TREAT WEEDS - AHCPMG201A

WEED CONTROL METHODS 

• Weed prevention:  Preventative weed control refers to any control method that aims to prevent weeds from being established in a cultivated crop, a pasture, or a greenhouse. Examples of preventative weed control would be using certified weed free seed, only transporting hay that is weed free, making sure farm equipment is cleaned before moving from one location to another, and screening irrigation water to prevent weed seeds from traveling along irrigation ditches.

• Early detection and eradication:
• Biological control: Releasing a weed's native natural enemy such as insects, grazing animals or disease
• Cultural control:   Cultural weed control refers to any technique that involves maintaining field conditions such that weeds are less likely to become established and/or increase in number. Examples of cultural weed control would be crop rotation, avoiding overgrazing of pastures or rangeland, using well-adapted competitive forage species, and maintaining good soil fertility.
• Physical control: Removal of weeds by mowing, chainsaws, brush cutters, mulching, tilling, burning, grazing or by hand.  i.e.  HAND-PULL, DIG-OUT & MECHANICAL REMOVAL.
• Chemical control: Use of chemicals, such as herbicides
• Integrated weed management: Using a range of the above control measures
• Ongoing maintenance

http://www.environment.gov.au/biodiversity/invasive/weeds/management/index.html

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Understanding Weed Killers

Grooming a gorgeous lawn requires persistence and patience as you work to eradicate weeds. Herbicides are a key weapon in the lawn weed control arsenal. Two types of herbicides are commonly used: pre-emergent and post-emergent. The names describe when the herbicide kills weeds. Pre-emergents kill weeds before sprouts emerge from soil. Post-emergents decimate actively growing weeds that have already emerged from soil.

Pre-Emergent Herbicides

These herbicides don’t stop weed germination, but rather interrupt the process before a sprout pushes through soil. A common example of a pre-emergent herbicide is a crabgrass preventer, which prevents crabgrass seeds from establishing new plants.

Secrets to Success

• With pre-emergent herbicides, it’s vital to treat the entire lawn area. If you miss a spot, weeds can sprout there.
• Most pre-emergents require watering in, even liquid forms applied using a hose-end sprayer. With liquid herbicides, the volume of water used to disperse the weed killer is not great enough to wash the material into soil, where weed seeds lie waiting to germinate. That’s why you have to water after application.
• Use caution when applying pre-emergent herbicides to newly seeded lawns – or to areas you plan to seed. Read the label carefully. For most products, the label stipulates how many mowings, after seeding, to wait before application. The label also states how long to wait after application before sowing lawn seed.

Post-Emergent Herbicides

These herbicides tackle both perennial and annual broadleaf weeds (weeds with leaf shapes that don’t resemble grass), and some even control grassy weeds (weeds that resemble grass). Choose post-emergent herbicides to control existing weeds in a lawn. It’s an ideal herbicide for spot-treating lone offenders.

Secrets to Success

• Young, actively growing weeds die most easily and create less of an eyesore than mature weeds, which might require repeat applications for complete kill.
• Inspect the lawn frequently (while mowing is a good time) to look for new weeds that have germinated and require treatment.

Timing!

For both pre- and post-emergent herbicides, timing is critical. While post-emergent herbicides kill weeds at any point in the growth cycle, you’ll have the best success spraying young, actively growing weeds. Mature weeds may require repeated applications for total kill.

With pre-emergent herbicides, you’ll want to apply the chemical prior to the time weed seeds start germinating. If you apply too early, these herbicides will have degraded and are useless when seeds start to germinate. Most pre-emergent crabgrass killers remain active in soil for six to eight weeks.

Weed seed germination occurs when soil reaches the correct temperature. The best way to determine the ideal time to apply pre-emergents is to contact your local extension agent or master gardeners, who have access to regional soil temperature data.

Other ways to gauge application time include using bioindicators, such as plants whose growth signals the correct time for application. For instance, in northern climates, spring crabgrass applications are often timed when forsythia is blooming, which frequently (but not always) occurs when soil temperatures are in the 50° F range. Another option is to time applications based on the calendar. For example, if you typically apply a pre-emergent herbicide in mid-April with success, then continue that routine.

Of course, you can avoid the issue of proper application timing altogether by purchasing a weed control product that combines both pre- and post-emergent herbicides. This type of product kills existing broadleaf weeds and keeps them from returning for as long as six months.

Information from BayerAdvanced.com

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Question 11.
List the advantages and limitations of using heat or steaming as methods of weed control.

Thermal Weeding

Thermal weeding is a method where high temperatures are applied to weeds, causing the plant to die. Thermal weeding is particularly useful in situations where conservation or health considerations are high and weed density is low such as waterways where herbicide use is not permitted.

Best results are obtained when follow up weed control is undertaken 4-6 weeks after treatment. In addition, weed control should be conducted periodically after that for example to control weeds over a period of a year it is likely that between 3-5 applications will be necessary, depending on rainfall and the extent of the weed seed bank.

This method is most effective on young annual weeds and least effective on older perennial weeds. In some cases control of perennial weeds will be ineffective however this depends on the species present and its age.

There are several thermal methods that can be used to control weeds:

• Flame weeding
• Steam weeding
• Bio-thermal weeding

Flame Weeding

A flame weeder uses LP gas to produce a flame which produces enough heat to vaporise the water in plant cells. As a result, this moisture loss inhibits photosynthesis killing the weed. A flame weeder has also been shown to stimulate the germination of native plants, while killing the seeds of annual weeds such as Devils Pitchfork, Bidens pilosa. The only disadvantage to flame weeding is the cost of gas and the risk of fire.

Steam Weeding

A steam weeder works by causing the temperature of water in plant cells to rise causing the cells to rupture. This causes the plant to dies from the outside back to the root system. Steam weeding has been shown to be more effective at killing plants than flame weeding. However, they require a lot of water and energy to heat the water.

Information from Dragonfly Environmental.net.au

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