The Imtrader Ed.3 – Herbicide Control of Mature Caltrop Trial

Written by Michael Macpherson, Imtrade Australia and Elly Wainwright, Liebe Group

Key Messages

  1. Bipyridyls provide 100% brownout of caltrop.
  2. The addition of Sharpen (saflufenacil) to Paraquat will provide quicker brownout than Paraquat but an equivalent kill rate.

Aim
To investigate the response of caltrop to single knock post emergent sprays in the summer period.

Background
Caltrop (Tribulus terrestris) also known as bindii, goats head, yellow vine and cat’s eye, cat head and puncture vine is a summer annual herb, it has a sprawling flat habit and extensive tap root system. The seed that is produced by caltrop is formed continually in the summer months and one plant can produce upward of 20,000 seeds per plant (Department of Primary Industries, 2010) that will remain viable in the soil for five years (Wilen, 2006).

The seeds are easily picked up by shoes, paws, wools and vehicles helping it get dispersed over wide areas. It is a problem in agricultural areas as it extracts soil moisture and can thrive in very dry conditions making it hard to kill. Wheat emergence was reduced by 22% in 2003 and subsequently reduced wheat grain yield by up to 40% in two out of three years when caltrop was the dominant summer weed species. This means caltrop may have a strong allelopathic effect on wheat emergence (Hashem et al 2006).

Method
The Liebe Group and Imtrade Australia ran a trial at the Carter’s property in east Wubin to test single knock post emergent sprays on well established caltrop in a summer fallow situation. The chemistries used were bipyridyls (Paraquat 250, Spray.Seed, Para-Trooper) and glyphosate with and without group I or G additives as ‘spikes’.

Comments
The bipyridyl herbicides (treatments 3, 4, 5) provided complete control. The addition of Sharpen (saflufenacil) to Paraquat provided faster brownout, but equivalent control to Paraquat alone. Glyphosate 450 at 1.5 L/ha did not provide acceptable levels of control however, the addition of 2,4-D LV Ester provided equivalent control to that of the bipyridyl chemistries. Sharpen (Saflufenacil) as a standalone was not effective.

Acknowledgements
The Carter family for hosting the trial.
Paper reviewed by: Dr Abul Hashem, DAFWA.

References:
Department of Primary Industries (2010) Regionally Prohibited Weed Information Sheet – Caltrop.
Hashem, A., Pathan, S. and Osten, V. (2006). Summer weeds can reduce wheat grain yield and protein. Department of Agriculture and Food Western Australia, Perth. Proceedings of Crop Updates: weed updates 2006 ed, A. Douglas. pp 70-73.
Wilen, C., How to manage pests. Pests in gardens and landscapes: puncture vine. University of California.
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