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122 Cards in this Set
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to select the best herbicide for a particular weed, we need to understand how herbicides ...
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are applied
are absorbed kill can be used to kill only the target weed and NOT the good stuff |
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HERBICIDE CLASSIFICATION
****************************** herbs are either applied ... |
directly to the plant foliage
to the soil where germinating seedlings and weed roots or shoot absorb the herbicide. |
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"Foliar applied" herbs are sprayed onto ...
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the foliage of plant, leaves stems shoots buds.
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What is SOIL APPLIED herb?
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soil applied herbicides
granules sprays Both granules and sprays go into the soil Both granules and spray get incorporated into soil by: water (irrigation, rain) mechanical (rotary tillage, raking) Soil herbicides target germinating seedlings inhibit their growth OR absorbed by the roots and translocated to shoots and leaves killing the plant. |
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These are common herbs:
Basagran BASA GRAN Roundup 2,4-D Gallery Casoron Preen First 3 are Foliar app. Next 3 are soil app. But what kind of action? |
These herbs have:
Basagran = Contact Roundup = Translocates 2,4-D = Translocates Gallery = Inhibits seedling Casoron = Translocates Preen = Inhibits seedling |
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Plants absorb herbs into their tissue but herb movement and action can differ depending on ...
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chemical used and the target plant.
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Herbicides only need to kill what?
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Annual & Biennials
herbicide need only kill the shoots Perennials Herbicides need to move to roots to kill |
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CONTACT HERBICIDES
contact herbicides are foliar applied (think about it duh) They only kill plant parts they contact directly. They don not what? |
move thru a plant
they kill any contacted green areas on plant ie leaves stems shoots This can include tree and shrub bark that is thin or green. This can include tree and shrub bark that is thin or green. Ruptures cell membranes so it leaks out. ***************************** (action is quick, few hours to few days) |
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Contact herbicides require uniform spray coverage over the ...
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entire weed
ONLY AREAS THAT THE CHEMICAL CONTACTS DIES! |
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These weeds require uniform spray coverage over the entire weed. Only the areas that the chemical contacts ...
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die.
So if just a drop gets on a leaf, it will show a dead spot there. 'only the plant tissue to which they touch' |
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Why are contact herbicides not normally used to control perennials?
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Perennials have roots systems the contact herbicide can't get to to kill the plant. The contact herb will wipe out the leaves but the plant is still alive. You CAN repeately put it down and eventually kill perennials. So?
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so not too many contact herbicides are used in turf and ornamental beds.
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Why are few contact herbicides used in turf and ornamental weed control?
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contact herbs will work on targeted annual weeds but only kill the shoots of perennial weeds, leaving underground ro resprout.
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True or False
Contact Herbicides are used around turf and ornamentals |
False
Contact herbicides are NOT used around turf and ornamentals because contacts are designed to only kill the foliage it comes in contact with, Not designed to seek out the root systems ****************************** |
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TRANSLOCATED HERBICIDES that are foliar applied
****************************** are sometimes referred to as |
SYSTEMIC HERBICIDES
absorbed thru foliage or shoots & move thru plant (use water & sugar pipelines) |
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Translocated or foliar applied herbs are referred to as systemic herbs, are absorbed thru foliage or shoots and move thru plant. How?
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move w/ the water and sugar transport system to roots or growing tip of plants.
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How can you see or tell a systemic foliar applied herbicide is killing a plant?
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systemic foliar applied herbs use plants water/sugar pipelines to move to where the plant is growing so shoot tips and roots will get the poison. You will see shoot tips getting it but not roots.
Good control with Foliar systemic herbs requires: actively growing plants (if plants are stressed, not moving water/sugar, it don't work) |
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Translocatable herbicide sprayed on a leaf will move how?
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mov out to leaf tips OR
mov thru leaf to plant stem and then up or down plant |
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Because translocated chemicals move within a plant, they kill perennial plants and do or donot need to be applied uniformly?
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since some systemic (translocated) foliar applied herbicides work the way they do, they don't need to be uniformly applied for good results.
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MOST foliar applied herbicides used in turf and ornamentals are what?
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translocated herbicides.
2,4-D glyphosate dicamba MCPA |
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SEEDLINGS and ROOT INHIBITION HERBICIDES
seedling / root inhibitor heribicide is soiled applied is also called a? **************************** |
residual herbicides.
applied to the soil inhibits cell division or root and shoot growth in germinating seedlings. Cool, seeds can't push up shoots and roots by inhibiting cell division |
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herbs applied to the soil surface must move to weed's root zone or the zone where weed seeds germinated to become available for absorption by weeds. duh.
How does this herb get into the plant once there in the soil? |
the herbicide must be in soil/water solution for uptake. rain will get this to happen or watering the fields, or mechanical w/ a tillage, or by just using direct soil injection. (don't apply herb until soil is wet)
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Discussion is
SEEDLING/ROOT INHIBITION HERBICIDES soil applied. These chemicals stay active in the soil for extended periods of time. This is referred to as: RESIDIUAL ACTIVITY Lots of things more than the chemical influence residual activity. What are they? *************************** |
rate of application
soil type rainfall susceptiblity of the weed LONG TERM RESIDUAL herbicides can stay hot longer than a year |
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Soil residual herbs need to be placed correctly or INCORPORATED to become active.
So where should the soil residual herbs be to be active? |
where the weed's seeds or roots are!
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Also be aware not to place the soil residual herbicide where it can come into contact with good vegitation roots and shoots!
Soil residual herbs have little effect on plants when sprayed on foliage. so how does it work? |
the main effect occurs when it is absorbed by underground shoots or roots in the soil
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HERBICIDE SELECTIVITY
whats makes chemical control better that tillage ops? |
its selectivity!
control weeds while doing little or no damage to disirables. This is called SELECTIVE HERBICIDES |
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NONSELECTIVE HERBICIDES kill what?
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almost all plants, weeds and desirables.
A plant is either: SUSCEPTIBLE (injured/killed) TOLERANT )survives w/o injury) |
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WHATS AN ADVANTAGE TO USING HERBICIDES OVER TILLING UP WEEDS?
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HERBICIDE CAN HIT JUST THE TARGET WEEDS. TILLAGE IS ALL PLANTS. THIS IS USING
SELECTIVE HERBICIDES |
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SELECTIVE HERBICIDES depend:
kind of chemical how and when applied what enviro conditions are How do you lose selectivity? |
applicator mistakes
applying herb when desirables are under stress just getting it on desirables at vulnerable growth stage |
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TO MAKE A HERB SELECTIVE TAKES MORE THAN JUST THE CHEMICAL! LIKE HOW?
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MANY INTERRELATED FACTORS
THE KIND & AMT HERB USED HOW & WHEN IT IS APPLIED UNDER WHAT ENVIRO CONDITIONS |
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CLOSELY RELATED PLANTS MAY RESPOND DIFFERENTLY TO APPS FROM SAME SPRAYS. BUT???
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YOU MAKE A MISTAKE USING THIS STUFF AND SELECTIVITY IS LOST!
(THE DESIRABLE PLANTS MIGHT BE UNDER STRESS OR IN VULNERABLE GROWTH STAGE |
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WE MUST UNDERSTAND REASONS HERB SELECTIVITY TO AVOID ...
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INJURING DESIRABLE PLANTS
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THERE ARE 2 GROUPS OF SELECTIVITY FACTORS. WHAT?
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PLANT FACTORS
CHEMICAL & APP FACTORS |
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PLANT FACTORS w/ SELECTIVIT
You squirt roundup on some plants and one dies but another doesn't? why? |
the combination of a plants structure and physiology (chemical makeup of the plant)
again structure physiology |
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STRUCTURE
FOLIAR APPLIED HERBS MUST REMAIN ON THE LEAVES AND STEMS TO ENTER THE PLANT. SO? |
THE PLANT'S
LEAR ANGLE SIZE HAIRINESS THICKNESS OF WAX AFFECT RETENTION AND ABSORPTION OF FOLIAR HERB APPS. SO, PLANTS W/ UPRIGHT LEAVES, HAIRY LEAVES, HARD TO WET LEAVES OR WAXY LEAVES LESS TO RETAIN HERB SPRAY. THESE STRUCTURES HELP MAKE PLANT EITHER SUSCEPTIBLE OR TOLERENT |
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PLANT PHYSIOLOGY
SELECTIVITY DEPENDS ON HOW PLANT RESPONDS TO HERB SPRAY AFTER IT ENTERS IT. BUT TO KILL THE PLANT WHAT? |
THE HERB MUST INTERFERE WITH VITAL PLANT PROCESSES.
HOW ABOUT THIS...CERTAIN PLANT PROCESSES CAN ALTER HERBS INTO HARMLESS CHEMICALS! |
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WHAT IS IT CALLED, THE PROCESS OF CHANGING A ENTERED CHEMICAL INTO SOMETHING HARMLESS?
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METABOLISM
DEXTOXIFICATION BREAKING DOWN PRODUCTS INTO NEW MATERIALS. IF A PLANT CANNOT METABOLIZE HERB FAST ENOUGH, IT INJURES OR KILLS IT |
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SUSCEPTIBILITY VARIES W/ PLANTS. LABELS WILL TELL YOU WHAT PLANTS ARE TOLERENT AS WELL AS WHAT HERB WILL KILL!
SO WHAT? |
CHECK THE LABELS FOR USE ON TURFGRASSES AND ORNAMENTALS!
GOOD GRASS VARY IN THEIR SELECTIVITY TO HERBS !!!! SO YOU SPRAY A LAWN W/ DIFERENT GRASSES AND WOW! SOME OF IT DIES!!! |
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CHEMICAL & APPLICATION FACTORS
lots of physical factors affect herb selectivity what? |
how much used
the formula used when its applied where its applied addition of Adjuvants |
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APPLICATION RATES
some herbs are selective at lower rates of apps. BUT... when that same herb is applied at HIGHER rates ...? |
the herb can become
NONSELECTIVE so there is a narrow margin of safety. this marjin of safety is difference b/t control and disaster to good plants |
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FORMULATION
its not only the active ingredients but what? |
also HOW herb is formulated influences its selectivity
a granular and liquid may have same actvie ingredients but not the same selectivity adavantage. |
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EX of a Formula can have same active ingredient but act different.
grunular formula can make a herb bounce and roll off a good plant and go into the soil. this then gets this formula to the seedlings IN the soil! A liquid formula w/ same active ingredient could ... |
not have the same selectivity advantage like this bounce and roll so can harm good plants as well as bad weed seedlings
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(continued discussion about Herbicide Selectivity)
APPLICATION TIMING many herbs only work at certain times! the label will state this. why? |
time of app related to plant growth stage of DESIRABLE plants or weeds, back and forth. Need to know label terms as they relate to app timing
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PREPLANT TREATMENT is ?
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any app made b/f seeding or transplanting desirable plants or turfgrass.
The Preplant-soil-incorporated is a common treatment. It mixes herbs into soil where weeds germinate. This is a common app in ag settings. ***************************** (The book showed a picture of a disk sprayer applying herb to the ground which then got disked to incorporate into the soil) |
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don't go to sleep. the discussion is Herb selectivity.
A herbicide thats volatile means? |
it will go to a gas form,
it means evaporate! Photodegradable means same thing but the point is: either photodegradable or volatile, it must be immediately incorporated into the soil by water or machanical ways before evaporating away |
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whats PREEMERGENCE TREATMENT?
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made b/f weeds emerge!
Most commonly used herb in ornamental & crabgrass control in turf is preemergent **************************** |
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Preemergents are applied to the soil and are active on ...
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germinationg seedlings.
they do NOT affect est plants IF handled properly. Landscape guys use this stuff when planting woody ornamentals, ground cover, beddign plants, veetable gardens |
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HERBICIDE ZONE is?
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this is SELECTIVITY working by keeping herb in weed zone above desirable roots.
pp 9 |
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There is techniques also where you can use nonselective preemergent herbs as selective herbs if you do it right. Give EX
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use the nonselective herb in the soil where weed roots or seeds are but NOT where desirable roots are not growing. So this selectivity depends on root depths of plants & weeds. To do this, remove shallow roots or germinating seeds from the deep rooted area, select a herb that remains near the soil surface where it only gets to the weeds.
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Soil condition in important here too. some herbs work better just on clean soil. Stuff in the way like plants, leaves, mulch, etc do what?
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this stuff can bind w/ the herb and reduce its ability to move into the soil
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POSTEMERGENCE TREATMENT
when is postemergence treatment done? |
after weeds come up (emerge)
*************************** which is when desirables are also growing as well. Postemergence can be either nonselective or selective in action, handle with care! |
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ACCURATE PLACEMENT
accurate placement of nonselective herbs can help what? |
minimizes injury to desirable plants.
1) place herb in soil above or below root zone as discussed 2) keep herb off desirable veg when spraying (EX spray hitting between rows of corn hitting just the weeds, spray is not getting on the cron stalks. this is a directed spray. |
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HERBICIDE PLACEMENT
equipment that can shield direct spray wiper roller treatments This is all referred to as DIRECTED SPRAYS which limit contact w/ desirables. |
Wiper treatment is applying contact OR translocated herb directly on weeds. WIPER.
Wicks do this, using rope, rollers covered w/ carpet or absorbent pads soaked w/ herb. This stuff gets directly wiped on the weeds. It gets wiped off AND doesn't touch the good plants. |
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MODES OF HERBICIDE ACTION
**************************** All herbicides control plant growth but do it differently. 6 ways to control plant growth, 6 modes of action for herbicides. growth regulators synthesis inhibitors lipid inhibitors seedling growth inhibitors photosynthesis inhibitors cell membrane disrupters |
HERBICIDE MODE OF ACTION
how herbicides work on weeds |
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HERBICIDE GROWTH REGULATORS DISRUPT WHAT?
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HORMONE BALANCE AND PROTEIN SYNTHESIS! Cause growth abnormalities.
2,4-D is a plant growth Regulator First successful systemic herbicide ever developed Causes uncontrollable unsubstanual curling growth of the leaves and stem curl over and kills the plant Growth regulators selectivity kill broadleaf weeds in grass! This means it has to be systemic, it translocates so its not a contact herbicide but does enter thru leaves. |
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How does grass tolerate you putting a growth regulator on it when you treat the lawn for weeds?
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Grass can usually tolerate growth regulator chemicals, but injury can occur if applied at the wrong growth stage or at hi rates!
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Whats a early symptom of a plant getting zapped by a growth regulator herb?
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EPINASTY epinasty
abnormal bending or twisting of shoot tips. |
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How does most growth regulators enter a plant?
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thru the leaves, but there is of course some root uptake.
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The AMINO ACID synthesis INHIBITOR prevents
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production of amino acids
building blocks for proteins and plant development. |
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Herbicides that mode of action
AMINO ACID SYNTHESIS INHIBITORS prevent plant making proteins, needed for normal plant development. ****************************** Whats a famous product that uses Amino Acid Synthesis as a heribicide mode of action? |
ROUNDUP
Look for symtoms like stunting of plants yellowing (chlorosis) purpling of leaves |
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Lipid Inhibitors do what?
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prevent production of fatty acids crucial to cell membranes and new growth.
***Lipid Inhibitors used against annual and perennial GRASSES while broadleaf plants are tolerant. ****************************** |
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What are lipid inhibitors good on?
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annual and perennial grasses
but broadleaf plants are tolerent. Symptoms include: yellowing stunting browing of leaves |
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SEEDLING GROWTH INHIBITORS
*************************** They interfere w/ new plant growth, stopping normal seedling root or shoot devel. How MUST SEEDLING GROWTH INHIBITORS be used? |
**Must be applied to the soil to act on emerging weed seedlings.
You'll see stunted swollen roots on emerging seedlings |
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We are still discussing
MODES OF HERB ACTION ************************** There is a PHOTOSYNTHESIS INHIBITOR what does this do? |
interferes w/ photosynthesis (conversion of water and carbon dioxide to sugar in the presence of sunlight)
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what is the result of PHOTOSYNTHESIS INHIBTORS?
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buildup of toxins.
Root & foliar absorbed products translocate Nitrile & benzothiadiazole do not translocate; apply them postemergence for contact action. |
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CELL MEMBRANE DISTRUPERS
EXCLUSIVELY CONTACT HERBS destroy plant tissue by rupturing plant cell membranes. a contact herbicide. Excellent for? |
foliage burndown
control of annual weeds Cell Membrane Distrupters have NO mobility MUST be applied postemergence ***************************** rapid wiliting then browing (necrosis) |
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ENVIROMENTAL INFLUENCES ON HERBICIDE AVAILABILITY AND UPTAKE
the enviroment influences herb activity what 2 ways? |
herb mut be available for absorption by the weed
the enviroment influences how activily plants grow. how activily they take up the herbicide. |
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Enviromental factors like soil and climate affect herb availibitity.
****************************** Again soil and climate affect ... |
herb availibility.
temps humidity precipitation are dominant factors affecting herb performance. |
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(discussion is Enviro Influences on Herb Uptake)
SOIL FACTORS different soils interact differently w/ uptale of Herbicides like: Adsorption! What about this? |
Adsorption (this is review)
ionic bonding to sand silt organic material clay Point is, Herbicide molecules adsorbed to soil are INACTIVE Therefore roots & seedlings can only absorb herbicide molecules present in soil water! Molecules tightly bonded to soil cannot be absorbed OR degraded by bacteria! |
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Does strength of binding b/t herbicide molecules and dirt affect herbicide movement or lack of in soil and root absorption?
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Yes
This discussion goes into sand silt clay organic shit |
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(sandy soil has few adsorptive sites so herbicides LEACH thru. Soil w/ clay and organic hold herbicides)
We will be doing either: soil residual work or selective weed control But KNOW THE SOIL DUDE! Look at it! Read the label for directions pertaining to soil conditions |
Review:
Most Herbs will leach thru sandy dirt diluting herbicide (Leaching can damage deep roots too!) Selectivity is lost in sandy stuff...So...guess what? hi concentration of herbicide leachs through to a depth where if kills everything planted! Loam & silt hold herbicide near soil surface. Guess what? Deep rooted plants don't get hurt and weeds get killed!!! Organic shit ties up so much herbicide at soil surface it dont get to weeds. So use higher rated herbicide in organice soil. Clay ranges b/t silt and organic in herbicide bonding |
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Herbicides vary in binding properties. Herbs that lack ionic properties tend to leach thru soil. The strength of binding b/t herb and soil ...
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strongly affects herb movement or lack of movement in soil and availibility for root absorption.
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SOIL TEXTURE
texture means ... |
size of the soil particile
so different soil types have different capacities to bind herbs. EX sand is coarse no charge sites so sand vrs soil, sand has less surface area than silt or clay. so less adsorption sites! (for herb to bond to) |
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Silt is intermediate in surface area per given volume of soil. So?
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So silt has more adsorptive sites than sand but FEWER than clay or organic matter
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sand is coarse
silt in intermediate Clay is fine. Has large surface area per given vol of soil...so ? |
more adsorbption sites than sand or silt. More ionic bond sites in clay. look at the picture. Clay moelecules lined up like soldiers, have lots and lots of Adsorption sites compared to sand. So,
herb will stick, will work better with clay than sand or silt. |
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Also, organic stuff is way more adsorptive w/ sites to tie up both + and - charged herbs. Organic matter is like a magnet and has ...
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more influence on herb adsorption than any other factor in the soil..
++++++++++++++++++++++++++++++ |
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So, since sand has few adsoption sites, most herbs do what?
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leach thru a sandy profile. Soils w/ clay or organic stuff tie and bond herbs!
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So when we use herbs we HAVE to know what kind of soil were dealing with! The soil properties. So what?
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read the label as they pertain to soil you got.
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AGAIN
most herbs readily leach through sandy soils, which ? |
dilutes the herbicide.
By the way, leaching injures deep roots. think about it. Also leaching dilutes the herb reducing weed control. |
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Selectvivity is all messed up in sand or loamy soils. why?
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because a hi concentration of herbs may leach to a depth where it kills both good and bad plants.
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Loam and silt hold herbs near soil surface. so?
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Deeply rooted plants aren't affected. and weeds get zapped.
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Organic soils tie up so much herb near surface that ...
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not enough gets to control weeds! You may need a higher rate of herbicide!
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Herbs applied to soil surface must ....
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move to weed's root zone OR where weed seeds germinate to become avaliable for absorption by the weeds.
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Herb must be present in soil water solution for plant uptake. So?
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you can move herb into the soil by adding water to soil. If not, inject herb directly into soil by soil injection. MOST herbs generally should not be applied until water is or soon goes on it so it goes into the soil.
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Some nonselective herbs (again) may be used selectiviely based on ...
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their placement in the soil. This selectivitiy depends on:
root depths of ornamentals & weeds meaning putting herb in target weeds root zone, not the ornamental root zone. So to remove shallow germnating weeds from deep rooted ornamentals, select herb that remains near soil surface and is avaliable to the weeds. |
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(discussion is Enviomental influences on herbicide avalibility and uptake
CLIMATIC FACTORS include: temp humidity precipitation wind what? |
temps
humidity precipitation wind all influence weed control and enviro safety |
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TEMPERATURES
read label to see if you must monitor the temp outside b/f applying. Do temps matter? |
Label might say do not apply if temp might fall below 40 or above 90 degrees or 90 degrees for the next 3 days.
Why? hi or low temps stress the plants and their ability to tolerate the herbicide! Stressed plants can't do poisons! |
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PRECPIPITATION
rainfall on a newly applied foliar herb can ... |
wash it off, reduce control.
read the label. You will see the rain free interval needed. Rain moves herb into soil. BUT excess rain leachs herb thru past target! |
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Water stressed weeds are less susceptible to foliar applied herb. why?
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wax layer on leaves of water soggy plants, can't uptake herbicide or slow down of plants metabilsm.
THE MORE ACTIVE A WEED IS GROWING, EASIER IT IS TO CONTROL W/ HERB. |
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Humidity
when a plant grows in humid conditions, a foliar applied herb enters the plant ... |
easier and rapidly.
Hi himidity , weed leaf is more succulant and has thinner wax layer (cuticle) |
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WIND
intensifys effects of drought and hi temp stess! What does dry hot weather make a plant do? |
causes leaves to thicken wax layers to harden. This makes it harder for herb to penetrate leaves
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WEED GROWTH STAGE INFLUENCES ON HERBICIDE ACTIVITY
the growth stage of a weed strongly influences ... |
herb uptake and translocation.
Again the growth stage. Weeds develop in 4 stages: seedling vegetative flowering maturity one growth stage is generally most vulnerable to diff weed control stategies! So one stategy failure means do something else during a particuluar growth stage. Either change herb OR increase herb rate. |
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In general, when are plants most susceptible to postemergence herb?
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1)as seedlings when rapid growth takes place
2)in perennials, when rapid growth has ended and the plant replaces exhausted food reserves in the roots! **************************** |
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The seedling growth stage is susceptible in all weeds, annuals, biennials, perennials. Most weeds come from seeds. This is where ... |
the weed is most easily controlled than any other growth stage. Both for mechanical AND chemical control.
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ANNUAL PLANTS
Vegatative: Plants in vegetative state use most of their energy to produce... |
stems leaves and roots.
Control is possible BUT more difficult than at seedling time. So, control in the growth stage takes more herb! |
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FLOWERING
during this period of plant growth, most of weed's energy goes into seed production. This is what? |
the most difficult to kill older annuals w/ chemicals now. Foliar herb apps. at this time MAY prevent seed production.
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MATURITY
***************************** Maturity and seed set completes the life cycle of annals. so ? |
Chemical control at maturity is not effective or practical at this stage.
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So, as the annual gets older, the less ....
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control you have on it when applying a herbicide.
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CONCEPT TO PONDER
if a herb gives 100% control at seed time on annuals, the same herb and rate applied at vegetative state may only give ... |
75% control and
40% during flowering stage SO, making apps at maturity does NOTHING. |
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So for best results w/ tillage and postemergence herbs, control seedlings asap emergenece. why?
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its easiest to kill weeds at this stage. SEEDLINGS
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BIENNIAL PLANTS
takes 2 years to do what annuals do in 12 months. first year, it only forms ... |
rosette and tap root
next year it flowers, matures and dies. |
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BIENNIAL PLANTS take 2 years to do what annuals do in one. so first year the plant forms a basal leaves (ROSETTE) and taproot. 2nd year flowers matures and dies. best time to kill it is as a seedling, Next good time is when it makes the ...
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the rosette. Controls decreases as plant starts to bolt its flower stalk and decreases even further as the plant flowers.
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PERENNIAL HERBACEOUS PLANTS
Because perennials have different growth stages, what? |
control is easiest with perennials at different growth stages, depending on herbicide and weed.
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Like annuals ans biennials, Perennials are easily controlled during seedling stage. How do you control established Perennials?
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Est. perennials require tranlocation herbs into its UNDERGROUND system ie roots rhizomes tubers.
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2 factors to understand for perennial weed control:
plants store sugar in roots at winter. Use sugar in spring to grow shoots, depleting root reserves. what happens in the summer? |
summer and fall, plants restock roots w/ sugars for next year's growth.
this is first thing to know about Perennials |
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What next about Perennials?
Translocated herb move w/ flow of plant sugars! so? |
to move herb into roots, apply herbs when flow of sugars is downward to roots, during summer and fall growth!
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VEGETATIVE
herbs don't do well when the plant is at vegetative stage. It does get better as the plant approaches bud stage. whats happening here? |
Sugars are moving up the stem to new growth so herb isn't getting moved to root system. ah ha! But some herb work during this stage.
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FLOWERING
at this stage plant energy is totally making flowers and seeds. Food is transported to roots. So? |
chemical control is most effective just prior to flowering (bud stage). Glyphosate is most effective during early to midflowering.
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MATURITY
AFter seeds set, flowering parts die off OR become inactive. So? |
most herbs are ineffecive at this Maturity stage. Underground roots and stems are alive thru winter to send new growth up following spring
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FALL REGROWTH
Some Perennials make short shoots in the fall. These shoots are to make more sugar for winter storage. So? |
Hit them w/ herb at this time to get that herb to follow sugar trail to roots. Apply to foliage before killing frost to ensure translocation
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So, w/ Perennials, control is greates at seedling bud early flower and fall regeneration. so?
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control is lowest for perennials during vegetative and mature cycles.
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For the best control of established perennials do what?
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plan herb apps to both:
yearly growth cycles herbicide your using |
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In general, when are plants most susceptible to postemergence herb?
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as seedlings when rapid growth takes place
in perennials, when rapid growth has ended and the plant replaces exhausted food reserves in the roots! |
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The seedling growth stage is susceptible in all weeds, annuals, biennials, perennials. Most weeds come from seeds. This is where ...
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the weed is most easily controlled than any other growth stage. Both for mechanical AND chemical control.
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Control is best with most herbicides during the period just prior to ...
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flowering (bud stage) or
during fall regrowth |
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FLOWERING
during this period of plant growth, most of weed's energy goes into seed production. This is what? |
the most difficult to kill older annuals w/ chemicals now. Foliar herb apps. at this time MAY prevent seed production.
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HERBICIDE TOLERENCE and
RESISTANT WEEDS what is herbicide tolerance? |
herbicide resistance is a recently evolved tolerance!
****************************** Heribicide Tolerance is when a plant is naturally tolerant |
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We know:
Herbicide Tolerence is natural to a particular plant Herbicide Resistance is a recently evolved DNA something resistance to a herbicide (this is BAD) What is Herbicide Suscepitibility? |
Plant is KILLED by herbicide action!!! ah ha!
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HERBICIDE RESISTANCE
similar to tolerence in that weeds survive herb apps. Resistant weeds have evolved ...? |
tolerence to a herb that has been used over and over.
Sometimes that weed is also resistant to other herbs in same family. Herb resistant weeds are increasingly big problem. |
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first reports of herb resistant weeds came in mid 60s. so what do we do now?
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develop new stategies to prenvent resistance development.
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so herb resistance works like this:
you use a herb to kill 100 weeds but one survives b/c its resistant. it goes to seed. you try to kill 100 of those and what happens? |
6 survive that so now you have 6 resistant weeds going to seed! this is how it happens. and you keep throwing same herb on this resistant plants making them even more resistant! so each year control goes down and down. this is because the herb is doing its job BUT the number of resistant plants increases.
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Resistance being developed to herbicides is a big problem!
so there are stategies to minimize development of heb resistant weeds. like what? |
use other methods other than chemical
rotate use amoung herb families do NOT use higher rates when it doens't work 100% Kill ALL the targeted weeds even if you have to stomp on them! Use Herbicide combinations |
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So use procedures BEFORE resistance becomes evident. why?
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once resistance sets in, already large number of resistant seeds are in the soil already! SO once you notice the problem, its there for good
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