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Weeds > Herbicide History week 6 > Flashcards

Herbicide History week 6 Flashcards

1
Q

What is a herbicide

A

Any agent that controls Weed
Mostly synthetic but some natural
$25 billion sold annually

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2
Q

Group I

A

Phenoxys
1st used
2, 4 D
Twisting

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3
Q

Group C

A

Pre emergent
First to develop resistance
Choloris

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4
Q

Systemic Herbicide

A

Travels through plant in 7-10 days

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5
Q

Contact herbicides

A

Burn down of folliage due to contact 1-3 days

Paraquat and diquat

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6
Q

Group B

A

Highly specific
Selective
g/Ha
Herbicide resistance

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7
Q

Attributes of successful herbicides

A 
Reliable and cost effective
Safe
New mode of action
Low use and low cost
Safe to enviro and crop and people
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8
Q

Organic Herbicides

A

Plant Based ingredients
Not soil persistant
Low specidfic activity = expensive and not effectiv

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9
Q

Methods of breakdown of herbicides

A

By soil
Chemical breakdown - UV exposure, sun, hydrolysis
Then moves to site of action - cell wall, enzymes, cellular machinery

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10
Q

Group D signs

A

Stunted Roots

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11
Q

Susceptable

A

Population controlled by a relevant rate of herbicide

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12
Q

Resistance

A

Commercial failure of herbicde on a population previously controlled by herbicide

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13
Q

Tolerant

A

SPecies not affected by herbicde

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14
Q

Target Site resistance

A

Modification of the site of action preventing the herbicide from binding

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15
Q

Non-target site resistance

A

Due to other mechanisms

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16
Q

Forms of Non target site resistance

A

Enhanced Metabolism
Reduced Uptake
Altered rate of translocation

17
Q

Plant Factors of resistance

A 
Genetic Variation
Seed production - more seed = more resistance
Gene dominance or resistance
Inc. geneations/yr = inc. resistance
No Dormancy = inc. resistance
18
Q

Chem factors of resistance

A

Target site altered
Only one mode of action
Herbicide persitance- resistance quicker in post emerg
Longer persistance or herb = more generations exposed
Efficacy - better the herb the quicker resistance

19
Q

Spraying below recommended rate

A

Inc. effective rate

20
Q

Human Factors of resistnace

A

Repetition of herb
Application efficiancy
Other controls used

21
Q

Why is ryegrass so resistant

A

Large numbers/areas 20000/m
Sown as pasture plant
Cross pollinated inc. genetic variability
Highly competitive
Short seed bank life
High initial frequence of resistance genes

Weeds (12 decks)

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