R2103 2.3 Describe how weeds and be controlled

Question 1

What is a contact herbicide?

Post-emergent herbicides. Non-selective.

Answer 1

1. Rapid effect, killing all top growth
2. Ideal for clearing ground prior to planting
3. Does not kill root system or stems of perennial plants, but repeated application will exhaust them
4. May require repeated applications
5. Trade name - Weedol Max

Question 2

What is a residual herbicide?

Pre-emergence herbicides. Non-selective

Answer 2

1. Non-selective and remain in soil
2. Kills germinating seeds and shoots from perennial roots
3. Can be transported in soil by percolating water and in surface run-off
4. Can be used with care around shrubs and bushes, but not where bulbs are planted

Question 3

What is a selective herbicide?

Answer 3

1. Will kill broad leaved weeds and not grasses
2. Action is systemic, absorbed into tissues with a hormonal effect on growth rates

Question 4

One situation for the use of a contact herbicide

Answer 4

1. Clearing ground prior to sowing or planting
2. Useful against liverworts

Question 5

One situation for the use of a residual herbicide

Answer 5

1. Kill seeds and shoots of perennial roots
2. Can be used in combination with other weed killers on paths and gravel and will keep them weed free for growing season if applied in spring
3. Can be effective against Creeping thistle

Question 6

One situation for the use of a selective herbicide

Answer 6

1. Usually applied to lawn as part of weed and feed application
2. Monocots and dicots affected differently. Mocots less susceptible to the chemicals.
3. Do not apply to lawn less than six months old, either seeded or turfed
4. Herbicide is usually broken down by soil bacteria but can persist in tissue of treated plants so any dead material and grass cuttings should not be added to compost heap.
5. Trade name - Bio Top Lawn

Question 7

Active ingredient of a contact herbicide

Answer 7

Pelargonic Acid
Natural fatty acid removes cuticle allows plant to dry out. In theory should be effective of plants with a waxy foliage such as liverworts

nonoaic acid

Question 8

Active ingredient of a residual herbicide

Pathclear

Answer 8

Diflufenican
Works by inhibiting carotenoid biosynthesis

Question 9

Active ingredient of a selective herbicide

Bio Top Lawn

Answer 9

Mecoprop-P (MCPP)
Absorbed by plant leaves and translocated to roots.
Affects enzyme activity and plant growth.
Acts slowly over 3-4 weeks

Question 10

Active in ingredient of systemic (translocated herbicide)

Roundup

Answer 10

Glyphosate
Acts on an enzyme which produces essential amino acid so reducing the production of protein in the plant and inhibits plant growth

Question 11

What is a systemic (translocated) herbicide

Non-selective

Answer 11

1. Active ingredient is taken up by foliage and transported down to the rest of the plant, including over wintering stems and roots.
2. Should be plenty foliage so that maximum amount of active ingredient is absorbed
3. Works slowly
4. Trade name - Roundup

Question 12

One situation for the use of a translocated herbicide

Answer 12

1. Not usually absorbed by soil so it be used to clear ground prior to planting.
2. Less useful on paths and gravel as seeds germinate and re-infest area
3. Effective against ground elder