Protection of Crops

Protection of crops

Protection of crop, native and other non-target plants
With all herbicides it is vital to avoid contact with foliage, green stems or fruit of crops, desirable plants and trees since severe injury or destruction may result. Do not apply under weather conditions or from spraying equipment that may cause spray to drift onto nearby susceptible plants/crops, cropping lands or pastures. Do not contaminate dams, rivers or streams with product or used container. Do not apply to weeds growing in or over water or across open bodies of water.

How to apply herbicides

Foliar spraying involves diluting the herbicide with water or another dilutent as specified on the product label, and spraying over the foliage to the point of runoff, until every leaf is wetted, but not dripping. Spraying is most efficacious on flat weeds, ground covers, grasses shrubs, and dense vines less than 6 m tall so that complete coverage is achieved. Advantages include speed and economy, but disadvantages include the potential for spray drift and off-target damage.

Basal bark spraying involves mixing an oil soluble herbicide with a dilutent recommended by the herbicide manufacturer and spraying the full circumference of the trunk or stem of the plant and is suitable for thin-barked woody weeds and undesirable trees. It is also an effective way to treat saplings, regrowth and multi-stemmed shrubs and trees. This method works by allowing the herbicide to enter underground storage organs and slowly kill the targeted weed.

Stem injection involves drilling or cutting through the bark into the sapwood tissue in the trunks of woody weeds and trees. A herbicide is immediately placed into the hole or cut within 15 seconds of drilling the hole or cutting the trunk. The aim is to reach the sapwood layer just under the bark (the cambium growth layer), which will transport the chemical throughout the plant. This method kills the tree or shrub where it stands, and only those that can be safely left to die and rot should be treated this way.

Another method referred to as the ‘drill and fill method’ or tree injection is used for trees and woody weeds with stems or trunks greater than 5 cm in circumference. A battery-powered drill is used to drill downward-angled holes into the sapwood about 5 cm apart. The placement of herbicide into the hole is usually made using a backpack reservoir and syringe that can deliver measured doses of herbicide solution.

Similarly the ‘axe cut method’ or frilling or chipping involves cutting through the bark into the sapwood tissue in the trunk, and immediately placing herbicide into the cut. This method can be used for trees and woody weeds with stems or trunks greater than 5 cm in circumference.

Cut stump application is where the plant is cut off completely at its base (no higher than 15 cm from the ground) using a chainsaw, axe, brush cutter or machete. A herbicide solution is then sprayed or painted onto the exposed surface of the cut stump emerging from the ground, with the objective of killing the stump and the root system.

Stem scraping also called bark stripping or stem painting is used for plants and vines with aerial tubers. A sharp knife is used to scrape a very thin layer of bark from a 10 cm section of stem. Herbicide is then immediately applied to the exposed soft underlying green tissue.

The wick application method uses a wick or rope soaked in herbicide from a reservoir attached to a handle to wipe or brush herbicide over the weed.

For up to date chemical products listed for a particular weed the Agricultural Pesticides and Veterinary Medicines Authority (APVMA) website provides an excellent search engine. Simply type the weed you are interested in controlling in the ‘disease/pest’ search field and hit search. The search will bring up all the products and their labels to help you determine the rate of chemical required for the job at hand. https://services.apvma.gov.au