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AGR 549 (Weeds) > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What are the 6 different methods of seed dispersal?

A
  1. Mechanical
  2. Wind
  3. Water
  4. Human-aided
  5. Animal-aided
  6. Machinery
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2
Q

What is mechanical seed dispersion?

What are two example plants?

A

The spreading of seeds through “latching” using burs.

  1. Cockleburs
  2. Burdock
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3
Q

What is wind seed dispersion?

What are two example plants?

A

Spreading of seeds by being blown by the wind because they are attached to a pappus.

  1. Dandelion
  2. Canada Thistle
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4
Q

What is water seed dispersion?

What is an example plant?

A

Spreading of seeds by water. They have some manner of flotation like a bladder.
1. Curly Dock

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5
Q

What is human-aided seed dispersion?

What has reduced this?

A
  • Spreading of seeds by humans. This is due to seed contamination during planting.
  • The availability of certified seed.
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6
Q

What is animal-aided seed dispersion?

A

Spreading of seeds by animals primarily through their digestive tracts.

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7
Q

What is machinery seed dispersion?

A

Spreading of seeds by being on machinery and falling off of it during moving and use.

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8
Q

What is the “cardinal” rule of weed management?

A

Always buy and plant clean seed.

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9
Q

(T/F) If a seed passes through an animal’s digestive tract, it reduces but does not eliminate that seed’s viability.

A

True

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10
Q

What are the 6 (causes/contributors) (of/to) seed dormancy?

A
  1. Light
  2. Immature Embryo
  3. Impermeable seed coat
  4. Inhibitors
  5. Oxygen
  6. After-Ripening
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11
Q

What is the metabolic switch that activates seed germination in some weeds through light exposure?

A

Phytochrome

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12
Q

What is the given ratio-equation given to explain how light exposure activates germination?

A

(favors far-red)Pr->

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13
Q

What red light/far red light ratio favors germination?

A

Higher amount of red light than far red light.

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14
Q

(T/F)Tillage can expose enough light to weed seed to induce germination.

A

True

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15
Q

How was light exposure caused by tillage remedied?

A

Night time tillage

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16
Q

___ out of ____ species of weeds exposed to light during tillage germinated because of the exposure.

A

13 out of 17

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17
Q

How does immature embryos cause seed dormancy?

A

Some weeds drop their seed embryo immaturely and they slowly develop while in a state of dormancy.

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18
Q

How does impermeable seed coat cause seed dormancy?

A

Some weed seeds do not allow water or oxygen into it initially. The seed must be scratched or worn/weathered down 1st.

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19
Q

What plants are impermeable seed coats common in?

A

Clovers

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20
Q

What process does is required for crops that have impermeable seed coats before they can be planted and will germinate?

A

Scarification

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21
Q

How do inhibitors cause seed dormancy?

A

They form a chemical/mechanical combination that prevent germination until they’re weathered out of the seed.

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22
Q

How does oxygen cause seed dormancy?

A

Some seeds are too far from the soil surface to recieve enough oxygen for them to germinate. Once they become close enough to recieve the required amount, they will germinate.

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23
Q

How does after-ripening cause seed dormancy?

A

Some embryos (seeds) are mature but must “ripen” before they germinate.

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24
Q

What crop was an example of after-ripening where it caused issue?

A

Hard-white wheat

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25
Q

What were the 3 classes of seed dormancy?

A
  1. Innate
  2. Enforced
  3. Induced
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26
Q

Define Innate Dormancy.

A

The initial dormancy of a seed (all plants have)

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27
Q

Define Enforced Dormancy.

A

Seed has:

  • no water
  • temperature is incorrect
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28
Q

Define Induced Dormancy

A

Variances caused by the seeds living condition like:

  • seed is buried too deep
  • co2 levels in soil is too high
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29
Q

(T/F)Forms of dormancy can change many times before seed germination.

A

True

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30
Q

What was one example plant that switches dormancy forms?

What changes as it changes forms?

A

Buckhorn Plantain

It needs no light in it’s Innate form but needs light in Induced form

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31
Q

What is stratification?

A

When an imbibed seed is exposed to chilly temperatures for various periods of time.

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32
Q

Give an example of a plant changing through all 3 forms of dormancy.

A

Buckhorn Plantain:
Plant was just harvested: Innate
Seed over-winters and temp. is too cold: Enforced
Seed is buried too deep via tillage: Induced

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33
Q

What plant survived and germinated 120 years after being exposed to dormancy?

A

Moth Mullein

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34
Q

What are the 5 forms of weed control?

A
  1. Preventative
  2. Mechanical
  3. Cultural
  4. Biological
  5. Chemical
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35
Q

What is the recommended form of weed control?

A

No single one, but a combination of many is recommended.

36
Q

How does preventative weed control work?

A

By not allowing the establishment of certain types of weeds on your farm to begin with.

37
Q

What is a couple examples of attempts at preventative weed control on large-scales bases?

A
  • Federal Noxious Weed Act

- State Seed Laws

38
Q

What did the Federal Noxious Weed Act do?

A

was enacted to prevent weeds of foreign origin from entering the U.S.

39
Q

What do state seed laws do?

A

Establish list of prohibited weeds for each state. Are set individually by state. Contaminted seed batches containing “banned” weeds on these lists cannot be sold within the governing state.

40
Q

What are 5 weeds on the KY State Noxious Weed list?

A
  1. Canada Thistle
  2. Johnsongrass
  3. Balloonvine
  4. Quackgrass
  5. Purple Moonflower
41
Q

(T/F) You can petition the KY Ag Council to force your county to control weeds on private property?

A

True

42
Q

What were 3 types of mechanical control mentioned?

A
  1. Tillage
  2. Mowing
  3. Handhoeing
43
Q

What 2 types of weeds are better controlled by tillage?

A
  • Biennials

- Simple Perennials

44
Q

What 2 types of weeds are made worse by tillage?

A
  • annuals

- creeping perennials

45
Q

The soil should be _______ for tillage to be the most efficient.

A

dry

46
Q

_____ is critical for tillage to be successful in weed control of creeping perennials.

A

timing

47
Q

What is an example of timing being critical for controlling creeping perennials?

A

Johnsongrass

48
Q

(T/F) Repeat tillage is often needed.

A

True

49
Q

What is the “ideal sequence of events” for tillage?

A
  1. There is a period of warmth and moisture
  2. Weed emergence
  3. Till
  4. Dry Period
  5. Warmth and moisture
  6. more weed emergence
  7. till
  8. dry period
50
Q

Total dependence on tillage reduces chances for _______.

A

early planting

51
Q

____________ can be an effective addition to weed control practices where tillage has been conducted.

A

Selective cultivation

52
Q

What is tillage?

A

The mechanical mixing of soil.

53
Q

What is mowing?

A

The trimming of plants growing mechanically.

54
Q

What are the 2 ways mowing aims to control weeds?

A
  • prevents seed formation

- depletes underground food sources

55
Q

____ mowing is required.

A

repeat

56
Q

Canada thistle seed is viable ___ days after pollination. Shattercane seed is viable ____ days after pollination.

A
  • 8

- 10-15

57
Q

Mowing is most effective when combined with a ___________.

A

competitive crop

58
Q

What is the most economical system of weed control?

A

Tillage combined with chemical control.

59
Q

(T/F) Tillage is essential to crop production.

A

False as proven through no-till/min-till

60
Q

What is no-till?

A

Planting into chemically eradicated cover crop.

61
Q

What is primary tillage?

How deep is it?

A

the initial breaking and disturbance of the soil.

6”

62
Q

What are 3 implements of primary tillage?

Which is the most and which is the least common currently?

A
  • moldboard plow-least common
  • chisel plow-most common
  • heavy disk plow
63
Q

What is secondary tillage?

A

Is follow-up tillage after primary tillage has been performed. It is done to prepare the seed bed.

64
Q

What are 5 implements of secondary tillage?

A
  • field cultivator
  • disk harrow
  • rotary hoe
  • spring tooth harrow
  • cultipacker
65
Q

What is interrow cultivation?

Happens in this example crop:

A

light tillage between crop rows to control weeds.

Tobacco

66
Q

What is nighttime tillage most effect against?

What were the 3 specific example plants?

A

Small broadleaf weed species

  • Pigweed
  • Smartweed
  • Wild Mustard
67
Q

Is nighttime more fitting as a primary or secondary tillage?

A

Secondary

68
Q

What is conservation tillage?

A

Any type of tillage that leaves at least 30% of the soil surface covered with crop residue after harvest.

69
Q

What are 3 examples of conservation tillage?

A
  1. No-till
  2. Minimum-till
  3. Strip-till
70
Q

What is the issue with night tillage?

A

Is expensive because of glasses required and doesn’t help with all weeds.

71
Q

What were the 4 “other” types of mechanical weed control?

A
  • Mulch
  • Flooding
  • Fire and heat
  • harrington seed destructor
72
Q

How does the harrington weed destructor work? How effective is it?

A

Catches chaff out of back of combine and turns everything that passes through to powder including weed seed. Is very effective.

73
Q

What is downside to seed destructor?

A

extremely expensive

74
Q

What are some advantages of no/min. till?

A
  • prevents soil erosion
  • improves soil structure
  • better water infiltration rates
  • less limitations due to soil moisture (b/c it holds moisture better)
  • lower cost because of lower energy needs to utilize
75
Q

What are some disadvantages of no/min. till?

A
  • increased problems with perrenial weeds
  • lower average soil temps in spring delay planting
  • more insect/disease pressure
  • greater management skills needed
76
Q

What are some disadvantages of tillage?

A
  • causes soil erosion
  • untimely rainfall can delay
  • deleterious effects on soil when worked wet (clodding, ruts, etc.)
77
Q

What are some advantages of tillage?

A
  • easier (skill-wise) than no-till
  • Better control of simple perennials
  • warms soil quicker in spring
78
Q

What are 3 methods of cultural weed control?

A
  • planting smother crops
  • planting competitive crops
  • utilizing crop rotation
79
Q

What is a smother crop?

What are 2 examples?

A

a solid-seeded crop that is vigorous and thick and can inhibit weed growth.

  • Wheat
  • Alfalfa
80
Q

What are competitive crops? What are 2 determining factors of competitive crops?

A

Crops that canopy quickly.

  • plant pop.
  • row width
81
Q

How does crop rotation help control weeds?

A

Every crop has characteristic weeds that grow along with it. Rotation can help control buildup of these weeds.

82
Q

What is allelopathy?

A

It is when one plants produces toxins and puts them into the ground around it to injure or kill surrounding plants and reduce its competition.

83
Q

What are two plants that are allelopathic:

A
  • Walnut Trees

- Quackgrass

84
Q

What are two cover crops that have shown to be allelopathic:

A
  • Wheat

- Rye

85
Q

What herbicide was isolated from an allelopathic plant?

A

Mesotrione (callisto)

AGR 549 (Weeds) (3 decks)

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