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Weed Science > Weed Test 2 > Flashcards

Weed Test 2 Flashcards

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Biology 101 flashcards
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

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

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

A

temperature
soil properties
other factors that affect plant growth

24
Q

Weed density and yield loss depends on

A 
crop grown
weed species present
duration of competitor
climate
impact of weed seed production on future cropping system
25
Q

true allelopathy

A

toxic compounds that are released directly into the environment by the plant

26
Q

functional allelopathy

A

compounds that are released into the environment but before toxic. Must be transformed by microorganisms

27
Q

auto-allelopathy

A

plant secretes a substance which inhibits the germination of other seed from the same species

28
Q

below-ground root competition

A

individual compete for space, water, and nutrients which all differ in distribution, mobility, molecular size, and other aspects

29
Q

above-ground competition

A

individuals normally compete only for light and space

30
Q

Competition for consumable environmental resources

A 
competition for water
nutrients
lights
CO2
O2
31
Q

2 types allergenic plants

A

plants that produce skin eruption as result of bodily contact
plants affect respiratory tract through inhalation such as pollen

32
Q

FIFRA

A

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
Q

pesticide labels

A 
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
Q

herbicide labels

A

herbicide is a type of pesticide used to kill weeds
2 classifications:
general use pesticides
restricted use

35
Q

general use pesticide

A

no unreasonable adverse effects on environment

safe to apply

36
Q

restricted use pesticide

A

sold only to trained and certified applicators

restriction due to drift, environmental, or toxicity concerns

37
Q

directions for use

A 
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
Q

types of label registration

A

section 3
section 5
section 24c
section 18

39
Q

section 3

A

main registration of a product label

every product has this

40
Q

section 5

A

allows for field testing of a pesticide currently under development
(only good for short period, have to reapply every 1-2 years)

41
Q

section 24c

A

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
Q

section 18

A

emergency crisis of invasive species requiring unregistered pesticide (very limited area/short time)
grower groups, extension specialists etc apply (not companies)

43
Q

Signal words

A

danger- highly toxic, category 1
warning- moderately toxic, category 2
caution- slightly toxic, category 3,4

44
Q

ways pesticides enter the body

A

orally- mouth
dermal- eyes and skin
inhalation- lungs

45
Q

prevention of pesticide exposure

A

wear appropriate pesticide protective equipment that is waterproof or chemical resistant

46
Q

types of PPE

A 
body covering
head covering
shoes/boots
gloves
respirator/mask NIOSH/MSHA approved
eye protection
47
Q

herbicide selectivity

A

differences in response of plant species to a given herbicide
rate of herbicide required to kill one species is safe on another species

48
Q

factors affecting selectivity

A

physical- influence contact between herbicides and plant surfaces
biological- caused by differences among plants
physiological- caused by the different ways plants function

49
Q

herbicide resistant weeds in arkansas

A 
annual ryegrass
common ragweed
palmer amaranth
johnsongrass
pigweed
50
Q

causes of herbicide resistance

A

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
Q

management strategies to prevent or delay herbicide resistance

A

crop and herbicide rotation
herbicide combinations
rotation of herbicide modes of action
tillage

Weed Science (6 decks)

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