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Australian Herbicide Resistance Initiative (AHRI)

Crop seed contamination survey

Crop Contamination

Surveys were conducted on WA farms in 1999, 2008 and 2015 to address the issue of resistance mobility by seed movement by assessing grain samples (wheat, barley, lupins, canola) which were taken from crop planting seed stocks.

Map

2008

Most Australian farmers grow and conserve their own crop seed (especially cereals), however this seed can be contaminated with weed seed. Some seed cleaning operations are only partially effective and therefore weed seed is seeded into paddocks with the crop seed. For weeds such as ryegrass, wild oats, and wild radish, this weed seed can be herbicide resistant and it is therefore possible for farmers to unwittingly introduce herbicide resistance to crop fields.

Surveys were conducted on WA farms in 1999 (Powles & Cawthray) and 2008 (Michael et al) to address the issue of resistance mobility by seed movement by assessing grain samples (wheat, barley, lupins, canola) which were taken from crop planting seed stocks. This crop seed was then sieved to identify and quantify the level of contaminating weed seed and this weed seed was evaluated for herbicide resistance status. Information was collected on whether the crop seed had been seed-cleaned and perceptions as to contaminating weed seed.

The 2008 survey revealed that:

  • Nearly all of the surveyed WA farmers used or employed crop seed cleaning techniques
  • Significant weed seed remained in crop seed samples, especially ryegrass and wild radish.
  • Many WA farmers are unknowingly introducing weed seed and herbicide resistance into their paddocks
  • Cleaned crop seed had significantly lower levels of contamination thanuncleaned crop seed
  • 25% of crop samples were weed free, indicating that it is possible to achieve clean crop seed

2015

Most Australian farmers grow and conserve their own crop seed (especially cereals), however this seed can be contaminated with weed seed. Some seed cleaning operations are only partially effective and therefore weed seed is seeded into paddocks with the crop seed. For weeds such as ryegrass, wild oats, and wild radish, this weed seed can be herbicide resistant and it is therefore possible for farmers to unwittingly introduce herbicide resistance to crop fields.

A follow up surveys were conducted on WA farms in 2015 to address the issue of resistance mobility by seed movement by assessing grain samples (wheat, barley, lupins, canola) which were taken from crop planting seed stocks. This crop seed was then sieved to identify and quantify the level of contaminating weed seed and this weed seed was evaluated for herbicide resistance status. Information was collected on whether the crop seed had been seed-cleaned and perceptions as to contaminating weed seed.

The 2015 survey revealed that:

  • Nearly all the surveyed WA farmers used or employed crop seed cleaning techniques
  • Significant weed seed remained in crop seed samples, especially ryegrass and wild radish.
  • Many WA farmers are unknowingly introducing weed seed and herbicide resistance into their paddocks
  • Cleaned crop seed had significantly lower levels of contamination than uncleaned crop seed
  • 41% of crop samples were weed free, indicating that it is possible to achieve clean crop seed
  • 75% of samples were contaminated with volunteer cereals and legumes
  • The average level of contamination was 18 weed seeds/10kg sample
  • Ryegrass was present in 49% of samples
  • Wild radish, wild oat and brome were present in 16%, 12%, 11% of samples respectively
  • Independent seed cleaning contractors (either in town or mobile contractors) had significantly cleaner crop seed samples than on farm cleaning methods
  • In town cleaners averaged 10 weed seeds/10kg crop seed, mobile cleaners 17 weed seeds/10kg crop seed and on farm cleaning 144 seeds/10kg crop seed
  • Uncleaned samples had around 1841/10kg (mostly ryegrass in cereals)

**Uncleaned samples had 45-160 times higher levels of contaminations; therefore, any sort of grain cleaning will have significant effects of the level of weed seed contamination.

Related Publications

Michael, P.J., Owen, M.J. and Powles S.B. (2010) Herbicide-Resistant Weed Seeds Contaminate Grain Sown in the Western Australian Grain Belt. Weed Science, 58, 466-472.

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