Lecture 15 - Group 9

Question 1

mode of action of group 9

Answer 1

inhibitors of aromatic amino acids

Question 2

what is the only chemical in group 9

Answer 2

glyphosate

Question 3

what is the most widely used herbicide on the planet

Answer 3

glyphosate

Question 4

what kind of weeds does glyphosate (group 9) control

Answer 4

non selective, so it works on both annual and perennial grass and broadleaf weeds

Question 5

grasses are ______ susceptible than broadleaves to group 9/glyphosate

Answer 5

more

Question 6

how many different salts is glyphosate supplied as

Answer 6

4

Question 7

what do you want to avoid when using glyphosate and how can you fix it

Answer 7

using hard water, as it can deactivate herbicide prior to spraying
AMS can overcome this problem

Question 8

how does group 9 mode of action work

Answer 8

works on shikima pathway and inhibits EPSP synthase, which is essential in creation of aromatic amino acids, and cause buildup of toxic intermediates and blocks formation of cytochrome and chlorophyll a

Question 9

symptoms of group 9

Answer 9

• see symptoms on newest leaves
• yellowing in growing point
• growth ceases quickly
• necrosis in 1-3 weeks
• leaf twisting sometimes
• purpling and yellowing

Question 10

selectivity of group 9

Answer 10

• timing of application can influence selectivity
• have glyphosate resistant crops
• cuticle thickness

Question 11

2 main mechanisms of resistant weed biotypes

Answer 11

• altered target site
• reduced translocation

Question 12

how many species have developed resistance to glyphosate

Answer 12

32 species

Question 13

mode of action of group 10

Answer 13

inhibitors of glutamine synthetics

Question 14

group 10 herbicides

Answer 14

glufosinate ammonium

Question 15

what is group 10 used on

Answer 15

non selective, contact herbicide, but is weak on perennial weeds

Question 16

how does group 10 mode of action work

Answer 16

bind to active site of GS and cause accumulation of excess of ammonia and deplete amino acids that use N. Also indirectly inhibit photosynthesis due to lack of glutamine

Question 17

symptoms of group 10

Answer 17

• spotted bronzing
• chlorosis and wilting in 3-5 days
• necrosis in 1-2 weeks
• symptoms increase from bright sunlight, high humidity, and moist soil

Question 18

basis of selectivity of group 10

Answer 18

almost non-selective, as it is metabolized in all plants but not quickly enough to avoid toxicity

Question 19

peculiarities of group 10

Answer 19

• control is reduced at less than 10C, low humidity, fog, or dew
• has herbicide resistant crops
• relatively low risk of resistance