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DHRT3170 WEEDS > Exam > Flashcards

Exam Flashcards

1
Q

What do weeds compete for? What is allelopathy?

A

4 things - light, water, nutrients, and space.

Allelopathy - the production of phytotoxic compounds that reduce the germ of other plants.

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2
Q

What is the key environmental condition required for biennial plants to begin reproductive development? How does this relate to time of control?

A

30 days of below 0 degrees
Control in the fall before this cold period

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3
Q

5 types of vegetative reproductive structures for creeping perennials.

A

Rhizome - horizontal underground stem
Tuber - enlarged tip of a rhizome
Bulb - piece of stem tissue surrounded by modified leaves
Stolon - horizontal, aboveground stem
Creeping Root - horizontal and vertical roots

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4
Q

What are the shared characteristics of grasses and grass-like weeds?

A

elongated leaves
stems enclosed in leaf sheaths

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5
Q

What problems does weed interference cause?

A

competition for light, nutrients, space, and water

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6
Q

What three factors determine the competitiveness of a weed?

A

Time of emergence relative to the crop.
Growth form of the weed.
Weed density.

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7
Q

What is the critical weed free period that most plants need to avoid a reduction in growth?

A

Depends on the crop but during germination.

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8
Q

Is weed density more important in competitive or non-competitive crops? (graphs)

A

non-competitive

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9
Q

What is the importance of a weed seed bank?

A

A reservoir of new individual plants.
Seed bank can be depleted or added to each year.
Overwintering.

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10
Q

What mechanisms of dormancy are found in weeds. Describe.

A

Immature embryos - time required after release to develop and germ (cow parsnip)
Physiological - cold or warm strat, light strat (common groundsel)
Physical - hard seed coat (ragweed or cocklebur)

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11
Q

How long can lamb’s quarters and velvetleaf remain in the soil? Why? How does this influence management?

A

40 years
Hard seed coat, resistant to moisture loss and rot
will have to deal with it for a while, don’t let it go to flower

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12
Q

Why are veg reproductive structures so effective at carrying out overwinter survival, rapid establishment, and spreading quickly?

A

Produce buds that over winter.
Large roots or veg pieces store a lot of carbs.
Get moved by equipment to different places.

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13
Q

How do you distinguish burcucumber and wild cucumber?

A

BC - shallow lobes and deep petiole lobe, cluster of flowers on stalk, cluster of fruit
WC - deep lobes and shallow petiole lobe, flower in leaf axil, one fruit

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14
Q

How does virginia creeper and poison ivy look different

A

VC - palmately compound
PI - trifoliate

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15
Q

What are the life cycle, method of reproduction and key environmental requirement of Canada goldenrod?

A

CP
seed and rhizome
shade avoidance

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16
Q

Life cycle and reproductive method of garlic mustard

A

biennial and seed

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17
Q

Implications of garlic mustard for nursery production?

A

Mytotoxic, limits uptake of nutrients by deciduous trees

18
Q

Which weeds grow in compacted soil (C), dry gravelly soil (D), saturated soils (S)?

A

C - common knotweed, bicknell’s geranium
D - pineappleweed, toadflax, common mullein
S - common burdock, bull thistle, cattail

19
Q

Weed management in residential landscapes

A

cultural management
soil amendments, nutrition, irrigation
mulches
weed free nursery stock
bio weed control

20
Q

How can crop selection be used to suppress weeds?

A

most appropriate crop for the area, planting densities, and variety

21
Q

What is the biennial lifecycle and best time to control?

A

First year is vegetative, second year is reproductive. 30 days below 0 degrees
control in fall of first year

22
Q

Glyphosate resistance and dispersal of Canada fleabane

A

Can travel up to 500km and we cannot effectively used herbicides against it

23
Q

Name a weed that acts as an alternate host for cucumber mosaic virus and how does it enter ghs?

A

Curled dock
insects with mouth sucking parts (aphids)

24
Q

What soil condition does lambsquarter tolerate and how?

A

Saline soils, possesses salt glands to expel salt

25
Q

Why is horsetail hard to kill with herbicides?

A

The phloem are not arranged in long strands, they are broken up

26
Q

Why is velvetleaf hard to kill at night?

A

Leaves droop, poor coverage

27
Q

Describe appearance of two types of leaves in henbit

A

Lower leaves are petiolated and upper leaves are sessile

28
Q

Three features that enhance the invasiveness of field bindweed

A

vining growth
rhizomes
seeds

29
Q

What type of soil and light conditions does eastern black nightshade grow best in?

A

high nitrogen and full sun

30
Q

what soil conditions are plantains well adapted to and what features help with that?

A

compacted soils
taproots

31
Q

Rough cinquefoil looks like strawberries, how to tell apart?

A

RCF - serrated all of the margin
S - serrated on half

32
Q

How does seed dispersal allow for creeping woodsorrel to exist in ghs?

A

Explosively discharged with mucilage, can stick on windows

33
Q

What soil conditions does sweet violet live in and reproduce?

A

high OM and low pH
seed and rhizome

34
Q

What effect does early planting have on weed populations and what are two disadvantages of planting early?

A

relative time of emergence
1 frost damage
2 too wet = compaction

35
Q

How can soil amendments with high C:N ratios negatively affect crop competitiveness and microbial
activity?

A

The amendments add WHC and nutrients, but high C:N will reduce MOO activity

36
Q

For how long and at what temperature do
soil amendments need to be composted to
keep them as weed free as possible?

A

30 days at 30 degrees and for field bindweed 50 degrees

37
Q

How can excess fertility negatively affect
crop competitiveness and microbial activity?

A

Root injury and reduced growth of microbes

38
Q

How do frequency of irrigation and amount of water used influence weed emergence and growth?

A

– Light, frequent irrigation favours germination of
small seeded annual weeds.
– Heavier, less frequent irrigation favours
germination of larger seeded weeds from
deeper in soil.

39
Q

In general what range of depth and when should mulches be applied?

A

4” in the fall

40
Q

Mulch types and advantages and disadvantages of each

A

Degradable
A- cheap and adds OM
D- apply more frequently
Persistent
A- apply less often, consistent
D- expensive, no OM

41
Q
A

DHRT3170 WEEDS (3 decks)

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