Bifora (Bifora testiculata) is an annual weed in cropping regions. Its presence in grain and hay is considered contamination and will therefore also reduce their market value.
Bifora is found mainly in South Australia with very few occurrences in Victoria and the Northern Territory, and some undocumented reports in New South Wales. In South Australia, it competes with cereal, legume and brassica crops. When uncontrolled can contribute to yield loss. Its presence can also increase crop input costs, which in turn will lead to reduced gross margins.
Bifora is easy to identify.
- Grows approximately 35 cm tall
- Spear-shaped and hairless cotyledons with round to pointed apex
- Seedling leaves are hairy and divided into three segments, with each segment further divided into three.
- 1-2 cm white flowers with five petals in terminal clusters
- Pairs of wrinkly skull-shaped seeds with two holes near a beak and three brown stripes along their back.
You’ll recognise Bifora not only through its appearance, but through the strong coriander-like odour it emits when crushed. It is often referred to as ‘carrot weed’ due to its carrot-like leaves.
Bifora is difficult to control due to the lack of effective post-emergent herbicide options and the persistence of the seed in the seed bank. Approximately 25 per cent of seeds from the previous season will germinate in the first year, with the remaining lingering in the seedbank for up to eight years.
Most effective controls can be implemented with early identification and action. Cultivation of the soil profile can help to disturb the seed bank and therefore lead to greater germination rates, which in turn will increase the weed population that can be targeted in an initial knockdown.
While there are limited easy and cost-effective ways to control Bifora in legumes and brassicas, early post-emergent control (before the four-leaf stage) is considered most effective in cereals with a 90 per cent control in wheat and barley. Control in pre-emergent and late post-emergent applications is possible, but is considered less effective.
Given that better control can be obtained in cereals, it is therefore best practice to take action in cereal crops to reap the benefits of reduced weed numbers in rotations where Bifora control options are limited. Mixes containing halauxifen/florasulam (ie Paradigm) show great results in reducing plant numbers in cereal crops*. An effective method of control is to start with Paradigm or Affinity as a first clean, then follow up with 2-4,D Amine later in the season to knock the second germination of plants that were not knocked out previously. Below is a table displaying some chemical options that can be used, and the times at which to spray.
|CHEMICAL||BRAND NAME||GROUP||TIME OF APPLICATION||NOTES|
|Imazethapyr||Spinnaker||B/2||Pre-emergent||For use in some legumes|
|Chlorsulfuron||Glean||B/2||Pre-emergent||For use in some cereals|
|Metsulfuron Methyl||Ally||B/2||Early post-emergent||For use in some cereals|
|Carfentrazone||Affinty Force||G/14||Early post-emergent||For use in cereals|
|Metribuzin/carfentrazone||Aptitude||C/G 2/14||Post-emergent||For use in cereals|
|Halauxifen/florasulam||Paradigm||I/B 4/2||Post-emergent||In cereals with LVE MCPA|
|Amine||2,4-D Amine||i/4||Late post-emergent||For use in cereals|
|Paraquat/diquat||Spray Seed||L/22||Crop topping||Only late germination|
Note: ensure the label is followed regarding crop choice, rate of application and timing of application.
It is important to still consider other in-season control options for Bifora given it generally germinates later than most crops. Desiccation or crop-topping, where applicable, are other methods that can be utilised in managing the weed prior to seed set, but timing of chemical application can be difficult given that Bifora may have already set seed at this point. This will lead to reduced seed in the seedbank and therefore help to reduce Bifora numbers in following seasons.
The seedbank can blow out through the cropping rotation in legume and brassicas due to a lack of current available chemistry options. It is also worth noting that integrated pest management methods (such as harvest weed seed management) should also be employed to reduce reliance on chemical control.
Elders offers a range of pre-emergent and crop protection products. View the range.
For more help on controlling Bifora and other cropping weeds speak to your local Elders branch
Article written by Zoe Fulton, Graduate Agronomist based at Elders Jamestown (SA).