Weed and Orchard Floor Management

John Strang Extension Fruit & Vegetable Specialist

University of Kentucky Department of Horticulture

Orchard Weed Control – Why? • Weeds compete for

water, nutrients, light and space

• Weed Control – Increases tree growth

• Tree growth can be reduced by 1/3 or more where weeds are not controlled and more in dry seasons

– Increases fruit size – Reduces water use

• Weeds also tie up N and water late in the season – Promoting tree hardiness

development

EverCrisp® MAIA First Release

Orchard Weed Control – Why? • Weeds interfere

with pollination – Control

broadleaves with 2,4-D amine prior to fruit crop bloom

– Dandelion, Yellow rocket, Mustard

• Move bees in at ~10% fruit crop bloom

Orchard Weed Control – Why?

• Weeds interfere with harvest – Poison ivy

– Thorny blackberries

– Honeyvine milkweed

– Johnsongrass

Orchard Weed Control – Why? • Weeds harbor pests

– Blackberries • Sooty blotch &

Flyspeck

– Dandelions • Viruses

– Legumes (clover) • Plant bugs

• However, weeds also harbor some beneficial insects

Orchard Weed Control – Why?

• Weeds provide cover for rabbits and voles – Particularly a problem

with a snow cover

Orchard Weed Control – Why? • Allelopathy • Some plants produce

chemicals that are detrimental to tree growth

• Black walnuts – Juglone

• Can inhibit growth or kill – Apples – Blueberries – Blackberries

Types of Weeds Annuals

• Germinate, grow, set seed & die in one season. – Winter annuals

• Chickweed • Red dead nettle,

Henbit

– Summer annuals • Foxtail • Pigweed/Amaranth • Common

lambsquarters

Types of Weeds Biennials

• Grow as a rosette the first year and then flower and die the second year

• Musk thistle • Poison-hemlock

– Most poisonous plant in N. America

Annuals & Biennials • Ideally we kill these

before they set seed.

Musk thistle Photo courtesy: Wikipedia

Poison-hemlock

Pigweed or Amaranth

Types of Weeds Perennials

• Grow for many years – Simple perennials

• Dandelion

• Broadleaf dock

– Bulbous perennial • Wild garlic

– Creeping perennials • Johnsongrass

• Blackberry

• Bindweed

• Canada thistle

Photo courtesy: Wikipedia

Perennials Generally Most Difficult to Control

• May have their top killed, but continue to grow by underground roots

• If tilled up they may propagate from root pieces

• At bloom nutrient reserve flows to the roots – An ideal time to use a

systemic herbicide

• Many perennials continue to develop seed to maturity even after they are killed

Horse nettle

Site Preparation Get Perennial Weed Problems Under Control the Year

Before Planting

Johnsongrass

Thorny blackberry

Poison ivy & Creeping euonymus

Honeyvine milkweed Yellow nutsedge

Weed Control Methods

• Cultivation

• Mowing

• Mulching

• Flaming

• Herbicides

Clean Cultivation

• Used extensively in the past

• Maximizes tree growth

• Reduces water loss

• Reduces soil organic matter

• Extensive erosion and soil loss

Strip Cultivation • Organic

• Reduces erosion

• Can’t use on wet soil

• Damages tree roots with deep cultivation

• Knocks low fruit off trees

• Slower and more expensive (due to labor) than herbicides

Weed Badger

Strip Cultivation

• Wonder Weeder – Harris Manufacturing

Burbank, WA www.wonderweeder.com

– Front mounted cultivator

– Essentially no tree damage

Mowing • Fruit trees don’t compete well with grass for N or water

• Apple trees mowed monthly and grown in complete sod were stunted in early years and slow to produce

• Trees caught up (adapted) after 17 years and became almost as productive as trees in herbicide or mulch strips (Ian Merwin, NY)

Perfect mower with swinging arm

Mulching • Expensive to apply • Nitrogen

– Applied 4” of bark mulch every 3 years

– Ties up N first 8 years – Releases too much N (100

lb/A/yr) after this – Over 17 years O.M. increased

from 4.5 to 9% – Substantially increased tree

growth, but not yield, but second best weed control method (Ian Merwin, NY)

• Increases vole habitat and tree damage

Mulching Landscape Fabric

• Not a good choice for fruit trees

• Provides excellent protection for voles from hawks

• Leads to severe vole damage in winter

Flaming

• Organic

• Expensive in terms of labor/time and propane

• Weeds re-grow quickly

• Not very practical

Herbicide Strips • Glyphosate + 2 residual

herbicides, Karmex & Solicam (Ian Merwin, NY)

• Six ft. wide weed-free strip • Least weed competition • Apple trees were not as

productive over long term – Substantial erosion & soil

deterioration – Greater nutrient & pesticide

losses – Fairly high surface feeder root

mortality because soil too hot and dry during summer

Herbicide Strips • Two glyphosate applications

May-Aug, 6 ft wide strip (Ian Merwin, NY)

• Usually produced highest yields and optimal tree growth over 17 years

• Fairly weedy during dormant season – Dandelion, yellow rocket,

common groundsel, ground ivy, crabgrass & moss

– Mowed with adjustable batwing mowers to shorten weeds beneath trees and discourage voles

• Ground cover competition occurs when trees not growing actively and carrying a crop

• Lowest annual maintenance cost

In Row Weed Free Strip Width (Ian Merwin, NY)

• Strips 2, 4, 6’ wide

• Trees drip irrigated

• No effect of strip width – Trees yielded the

same in 2’ and 6’ wide strips

Weed Control Timing, NY

Best period for weed control is May, Jun., July and a little in Aug.

Summary of Ian Merwin’s NY 17 Years of Weed Control Work

• Use grass alleys, preferably with fine-leaf fescue turfgrass

• Use a narrow weed control strip in tree rows – 2 ft wide

• Use post-emergence herbicides only – Prefers glyphosate over

gramoxone – Kills weeds completely and is

safer for applicator – Paint trunks of trees to

reduce herbicide uptake – Use a shielded sprayer

• Suppress groundcover vegetation in May and June

Herbicide Types

• Pre-emergence – Applied before weed

seeds germinate or emerge

– Kill weed seeds as they germinate

• Post-emergence – Kill weeds that have

emerged • Contact

– Gramoxone – Aim

• Systemic – Glyphosate – Poast, Select

Pre-emergence Herbicides • Create a herbicide barrier

at soil surface • If grass too tall herbicide

may not get to the soil • Normally need to be

rained in to activate – Devrinol 24 hrs – Princep several weeks

• Will kill fruit tree roots if moved down into soil – Soil not settled around

roots after planting – Young trees most sensitive – Too high a rate

• Some Pre-emergence herbicides also have post-emergence activity – Sinbar, Chateau

• Alion • Casoron • Chateau • Devrinol • Goal • Karmex • Kerb • Matrix • Princep • Sandea • Sinbar • Solicam • Surflan

Pre-emergence Herbicides Trade Name Common Name

Alion Indaziflam

Casoron Diclobenil

Chateau Flumioxazin

Devrinol Napropamide

Goal Oxyflorfen

Karmex Diuron

Kerb Pronamide

Matrix Rimsulfuron

Princep Simazine

Sandea Halosulfuoron

Sinbar Terbacil

Solicam Norflurazon

Surflan Oryzalin

Generic Herbicides

• Common name – Glyphosate

• Trade names – Roundup WeatherMax

– Roundup PowerMax

– Touchdown

– Glyphomax

– Rattler Herbicide

• Most of the generic glyphosate products differ in the surfactant included and in the amount of active ingredient

• Check the common name to be sure of the product that you are purchasing

Post-emergence Herbicides Contact

• Gramoxone – Restricted use

– Very dangerous to applicator

– Burn down - Kills tender plant tissue that it hits

– Not good on perennial weeds

Post-emergence Herbicides Systemic

• Growth regulator types

• Weeds need to be growing and not stressed for these to work

• Selective grass materials – Poast, Select, Fusilade

– May not be cleared on bearing fruit trees

• Selective broadleaf materials – 2,4-D

• Volatility and drift

• Amine vs ester form

• Grapes are very sensitive

Post-emergence Herbicides Systemic

• Glyphosate – Translocated to roots – Much more effective on

woody plants and fruit crops after ~July 15

– Once translocated to roots it keeps coming back for a number of years

– Affects tree winter hardiness development

– Roundup surfactant is very good at moving material into fruit trees

– Do not use to control suckers

– Peaches are very sensitive to glyphosate and are easily killed

Second season after application

Herbicide Combinations

• Recoil – Glyphosate + 2,4-D

• Pre-emergence and post-emergence materials are often applied together – Glyphosate + Princep

• Two post emergence materials are often applied together to improve the spectrum of weed control – Sinbar + Karmex

Herbicide Combinations • Two post emergence

materials are often applied together to improve the spectrum of weed control

Herbicide Selection

• Based on – Type of fruit

• All herbicides are not cleared on all crops

– Tree age

– Season of application

– Type of weed/weeds to be controlled

Herbicide Resistance Management

• Avoid using the same product year after year

• Rotate herbicide modes of action – Helps keep weeds

resistant to one herbicide from propagating

– Helps to keep weeds that are not killed by one herbicide from building up

• Use a tank mix of herbicides – Provides a broader

spectrum of weed control

– May be able to reduce the herbicide rate used

HRAC Codes Trade Name

Common Name

Chemical Group

HRAC Code1

WSSA Code

Casoron 1.4 CS dichlobenil nitrile L 20

Casoron 4G dichlobenil nitrile L 20

Chateau WDG flumioxazin N-Phenylphthalimide E 14

Devrinol 50DF napropamide acetamide K3 15

Karmex 80DF diuron urea C2 7

Poast sethoxydim cyclohexanedione A 1

Princep 4L simazine triazine C1 5

Rely 280 glufosinate phosphinic acid H 10

Roundup glyphosate glycine G 9

Sandea 75DF halosulfuron-methyl sulfonylurea B 2

Surflan AS oryzalin dinitroaniline K1 3

Treevix salflufenacil pyrimidindione E 14

Ultra Blazer acifuorfen diphenylether E 14

1Herbicide Resistance Action Committee

Weed Control Recommendations

• Read the label

Photo courtesy: Montana State Univ.

Work to keep problem weeds from building up in the orchard

• ID the weed – Study the weed’s life

cycle and means of propagation

– Try to keep the weed from developing seeds and multiplying

• Look for a material that will control it

Weed Control for More Southern Orchards

• Use grass alleys, preferably with fine-leaf fescue turfgrass

• Use a narrow weed control strip in tree rows – 2 ft wide if irrigated, wider

w/o irrigation • Use pre-emergence and post-

emergence herbicides – Our pre-emergence herbicides

don’t last all season – Rotate pre-emergence

herbicides to broaden spectrum of weed control from year to year

– Use generic glyphosate to kill perennial weeds with a shielded sprayer • Painting young tree trunks will

help • Use spot treatments on

difficult weeds

– Use other appropriate post emergence herbicides for problem grasses • Poast, Select

• Suppress ground cover vegetation from May up into August

• Use adjustable batwing mower to cut weeds beneath trees in September and maintain some ground cover over winter

• Use a flail mower to chop up fruit on the ground

• Put out vole control poison in late September

Herbicide Application Methods • Herbicide boom sprayer

– Don’t attempt to apply pre-emergent materials with a hand gun sprayer

• Spot application – Post-emergent materials

• Wick application – Glyphosate – Make a

water solution of 33-75% product

– May be wicked on taller weeds and not damage grass below

– Don’t use a wick when weeds are wet

– Bag & keep wet after use

Herbicide Mixing

• Fill tank ½ full with water • Start pump and begin

circulation and agitation • Add herbicides beginning

with the least soluble material – Wettable powders (WP) &

Dry flowables (DF) – Emulsifiable concentrates

(EC) – Soluble concentrates – Surfactant

• Maintain good agitation and spray

• Herbicide incompatibility – More likely with EC & WP

combinations • Buffering agents to pH 7

(neutral) – Buffercide – Buffer-X – Unifilm B – Li 700 Acidphactant

• Mix only enough herbicide

so that it is all used in one day

Herbicide Rate

• Use lower rates on sandy soils with low organic matter

• Use higher rates on heavier/clay soils with high organic matter

Surfactants

• Modify the surface properties of water and improve – Spreading – Sticking – Wetting and/or

emulsifying characteristics of spray solution

• Use for most post-emergence applications

• Typically use nonionic surfactants

• Read the label • Some herbicides already

contain surfactants

Herbicide Sprayer

Diagram courtesy: Linda Talbot, Southwest Missouri State Univ.

Sprayer Nozzles

• Angle of spray

• Droplet size

• Pattern of dispersal – Solid cone

– Hollow cone

– Flat fan • Tapered – for overlapping sprays

• Even – *For band spraying

– Solid stream

SS 8002 E

Stainless Steel

80° Angle

.2 gal/min output at std. 30 psi

Even band application

80°

Nozzles

• Nozzle screens prevent nozzle plugging

• Use only 50 mesh screens with wettable powders

• Use only non drip nozzles

• If you double your tractor speed you double the gallons applied

• If pressure is increased 4X the output is doubled

• As the pressure is increased and/or nozzle size is decreased, chances of spray drift increase.

Sprayer Calibration

• Calibrating Orchard Weed Sprayers – Washington State University

– Timothy Smith

• http://county.wsu.edu/chelan-douglas/agriculture/treefruit/Documents/CalibratingWeedSprayers.pdf

Building Your Own Herbicide Sprayer Video

Dr. Joe Masabni

• Gator

• ZTR Mower

• Small Tractor

• http://www.youtube.com/watch?v=xtRjfaYrl38

Spraying –Drift Control • Reducing spray drift

– Avoid periods with high or gusty winds

– Lowest drift potential at wind speeds between 3 & 10 mph

– Wind speeds lower during morning or evening

– Use high flow rate nozzles that produce larger droplets

– Low drift nozzles reduce the number of very small droplets • Turbo TeeJet • TruboDrop Nozzle

– Drift inhibitors – Make applications at

lowest possible height from ground

– Droplet evaporation is highest when it is dry and hot

Shielded Sprayer

Reasons for Poor Weed Control • Improper sprayer

calibration • Improper herbicide

selection • Improper rate used • Improper application

timing • Uneven or excessive

ground speeds – Recommend spraying at

3-5 mph • Too little water applied

per acre – Typically 20-40 gal/A

• Drought conditions - herbicide is not activated

• Clogged nozzles – Watch closely, carry tools for cleaning & extra nozzles

• Pre-emergent herbicides do not normally hold up all season in our area

Sinbar injury

Reasons for Poor Weed Control • Wrong rate per acre

– 43,560 sq ft

– Amount of herbicide put in tank

– A large portion of an acre of fruit is not sprayed

– A 4-ft wide strip 10,890 ft long equals an acre.

43,560 sq ft/A

4 ft row width

– If rows are spaced 20’ apart this is enough for 5 acres of fruit

• Make sure you measure out the product and put it in the tank! – Perennial crop

= 10,890

Glyphosate used mistakenly as surfactant on 40 acres

Problem Weeds Yellow nutsedge

• Perennial with 3-angled stems

• Propagates primarily from tubers as well as from rhizomes

• Cultivation spreads it • Control

– Multiple sprays of glyphosate

– Sandea

Problem Weeds Poison ivy

• Deciduous woody vine

• Control – Pull down off of

trees and spray with glyphosate Aug- Sept time period

– Cut stems off and paint with concentrated glyphosate • Keep glyphosate off

of fruit tree trunk

Trumpetcreeper

• Aggressive deciduous, woody vine

• Reproduces by seed, root sprouts and stems that root in contact with ground

• Control – Cold hard steel

Weed Control • Essential for

facilitating orchard operation

• Vigorous tree growth

• Increasing fruit size and quality