems Supplement to good harvest and storage management practices

Control of Storage Diseases In the future ? No new chemical products in the pipeline BioCide is developing granular products for time-release uses Help overcome short reaction times of chlorine dioxide and improve in-storage distribution Further out … Bacterial antagonists to common diseases