Field & Storage Management to Minimize Storage Rot Losses

Transcription

1 Field & Storage Management to Minimize Storage Rot Losses Neil C Gudmestad University Distinguished Professor Department of Plant Pathology North Dakota State University

2 Potato Storage Rots Wet Rots Leak Pink Rot Late Blight Tuber Rot Bacterial Soft Rot Erwinia/Pectobacterium Clostridium Bacterial Ring Rot Abiotic (Field Frost) Dry Rots Fusarium Dry Rot Early Blight Tuber Rot Black Pit (A. alternata)

3 Important Potato Storage Rots Dry Rot- usually occurs after dry seasons and poor digging conditions, PNW developed russets very susceptible Late Blight Tuber Rot- can follow LB foliar infection Pink Rot- probably most important water rot Leak- difficult to control, can lead to secondary rot Bacterial Soft Rot- most frequently a secondary disease following other wet rots

4 Pink Rot Caused by Phytophthora erythroseptica Infection through stolons, eyes, and wounds made at harvest High soil moisture favors infection Some cultivar resistance but chemical control important: mefenoxam or phosphonates

5 Courtesy J. Miller, Miller Research

6 Courtesy J. Miller, Miller Research

7 Disease control (%) Pink Rot Mefenoxam provides excellent control of sensitive P. erythroseptica Resistance in Pe prevalent in ID, MN, ME; present in ND, MI, WI Mefenoxam applied (g a.i. / ha) In-furrow at planting In-furrow at planting + sidedress One foliar application Two foliar applications Taylor et al., Plant Dis. 88:

8 Primarily caused by Pythium ultimum Soil borne fungus Infections primarily through wounds made at harvest Tuber pulp temps >65F favor infection Release of excess moisture can cause severe 2º infection Leak

9 Disease Control (%) Leak Mefenoxam provides moderate control but only with IF application Resistance to mefenoxam in P. ultimum reported in WA Phosphorous acid does not control leak In-furrow at planting In-furrow at planting + sidedress One foliar application Two foliar applications Taylor et al., Plant Dis. 88:

10 Infection incidence (%) Post Harvest Pink Rot Challenge Inoculations Mefenoxam Resistant P. erythroseptica Isolate 29 Days after harvest 64 Days after harvest Days after harvest 91 Days after harvest 120 Days after harvest 20 0 Non-treated Ridomil 4EC (6.1oz IF) Ridomil 4EC (12.2 oz IF) Phostrol (1 appl) Phostrol (2 appl) Phostrol (3 appl) Phostrol (post harvest)

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14 Effect of Pink Eye on Pink Rot Development a b % b 10 c 5 0 No Pinkeye Ridomil Applied No Pinkeye NO Ridomil No pinkeye visible in tubers chosen - Ridomil Applied Taylor and Gudmestad, 2006 Treatment Pinkeye visible in tubers chosen - Ridomil Applied

15 Variety Resistance to Storage Rots

16 Incidence (%) Comparison of potato cultivars for resistance to Phytophthora erythroseptica based on paired values of incidence of infection (resistance to infection) and severity of rot penetration (resistance to colonization). 100 Red Cultivars Russet Cultivars White Cultivars Snowden Shepody-NL FL Russet Norkotah Viking Red LaSoda Kennebec Itasca La Rouge FL-1867 Goldrush FL-1879 Shepody FL-1625 Yukon Gold Dark Red Norland Russet Burbank- FL-1533 Red Pontiac FL-1831 NLLR Superior NorDonna Russet Burbank-NL Norland NorValley Pike LaChipper Russet Burbak Norchip FL-1833 Ranger Russet Liberty Russet 30 Atlantic Salas et al., NDSU Severity (mm)

17 Incidence (%) Penetration (mm/day) Reaction of Cultivars and NDSU Breeding Selections to Pink Rot Tuber Rot Moderately Susceptible Highly Susceptible 80 Ebt6-2-3 Russet Norkotah Russet Norkotah Ebt Snowden Silver ton Ebt Bannock 50 Ebt Altura P2-4 Ebt Moderately Resistant ND Russet Burbank Shepody Ebt6-5-2 Red Norland Ebt Premier AOND Russ ND ND Atlantic Ebt6-5-5 J103-K Highly Resistant J101-K6 Ranger Russet R ND028801CB-2 ND Umatilla AOND Russ 0 J138-A12 ND6961B-21PY

18 Incidence (%) Comparison of potato cultivars for resistance to Pythium ultimum based on paired values of incidence of infection (resistance to infection) and severity of rot penetration (resistance to colonization) Liberty Russet LaChipper Pike Superior Norland Itasca Yukon Gold Viking Shepody FL Russet Burbank- Shepody - NL Dark Red Red Pontiac NLLR La Rouge Ranger Russet Norland Red LaSoda Goldrush NorChip FL Russet Burbank - NL Atlantic FL Russet Norkotah NorDonna NorValley FL Russet Burbank FL FL Kennebec FL FL Snowden Red Cultivars Russet Cultivars White Cultivars Severity (mm) Salas et al., NDSU

19 Incidence (%) Comparison of NDSU breeding selections for resistance to Pythium ultimum J101K6A22 Etb ND 8266A-2R ND 7386Ab-20 ND 7443Ab-181 ND 6956b-13 ND 7443Ab-44 Russet Norkotah ND 5822C-7 Atlantic ND Y Red Norland ND 8266A-1R Moderately Susceptible Highly Susceptible Snowden Highly Resistant Etb Penetration (mm) Moderately Resistant

20 Impact of Water Management on Storage Rot Development

21 How Does Soil Moisture Affect PR/L? Pink rot and leak pathogens are primitive funguslike organisms These organisms are highly dependent on high soil moisture for survival Pe and Pu produce zoospores with flagella Pu is also a saprophyte living off dead residue, its population increases over the growing season under high soil moisture conditions High soil moisture conditions at end of season promote disease development

22 High Soil Moisture Defined High soil moisture conditions that promote soil borne disease development are those where soils are >90% of field capacity A combination of either rain and/or irrigation can provide the suitable environment for infection and disease development High rainfall amounts (>2 generally) early in the growing season and significant rainfall (>1 ) after an irrigation are all scenarios that contribute to the development of disease

23 How Does Soil Moisture Affect Pink Eye? There is no pathogenic cause of pink eye Current evidence suggests that pink eye is the result of localized hypoxia (E. Lulai) Under field conditions pink eye development is associated with high soil moisture conditions and warm soils (>80F) Areas of early senescence are susceptible When dying plants cannot remove moisture from soil, soil saturation occurs, and sun heats soil = pink eye!

24 Impact of Bruises, Wounds & Tuber Pulp Temperatures at Harvest

25 Effect of Temperature on Post-Harvest Rot Pink Rot (wounded tubers) Pink Rot (non-wounded tubers) 60 % Salas, et al., 2000 Temperature (F)

26 Incidence (%) 100 Effect of Wounding and Inoculum on Pink Rot Incidence Not Inoculated Low High a 80 a b b 20 0 a a a c Not wounded Skinned Cut Wound severity alas, et al., Plant Dis. 84: c

27 Infection (%) Effect of Wounding on Disease Incidence of Non-Treated Tubers 100 a b Wound Eye c Pink Rot Leak d Taylor et al., Plant Dis. 88:

28 % Disease Incidence Effect of Methods of Applicaton of Mefenoxam on Incidence of Pink Rot on Non-Wounded and Wounded Tubers Non-Wounded Wounded Nontreated At Planting Planting + Sidedress Nickel Tubers Nickel + 14 Days

29 Potato Tuber Anatomy Vascular Ring µg/ml Metalaxyl Medullary Tissue Metalaxyl concentration = µg/ml Cortex Periderm Bruin et al., 1982

30 Summary/Conclusions Although there are multiple storage diseases, wet rots tend to be the most destructive Soft rot bacteria are generally secondary pathogens that contribute significantly to storage losses Pink rot and LB tuber rot can be easily managed with phosphonate applications and/or varietal resistance Determining the susceptibility of potato varieties is an important decision aid and management tool

31 Summary/Conclusions Cultural practices also important in management of pink rot and leak Avoid wet soil conditions (>80% FC) in August/September Do not exceed 65F (18C) tuber pulp temperatures at harvest High bruise-free scores will also minimize infections that occur in storage/postharvest