Herbicide control methods

Herbicides control weeds (called invasive plants in the Biosecurity Act 2014) either by speeding up, stopping, or changing the plant's normal growth patterns. This affects the plants by drying out the leaves or stems, or by making it drop its leaves.

Types of herbicides

The use of herbicides is sometimes the only practical and selective method of managing certain weeds. Herbicidal applications are usually cost-effective control methods in bushland areas, particularly when funding is scarce.

In many cases, weeds are only susceptible to 1 specific herbicide, and it is important to use the correct product and application rate for control of that particular plant. Common mistakes include incorrect identification of the invasive plant or using inappropriate products chosen solely on price. In most cases, plants must be actively growing to be vulnerable to herbicide treatments.

There are 5 types of herbicides:

• broad spectrum - these work on a wide variety of weeds
• selective - these work on a narrow range of weeds
• contact - these destroy plant tissue at or near the point of contact (they do not spread around the plant), and require even coverage in their application
• systemic - these move through the plant's circulation system, and can be injected into the plant
• residual - these can be applied to the soil and destroy by root uptake. They remain active in the ground for a certain length of time, and can control germinating seedlings.

Safeguards for using herbicides

The Australian Pesticides and Veterinary Medicines Authority (APVMA) controls and regulates pesticides, including herbicides. APVMA assesses chemical products for toxicology, efficacy, environmental impact, residues, breakdown times and occupational health impacts. The APVMA scheme is recognised as one of the world's most rigorous safeguards.

Herbicide label information

It is extremely important to read and adhere to the information on the herbicide label.

This includes:

• signal heading (indicating the product's hazard level)
• trade name
• claims for use
• active constituent
• net contents
• directions and limitations
• withholding period
• storage instructions
• safety directions and first aid
• dangerous goods notification
• expiry date
• mode of action (type of herbicide)
• important notes.

By law, herbicides can only be used in accordance with the claims for use on the label. Most environmental plant applications are not listed on herbicide labels. In these cases, it is necessary to obtain an off-label permit.

Off-label permits for the use of herbicides

As the majority of environmental weeds are not listed under their species names for herbicide registration, an off-label permit has been approved by APVMA to assist Biosecurity Queensland, local government and environmental groups in managing these weeds.

Herbicides have been approved for use against a large variety of environmental plants. It is a requirement that all persons using products covered by this off-label permit comply with the details and conditions listed in the permit. Find out how to apply for a permit.

Also consider...

• Read the listings of restricted, prohibited and other invasive plants, which includes information on how to control various weeds.
• Use the APVMA permit search to get the most up-to-date herbicide registration information.