Weed Science (Lecture)

Question 1

Paraquat

Answer 1

ETC thief, characterized by rapid death upon foliar application. Post-emergence or pre-planting control

Question 2

Diquat

Answer 2

ETC thief, characterized by rapid death upon foliar application. Post-emergence or pre-planting

Question 3

Triazine

Answer 3

ETC blocker. Applied to soil as a persistent pre-emergence herbicide. Affected plants turn yellow, then brown. Starts in leaf margin (xylem transport) and builds up in veiny pattern.

Question 4

2,4-D

Answer 4

Phenoxy-type growth hormone regulator. Mimics IAA. Foliar application. moves in phloem to target growing areas. Post-emergence. Symptoms are twisting leaves, abscission, odd growths, loss of apical dominance.

Question 5

Dicamba

Answer 5

Benzoic acid growth hormone regulator Mimics IAA. Foliar or soil application. moves in phloem to target growing areas. Pre and post-emergence. Symptoms are twisting leaves, abscission, odd growths, loss of apical dominance.

Question 6

Chloramben

Answer 6

Benzoic acid growth hormone regulator. Mimics IAA. Soil application. moves in xylem to target leaves Pre-emergence. Symptoms are dying seedlings.

Question 7

Picloram

Answer 7

Phenoxy-type growth regulator. Soil-applied extremely potent and persistent. Kills seedlings before emergence.

Question 8

Trifluralin

Answer 8

Dinitroanline type Mitotic Inhibitor. Soil applied pre-emergence herbicide. Inteferes with microtubule polymerization. Root and cell swelling, seedlings do not grow. Warning: Does not work on oily seeds.

Question 9

Asulam

Answer 9

Carbamate-type herbicide. Mitotic Inhibitor. Soil-applied, inhibits sprouting

Question 10

CIPC

Answer 10

Carbamate-type herbicide. Mitotic Inhibitor. Soil-applied, inhibits sprouting

Question 11

EPTC

Answer 11

Thiocarbamate-type Mitotic Inhibitor. Pre-emergence soil herbicide. Blocks production of Acetyl-CoA to prevent growth of first leaf.

Question 12

Triallate

Answer 12

Thiocarbamate-type Mitotic Inhibitor. Pre-emergence soil herbicide. Blocks production of Acetyl-CoA to prevent growth of first leaf.

Question 13

Cycloate

Answer 13

Thiocarbamate-type Mitotic Inhibitor. Pre-emergence soil herbicide. Blocks production of Acetyl-CoA to prevent growth of first leaf.

Question 14

Roundup

Answer 14

Glyphosate-type Amino Acid Biosynthesis inhibitor. Foliar-applied only systemic herbicide, moves through phloem. Characterized by wilting & wrinkling in leaves, new growth affected first, chlorosis/necrosis.

Question 15

Chlorsulfuron

Answer 15

Amino Acid Inhibitor. Foliar/soil? Applied as a pre-emergence herbicide. Blocks conversion of pyruvate into proteins.

Question 16

Wild Oat Persistence Strategy

Answer 16

1. Variability in seed dormancy
2. Co-adaptation of seed dormancy and viability
3. Modification of dormancy by environmental factors

Question 17

Wild Oat Control Strategies

Answer 17

Wild oats and seedlings emerge at different times
Cultivation promotes wild oat germination
Competitive advantage given to crop

Question 18

Knapweed Persistence Strategy

Answer 18

Large & easy to maintain seed bank
Difficulties in predation
Strong competitor due to deep roots & allelopathy

Question 19

BC Approach to Control of Knapweed

Answer 19

Containment via education & control + biological control using 3 species.

Question 20

Conditions for livestock poisoning by weeds

Answer 20

• lack of other forage due to overgrazing, grazing pressure due to drought
• recent herbicide applications
• Specific plant life cycles or physiological reactions to climate

Question 21

Eurasian water milfoil persistence strategy

Answer 21

Vegetative reproduction by stolon and fragmentation + seed production to enable dormancy.
High competitive ability in water

Question 22

Eurasian water milfoil control strategies

Answer 22

Harvesting
Water drawdown
Bottom barriers
Biological control
Rototilling