Weeds L4 Flashcards
Weed ecology
study of interactions or relationships between weeds and their environment and their adaptive mechanisms to enable them to do well in maximum disturbance
pest hexagon
interaction network of just pests
ecological or interaction network
Includes abiotic interactions as well as who eats who
Trophic/food/consumption network or food web
who eats who (can be very small or very large)
what are the most successful weed management programs based on
an adequate ecological understanding of weeds
Why do humans have a strong influence on weed ecology
we create their environment and spread them around, as well as influence their genetics (herbicide resistance)
primary succession
already unfolded over geological times
secondary succession
repressed by agriculture in agroecosystems
Weeds in moist mixed grassland
needle-and-thread grass
northern porcupine grass
thick-spike wildrye
western wheatgrass
How does farming practices disrupt the normal plant succession?
farming works to maintain the early succession stages by fighting normal progression
How do a grassland ecosystem and an agroecosystem differ?
they differ in intensity and frequency of disturbance because of management levels
open ecological niche
an empty location, site, or microsite
open ecological niche characteristics
High light intensity and quality
available soil nutrients
suitable environmental conditions
no major competitors/low risk of enemies
Characteristics of weeds
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
Why is there a shift towards ecology-based weed management
herbicides are starting to fail because of herbicide resistance and old practices are no longer working
what needs to be considered before choosing a weed control method?
weed species, crop, field situation, environmental conditions
Weed-crop interaction
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
What resources do weeds compete with crops for?
light, nutrients, water, space
factors that influence competitiveness in weeds
Time of weed emergence in relation to crop
weed density
growth rate and growth form
adaption to stress
allelopathy
Weed-crop interaction - time of weed emergence in relation to crop
first plant to emerge gets first dibs on water, nutrients, and light, giving it a competitive edge
What time do weeds have the most effect on crop yield
weeds emerging prior to or with crop in first 4-6 weeks
What affect do late emerging seeds have
don’t affect crop yield, but can contaminate crop, reducing its quality
interfere with harvest operations
Weed-crop interactions: weed density
biomass, shape, and height of weed have strong impact on effect of density on crop yield
Weed-crop interactions- Growth rate and form
rapid development of canopy and extensive root system
dense canopy
tall or climbing
Weed-crop interactions - Adaption to stress
the greater the weed’s ability to adapt to stress the greater the competitive ability
Examples of abiotic stresses
shade, drought, wet soil conditions, low soil fertility
Weed-crop interactions - allelopathy
produce toxins that enter soil and prevent normal development of other plants (plants protecting their own space)
What can allelopathy result in?
inhibition of germination, formation of abnormal seedlings, prevention of root elongation, abnormal cellular physiology
Examples of allelopathy
Black walnut produces juglone excreted from the roots
Wheat straw can inhibit the growth of bermudagrass
How does water affect the environmental conditions of weed-crop interactions?
Weeds commonly found in humid or irrigated regions are more competitive in moist conditions.
Weeds in dry habitats grow better in dryer conditions
How does soil nutrients and pH affect the environmental conditions of weed-crop interactions?
The plant species more adapted to the soil conditions will be more competitive. When fertilizer is added, it typically stimulates weed growth (more competitive)
How does light and shading stress affect the environmental conditions of weed-crop interactions?
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
How does temperature affect the environmental conditions of weed-crop interactions?
dictates when and where weeds can grow. Growing degree days also determine whether a weed can be competitive
Weed interactions with other pests/ organisms
can act as reservoirs for insects and pathogens
hinder application of pesticides (insecticide, fungicide) by intercepting it
herbicides could be incompatible with other pesticides
