Transcript Unit 3: Weed Control for Small Grains, Pasture, & Forage

Unit 3: Weed Control for
Small Grains, Pasture, &
Forage
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Unit 3 Objectives:




Discuss the importance and options of
chemical weed control
Identify the major areas of concern w/ each of
these crops
Preplant vs. Postemergence herbicide options
and the efficacy of each
Understanding of the harvest/feeding
restrictions after application
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Introduction

If well established, these plants usually
compete very well


Minimizes the need for chemical application
Sometimes control is needed

Ex. Winter wheat and garlic
 Risk of dock if garlic population is too high

Small Grains

Best control is done before the crop is
established in the fall


Especially broadleaves
Tillage also aids in control of weeds
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Proper seeding rate, optimal fertility, timely
planting will also help



Crop is established faster
Competes w/ weeds more effectively
Annual Grass problems

Downy Brome & Cheat




Are significant competitors w/ wheat
Few label clearances for control
Tillage is best option
Severe infestations may alter cropping decisions
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Using Postemerge Herbicides for Broadleaf
control

Nature of the weed problem
 ID and check infestation
 Size of the weed

Stage of the Crop
 Most herbicides are applied after full-tiller until boot
stage
 Don’t apply from boot to hard-dough stage

Herbicide Activity
 Determine crop tolerance and weed susceptibility
 May use broad spectrum tank mix for best control
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Presence of a Legume Underseeding
 What are they referring to?
 Some formulations can cause significant damage

Economic Justification
 Do a cost/benefit comparison
 What factors must be considered?

Seedling

Stage 1
 Coleoptile emergence (sheath that surrounds the
shoot)
 All other leaves follow in this same succession
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Tillering

Stages 2-3
 Shoots (tillers) emerge on opposite sides of plant from
buds in the axils of first and second leaves
 Next tillers arise from a shoot above the 1st and 2nd
tillers or from tillers themselves
 Results in several shoots

Stages 4-5
 Leaf sheath lengthens
 Appearance more like a stem
 True stems actually concealed w/in the leaf sheaths
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Jointing

Stage 6
 Stem & leaf sheaths elongate rapidly
 First node becomes visible at the base of the shoot

Stage 7
 Second node is visible
 Next to last leaf is emerging, but barely visible

Stage 8
 Flag leaf visible, but still rolled

Stage 9 Preboot
 Ligule of the flag leaf is visible
 Head begins to enlarge w/in the sheath
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Stage 10 Boot
 Sheath of flag leaf completely emerged
 Distended due to enlarging, but not yet visible head

Heading

Stages 10.1 to 10.5
 Heads of the main stem emerge first
 Stem continues to lengthen until head is raised several
inches above the upper leaf sheath

Flowering

Stages 10.5.1 to 10.5.3
 Flowering in order of head emergence
 Unpollinated flowers have no kernels
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Stage 10.5.4 Premilk
 Flowering is complete
 Inner fluid is abundant and clear in developing kernels

Ripening

Stage 11.1 Milk
 Kernel fluid is milking white (starch)

Stage 11.2 Dough
 Kernel is soft yet beginning to dry (more starch
accumulation)
 Leaves and stems begin to yellow

Stage 11.3
 Kernel is hard and difficult to split w/ the thumbnail
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Stage 11.4
 Kernel is completely ripe
 Fragments when crushed
 Plant is dry and brittle

Annual Broadleaf Control




Postemergence herbicides provide good control
Aim, Banvel, Clarity, Buctril
Must be applied during recommended stages of
growth to minimize crop damage
Perennial Broadleaf Control


Difficult to control w/ the low recommended rates
Higher rates can cause severe crop damage
Unit 3: Weed Control for Small
Grains, Pasture, & Forage



Tillage in combination w/ herbicide before planting
can provide better control
Banvel, Clarity
Stinger
 Also gets Canada Thistle

Harmony GT
 Control Wild Garlic
 Apply in spring (.3-.6 oz/ac)

Harmony Extra
 Chickweed, henbit, common lambsquarter, smartweed,
mustard

Glyphosate
 Can be applied before harvest
 After hard-dough, but >7d before harvest
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Grass Pastures

Broadleaves can cause extreme problems
w/out control



Direct competition w/ forage grasses
Negatively impacts nutrition potential and longevity
of pastures
Some weeds poisonous
 White Snakeroot
 Hemlock
 Tremors, nervousness, coma, death, etc.
 All cattle, can be passed in milk
 Extreme to moderate toxicity
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Mowing & grazing will help control annual
weeds, but perennials continue to grow from
rootstocks





Perennials cannot be controlled w/out a long term
plan and can persist for many years
Mowing along w/ rotational grazing will provide fairly
good control, and keep grass competitive
What are some herbicides that would provide
good control of perennials? Rates?
Restrictions?
Proper weed ID is critical
Application timing also important
Unit 3: Weed Control for Small
Grains, Pasture, & Forage


Treatments will vary from spring for annuals
and biennials to summer during growth for
perennials, even fall application may be best
Forage Legumes

Weed pressure can reduce the vigor of legume
stands



Reduce forage yield
Reduce forage quality
Establishment


Prepare a firm, weed-free seedbed
Select an appropriate variety and follow nutrient
recommendations
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

If seeding w/ a companion crop:
 Seed companion crop at half rate for grain production
 Legume will have better chance to survive w/ less
stress

If seeding w/out a companion crop:
 Use appropriate herbicides for weed control

Preplant-Incorporated Herbicides

Balan, Eptam, Treflan




Preplant incorporation for legumes not seeded w/ a
companion crop
Control most annual grasses and some broadleaves
Must be thoroughly incorporated to prevent loss
Apply shortly before seeding to provide longest
control
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

If weed pressure doesn’t prohibit yield or
quality:




Control w/ herbicide may not be necessary
Simple mowing will help control
Ex. Winter annuals don’t compete after first cutting
hay
Postemergence Herbicides



Poast Plus, Select, Pursuit, Raptor
Control for annuals and perennials
Established Legumes

Best option is to maintain a dense, healthy stand
Unit 3: Weed Control for Small
Grains, Pasture, & Forage


Chemical weed control often limited to late fall or
early spring applications
Late fall application
 Apply after the last cutting taken
 Weeds are small and susceptible

Grass weeds are very hard to control in established
alfalfa
Chickweed
Downy Brome
Cheat
Common
Lambsquarters
Crabgrass
Fall Panicum
Foxtail
Poison Hemlock
Henbit
Johnsongrass
Pigweed
Quackgrass
Shattercane
Smartweed
White Snakeroot
Yellow Nutsedge
Unit 3: Weed Control for Small
Grains, Pasture, & Forage

Unit 3 Assignment

Identify 5 specific herbicides for control of
annual and perennial weeds in both pasture
and legume forage programs





Active ingredient
Application rate
Timing of application
Withholding time for grazing, hay, or meat
Classify the weeds in this slideshow as annuals
or perennials