Nematodes in Vegetable Crops• Combining chemical, cultural and biological control, can achieve...
Transcript of Nematodes in Vegetable Crops• Combining chemical, cultural and biological control, can achieve...
Nematodes in Vegetable Crops
Inga Zasada - USDA-ARS Research Plant Pathologist and NematologistHannah Rivedal - OSU HAREC Plant Disease Diagnostician
What you should take away from our presentation...
• Biology of important nematodes in PNW vegetable production• Occurrence of nematodes in specific vegetable crops• Management of nematodes in vegetable crops• Sampling recommendations for laboratory submissions
Introducing Nematodes• Most abundant multi-cellular animals on the planet• Unsegmented aquatic roundworms• Occur in many environments: soil, freshwater, marine, animals
Plant-parasitic Nematodes
10%
Animal Nematodes
15%
Free-living Nematodes
25%
Marine Nematodes
50%
This is what you see…
But how do you interpret this information?
This is what we see…
How do nematodes feed on plants?
All plant-parasitic nematodes
have a protrusible spear
Stylet
Where do nematodes feed on plants?
Sedentaryendoparasite
Migratoryectoparasite
Migratoryendoparasite
Picture from Kathy Merrifield
Pictures from Nemaplex
Widely prevalent nematodes in the PNW
Also of interest in vegetables – Ditylenchus (stem and bulb nematode)
Data from 38,022 diagnostic soil samples from the PNW from 2012-2016
Root-knot Nematode
Vegetable hosts:Carrot, lettuce, onions,
parsnips, cabbage, cucumber, tomato, etc...
Species in the PNW:M. hapla
M. chitwoodiSedentary endoparasite
From MacTode
Pictures from ipcnet.org
Symptoms: Root galling and branching, reduced yield, wilting
Most damaging nematode in the
PNW
Picture from Kathy Merrifield
Symptoms:Lesions on roots, excessive rooting,
reduced yield, stunting
Root lesion Nematode
Most prevalent nematode in the PNW
Migratory endoparasite
Species in the PNW:P. penetransP. neglectus
P. thorneiPictures from Nemaplex
Stubby root Nematode
Stunt Nematode
Migratory endoparasite
Reported hosts in PNW:Onion, corn, potato, alfalfa, wheat,
mint, beet
Impact of this nematode on vegetables in the PNW is NOT KNOWN
Paratrichodorus allius is an important parasite in onion
Densities as low as 4 nematodes/250 cc soil
can cause damage (Ingham)
Picture from Nemaplex
Picture from MacTode
Picture from MacTode
Pin Nematode
Spiral Nematode
Migratory ectoparasite
Impact of this nematode on vegetables in the PNW NOT KNOWN
Even when present at high densities this nematode does not cause damage
Picture from Nemaplex
Picture from MacTode
Picture from MacTode
Stem and bulb nematode
Picture from Agriculture Canada
Migratory endoparasite
Two species found in the PNW:Ditylenchus dipsaci and D. destructor
Picture from MacTode
Reported hosts in PNW:Onion, garlic, strawberry, alfalfa
What nematodes are of concern in vegetables?
Veggie Crop Plant-parasitic NematodeOnion Stem and bulb, root lesion, stubby root, root-knotCarrot Root-knot, root lesion, stubby rootSweet corn Root lesionPea/bean Root-knotAsparagus Root lesionMelon Root-knot, root lesion, stubby rootPepper Root-knot, root lesionTomato Root-knot
Information from UC IPM Management Guidelines and PNW Disease Handbook
Little “threshold” information for PNWNematode Mean population densities in
PNW (per 250 cc soil)Root-knot 240Root lesion 256Stubby root 29Stunt 98Pin 462Spiral 171
Data from 38,022 diagnostic soil
samples from the PNW
Nematode Mean population densities in PNW (per 250 cc soil)
Root-knot 107Root lesion 393Stubby root 30Stunt 102Pin 250
Nematode Mean population densities in PNW (per 250 cc soil)
Root-knot 103Root lesion 86Stubby root 25Stunt 27Pin 288
Nematode Management
Challenges with Nematode Management
• Nematode Lifestyle• Mobility out of zone of activity• Broad host range• Diagnostic challenge• Longevity
• Fumigation Regulations/Registration• Methyl Bromide no longer available• Buffer zones• Registered products
• Costs• Financial• Time• Space
Host Resistance• What it is
• Host plants with genetics that kills or disrupts nematode lifecycle
• Why it works• Avoids infection altogether• Reduces nematode population in roots
• Variations• Grafting onto resistant rootstock
• Drawbacks• Not effective for migratory nematodes• Time consuming to ID genes
From MacTode
Crop Rotation
• What it is• Rotating a field out of a susceptible crop
for multiple growing cycles
• Why it works• Reduces pathogen population in the soil
• Drawbacks• Host range of the nematode matters!• Rotation crops may not be economically
viable
Susceptible Crop
Trap Crop
Nonhost Crop
Resistant Host
Fallow
Green Manure
Biofumigation
• What it is• Growing a Brassica crop that is chopped and
incorporated into the soil
• Why it works• Isothiocyanate - natural volatile compound
produced by chopping Brassica crops
• Drawbacks• Variable concentration of isothiocyanate• Variable tolerance of nematodes• Timing
Courtesy: P.P. Reddy
Courtesy: Cavendish Farms
Soil Solarization
• What it is• Passive heating of soil covered with plastic mulch
• Why it works• Increases soil temperature to kill juveniles and
eggs• Best in shallow soils/shallow distribution of
nematodes
• Drawbacks• Requires the heat of summer to be effective • Takes field out of production• Expensive
Courtesy: University of California
Courtesy: HGTV.com
Integration of Management Strategies
• Combining chemical, cultural and biological control, can achieve reduction in nematode damage and may help control other pathogens or improve soil fertility
• Requires an understanding of:• Nematode Biology• Control Mode-of-Action• Cost• Nematode Populations
Sampling for Nematodes
• Considerations• Goal of sampling
• Current population in soil• Identification of disease
problem• Leadtime
• Able to implement control measures
Courtesy: MacTode
Sampling for Nematodes – Population Assessment
• Timing • After harvest or before planting, with enough lead
time to implement management• Adequately moist soil
• What to bring• Random sample of soil from field of interest
• Nematodes not evenly distributed - plan to sample whole fields
• Break large fields into manageable sections• Collect 15-20 soil cores/shovels per section/field
• 6-12” cores, collect samples from previous rows• Mix thoroughly and submit at least 1 pint• Keep cool on way to submission
Courtesy: MacTode
Courtesy: Spectrum Analytic
Sampling for Nematodes - Diagnostics
• Timing• In growing season, symptoms present
• What to bring• Soil and affected roots/plant material
• Samples from around/within affected area and healthy area
• 6-12” cores - depending on roots of crop• Photos of pattern in field
• What a diagnostic clinic will want to know
• Symptoms• Pattern/Distribution• Cultivar• Field Inputs
Courtesy: MacTode
Nematology Labs in PNW
• University Labs• OSU Nematode Testing - bpp.oregonstate.edu/bpp/nematode-testing-service• U of I Nematode Testing – Parma Research and Extension Center, Parma, ID
• Private Labs• Northwest Agricultural Consultants – nwag.com/lab-services• Agnema - sites.google.com/view/agnema/home• Western Laboratories, Inc. - westernlaboratories.com/• A&L Labs – http://www.al-labs-west.com/
• Diagnostic Clinics• OSU HAREC Plant Clinic - blogs.oregonstate.edu/harecppath/services/• WSU Pullman Plant Clinic - plantpath.wsu.edu/diagnostics/
Takeaways
• A diversity of nematodes are present in the PNW
• Threshold data is not yet robust for PNW Vegetable Crops
• Management of nematodes is complicated and requires information and integrated techniques