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

2. 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

3. 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

4. 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

5. Control of Storage Diseases
Alternate options
Purogene
Oxidate
Ozone

6. 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

8. 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

9. 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

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

11. Control of Storage Diseases
Effect of Purogene on the amount of rot found on tubers (MANITOBA)
Cultivar Concentration Avg Rot per Tuber (%)
Russet B
Shepody
Shepody

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

13. 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

14. 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

15. 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

16. 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

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

18. 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

19. 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

20. Control of Storage Diseases
Oxidate - Efficacy

21. Control of Storage Diseases
Oxidate - Efficacy

22. Control of Storage Diseases
Oxidate - Efficacy

23. Control of Storage Diseases
Oxidate - Efficacy

24. 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

25. 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 = $ /tonne
1% in humidification system = $1.78 per injection
How many injections into system over 5 month period?

26. 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 ??

27. 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

28. 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

29. Control of Storage Diseases
Generator unit, outside storage

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

31. 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)

32. Control of Storage Diseases
Ozone – Efficacy

33. Control of Storage Diseases
Ozone – Efficacy

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

35. 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

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

37. 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 ?

38. 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

39. 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