How do we manage weeds?

Learning Outcomes:

• Students can describe different methods used to manage weeds.
  
• Students can explain the different safety procedures used with each control method.
  

Resources Required:

1. Pest Plant Fact Sheets from the local or regional council
2. Plant Pests of the local area

Activities:

1. Investigate the different control methods used by Pest Plant Officers and land owners in the fight against weeds. Use the Pest Plant Fact Sheets for your research. Be sure to include any important safety tips when using different control methods!

   You may find a chart helpful to record your findings with the headings 'Weed', 'Control methods', 'Safety tips'.

2. Wild Weed Crime File - Wanted for crimes against the environment! Create a crime file poster with all the important facts about your weed!

Extra Activities:

1. Independent close reading and inquiry- explore the different methods of control for weeds as listed in the Pest Plant fact sheets.
   
2. Investigate the differences between the use of chemical and organic control methods. Think about cost, the length of time for eradication to occur and impacts on the environment.

Reflection:

How does your regional council manage weeds?

What safety tips do we need to consider when using each method of control?

Teachers' Notes:

Regional Council and Department of Conservation Management Strategies gives an indication of the relative importance of the weeds that Pest Plant Officers actively control.

Weed Control Methods

There are four basic weed control methods:

1 Mechanical control

At the simplest level, this involves simply pulling weeds out by hand. In some situations machines may be used to mow weeds. Machinery is often used to dig out willows on a river bank or to crush gorse in a paddock. Diggers are often used to remove aquatic weeds that are choking drains. Boats with special equipment have been used to remove weeds from lakes.

2 Chemical control

There are hundreds of chemical formulations, herbicides, which are used for the control of weeds. They act in different ways and have different uses. They are all toxic to a greater or lesser extent and should be used with caution. Children should never be allowed to use them and adults should always wear protective clothing and follow the label instructions carefully.

There are two main groups of herbicides:

Those which act on contact with the plant and only destroy the plant material directly exposed to the chemical and have no effect on the root system, e.g. paraquat (Preglone).

Those which are systemic , i.e. the herbicide is translocated from the leaves around the plant in its sap so that the entire plant is killed, e.g. glyphosate (Roundup). Some herbicides, such as glyphosate, will kill many different kinds of plants. Others are more selective such as Grazon which has little effect on grasses and is therefore often used by farmers.

Some herbicides remain in the soil for some time, e.g. Escort, while others are quickly biodegradable, e.g. glyphosate. Some are particularly toxic to fish and should never be used near waterways. Spray drift can be a problem, damaging nearby plants or people. Orchardists are particularly wary of this problem.

3 Cultural control

In this category are activities such as:

• Planting native plants which will eventually shade out weeds.
  
• Careful stock management on farms which can minimise the spread of some weeds.
  
• Gardeners disposing of their weeds responsibly and not dumping them down a convenient nearby bank.
  
• Not allowing nurseries to propagate or sell invasive plants.

4 Biological Control

Notes in next worksheet.

Download -How do we manage weeds? doc