Weed ecology Flashcards
What is a weed?
- Any plant that is objectionable/dusturbing or interfering with activities or welfare of humans
- Plants growing where they are not wanted
- Uninvited plant
- Out of place
- Adversely affect the use, economic value and aesthetic aspect of the land and water they infest
=> every plant can be a weed
What is weed ecology?
Study of:
- Growth characteristics of weeds
- Adaptation/survival mechanisms of weeds
that enable them to exploit environmental resources and successfully colonize new habitats often at the expense of other neighboring plants
(crops)
What is the difference between agricultural and natural systems in the context of weed ecology/vegetation?
Nature has a climax vegetation where plants can grow,
climax vegetation => vegetation best adapted to a location, which is a stable system that can live on its own, as its adapted.
In agriculture=> disturb this climax vegetation. Agricultural vegetation => not a climax, not stable on its own. A lot of input in the system is needed.
Nature wants to recover this system, which is what is causing the problem with weeds.
Understanding the ecology of weeds allows us to understand the strenghts and weaknesses of weeds.
Why are weeds unwanted?
They are the greatest biological challenge to agricultural production whether conventional or organic.
- Reduce yield by competition for LIGHT, WATER, and NUTRIENTS and/or ALLEOPATHY
- reduce the QUALITY of the crop and livestock products
- Can POISON humans and livestock
- Can harbor PESTS which attack crops
- Retain MOISTURE (decay and diseases)
- Increase the COST OF HARVESTING
- Hinder WATER flow and increase IRRIGATION COSTS
- Cause high PRODUCTION COSTS if removed
- Cause high SOCIAL COSTS in less developed countries since many people spend their entire life (hands) in weeding
Do weeds have beneficial effects? Name some examples….
Example of water hyacinth=> tchibo selling baskets made of it
Example of Common Purslane => is edible, can be eaten and is used in Mexican cooking
What are some beneficial effects of weeds?
- Can be useful plants
- Break up of monocultures
- Reduce soil erosion (improvement of soil structure, promotion of soil microorganisms and biological activity)
- Reduction in nutrient and pesticide runoff
- Promotion of beneficial organisms, distraction of pests
- Promotion of biodiversity
- …
What makes a plant a weed? What are some characteristics?
- Harmful to humans, animals and/or crops
- Ability to adapt to varying environments (plasticity and tolerance, capale of some out-crossing => maintains genetic diversity and adptability to new environments, crop mimicry…)
- Strong weed/crop interaction and self-compatibility
- Reproduction: high reproductive capacity and rapid seedling growth (different propagation methods, seed dormancy=> basic survival on longer time)
- Usually present in large populations w/o being planted
What is interference?
- The detrimental effects of one species on another resulting from their interactions with each other
- Can bin inter-specific (between individuals of different species, or intra-specific (among individuals from same species)
- takes place above and below ground
- Generally involves COMPETITION (resource interference) and ALLELOPATHY (biochemical interference)
What are some influencing factors of interference between plants?
- Species and density of weeds
- Species and variety of crop, seeding rate and spatial arrangement
- Availability and growth factors
- Environmental factors (climate, soil)
- Onset and duration of weed/crop association => critical period of weed interference
=> not every situation we have the same conditions and same interference between plants (weed and crops)
=> yield loss can be highly is variable
How do we classify weeds?
- Botanical (taxonomy)
- Life cycle or history (annual, biennial, perennial)
- Habitat (terrestrial, aquatic)
- Physiology (autotroph, parasitic)
- Ecological affinities (wetland, gardenland, dryland)
- Morphology (woody/herbaceaus; monocot/dicot)
(native, alien invader/invasive weed, agricultural weed, noxious - Origin & degree of undesirability weed)
What are the 3 different types of lifecycles of weeds?
ANNUAL WEEDS
BIENNIAL WEEDS
PERENNIAL WEEDS
What are characteristics of annual weeds?
- Germinate and flower within 1 y
- reproduce generative by seeds
- Shallow, tap root system
What are characteristics of biennial weeds?
- Germinate and flower within 2 years
- Reproduce generative by seeds
What are characteristics of perennial weeds?
- Deep root system: rhizomes, stolons, tubers
- Reproduce primarily vegetative
- Need food resources to sustain plant through dormancy
What is the right time to control an annual weed?
Seedling stage (after germination, before establishment)
