Lecture 13 - Group 1-3

Question 1

how many sites of action/mode of actions are there

Answer 1

28 in total (16 used in canada)

Question 2

what mode of action are Group 1

Answer 2

inhibitor of fatty acid/lipid biosythesis

Question 3

what are group 1 used o

Answer 3

control annual grass weeds in broadleaf and cereal crops

Question 4

group 1 only works on ACCase in _______

Answer 4

grasses

Question 5

3 classes of group 1 herbicides/ACCase inhibitors

Answer 5

• aryloxyphenoxy propiontes (fops)
• cyclohaxanediones (dims)
• phenylpyrazolin (dens)

Question 6

chemicals in the fops class

Answer 6

clodinafop - propargyl
diclofop
fenoxaprop-p-ethyl
fluizaprop-p-butyl
quizalofop

Question 7

chemicals in dims class

Answer 7

clethodim
sethoxydim
tepraloxydim
tralkoxydim

Question 8

chemicals in the dens class

Answer 8

pinoxyaden

Question 9

how does the mode of action in group 1 work

Answer 9

it inhibits the enzyme acetyl CoA carboxylase (ACCase), which is essential for the fatty acid biosynthesis production for membranes

Question 10

chlorosis

Answer 10

plant yellowing due to loss of chlorophyll

Question 11

necrosis

Answer 11

localized death of living tissue

Question 12

symptoms of group 1

Answer 12

-chlorosis (mostly on new growth)
- necrotic tissue
- newest leaf pulls out easily

Question 13

2 forms of selectivity

Answer 13

1. enzyme binding affinity
2. differential metabolism

Question 14

dicots have _____ enzyme binding affinity
monocots have ______ enzyme binding affinity

Answer 14

low, high

Question 15

peculiarities of group 1

Answer 15

• phenoxys herbicides reduce translocation and increase metabolism of fops
• not always cross-resistance between fops and dim (but do have cross resistance with new dens)

Question 16

what is the mode of action for group 2

Answer 16

inhibitors of branched chain amino acid biosynthesis

Question 17

what groups work on amino acids

Answer 17

group 2, 9, and 10

Question 18

what does group 2 control

Answer 18

a broad spectrum of grasses and broadleaf weeds

Question 19

t/f: group 2 is the smallest group of herbicides in the world

Answer 19

f, it is the largest

Question 20

do group 2 have persistance problems

Answer 20

yes, some are highly persistent in the soils

Question 21

what makes group 2 so popular

Answer 21

it has low dose chemistry

Question 22

t/f: group 2 has lots of resistance

Answer 22

t

Question 23

how does the group 2 mode of action work

Answer 23

it inhibits the synthesis of branched chain amino acids synthesis, which results in protein breakdown, loss of enzymes for reactions, and no growth

Question 24

symptoms of group 2

Answer 24

• stunting, no growth in newest leaves and cant make new ones
• chlorosis, reddening, and purpling in growing points
• slow plant growth
• internode shortening
• flattened anvil top in flowering parts
• branching in dicots

Question 25

peculiarities in group 2

Answer 25

- very low dose chemistry (creates residue issue) - great concern over resistance - Herbicide resistant crops

Question 26

what is soil persistence influenced by

Answer 26

- moisture - pH - organic matter - temperature

Question 27

_____ pH soils increase persistence of SU (group 2)

Answer 27

high

Question 28

____ pH increase persistence of IMI

Answer 28

low

Question 29

continued use of group 2 can lead to _____

Answer 29

stacking

Question 30

stacking

Answer 30

accumulation of small amounts of reside over time in soil that can cause problems

Question 31

mode of action of group 3

Answer 31

inhibitors of cell division (mitotic inhibitors)

Question 32

what are group 3 also called

Answer 32

dinitroanilines (DNA's) or the yellows

Question 33

types of chemicals in the DNA's (group 3)

Answer 33

trifluralin and ethafluralin

Question 34

what does group 3 work on

Answer 34

it is on selective grass and dicot weed control

Question 35

how is group 3 applied

Answer 35

is pre-emergent, soil applied

Question 36

how does the mode of action of group 3 work

Answer 36

binds to B-tubulin to prevent polymerization to create microtubules, preventing mitosis from occurring (no growth)

Question 37

symptoms of group 3

Answer 37

- germinating and emerging seedlings dont grow - root swelling and inhibition of secondary roots and hypocotyl - club/stubby and brittle roots - some grass may turn purple at base

Question 38

basis of selectivity on group 3

Answer 38

- unclear basis for selectivity - maybe differential due to seed lipid content - grasses based on anatomical differences, herbicide placement, and seed depth

Question 39

how can some cereals avoid control from herbicides

Answer 39

mesocotyl elongation does not put coleoptile node near surface, so it avoids damage from herbicides