disease control products for stored potatoes jill thomson and doug waterer dept of plant sciences,...

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


• 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


• 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


• Alternate options– Purogene– Oxidate– Ozone


• 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


• 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


• 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


• Purogene Efficacy against Soft rot– MB data– some control

020406080

100

% Soft Rot

0 50 100 400

PPM Purogene

Soft Rot Control with Purogene

Russets Shepody 1 Shepody 2


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


• Purogene vs Late Blight– MB data– Tubers treated immediately after inoculation – some control

020406080

100

Trial 1 Trial 2 Trial 3 Trial 4

Control Purogene


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


• 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


• 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


• 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


• Oxidate– BioSafe– Hydrogen Peroxide + acetic acid – applied as spray to potatoes going

into storage and/or– added to ventilation air


• 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


• 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


• Oxidate - Efficacy



0

5

10

15

20

25

Ave

rage

% d

ry

rot

0 1% 2%

Oxidate treatment

FDR development after Oxidate treatment for 16 weeks

ShepodyNorland



0

20

40

60

80

100

Inci

den

ce s

ilver

sc

urf

(av.

%)

0 1% 2%

Oxidate treatment

Silver scurf development after Oxidate treatment for 16 weeks

ShepodyNorland



0

1

2

3

4

5

Sof

t ro

t (

%)

0 1% 2%

Oxidate treatment

Soft rot development after Oxidate treatment for 16 weeks

ShepodyNorland


• 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


• 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?


• 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 ??


• Ozone – various manufacturers– O2 + high energy = O3 (gas) – applied at high levels to potatoes

going into storage and/or– added to ventilation air


• Ozone – works by oxidation reactions– lab studies indicates effective against range of

bacteria and fungi– inactivated by soil– no residual activity – continuous treatment recommended


• Generator unit, outside storage


• Monitoring equipment mounted above conveyor. Injection of O3 into conveyor system, removal of excess O3.


• 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)


• Ozone – Efficacy

01020304050607080

% I

ncid

ence

1 day 1 wk 3 wks

Exposure time

FDR on surface-inoculated tubers

OZONEControl


• Ozone – Efficacy

05

1015202530

% I

ncid

ence

1 day 1 wk 3 wks

Exposure time

Silver scurf after ozone treatment

OzoneControl


• Ozone – Efficacy– O3 applied loading into storage

0

5

10

15

20

Ext

ent

of F

DR

d

amag

e (s

q.c

m)FDR development in wounded,

inoculated tubers

NorlandYukon Gold


• 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


• Ozone - Economics– generators + power

– 500 ppm during loading

– 2 ppm during storage ventilation

– $ ?


• 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 ?


• 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


• 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

disease control products for stored potatoes jill thomson and doug waterer dept of plant sciences,...

Documents

storage andor

storage humidifaction

affordable slide

ozone slide

aluminum slide

seed slide

disease control products

ventilation air slide