Natural Area Weed Management

Developed by: Fred Fishel, Ken Langeland (retired), Stephen Enloe, and Lyn Gettys

UF/IFAS Agronomy

Modified & presented by: Michelle Atkinson, Environmental Horticulture Agent

Disclaimer

The use of trade names in this presentation is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.

Study Materials

Applying Pesticides Correctly (SM-1)

Natural Areas Weed Management (SP-295)

https://ifasbooks.ifas.ufl.edu/

1-800-226-1764

Recertification

Every 4 years

CEUs16 NAWM + 4 Core

http://ceupublicsearch.freshfromflorida.com/

Pesticide Applicator Records

Applications of herbicides which carry the DANGER signal word on their labels require applicator records for those who work in natural areas

Florida’s Organo-Auxin Herbicide Rule

Examples: 2,4-D, triclopyr

Regulating and Categorizing of Pest Plants

Florida Noxious Weed List

Identification of Pest Plants

Early detection of new weed infestations is a

key component of integrated

management of pest plants in natural areas

Identification of Pest Plants

Plant Names

Common nameCan be confusing

It is not necessary to know both the scientific names and common names of plants for

certification testing, only the common name

Scientific nameGenus (the first part of the name)

Specific epithet (the second part of the name)

Ferns

Asian sword fern (Nephrolepis multiflora)

Sword fern (Nephrolepiscordifolia)

Herbaceous Species

Wetland nightshade (Solanum tampicense)

• Straggly, sprawling plant with prickly stems up to 16’

• Stem prickles are white to tan• Stems sparsely hairy• Leaves alternate with prickles

Herbaceous Species

Tropical soda apple (Solanum viarum)

• Bushy, prickly perennial to 6’• Stems armed with broadbased, straight

or downward pointing prickles• Leaves alternate and also prickly• Fruit green when immature, dull yellow

when ripe

Shrubs

Coral ardisia (Ardisia crenata)

• Evergreen, multi-stemmed shrub to 6’ tall Alternate, dark green waxy leaves with distinct scalloped margin

• White to pink flowers, stalked in clusters in leaf axis

• Bright red, spherical fruit

Shrubs

Shrub verbena (Lantana camara)

• Multi-stemmed, deciduous shrub to 6’• Square stems, bristly hairs, small

prickles• Opposite stalked leaves with blunt-

toothed margins, hairy, up to 6” long• Small multi-colored flowers in stalked,

dense, flat topped clusters

Vines

Air potato (Dioscorea bulbifera)

• Vigorously twining herbaceous vine up to 66+ feet

• Internodes round• Small or absent underground tubers• Aerial, usually round tubers in leaf

axis• Small fragrant flower in leaf axis

Vines

Japanese climbing fern (Lygodium japonicum)

• Fern with climbing, twining fronds to 90’ long

• Fronds are compound, triangular in shape up to8”

• Stems are wiry and green, black or orange forming dense mats

• Leaflets are lobed, stalked, with terminal lobes dissected

Vines

Old World climbing fern (Lygodium microphyllum)

• Fern with dark brown wiry rhizomes

• Climbing twining fronds to 90’• Leaflets usually unlobed, smooth

on undersides, stalked, leaving wiry stalks when detached

Vines

Cat’s claw vine (Dolichandra unguis-cati)

• Sprawling thicket forming shrub• Hairy stems with prickles• Alternate, twice compound leaves• Sensitive to touch• Small mauve to pink flowers (.5” across)• Brown-bristy, segmented, flat pod (3” X .5”)

Vines

Kudzu (Pueraria montana)

• Semi-woody perennial vine, high climbing, trailing to 65’

• Tuberous roots• Rope-like dark, hairy stems to 4” or

more diameter• Leaves alternate, with 3 leaflets, hairy

margins entire or deeply lobed

Grasses

Cogongrass (Imperata cylindrica)

• perennial grass that grows in loose or compact tufts from stout extensive rhizomes with sharp-pointed tips

Trees

Melaleuca (Melaleuca quinquenervia) • Evergreen tree with a slender

crown• Bark soft, whitish, many-layered,

peeling• Leaves alternate, simple,

grayish-green, narrow lance shaped, 4” long

• Smell of camphor when crushed

TreesBrazilian pepper

(Schinus terebinthifolius)

• Shrub or small tree with short trunk• Numerous long, arching, intertwined

branches• Leaves evergreen, alternate,

pinnately compound with 3-11 leaflets, when crushed smell peppery or turpentine

• Bright red spherical drupe

Trees

Chinese tallow (Triadica sebifera)

• Deciduous tree to 52’ with milky sap• Leaves alternate, entire, rhombic to

ovate, 1-2.5” wide• Petioles long and slender with 2

glands at apex

Introduction

Herbicides: chemicals used for killing plants or severely interrupting their normal growth processes

May be charged (polar or ionic) or uncharged (nonpolar)

The chemical makeup of an herbicide’s active ingredient determines its toxicity, solubility, absorption characteristics, behavior in plants,

behavior in soil, environmental fate, and selectivity

Toxicity of Herbicides Used in Natural Areas

Risk = Hazard x Exposure

Risk to wildlife is determined as the product of hazard and exposure

Toxicity of Herbicides Used in Natural Areas

Public HealthTests: acute, subchronic, chronic toxicityRoutes of entry, birth defects, tumors, cancer….etc

Residue tolerances are established at 100 or 1,000 lower than the

herbicide concentration tolerated by test animals

Herbicide SolubilitySalts of triclopyr amine, 2,4-D amine, glyphosate are water soluble

Water-soluble herbicides do not mix with oil, and oil does not mix with water

Absorption of Herbicides by Plants

Absorption: the process by which an herbicide passes from one system into another, e.g., from the soil solution into a plant root cell or from the leaf surface into leaf cells

Foliar Absorption

The cuticle is the first and most important barrier to the absorption of an herbicide on a leaf surface

Foliar Absorption

Surfactants added to spray mixes can help overcome surface tension and aid in uptake of the herbicide

Root Absorption and Behavior in Soils

Adsorption: the process whereby chemicals (including herbicides) are retained on the surfaces of soil particles

Most important factor by which herbicides become unavailable for uptake from soilsHumus is considered the most important soil constituent that affects absorption by plant roots

Stem Absorption

Stem Absorption

Stem Absorption

Terminology

Classify herbicides by following categories: • Pre-emergent vs. post-emergent• Selective vs. nonselective• Contact vs. translocated• Persistent vs. non-persistent• Their modes of action

Terminology

Pre-emergent vs. post-emergent• Root-absorbed herbicide example:

hexazinone• Foliage-absorbed herbicide examples: 2,4-D,

glyphosate• Both root- and foliage-absorbed examples:

aminopyralid, aminocyclopyrachlor, imazapyr

TerminologySelective vs. nonselective

Selective herbicides control only certain types of plants

Nonselective herbicides generally control most plants

2,4-D

Fluazifop-p

What about Glyphosate?

Terminology

Contact vs. translocated• Contact herbicides kill only the parts of the plant

they actually touch• Limitations where long-term weed control is

desired, such as in natural areas• Translocated herbicides are absorbed by roots or

leaves and carried in the plant sap throughout the plant Examples: glyphosate, 2,4-D

Terminology

Persistent vs. non-persistent• Usually reported as the chemical’s half-life• 10-day half-life of 2,4-D• More than 400 days under certain conditions

for aminocyclopyrachlor

Persistence refers to the time that an herbicide remains in the environment

Terminology

Herbicide Modes of Action

The way in which a particular herbicide disrupts a plant process is called its mode of action

Terminology

Act like natural plant growth regulators

Examples: 2,4-D, triclopyr

Auxin growth regulators

Translocate throughout the plant

Herbicide Modes of Action

Terminology

Translocated throughout the plant

May be nonpersistent, such as glyphosate

May be persistent, such as metsulfuron and imazapyr

May take a week to several weeks before symptoms appear

Are used at low rates – ounces per acre

Amino acid inhibitors

Herbicide Modes of Action

Terminology

Block photosynthesis in susceptible plants

Root uptake is the primary route for these herbicides to enter the plant

All persist in the soil and provide residual weed control

Example: hexazinone

Photosynthesis inhibitors

CO2 +

2H2O Chlorophy

ll

CH2O + H2O +

O2X

Herbicide Modes of Action

Factors That Affect Herbicide Activity

Water stress caused by drought conditions can reduce foliar and root uptake of herbicide and translocation

Herbicide Resistance Management

Select and use herbicides correctly

Herbicide Modes of Action

Resistance in General

Resistance can develop when the same pesticide or similar ones with the same mode of action are used repeatedly

Pests don’t change or mutate in response to a pesticide; the population changes

Resistance in General

Biotype: group of organisms within a species that has biological traits not common to the population

Herbicide Resistance Management

Integrated Weed ManagementUtilizing all available control methods:

Mechanical removalBiological controls

Herbicide Resistance Management

Integrated Weed Management

Don’t Be A Vector

Foliar Applications

Broadcast applications are used where damage to non-target vegetation is not a concern

Basal Bark Applications

The herbicide must be in an oil-soluble formulation

(emulsifiable concentrate)

Hack-and-Squirt Applications

Incisions should be angled downward at approximately 45° to hold herbicide in the cut

Herbicide (concentrated or diluted) is applied…

Treatments are specific and total vegetation control is not achieved

Stump Treatments

Herbicide (concentrated or diluted) is sprayed, poured, or painted on the cut surface

Application should be directed towards just inside the bark

where the active vascular tissue is present

Stump Treatments

Best results, especially for less susceptible species, are obtained if the herbicide is applied immediately after cutting with no more than five minutes between cutting and applying herbicide

Adjuvants

Adjuvant: any substance that is added to a pesticide spray mix to aid or modify the action of the pesticide or the physical characteristics of the mixture

Adjuvants

Surfactants: modify the properties of the medium at a surface or interface

Nonionic (uncharged)Anionic (negatively charged)Cationic (positively charged)

Nonionic surfactants are usually recommended for use with

herbicides

Adjuvants

Buffering agents: used to modify the pH of spray mixtures

Water conditioners: used to remove dissolved compounds such as carbonates and bicarbonates from water

Adjuvants

Antifoaming agents: used to overcome excessive foaming

Colorants: materials used to alter the color of a spray mix

Biological ControlClassical biological control: the introduction of reproducing populations of foreign insects or diseases

1967: alligatorweed thrips

1971: alligatorweed stem borer

1970s: two waterhyacinth weevils and a borer

2010: waterhyacinth planthopperHydrilla-specific leaf mining flies

Weevil and a moth for control of waterlettuce

Their development, however, takes years and cannot be expected to solve all invasive plant

problems

Biological ControlFuture implications

Development takes years

Programs are typically implemented by state and federal agencies

The use of herbivores in natural areas should be carefully considered before implementation due to potential issues

with non-target damage

Mechanical Removal

F. Laroche

M. Monroe

Prescribed Burning

Michelle Atkinson, Environmental Horticulture Agent UF/IFAS Manatee County Extension Service

Email: michelleatkinson@ufl.edu

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