Integrated Pest Management -- Weeds Basic Training for Agents University of Kentucky February 2006 J. D. Green and J. R. Martin Extension Weed Science.

Integrated Pest Management -- Weeds

• Basic Training for Agents• University of Kentucky

• February 2006

• J. D. Green and J. R. Martin• Extension Weed Science

• Plant and Soil Science

What is a WEED

• A plant growing where it is not wanted (a plant out of place). – Plants are considered weeds when they

interfere with the activities of man or his welfare.

• Plants which have adverse economic, health, and/or aesthetic consequences.

– Weeds often introduced species• Johnsongrass (Euroasia)• Kudzu (Japan)• Japanese Knotweed (Asia)

(#11)

Weed Classification• Annuals: (life cycle in one season)

– Warm Season• Foxtails, large crabgrass, broadleaf signalgrass• Cocklebur, Eastern black nightshade, giant ragweed,

ivyleaf morningglory, smooth pigweed, lambsquarters– Cool Season

• Italian ryegrass, little barley• Common chickweed, henbit, purple deadnettle

• Biennials: (life cycle up to 2 seasons)• Musk thistle (Nodding thistle)

• Perennials: (life cycle more than 2 seasons)• Johnsongrass, yellow nutsedge, honeyvine milkweed,

dandelion, wild garlic

(#11)

Reproduction Methods of Weeds

Perennials:• SIMPLE (no spreading propagules)

• Dandelions, Curly dock

• SPREADING (have vegetative propagules)– Root Buds; Creeping Rootstocks

• Honeyvine milkweed, Canada thistle– Rhizomes

• Johnsongrass– Bulbs

• Wild garlic, Yellow nutsedge– Tubers

• Yellow nutsedge

(#12)

Factors Affecting Weed-Crop Competition

• Row Spacing

• Crop Population

• Weed Species & Density

• Duration of Competition

• Weed Distribution

(#13)

Impact of Weed Species on Crop Yield

CockleburGiant RagweedVelvetleafMorninggloryLambsquartersPigweedsJohnsongrassCrabgrassFoxtail

more

lessco

mpe

titiv

enes

s

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7 8 9 10 11 12

Weed Density

Cro

p Y

ield

(%

)Impact of Weed Density on Crop Yield

Influenced by:• environment• time of weed emergence • crop canopy (row spacing)

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7 8 9 10 11 12

Max YieldRemovalWeed Free

Weeks After Planting

Cro

p Y

ield

(%

)Critical Period

Weed Management Tactics

Non-Pesticide Methods

Prevention

Mechanical

Cultural

Biological

Prevention

• Plant weed-free seed– Kentucky seed law (noxious weed seed)

• Eastern black nightshade• Balloonvine

• Avoid introduction of unwanted plants– Certified seed vs Bin run seed

• Sicklepod• Spurred Anoda

• Keep field borders clean

(#20)

Mechanical Controls

1) Tillage practices:– Primary tillage

• moldboard plow• chisel plowing

– Secondary tillage• disc / harrow• field cultivator

– Selective cultivation• Cultivator• Conservation-till cultivator

(#23)

JDGJDG

Common Pokeweed Control (%) with and without Cultivation in No-Tillage Corn at Three Locations 1996 (4 WAT)

Untreated 0 c 0 e 0 d

UntreatedCultivation

58 b 32 d 57 bc

Exceed + COC 95 a 88 ab 63 ab

Exceed + COCCultivation

99 a 94 a 77 a

Banvel (0.5 pt) --- 68 c 47 c

Banvel (0.5 pt)Cultivation

--- 80 b 63 ab

Woodford (#1) Woodford (#2) Hardin Co.

Mechanical Controls

2) Hand weeding: High value crops

• Tobacco• Vegetables• Organic grown crops

3) Mowing:– Pasture weeds

(#23)

Cultural Practices Know the Field History

-- Look for problematic weeds in the past

Cropping Sequence / Crop Rotations-- eg. Johnsongrass

Variety/Hybrid Selection-- use of herbicide tolerant crops

Seed or Plant Source-- certified seed vs bin run seed

(#24)

Cultural Practices Tillage System

-- impact on perennial weeds

Residue Management-- impact on soil-applied herbicides

Planting Date-- eg. Johnsongrass

Plant Population / Row Spacing-- crop canopy closure impact on weed/crop interference(eg. Less yield loss from cocklebur in narrow-row soybean)

(#24)

Biological Controls Musk Thistle control

Thistle-head weevil Thistle rosette weevil

Grazing pastures Cattle Goats

(#25)

Weed Management Tactics

Pesticide Control Methods

Herbicide Selection and Use

Crop GeneticsHerbicide Tolerant Crops

Factors that Affect Herbicide Selection and Use in Kentucky

Proper Weed Identification (Life Cycle) Incidence and Severity of the Pest (Weed)

Past History in the Field

Potential for Weed Resistance

Weed Stage of Development Before weed emergence After weed emergence (size & growth stage)

Crop Stage of Development

(#28)

Factors that Affect Herbicide Selection and Use in Kentucky

Effectiveness against the weed(s)

Persistence Beneficial for weed control longevity Problem for crop rotations

Chemical & Physical Properties of the Pesticide (liquid vs dry)

Mammalian Toxicity (paraquat vs glyphosate)

Environmental Hazard Ground and/or surface water impacts

(#28)

Factors that Affect Herbicide Selection and Use in Kentucky

Method of Pesticide Application Preplant Foliar, Preplant Incorporated, Preemergence (soil-applied), Postemergence

Soil Characteristics Soil type, texture, soil pH Application rates, Persistence, etc.

Pesticide Availability & Label Restrictions Economics Public Concerns

-- Potential environmental impact-- Biotechnology derived crops (GMO’s)

(#28)

Weed Management Decisions

Economics Environment

Efficacy

Factors Influencing Crop Injury Caused by Pesticides (Herbicides)

Crop/variety sensitivity-- spraying the wrong field -- crop growth stage

Weather Crop under stress conditions

Persistence-- rotational crop concerns

Rate and Formulation Method of Application (Timing) Incompatibilities of Pesticides

Tank mixture combinations Herbicide / Insecticide interactions

(#27)

Effect of Plant Growth Stage and Influence of Environmental

Factors on Weed Control and Herbicide Injury

Smaller weeds easier to control

Later stages of crop growthMore likely for crop injury to occur

Environmental stress Less weed control possible Increase potential for crop injury

Air Temperatureo Paraquat vs Glyphosate (Gramoxone) (Roundup)

(#37)

Types of Herbicide Interactions

Additive

Synergistic

Antagonistic

(#31)

Use of Adjuvants / AdditivesEnhance biological activity or improves

pesticide performance• Surfactants• Sticker-spreaders• Oils• Salts or Fertilizers

Minimizes handling and application problems• Compatibility agents• Foam retardant• Buffer agents• Drift control agents

(#29)

I. Activator Adjuvants

• Surfactants• Phytobland Oils• Oil-surfactant mixtures:

– Crop Oil– Crop Oil Concentrates– Methylated Seed Oils (MSO)

• Silicone derivatives• Nitrogen Fertilizers

Surfactant Surfactant = surface active agent

• Non-Ionic (most common type used)• Anionic• Cationic

Typically marketed as liquids that contain 50% to 100% active ingredient octoxynol, dooxynol, nonoxynol, oxysorbic

Reduce surface tension of water droplets; greater coverage of leaf surface

II. Utility Modifiers of Herbicidal Sprays

Used to alter undesirable characteristics of herbicide mixtures or to alter the spray mixture to enhance or stabilize the spray mixture

• Antifoam Agents

• Compatibility Agents

• Buffering Agents

• Drift Control Agents

GeneticHerbicide Tolerant Crops

(#21)

Selection:

-- from natural populations within a crop species

-- of herbicide tolerant mutants within a cultivar at the cell or whole plant level

Insertion of genes conferring tolerance

Herbicide Tolerant Crops

[Selection Method]

IMI-tolerant corn hybrids (1992)» Imidazolinone Resistant (IR) and Tolerant (IT)

corn hybrids» eg. LIGHTNING on Clearfield-corn hybrids

STS soybeans (1995)» Sulfonylurea Tolerant Soybean» Synchrony STS

POAST resistant corn (1995)» sethoxydim resistance» Poast Protected hybrids (PP-corn)

Herbicide Tolerant Crops

[Insertion Method]

ROUNDUP READY soybean (1996)» glyphosate tolerance» Introduced gene that increases production of EPSP synthase

LIBERTY LINK corn (1997) LIBERTY LINK soybean (1998)

» glufosinate-ammonium (i.e. phosphinothricin)» PAT gene inserted into the crop

ROUNDUP READY corn (1998)» glyphosate tolerance

Herbicide Tolerant CropsAdvantages / Benefits

Less risk of crop injury

Fewer carry-over problems with herbicides?

Broader spectrum of weed control

Use ‘environmentally friendly’ herbicides

Less expensive ??

(#21)

Roundup ReadyTM soybeans

High Acceptability by Crop Producers Convenience

one herbicide / rate selection / timing?

Clean fieldsbroad spectrum of weeds controlled

Ability to tackle problem weeds

Less intense scouting ??

Concerns with Herbicide Tolerant Crops

Herbicide tolerant crop may transfer resistance to related species (eg. Canola / mustards)

Herbicide tolerant crop may become a weed

Lead to fewer alternative weed control practices

More dependence on herbicides

Public acceptance or non-acceptance

Use of Herbicide Tolerant Crops

Will they help prevent weed resistance?

In some situations, they may provide an opportunity to rotate herbicides with different “modes of activity”

On the other hand, they can broaden the opportunity to use the same herbicide in both corn and soybeans

Part III: Integrated Pest Management• Competency Area 3.

– Pest Mangement Tactics• Herbicide Persistance

Discussion No. 34 – 37

Herbicide Persistence

Desirable• Weed control

Undesirable• rotational crop injury• environmental

contamination

(#34)

Persistence is a function of herbicide dissipation rate

• Herbicide Rate• Application Time• Soil type

organic matterClay (type & amount)

• Soil pHchemical degrade.microbial degrade.

• Adsorption

• Soil temperature

• Soil moisture

• Distribution in soil

• Repeat applications

• Cropping sequenceCrop/variety sensitivity

• Herbicide Formulation

Herbicide Persistence andRecrop Interval

Time

Her

bici

de C

once

ntra

tion

Recrop toleranceconcentration

Adverse: (drought, low temperature, extreme pH)

Optimum: (normal moisture, temp, pH)

Persistence of Herbicides Under Kentucky Conditions

Herbicide Half-life (days)Dual (metolachlor) 11Lasso (alachlor) 5Frontier (dimethenamid) 3Surpass (acetochlor) 3

Princeton, KY. 1995. Crider silt loam.

(#35)

Labeled Rotational Crop Intervals for Soil-Applied Herbicides

Herbicide

Corn

Soybean

Wheat

Atrazine# 0 S* 2F

Canopy 10 0 4

Scepter 9.5* 0 4

Command 3ME 9* 0 12*

Spartan 10 0 4

-------------(months, etc)------------

# Includes products that contain Atrazine (i.e. Bicep II, FulTime, Harness Xtra, etc.)

* Potential injury to rotational crop if conditions are extremely dry

Labeled Rotational Crop Intervals for Soil-Applied Herbicides

Herbicide

Tobacco

Alfalfa

Forage Grasses

Atrazine 2S 2F 2F

Canopy# 10 10 18

Command 3ME 0 16 16

Scepter 9.5 18 18

Spartan 0 X? X?

-------------(months)--------------

# Waiting period may be longer for high pH soils.

Recrop Interval* for Canopy

pH <7.0Field corn 10Tomato 10Cucumber 10Sweet corn & all others 18

* Months

pH >7.0181818

30

Part III: Integrated Pest Management• Competency Area 4 & 5.

– Pesticide Stewardship• Ground and Surface Water• Spray Drift and Volatilization

Ground and Surface Water Advisories[Herbicides with Water Quality Statements]

• Rate Restrictions– Maximum rates allowed:

• Soil Texture• Based on tillage system / Previous plant residue / Erodibility*• Depth of water table (eg. Balance)

• Setbacks– Do not mix or load within 50 ft of wells, rivers, intermittent streams, lakes, or reservoirs– Products should not be applied within 50 ft of wells or sink holes; within 66 ft of where field

surface water enters streams or rivers; or within 200 ft around lakes or reservoirs*

* Atrazine and herbicide products containing atrazine: (AAtrex, Bicep II Magnum, Degree Xtra, Harness Xtra, etc.)

(#42,43,45)

Safe Drinking Water Act (SDWA) - 1992

• Required public water utilities to begin monitoring for atrazine, and other substances regulated by SDWA (by January 1995)

• A water system is considered out of compliance if the running annual average is above the Maximum Contaminant Level (MCL)

– Atrazine MCL = 3 ppb (3 micrograms per liter)

• If atrazine is detected above the MCL, water utilities are required to notify the public and take action to reduce levels below MCL

Atrazine Re-Registration Update

January 2003 EPA issued an Interim Re-registration Eligibility Decision (IRED) to conduct an

innovative monitoring program on community water systems that are considered to be most vulnerable to atrazine (40 indicator watersheds)

Under an Memorandum of Agreement with Syngenta, atrazine will be intensively monitored in the most vulnerable watersheds where detections exceed the MCL. If established safety standards are exceeded after remediation efforts, the use of atrazine will be prohibited in that watershed.

Revised cancer classification • Atrazine “not likely” to be a human carcinogen

Addendum - October 2003 No scientific link between atrazine and prostate cancer Available studies do not provide sufficient evidence to show a

consistent, reproducible effect of atrazine on amphibian development

Situation - Kentucky• Two municipal water systems in Kentucky require intensive monitoring --

– Atrazine exceeded the MCL level (3 ppb) for three or more consecutive months (sampling period 1999 – 2002)

– These small municipal lakes used for public drinking water sources are fed by small watersheds; thus, atrazine use practices more easily mitigated in surrounding crop land

• Two additional community water systems are being intensively monitored because the atrazine concentration exceeded the MCL at one sampling time during the 2003 calendar year

– One sample site is part of a large watershed

Spray Drift / Volatilization

Spray VolumeWeather ConditionsPesticide Formulation

Eg. 2,4-D Ester vs 2,4-D Amine

AdditivesNozzle HeightDroplet SizeSpray Pressure

(#49)