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TERMINOLOGY

What is a weed??

http://ron.outcrop.org/images/dandelions.jpg

Weed definitions:

Any plant that is objectionable or interferes with the

activities of people

A plant growing where man wishes other plants, or

no plants, to grow and which has economical,

ecological, or aesthetic implication for man and or

his activities

(Bridges, Weed Technol. 8:392)

Weed definitions:

A weed is a plant whose virtues have not yet been

discovered.

Ralph Waldo Emerson

A plant out of place.

Volunteer Corn in Corn Weed control

The process of reducing weed growth and/or

infestation to an acceptable or adequate level

Could be considered subjective

What is control versus suppression as indicated on

herbicide labels?

What are we really wanting?

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Weed suppression

Any mechanism that greatly reduces or stops growth

and vegetative development of a weed without

killing many of the weeds

Weed eradication

The elimination of all live plant parts and viable

seeds of a weed from a site

Yellow starthistle was removed from the ND noxious

weed list because it is believed to have been

eradicated from North Dakota

At least no one has found a specimen in several years

What are some concerns about this declaration?

Suppressed turf??

http://theevanstonian.files.wordpress.com/2009/07/lawn-care.jpg

Brush Control

http://www.cotaticreekcritters.info/images/Snowberry-WB.jpg

Biocontrol of weeds

Control or suppression of weeds by the action of

one or more organisms through natural means, or by

manipulation of the weed, organism, or environment

Biocontrol agents in ND for leafy spurge

Dr. Rod Lym

http://www.ag.ndsu.edu/pubs/plantsci/weeds/w1183w.htm#Leafy

Aphthona flava Aphthona lacertosaAphthona nigriscutis

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• Dr. Rod Lym

• http://www.ag.ndsu.edu/pubs/plantsci/weeds/w1183w.htm#Leafy

Grass carp

Bacteria

What limitations might surround the success of bacteria as biological control agents?

Herbicide A chemical used to control, suppress, or kill plants, or

to severely interrupt their normal growth processes.

A chemical that is phytotoxic to a plant.

Phyto = plant

So herbicide is toxic

to a plant

Plant Growth Regulator

a substance used for controlling or modifying plant

growth processes without appreciable phytotoxic

effect at the dosage applied

Total Vegetation Control – killing of all plants with a non-

selective herbicide; generally a herbicide with soil

persistence (power substations, railroads)

Defoliant – A chemical which causes the leaves to drop from

a plant by forming the natural abscission layer early (cotton)

Desiccant – any substance or mixture of substances used to

accelerate the drying of plant tissue (potatoes, dry beans)

Fumigant – a chemical, such as methyl bromide ($$$) either

volatile liquid or gas, used so that the vapor of gas kills the

weed or pest. Broadly nonselective, kills: weeds, seeds,

pathogens, insects (vegetable or other high value crops)

Specific herbicide purposes Allelopathic substances

Chemical compounds produced by plants that affect the interactions

between different plants, including microorgansms

Most common in desert areas

Can be seen in ND (black walnut, spotted knapweed)

http://1.bp.blogspot.com/_6LWjP0sZ22w/SCuw1G4TMmI/AAAAAAAAAk4/4chE3oH

tZ4k/s1600-h/allelopathy.gif

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Seed protectant

• A substance applied to seed before planting to

control pests

AbsorptionAdsorption

Adsorption – the process by which a herbicide associates with a

surface

Absorption – The process by which a herbicide passes form one

system to another

Herbicide common name

an abbreviated name applied to a herbicide active

ingredient, usually agreed upon by the American

National Standards Institute and the International

Organization for Standardization (a.k.a. generic

names, also used in the drug industry)

Trade name

the trademark applied to a herbicide formulation

by its manufacturer

Chemical name

the name applied to a herbicide active ingredient

that describes its chemical structure according to

rules prescribed by the American Chemical Society

and published in the Chemical Abstracts Indexes.

Three names, same herbicide

Trade name =

Common name =

Chemical name =

Roundup WeatherMax®

glyphosate

N-(phosphonomethyl)glycine

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(2,4-dichlorophenoxy) acetic acid Dormancy

The state of inhibited germination of a seed or

plant organ growth in the presence of the required

conditions for initiating growth

Most of the time think “seeds”

Can also refer to buds on perennial plants

or tubers on perennial plants

Yellow nutsedge

http://www.uky.edu/Ag/ukturf/weed%2520id/Yellow%2520nutsedge.htm&docid=v9YSRgtOGR6-wM&img

Metabolite

a compound derived from metabolic transformation

of a herbicide by plants or other organisms

Metabolism is the process of metabolic

transformation of a herbicide to a nontoxic form

Slight changes mean big differences!

Using thin layer chromatography (TLC) scientists can

often identify metabolites

Non-target species

Residue

That quantity of a herbicide remaining in or on the

soil, plant parts, animal tissues, whole organisms,

and surfaces

Know how long your herbicide can persist in the soil.

PLAN ahead.

Crop rotations

Imazethapyr, Pursuit or Authority Assist

40 months before canola or sugarbeet

Bioassay if too dry or in certain soil pH

Bioassaybio = life

assay = to measure

Photo by: Jonathan Mikkelson

Quantitative determination of herbicide

concentration by use of a sensitive indicator plant or

other agent

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Active ingredient (ai)

The chemical in a herbicide primarily responsible for

its phytotoxicity and which is identified as the ai on

the product label

Goaltender® or Goal® 2XL

ai = oxyfluorfen

Goal is a 2 lb ai/gal

Goaltender is 4 lb ai/gal

Always check the label!

Acid equivalent (ae)

Buctril® or Buctril® 4EC

ai = bromoxynil esters

Expressed as the theoretical yield of parent acid from

the ai content of a formulation

Chocolate Chip Cookies Concentration

In the container

4 lb ai/gal

75% ai by weight

Formulation of chocolate in the finished product

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Rate

The quantity of herbicide ai or ae applied to the

area treated

If spraying the entire field, may be called the

“Broadcast” rate

Different than the water used in the application

(volume)

Broadcast rate

broadcast

rate

Broadcast rate equivalent

for banded treatments, it is the rate of herbicide

applied per unit area when only the band area is

considered

Broadcast rate equivalent (BRE)

broadcast

rate

broadcast

rate

equivalent

Broadcast rate and BRE

The rate is the same per treated area.

The applicator only compensates for less

area when calculating how much

herbicide is needed to treat the field.

Components of Formulations

There are many formulations

Many liquid formulations are either petroleum oil-

based or plant-derived oils (crop oils)

Industry (herbicide manufacturers) strives for a safe,

consistent formulation

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Crop oil concentrate

Includes an “emulsifier”, which is a chemical that

helps oil and water mix

Plant-derived oils float on water

Emulsifiers help distribute through mixture

Extender

inhibits organisms that breakdown

herbicides

Safener

substance that reduces toxicity of a

specific herbicide to a crop

may depend on the rate

Extenders and Safeners

EPTC = Eptam

EPTC + safener = Eradicane

EPTC + safener + extender = Eradicane extra

fenoxaprop-P (Puma, Tacoma) includes a safener

Plant responses due to herbicides

Phytotoxic

injurious or lethal to plants

Chlorosis

loss of green color (chlorophyll) from foliage

Chlorosis

http://www.btny.purdue.edu/Extension/Weeds/HerbInj2/Img/Large/085.JPG

Plant responses due to herbicides

Phytotoxic

injurious or lethal to plants

Chlorosis

loss of green color (chlorophyll) from foliage

Necrosis

Localized death of tissue usually charaterized by

browning and desiccation

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Necrosis

http://www.btny.purdue.edu/Extension/Weeds/herbinj2/Img/Large/003.JPG

Plant responses due to herbicides

Phytotoxic

injurious or lethal to plants

Chlorosis

loss of green color (chlorophyll) from foliage

Necrosis

Localized death of tissue usually charaterized by

browning and desiccation

Epinasty

that state in which more rapid growth on one side of a

plant organ or part (especially leaf) causes it to bend

or curl downward

Healthy sugarbeet

http://www.forestryimages.org/browse/detail.cfm?imgnum=5358214

Epinasty

http://www.ag.ndsu.edu/pubs/plantsci/rowcrops/a1085w.htm

2,4-D dicamba

Dr. Alan Dexter et al. 1994.

Vapor drift

the movement of a chemical as vapors (gaseous

form) from the area of application

dependent on a herbicide’s vapor pressure, which if

significantly high may cause a liquid herbicide to

vaporize and injure non-target plants distant from the

application site

volatility

http://turfgrass.cas.psu.edu/education/turgeon/Modules/11_WeedManagement/Herbicide_Fate/Images/HF5.jpg

Spray drift

movement of airborne spray (liquid or solid) from

the intended area of application

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Susceptibility

the sensitivity or degree to which a plant is injured

by a herbicide treatment

2019 ND WCG (p. 113-119)

ratings for weed control of specific weeds to specific

herbicides in ND

Herbicide tolerance

the inherent ability of a species to

survive and reproduce after a

herbicide treatment.

There was no selection or genetic

manipulation to make the plant

tolerant, it was naturally tolerant

Herbicide resistance

the inherited ability of a plant to

survive and reproduce following

exposure to a dose that would have

been normally lethal to the wild type.

In a plant, resistance may be naturally

occurring or induced by such techniques

as genetic engineering or selection of

variants produced by tissue culture or

mutagenesis

Types of Herbicide Application

Broadcast treatment

Band treatment

Directed application

Spot treatment

Basal treatment

Layby application

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Foliar application

Soil application

Preplant application (PP)

Preplant incorporated (PPI)

Preemergence application (PRE)

Postemergence application (POST)

Bed

A ridge of soil formed for planting crops above the

furrow on each side

an area in which seedlings or transplants are grown

for planting in the field later

Tillage

soil disturbance or displacement, such as to cover

crop residue, prepare a seed bed, and/or control

weeds

Tillage group discussion

What tillage are you familiar with?

What do you call it?

Types of tillage

Machinery used

http://upload.wikimedia.org/wikipedia/commons/d/d0/Rice_Cultivation_Vietnam.1024x768.jpg

No-till, minimum-till

http://whyfiles.org/241GM_2/images/corn_no_till.jpg

- planting a crop seed directly into stubble or sod with

no more soil disturbance than is necessary to get the

seed into the ground

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Cultivation

Mechanical soil agitation, possibly after crop

emergence for the purpose of killing weeds

blind cultivation: before the crop emerges

http://plantandsoil.unl.edu/croptechnology2005/UserFile

s/Image/siteImages/Tillage-LG.jpg

SOIL APPLICATION

ASPECTS OF HERBICIDES

Herbicide incorporation

To blend or mix a herbicide into the soil

Applied to surface (PRE) or mechanically incorporated (PPI)

Objectives

Place herbicide in position to maximize plant uptake

Promote control of emerging seedlings (root uptake)

Reduce volatility

Upper 2”

Weed seeds

Crop seed

Herbicide

Soil p

rofi

le

Soil injection

Placement of herbicide beneath the soil surface

using mechanization (blades, knifes, or tines)

Methyl bromide… very volatile

http://www.panna.org/driftImages/Telone-Application01.jpg

Soil sterilant

Herbicides designed to have activity by remaining active in the rooting zone and whose effects may be temporary or relatively long lasting

Vineyards, tree plantings, orchards, fencerows, ect.

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Leaching

Movement of a herbicide or nutrient downward with

water through the soil

Both desirable and undesirable aspects

Dependent on:

Herbicide adsorptive properties

Herbicide solubility

The amount of water moving downward

Lateral movement

Horizontal movement of the herbicide on the soil

surface or in the soil profile

Irrigation ditches

Volatile herbicides (EPTC)

Activate

The process by which a surface-applied herbicide is

moved into the weed seed zone to become

phytotoxic after rainfall, irrigation, or tillage

Term used to describe the desirable leaching into the

“kill zone”

PRE: Prowl H20, Dacthal

Persistent herbicide

A herbicide that when applied at the recommended

rate, will harm susceptible crops planted in normal

rotation after harvesting the treated crop, or that

interfere with regrowth of native vegetation in non-

crop sites for an extended period of time

Residual herbicide

A herbicide that persists in the soil and injures or

kills germinating weed seedlings over a relatively

short period of time

Persistent and/or residual herbicides

Names can be synonymous

Generally “persistent” is used to describe herbicide

in a crop rotation context

Accent® applied to corn will persist and injure the

following years onion crop.

Likewise, “residual” is used to describe a herbicides

duration within the cropping season

Outlook® has a short residual.

Estimated lengths in WCG p. 114-115

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Persistent and/or residual herbicides

Importance

the length of residual determines the time that a

chemical can be expected to provide weed control

Persistence determines which crops can be planted in

future years

Many factors determine herbicide persistence in the

soil (PLSC 453/653)

TYPES OF HERBICIDE ACTION

Auxin

One of the five plant hormones

Organic chemicals that stimulate plant growth,

causing cell elongation

With manipulating synthetic herbicides, this growth

causes epinasty (differential growth rates)

http://www.omafra.gov.on.ca/english/crops/field/news/croppest/2005/03cpo05a5f7.jpg

Selective and non-selective herbicides

Selective herbicides are used to kill unwanted

species while remaining safe to desirable species

Selectivity may be dependent on rates

Non-selective herbicides show no favoritism and are

toxic to all plants.

Roundup

Contact and translocated herbicides

Contact herbicides cause injury to the area of the plant where contact with the herbicide occurs (little to no movement in the plant)

Translocated herbicides move within the plant

generally downward through the phloem

Upward in xylem

Desirable for control of perennials or annuals with a growing point below the soil surface or vegetative reproductive capabilities

Translocated or systemic

Translocated generally refers to the movement of a

substance to a metabolic sink (plants)

Systemic term often used as synonym for

translocated herbicide

generally refers to the effect of an insecticide or

fungicide on the insect or plant

Potato insecticides

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Pesticide interactions

Interaction refers to the combined effect of

substances

Additive

Antagonistic

Synergistic

Additive effect

The additive effect is when the total response of the

mixture is equal to the sum of the two.

Herbicide X provides 50% control of dandelion

Herbicide Y provides 35% control of dandelion

50% + 35% = 85% control of dandelion

Antagonistic effect

The effect of one herbicide on another decreases

that herbicides effectiveness, such that it is less than

the sum of the two.

Herbicide X provides 85% control of yellow foxtail.

Herbicide Y provides 30% control of yellow foxtail.

Would expect 85% + (0.3 * 15%) = 90%

Actually observe 60-70% control

Anderson 1983, Pp. 600-601

Weed Control in Canola Systems

0

10

20

30

40

50

60

70

80

90

100

Select Raptor Select Draft +Select

Venice mallow Pigweed/mustard Yellow foxtail

Contr

ol (%

)

LSD (0.05) = 2 vema, 2 rrpw/wimu, 3 yeft

Clearfield SU-Resistant

Antagonism example

Diclofop-methyl: When 2,4-D is mixed with

Diclofop-methyl, the effectiveness of Diclofop-

methyl on wild oat is nullified.

Some antagonistic effects could be considered

beneficial when crop selectivity is increased.

Anderson 1983, Pp. 600-601

Synergistic effect

The total response is greater than the sum of the

herbicides in the mixture

Herbicide X provides 60% control of barnyardgrass

Herbicide Y provides 20% control of barnyardgrass

The synergistic effect of Herbicide Y on X increases X’s

control of barnyardgrass to 90%

Anderson 1983, Pp. 600-601

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Synergism example

2,4-D, mecoprop, and

dicamba (common

selective turf mixture)

result in much greater

control of broadleaf

weeds in turf than would

be expected from the

additive effect of each

applied separately.

Anderson 1983, Pp. 600-601

Mode of action (big picture)

General reason why the plant dies

All factors affecting herbicide phytotoxicity from

herbicide contact with the plant until the final

physiological effect (often plant death)

Contact and retention

Absorption

Translocation

Physiological effect

Site of Action (mechanism)

Specific biochemical processes affected by the

herbicide that result in the final phytotoxic effect

this includes the specific tissue, membrane, enzyme, or

physiological reaction affected, often at the cellular

level

Inhibition of PS II

Inhibition of ALS

TYPES OF PLANTS

Herbaceous Woody plants

http://www.bradygenome.org/soybean%20plant.jpg http://www.arbopals.com/images/arbopedia/elm1.jpg

GROWTH STAGES OF PLANTS

Germination

the process of initiation growth

Cracking

the time when the soil above the emerging crop seedlings begins to crack

Emergence

the event in seedling or perennial growth when a shoot becomes visible by pushing through the soil surface

Seedling

young plant from emergence until the first true leaf develops

Growth Stages of Dicots (legume ex.)

1st trifoliolate –

compound

leaves

unifoliolate –

first pair of

leaves

Cotyledon –

seed leaves

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Growth stages of grasses

spike: the early emergence stage of grasses in which only the coleoptile is visible or the first true leaves are still tightly rolled to form a “spike”

tillering: additional shoots (tillers) are developing from axillary buds in the crown

jointing: when stem internodes begin elongating so the terminal bud is aboveground

boot: inflorescence is enclosed in the upper flag leaf sheath; the flag leaf is swollen due to growth of the developing head

heading: when the seed head is emerging or a has emerged from the flag leaf sheath

Growth stages of Grasses (WCG p. 14)

http://www.ndsu.edu/fileadmin/weeds/4.1-Chart.pdf