Integrated Weed Control Integrated Weed Control Strategies in Organic FarmingStrategies in Organic Farming

Jim Shrefler, Jim Shrefler, OSU / WWARECOSU / WWARECCharles Webber, Charles Webber, USDA / ARSUSDA / ARS

Warren Roberts, Warren Roberts, OSU / WWARECOSU / WWARECMerritt Taylor, Merritt Taylor, OSU / WWARECOSU / WWAREC

““Lane Agricultural Center”Lane Agricultural Center”

Cooperators / CollaboratorsCooperators / Collaborators

OSU Scientists, SpecialistsOSU Scientists, SpecialistsUSDA ScientistsUSDA Scientists

GrowersGrowersNoble FoundationNoble Foundation

Kerr CenterKerr Center

While On The Soapbox …While On The Soapbox …

Why do we want to do this?Why do we want to do this?What are the problems with non-What are the problems with non-organic?organic?– Are we irrationally disregarding Are we irrationally disregarding

valuable technology?valuable technology?

Will organics be problem free?Will organics be problem free?Can exploration of organics lead to Can exploration of organics lead to conceptually new ideas?conceptually new ideas?What will the bottom-line be …..What will the bottom-line be …..– Should we consider multi-generation Should we consider multi-generation

sustainabilitysustainability??

Weed Control For OrganicsWeed Control For Organics- - Presentation Emphasis Presentation Emphasis - -

Yes - CropsYes - Crops– FruitsFruits– VegetablesVegetables– HerbsHerbs– Row CropsRow Crops

No - Other AreasNo - Other Areas– ForagesForages– TurfTurf– OrnamentalsOrnamentals

What is a Weed?What is a Weed?

““Plant whose virtues are yet Plant whose virtues are yet to be discovered”to be discovered”

““A plant out of place”A plant out of place”

Regardless, whether wild or Regardless, whether wild or cultivated, extraneous plants cultivated, extraneous plants in a crop can reduce yield, in a crop can reduce yield, quality and production costquality and production cost

General Management FactorsGeneral Management Factors

ExclusionExclusion

EliminationElimination

Prevent Prevent EstablishmentEstablishment

RemovalRemoval

AmeliorationAmelioration

General Management FactorsGeneral Management Factors- Exclusion -- Exclusion -

Field selectionField selection

Prevent new weedy Prevent new weedy species additionsspecies additions

General Management FactorsGeneral Management Factors- Elimination -- Elimination -

Prevent weed build-upPrevent weed build-upDestroy propagulesDestroy propagules– SolarizationSolarization– FumigationFumigation

Eradication – For Eradication – For minor infestations of minor infestations of certain weedscertain weeds

General Management FactorsGeneral Management Factors- Prevent Establishment -- Prevent Establishment -

HerbicidesHerbicides

CultivationCultivation

Cover cropsCover crops

GrazingGrazing

MulchesMulches– organic and syntheticorganic and synthetic

General Management FactorsGeneral Management Factors- Removal -- Removal -

MechanicalMechanical

ChemicalChemical

PhysicalPhysical– flameflame

– steamsteam

General Management FactorsGeneral Management Factors- Amelioration -- Amelioration -

Crop SelectionCrop Selection– crops that tolerate weedscrops that tolerate weeds

– crops that enable control crops that enable control of weedsof weeds

Give crop an edgeGive crop an edge– transplantstransplants

– planting dateplanting date

So, what can we do So, what can we do under the constraints of under the constraints of

organics?organics?

Weed Management for OrganicsWeed Management for Organics- Exclusion -- Exclusion -

Field selectionField selection– a good choicea good choice– knowledge needed of sitesknowledge needed of sites– usefulness depends on available usefulness depends on available

certified landcertified landPrevent weed additionsPrevent weed additions– critical for Organicscritical for Organics– “ “bring-ins” may contain weedsbring-ins” may contain weeds

Organic mulchesOrganic mulchesRaw manuresRaw manures

Weed Management for OrganicsWeed Management for Organics- Elimination -- Elimination -

Prevent weed build-upPrevent weed build-up– timely cultivation, tillagetimely cultivation, tillage– purposeful plantings – don’t let weeds purposeful plantings – don’t let weeds

take overtake over

Weed population reductionWeed population reduction– perennial management through perennial management through

grazinggrazing– fallow / tillage cyclesfallow / tillage cycles– solarizationsolarization– fumigants???fumigants???

Weed Management for OrganicsWeed Management for Organics- Prevent Establishment -- Prevent Establishment -

Preemergence “herbicides”Preemergence “herbicides”– corn gluten meal, mustard mealcorn gluten meal, mustard meal

Timely cultivationTimely cultivationStale seedbedsStale seedbedsCover crop managementCover crop management– Species important: e.g. ryeSpecies important: e.g. rye– Crop sequence (more detail later)Crop sequence (more detail later)

GrazingGrazingMulchesMulches– organic and syntheticorganic and synthetic

Weed Management for OrganicsWeed Management for Organics- Weed Removal –- Weed Removal –

“Stop ‘em in their tracks”“Stop ‘em in their tracks”

Mechanical – cultivationMechanical – cultivation– keep it shallowkeep it shallow

–minimize injury to the cropminimize injury to the crop

– Improve the root zoneImprove the root zone

Manual Manual – choose easy-to-use toolschoose easy-to-use tools

Weed Management for OrganicsWeed Management for Organics- Weed Removal (cont.)–- Weed Removal (cont.)–

“Stop ‘em in their tracks”“Stop ‘em in their tracks”

Chemical: Chemical: vinegar, pelargonate, etc.vinegar, pelargonate, etc.

– currently just contact activitycurrently just contact activity

– good foliage cover neededgood foliage cover needed

Physical: energy consumers!Physical: energy consumers!– flame flame

special equipment, directed flamespecial equipment, directed flame

best for small, annual weedsbest for small, annual weeds

– steam steam

Weed Management for OrganicsWeed Management for Organics- Amelioration -- Amelioration -

Crop SelectionCrop Selection– use crops that tolerate weedsuse crops that tolerate weeds

rapid growth, dense canopyrapid growth, dense canopy

– crops that allow weed controlcrops that allow weed control sweet corn – easily cultivatedsweet corn – easily cultivated

Give crop an edgeGive crop an edge– plant dateplant date– transplantstransplants

Specific Examples of TacticsSpecific Examples of Tactics

Cover crop managementCover crop management

Preemergence “herbicide”Preemergence “herbicide”

““Burn down” chemicalsBurn down” chemicals

Cover Crop ManagementCover Crop Management

Cereal Rye a classic exampleCereal Rye a classic example

Effective due toEffective due to– Biochemical constituentsBiochemical constituents– BiomassBiomass

Management involvesManagement involves– Coordination of rye growth with crop Coordination of rye growth with crop

plant date: plant date: – Rye destruction: rolling?, tillage?Rye destruction: rolling?, tillage?– Crop planting methodCrop planting method

Preemergence “Herbicides”Preemergence “Herbicides”BioherbicidesBioherbicides

Corn Gluten MealCorn Gluten Meal– Makeup: 9% nitrogen (fertilizer?)Makeup: 9% nitrogen (fertilizer?)– Available as powder, granule, pelletAvailable as powder, granule, pellet

Weed control propertiesWeed control properties– Certain peptides toxic to germinating Certain peptides toxic to germinating

seedsseeds– Works best under drying soil conditionsWorks best under drying soil conditions– Apply to surface or mix very shallowlyApply to surface or mix very shallowly

Burn-down ChemicalsBurn-down Chemicals

Pelargonic acid is a leading optionPelargonic acid is a leading option– Also called nonanoic acid & pelargonateAlso called nonanoic acid & pelargonate– Kills living plant tissue within hoursKills living plant tissue within hours– Contact action not systemic Contact action not systemic – Ammonium formulation for organic useAmmonium formulation for organic use

Control Control – Grasses: Small & before tillering is bestGrasses: Small & before tillering is best– Broadleafs: varies with speciesBroadleafs: varies with species– No crop selectivityNo crop selectivity