Exam Flashcards
What do weeds compete for? What is allelopathy?
4 things - light, water, nutrients, and space.
Allelopathy - the production of phytotoxic compounds that reduce the germ of other plants.
What is the key environmental condition required for biennial plants to begin reproductive development? How does this relate to time of control?
30 days of below 0 degrees
Control in the fall before this cold period
5 types of vegetative reproductive structures for creeping perennials.
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
What are the shared characteristics of grasses and grass-like weeds?
elongated leaves
stems enclosed in leaf sheaths
What problems does weed interference cause?
competition for light, nutrients, space, and water
What three factors determine the competitiveness of a weed?
Time of emergence relative to the crop.
Growth form of the weed.
Weed density.
What is the critical weed free period that most plants need to avoid a reduction in growth?
Depends on the crop but during germination.
Is weed density more important in competitive or non-competitive crops? (graphs)
non-competitive
What is the importance of a weed seed bank?
A reservoir of new individual plants.
Seed bank can be depleted or added to each year.
Overwintering.
What mechanisms of dormancy are found in weeds. Describe.
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)
How long can lamb’s quarters and velvetleaf remain in the soil? Why? How does this influence management?
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
Why are veg reproductive structures so effective at carrying out overwinter survival, rapid establishment, and spreading quickly?
Produce buds that over winter.
Large roots or veg pieces store a lot of carbs.
Get moved by equipment to different places.
How do you distinguish burcucumber and wild cucumber?
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
How does virginia creeper and poison ivy look different
VC - palmately compound
PI - trifoliate
What are the life cycle, method of reproduction and key environmental requirement of Canada goldenrod?
CP
seed and rhizome
shade avoidance
Life cycle and reproductive method of garlic mustard
biennial and seed
Implications of garlic mustard for nursery production?
Mytotoxic, limits uptake of nutrients by deciduous trees
Which weeds grow in compacted soil (C), dry gravelly soil (D), saturated soils (S)?
C - common knotweed, bicknell’s geranium
D - pineappleweed, toadflax, common mullein
S - common burdock, bull thistle, cattail
Weed management in residential landscapes
cultural management
soil amendments, nutrition, irrigation
mulches
weed free nursery stock
bio weed control
How can crop selection be used to suppress weeds?
most appropriate crop for the area, planting densities, and variety
What is the biennial lifecycle and best time to control?
First year is vegetative, second year is reproductive. 30 days below 0 degrees
control in fall of first year
Glyphosate resistance and dispersal of Canada fleabane
Can travel up to 500km and we cannot effectively used herbicides against it
Name a weed that acts as an alternate host for cucumber mosaic virus and how does it enter ghs?
Curled dock
insects with mouth sucking parts (aphids)
What soil condition does lambsquarter tolerate and how?
Saline soils, possesses salt glands to expel salt
Why is horsetail hard to kill with herbicides?
The phloem are not arranged in long strands, they are broken up
Why is velvetleaf hard to kill at night?
Leaves droop, poor coverage
Describe appearance of two types of leaves in henbit
Lower leaves are petiolated and upper leaves are sessile
Three features that enhance the invasiveness of field bindweed
vining growth
rhizomes
seeds
What type of soil and light conditions does eastern black nightshade grow best in?
high nitrogen and full sun
what soil conditions are plantains well adapted to and what features help with that?
compacted soils
taproots
Rough cinquefoil looks like strawberries, how to tell apart?
RCF - serrated all of the margin
S - serrated on half
How does seed dispersal allow for creeping woodsorrel to exist in ghs?
Explosively discharged with mucilage, can stick on windows
What soil conditions does sweet violet live in and reproduce?
high OM and low pH
seed and rhizome
What effect does early planting have on weed populations and what are two disadvantages of planting early?
relative time of emergence
1 frost damage
2 too wet = compaction
How can soil amendments with high C:N ratios negatively affect crop competitiveness and microbial
activity?
The amendments add WHC and nutrients, but high C:N will reduce MOO activity
For how long and at what temperature do
soil amendments need to be composted to
keep them as weed free as possible?
30 days at 30 degrees and for field bindweed 50 degrees
How can excess fertility negatively affect
crop competitiveness and microbial activity?
Root injury and reduced growth of microbes
How do frequency of irrigation and amount of water used influence weed emergence and growth?
– Light, frequent irrigation favours germination of
small seeded annual weeds.
– Heavier, less frequent irrigation favours
germination of larger seeded weeds from
deeper in soil.
In general what range of depth and when should mulches be applied?
4” in the fall
Mulch types and advantages and disadvantages of each
Degradable
A- cheap and adds OM
D- apply more frequently
Persistent
A- apply less often, consistent
D- expensive, no OM
