Weeds L4

Question 1

Weed ecology

Answer 1

study of interactions or relationships between weeds and their environment and their adaptive mechanisms to enable them to do well in maximum disturbance

Question 2

pest hexagon

Answer 2

interaction network of just pests

Question 3

ecological or interaction network

Answer 3

Includes abiotic interactions as well as who eats who

Question 4

Trophic/food/consumption network or food web

Answer 4

who eats who (can be very small or very large)

Question 5

what are the most successful weed management programs based on

Answer 5

an adequate ecological understanding of weeds

Question 6

Why do humans have a strong influence on weed ecology

Answer 6

we create their environment and spread them around, as well as influence their genetics (herbicide resistance)

Question 7

primary succession

Answer 7

already unfolded over geological times

Question 8

secondary succession

Answer 8

repressed by agriculture in agroecosystems

Question 9

Weeds in moist mixed grassland

Answer 9

needle-and-thread grass
northern porcupine grass
thick-spike wildrye
western wheatgrass

Question 10

How does farming practices disrupt the normal plant succession?

Answer 10

farming works to maintain the early succession stages by fighting normal progression

Question 11

How do a grassland ecosystem and an agroecosystem differ?

Answer 11

they differ in intensity and frequency of disturbance because of management levels

Question 12

open ecological niche

Answer 12

an empty location, site, or microsite

Question 13

open ecological niche characteristics

Answer 13

High light intensity and quality
available soil nutrients
suitable environmental conditions
no major competitors/low risk of enemies

Question 14

Characteristics of weeds

Answer 14

rapid seed growth and quick maturation
dual modes of reproduction
high tolerance to wide environmental conditions
Seed dormancy
aggressiveness
high capacity for dispersal and seed production
crop mimicry

Question 15

Why is there a shift towards ecology-based weed management

Answer 15

herbicides are starting to fail because of herbicide resistance and old practices are no longer working

Question 16

what needs to be considered before choosing a weed control method?

Answer 16

weed species, crop, field situation, environmental conditions

Question 17

Weed-crop interaction

Answer 17

gaining access to a resource by one plant will make it less available to another
weeds are most damaging if they have some advantage over the crop

Question 18

What resources do weeds compete with crops for?

Answer 18

light, nutrients, water, space

Question 19

factors that influence competitiveness in weeds

Answer 19

Time of weed emergence in relation to crop
weed density
growth rate and growth form
adaption to stress
allelopathy

Question 20

Weed-crop interaction - time of weed emergence in relation to crop

Answer 20

first plant to emerge gets first dibs on water, nutrients, and light, giving it a competitive edge

Question 21

What time do weeds have the most effect on crop yield

Answer 21

weeds emerging prior to or with crop in first 4-6 weeks

Question 22

What affect do late emerging seeds have

Answer 22

don’t affect crop yield, but can contaminate crop, reducing its quality
interfere with harvest operations

Question 23

Weed-crop interactions: weed density

Answer 23

biomass, shape, and height of weed have strong impact on effect of density on crop yield

Question 24

Weed-crop interactions- Growth rate and form

Answer 24

rapid development of canopy and extensive root system
dense canopy
tall or climbing

Question 25

Weed-crop interactions - Adaption to stress

Answer 25

the greater the weed’s ability to adapt to stress the greater the competitive ability

Question 26

Examples of abiotic stresses

Answer 26

shade, drought, wet soil conditions, low soil fertility

Question 27

Weed-crop interactions - allelopathy

Answer 27

produce toxins that enter soil and prevent normal development of other plants (plants protecting their own space)

Question 28

What can allelopathy result in?

Answer 28

inhibition of germination, formation of abnormal seedlings, prevention of root elongation, abnormal cellular physiology

Question 29

Examples of allelopathy

Answer 29

Black walnut produces juglone excreted from the roots
Wheat straw can inhibit the growth of bermudagrass

Question 30

How does water affect the environmental conditions of weed-crop interactions?

Answer 30

Weeds commonly found in humid or irrigated regions are more competitive in moist conditions.
Weeds in dry habitats grow better in dryer conditions

Question 31

How does soil nutrients and pH affect the environmental conditions of weed-crop interactions?

Answer 31

The plant species more adapted to the soil conditions will be more competitive. When fertilizer is added, it typically stimulates weed growth (more competitive)

Question 32

How does light and shading stress affect the environmental conditions of weed-crop interactions?

Answer 32

influences ability to compete for water and nutrients depending on time of weed emergence and growth rate. shaded plants typically have lower shoot-root ratio

Question 33

How does temperature affect the environmental conditions of weed-crop interactions?

Answer 33

dictates when and where weeds can grow. Growing degree days also determine whether a weed can be competitive

Question 34

Weed interactions with other pests/ organisms

Answer 34

can act as reservoirs for insects and pathogens
hinder application of pesticides (insecticide, fungicide) by intercepting it
herbicides could be incompatible with other pesticides