Drought conditions can increase the presence of new and existing weeds on your property.
Key points for managing weeds during and after droughts.
When bringing feed and fodder onto your property, you increase the risk of introducing new weeds found in other parts of Australia. Knowing where your feed and fodder has come from and what it is made up of can help manage any potential biosecurity risks.
If you are receiving donated fodder or feed, you can take these steps:
Other source of information
Drought creates dry soil conditions that prolong the viability of weed seeds. The fungi and bacteria that break seeds down need moisture to function. In dry soil, weed seeds do not break down, and remain completely viable, as if they have been kept in a paper bag in the cupboard.
Longevity of the seedbank of different weed species, assuming no replenishment.
Weed common name
Black Bindweed/climbing buckwheat
Bladder ketmia/wild cotton
Cobbler’s peg/farmer’s friend
Corn gromwell/white ironweed
False castor oil/thornapples
Citrullus and Cucumis spp.
Source: Tony Cook, NSW DPI.
Short-lived seeds (80 to 90% gone after one year, if no replenishment).
Moderate-lived seeds (50 to 80% gone after one year, if no replenishment).
Long-lived seeds (<50% gone after one year, if no replenishment).
There is further risk that contaminated fodder and grain could have herbicide resistant weed seeds – such as annual ryegrass. Herbicide resistance is widespread in the grain belts of South Australia and Western Australia – and large quantities of grain are often obtained from these areas when there are drought conditions in NSW.
After rainfall following drought conditions there can be an increase in livestock poisoning from weeds. Stock losses are attributed to direct plant poisoning and photosensitisation, with the main problems caused by:
In cropping areas, the immediate problem is fallow weeds, which quickly rob the soil of both valuable nutrients and moisture. A combination of cultivation and herbicide can control fallow weeds. The weeds likely to cause most concern are:
In pastoral and tableland areas, weeds that make remarkable recovery and spread include: