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Weed Science > Weed Test 2 > Flashcards

Weed Test 2 Flashcards

(51 cards)

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1
Q

Interference

A

interaction among species involving both competition and allelopathy

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2
Q

Competition

A

plants compete with one another for resource in short supply

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3
Q

Allelopathy

A

inhibition of one plant by another through the release of selective toxic metabolic by-products into the environment

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4
Q

Intraspecific interference

A

interference between plants of the same species

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5
Q

Interspecific interference

A

interference between plants of different species

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6
Q

Damage/competitive threshold

A

the weed population at which a negative crop yield response is detected

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7
Q

Economic threshold

A

the weed population at which the cost of control is equal to the crop value increase from control

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8
Q

Optimum economic threshold

A

economic threshold plus input of weed seed production on long term economics of weed management decisions

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9
Q

Period threshold

A

implies that there are times during the growing season in which weeds are more or less damaging than other times

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10
Q

Action/aesthetic threshold

A

point at which some control action is initiated and usually includes economic considerations along with other less tangible factors such as aesthetics, risk aversion, or sociological pressures

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11
Q

Resistance

A

acquired ability of a weed population to survive a herbicide application that was previously known to control the population

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12
Q

Tolerance

A

ability of a species to survive and reproduce after herbicide treatment

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13
Q

Cross Resistance

A

resistant to two or more herbicide families with SAME mode of action
single resistance mechanism

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14
Q

Multiple Resistance

A

resistant to two or more herbicides with different modes of action
may be result of two or more different resistance mechanisms

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15
Q

Dominant weeds dependent on

A

how long and how land has been used agriculturally
nature of the widely dispersed weeds in the region
method of reproduction
competitiveness and density of weed seed per unit area or volume of soil

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16
Q

Characteristics associated with competitive plants

A

shoot and root characteristics

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17
Q

Shoot characteristics associated with competitive plants

A

rapid expansion of canopy
overcast conditions: horizontal leaves or
sunny: slanted leaves
large leaves
c4 photosynthetic pathway
and low leaf light transmission
mosaic leaf arrangement for best light interception
climbing habit
high allocation of dry matter to build tall stem
rapid extension in response to shading

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18
Q

Root characteristics associated with competitive plants

A

early and fast root penetration of a large soil area
high root density/soil volume
high root-shoot ratio
high root length per root weight
high proportion of actively growing roots
long and abundant root hairs
high uptake potential for nutrients and water

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19
Q

Factors influencing competitiveness

A

variation between species and competing crop
variation in cultivars
variation in competitiveness between weeds of same genus
row spacing influence on weed competition
planting date
duration of a crop
geographic region
level of interference

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20
Q

Critical weed-free period

A
  • a longer critical period means crop is less competitive or the weed is more competitive than the crop
  • rainfall and planting date influence critical period
  • beginning of critical period influenced more by differences in weed densities and environmental factors
  • initiation of weed control based upon crop development stage and susceptible weed stage so better term is critical period of weed control
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21
Q

Environmental parameters involved in weed competition

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A

no competition as long as essential requirements are in excess
2 categories of environmental factors and plant responses:
consumable environmental resources
non-consumable environmental conditions

22
Q

Consumable environmental resources

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A 
water
nutrients
light
CO2
O2
plant response: an increase through a resource-limited phase to saturation level where another factor becomes limiting
23
Q

Non-consumable environmental conditions

Study These Flashcards
A

temperature
soil properties
other factors that affect plant growth

24
Q

Weed density and yield loss depends on

Study These Flashcards
A 
crop grown
weed species present
duration of competitor
climate
impact of weed seed production on future cropping system
25
true allelopathy
toxic compounds that are released directly into the environment by the plant
26
functional allelopathy
compounds that are released into the environment but before toxic. Must be transformed by microorganisms
27
auto-allelopathy
plant secretes a substance which inhibits the germination of other seed from the same species
28
below-ground root competition
individual compete for space, water, and nutrients which all differ in distribution, mobility, molecular size, and other aspects
29
above-ground competition
individuals normally compete only for light and space
30
Competition for consumable environmental resources
``` competition for water nutrients lights CO2 O2 ```
31
2 types allergenic plants
plants that produce skin eruption as result of bodily contact plants affect respiratory tract through inhalation such as pollen
32
FIFRA
federal insecticide fungicide and rodenticide act 1947 requires pesticides to be registered with the epa classified general or restricted requires applicators be certified for use of restricted penalties for pesticide negligence or requires pesticides be used as label states except sections 18 or 24c amendments
33
pesticide labels
``` legal document that is federal law includes: identifying information precautionary statements hazards to humans and domestic animals environmental hazards physical or chemical hazards directions for use ```
34
herbicide labels
herbicide is a type of pesticide used to kill weeds 2 classifications: general use pesticides restricted use
35
general use pesticide
no unreasonable adverse effects on environment | safe to apply
36
restricted use pesticide
sold only to trained and certified applicators | restriction due to drift, environmental, or toxicity concerns
37
directions for use
``` mixing instructions spraying instructions calibration information application directions (by region/crop, method of application, weeds controlled, rates by soil texture or weed stage, tank mix combinations) ```
38
types of label registration
section 3 section 5 section 24c section 18
39
section 3
main registration of a product label | every product has this
40
section 5
allows for field testing of a pesticide currently under development (only good for short period, have to reapply every 1-2 years)
41
section 24c
state in special need of federally registered product that will provide control company must apply for this label limited amount of acres can be used
42
section 18
emergency crisis of invasive species requiring unregistered pesticide (very limited area/short time) grower groups, extension specialists etc apply (not companies)
43
Signal words
danger- highly toxic, category 1 warning- moderately toxic, category 2 caution- slightly toxic, category 3,4
44
ways pesticides enter the body
orally- mouth dermal- eyes and skin inhalation- lungs
45
prevention of pesticide exposure
wear appropriate pesticide protective equipment that is waterproof or chemical resistant
46
types of PPE
``` body covering head covering shoes/boots gloves respirator/mask NIOSH/MSHA approved eye protection ```
47
herbicide selectivity
differences in response of plant species to a given herbicide rate of herbicide required to kill one species is safe on another species
48
factors affecting selectivity
physical- influence contact between herbicides and plant surfaces biological- caused by differences among plants physiological- caused by the different ways plants function
49
herbicide resistant weeds in arkansas
``` annual ryegrass common ragweed palmer amaranth johnsongrass pigweed ```
50
causes of herbicide resistance
monocultural cropping- planting same crop over and over using same herbicide consecutively or different herbicides with same mode of action often occurs in reduced cultivation practices
51
management strategies to prevent or delay herbicide resistance
crop and herbicide rotation herbicide combinations rotation of herbicide modes of action tillage

Weed Science (6 decks)

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