Chemicals are cheap, long lasting, and the ground is not disturbed. Mixes are useful. They will be unnecessary if the preventative and cultural measures are employed well and frequently. The best situation in which to use them is in preparing or clearing new ground or in inaccessible places and hard landscapes. Many of these items are only available to professionals as of recent new laws (1999). Chemical type & usage information correct as of 1997.

There are three main types: 3.1 Foliage Acting. 3.2 Soil Acting. 3.3 Selective.

3.0 Chemical

3.1 Foliage Acting

Chemicals acting on the plant, enter through the leaves.

3.1.1 Translocated

All types: Growing weeds: Inactive to soil. Moves from the leaves to the roots, destroying all. Used in vigorous growth.

3.1.1a Glyphosate

Inactive to soil. Do not use on lawns or beds. Kills all main weeds.

3.1.1b Amitrole

Control for cracks, crevices and paving.

3.1.2 Contact

Annuals : In-between shrubs: Growing weeds. Kills by direct contact, best for annuals.

3.1.2a Paraquat/diquat

Good for annuals. Also checks perennials. Any time, best in spring to kill overwintering annuals. Avoid all shrubs and green growth.

3.1.2b Dichlorophen

Algal growth, moss.liverwort on stone

3.2 Soil Acting

All Weed Seeds: Bare ground: In-between shrubs. Long lasting, residual. Applied to soil, and absorbed by roots of growing weeds, and then move to leafy growth. Best for emerging seedlings.

3.2.1 Propachlor

Good for annuals in borders and veg plots. Few weeks only

3.2.2 Simazine

High rates kill all weeds for 12 months. Low Rates: controls germinating seeds in shrub beds for 7 months. Use limited to Feb/March to moist free soils. May be damaging to shrubs.

3.2.3 Ammonium sulphamate

Controls many herbaceous plants, tree stumps, 12 week residual.

3.2.4 Dichlobenil

Applied around bushes and shrubs that are two years old to suppress perennials and annuals and germinating seeds. Acts for several months. Best in March or April when soil is moist. May damage some trees.

3.3 Selective

These kill broad leafed dicots, and leave narrow leafed monocots alone, or visa versa. Best used in lawns.

3.3.1 Alloxydium-sodium

kills perennial grasses.

3.3.2 Mecoprop/
2,4-D/ Dicamba

kills most broadleafs in a lawn.

3.3.3 Dichlorophen

Kills moss.

3.3.4 MCPA

In lawns for those resistant to the above

Weedkiller Use: Precautions

Precautions Before Using A Weedkiller.

Make sure you have purchased the correct chemical
Always read the manufacturers Instructions
Follow these instructions to the letter
Always don the appropriate protective clothing
Storage must be in a locked confined space, with no sunlight

Code Of Practice For Herbicide Usage

Only use approved herbicides
Alert river authorities if using near water
Avoid spillage, Apply correctly
Use appropriate approved clothing
Use appropriate approved applicator

Protection Of Public

Follow precautions as detailed in label.
Wash all containers and dispose of correctly
Erect signs to tell people you are spraying
Avoid drift in public areas

Protection Of Farm Animals Wildlife

Protect animals and wildlife from sprayed areas until diluted
Avoid drift to sensitive areas
Take precautions above near water areas

Protection Of Crops and Shrubs

Avoid spraying directly onto above
Do not harvest crops for recommended period
Do not plant crops where residual weed killer is used

Information Collated by James M. Burton as part of H.N.D. Course at Pencoed Agricultural College.
Chemical Information Correct as of 06:06:97. Always read and follow the instruction when using herbicides.