Lecture 4 Flashcards
How were all weeds initially removed
By hand
How were all weeds removed 3000 years ago
Animals were used to drag a hoe
After what year were row crops weeded by horse hoeing
Year 1731
What year were tractors introduced
1920
When was the first herbicide introduced
In 1946
Name the first herbicide that was introduced
2,4-D kills dicots but not most monocots
How many species of weed affecting food crops
About 30,000
Give examples of annual weeds
• Fat hen (Chenopodium album)
• Redshank (Polygonum persicaria)
• Annual nettle (Urtica urens)
• Charlock (Sinapsis arvensis)
• Red deadnettle (Lamium purpurium)
• Cleavers / Goosegrass (Galium aparine)
Give example of Ephemeral weeds
• Groundsel (Senicio vulgaris)
• Hairy bittercress (Cardamine hirsuta)
What are Ephemeral weeds
Completes more than one lifecycle in one season/ year, then dies
Give examples of Biennial weeds
• Ragwort (Senicio jacobaea)
• Wild carrot (Daucus carota)
Give example of Perennial Weeds
• Bishops weed / Ground elder (Aegopodium podagraria)
• Couchgrass (Agropyron repens) • Rhododendron ponticum
• Bracken (Pteridium aquilinum) • Dock (Rumex spp.)
Physiological characteristics for weed success
• High photosynthetic rate
• Rapid seedling growth
• Produce seed early in the lifecycle
• Highly adaptable
• No special environmental conditions required
Reproductive characteristics for weed success
• Self fertilised with some outcrossing
• Many seeds produced
• Seeds produced over a long period of time
• Will produce seed in unfavourable conditions • Pollinated by wind or many insect species
• Can reproduce vegetatively by stolons
Agronomic characteristics for weed success
• Weed and crop may look and grow similarly • Seeds mature at the same time as crop
• Tolerance to herbicides
• Seed remains viable in soil for long periods • Soil disturbance bring seeds to the surface
What are direction losses in weed competition
Loss due to competition for light , water and nutrients
Example of biochemical competition(ALLELOPATHY)
• Juglans nigra (Black walnut)
• Alianthus altissima (Tree of heaven)
• Oryza sativa (Rice)
Name an example of proflic weed dispersal
Groundsel 1000-1200 fruits
Mayweed 15,000 to 19,000 fruits
Rosebay willow herb - 80,000 seeds
Name an example of explosive weed dispersal
Himalayan balsam
Spurge
Yellow wood sorrel
Name an example of water weed dispersal
Himalayan balsam
Purple loosestrife
Dock spp
Name an example of wind weed dispersal
Dandelion
Horse weed ( Conya candensis)
Name an example of animal weed dispersal
Wild carrot
Curly dock
Give an example of a weed as hosts for pests
Nematodes eg potato root eelworm
(Globodora spp.) grow on weed species of Solanum
What disease does common chickweed cause (Stellaria media)
Tomato spotted wilt virus
What disease does Field bindweed(Convolvulus arvensis) cause
Cucumber mosaic virus
What disease does Mallow (Malva sp.) cause
Tomato yellow leaf curl virus
What disease does Nightshade (Solanum sp.) cause
Potato virus Y
What disease does Scarlet pimpernel (Anagallis arvensis) cause
Lettuce mosaic virus
What disease does Barberry (Berberis sp.) cause
intermediate hosts for wheat stem rust
Name the major weed of intensively managed high fertility grasslands
Dock
Describe the weed Nettle
Grows in clumps
Prevents grazing
Describe the weed Thistle
Discourages grazing
Makes hay and silage unpalatable
Describe a cultural weed control
Stale seed bed
Crop rotation
Describe a physical / mechanical weed control
Covering
Burying
Slashing
Mowing
Describe a biological weed control
Herbivory
Competitive plants
Describe a chemical weed control
Contact , systematic and residual , broad spectrum or selective herbicides
When will annual weeds often disappear
when they are out competed by a vigorous crop such as grass and may not need any treatment
Name an example of a noxious weed
Ragwort (Senicio Jacobea)
What animals is ragwort highly toxic to
cattle, horses, deer, goats, pigs and chickens.
What happens to an animal who has ingested ragwort
Animals liver accumulates copper causing ill health and death
Other than ragwort name 4 other noxious weeds
Creeping thistle (Cirsium arvense)
Spear thistle (Cirsium vulgare)
Curled Dock (Rumex crispus)
Broad leaved Dock (Rumex obtusifolius)
Example of non-native invasive weeds
Japanese Knotweed
Giant Hogweed
Giant Rhubarb
Himalayan Balsam
Montbretia (Crocosmia)
Rhododendron ponticum
What exactly is a weed
“Any plant not intentionally sown or propagated by the grower that requires management to prevent it from interfering from crop or livestock production”
