Bushfires and weeds
The risk of weed invasion on farms and the environment can dramatically increases following bushfires.
The spread of weeds can often be overlooked, as dealing with other pressing emergency response and recovery issues understandably takes priority and it is not until some months after the fire, when it starts to rain, that weeds become obvious.
Weeds can become a costly legacy to the farmer and the environment, but early detection and control can have positive outcomes.
There are many types of weeds that can be found after fire, but these can be can be placed into four distinct groups.
Fire adapted weeds
Fire adapted weeds are weeds that are well adapted to fire and fire can cause mass germination of the seed bank. They continue to grow vigorously and spread long after a fire. Many of these weeds are highly invasive and will displace native vegetation, increase fuel loads, harbour pest animals and diseases, as well as take up valuable farming land.
Some of these weeds like blue bell creeper are introduced natives from other parts of Australia. Some weeds such as gorse and Montpellier broom have been introduce from other parts of the world and are Weeds of National Significance (WoNS).
Pioneer weeds such as African daisy and thistles are fast growing annuals or short lived weeds that take advantage of the bare-earth and can make it difficult to establish pastures and crops, as well as contaminate produce.
They can also be found in native vegetation after fires but are outcompeted over time as the native species recover. On the farm it is important to control these weeds before they set seed because many of them have long lived seed and will persist in areas that are kept bare for amenity.
Other weeds that can be seen after fire are weeds that have survived the fire like bridal creeper and cape tulip. They may have been greatly controlled by the fire, but can grow vigorously from their bulbs or corms. These weeds are often highly invasive to our native bush and if left will displace native plants and animals over time. After a fire there is a great opportunity to eradicate these weeds from an area.
New weeds can also sometimes be seen after fire. The activities around fire emergencies and the recovery of fires (i.e. movement of vehicles and machinery) can greatly increase the spread weeds to new location.
Whilst traditionally the west end of Kangaroo Island only has a small proportion of the weed species compared to those found on the eastern end of the island and the mainland, there is now a risk of new weeds being found.
To minimise this risk, farmers and land managers can implement some simple actions which may save money, environmental values and avoid future stress whilst recovering from an emergency.
To help prevent spread of weeds on the farm it is best to confine new stock to one paddock for a week after purchase and to feed imported fodder in the same place or practice containment feeding. This should be in an area that can be checked for weeds biannually easily for summer and winter weeds.
Fodder should also be placed away from traffic to prevent the spread of weeds by vehicles and animals. To learn more about how to reduce the spread of weeds and prevent the establishment of new weed species, download the Livestock management guidelines and Fodder management guidelines.
A large part of part of successfully controlling weeds is early detection and identification of the weed, so appropriate control can be applied. This can sometimes be very difficult as plants like African love grass can be very difficult to identify until it starts flowering.
For help and advise you can ring your local Animal and Plant Control Officer or you can also find plenty of useful information and advice on how to identify and control weeds through the Weed Control Handbook, or by downloading the SA Weed Control app for your tablet or smart phone.