Virtual weed control

Photo of Lance Turner

Corrigin grain grower Lance Turner
has also been involved in a
GRDC-funded project assessing
the performance of the Harrington
Seed Destructor in comparison
with chaff carts and narrow
windrow burning.

PHOTO: Nicole Baxter

Image of a Ryegrass Integrated Management flyer
Image of a Ryegrass Integrated Management flyer

Recently launched at the Global Herbicide Resistance Challenge conference, the Ryegrass Integrated Management model is a decision-support system that enables growers and advisers to determine the most profitable and sustainable way to tackle herbicide-resistant ryegrass in cropping systems

An Australian Herbicide Resistance Initiative (AHRI) workshop using the Ryegrass Integrated Management (RIM) model set Western Australian grain grower Lance Turner on the path to overcoming his herbicide-resistant annual ryegrass problem.

Lance discovered herbicide-resistant ryegrass on his 4000-hectare Corrigin property in 1996 following three years of a continuous wheat/lupin rotation. Although he was advised to start dropping paddocks out of production, with the help of the RIM workshop he embarked instead on an aggressive and integrated management approach to ryegrass control.

“The AHRI RIM workshop was a turning point for the way I farm,” Lance says. “From then on my mission was to control the weeds first. Lower inputs and better yields followed.”

Having towed a chaff cart for the past seven years, about 95 per cent of Lance’s paddocks now have low levels of ryegrass, enabling him to reap the production benefits of sowing early each year.

RIM is now another tool in Lance’s integrated weed-management approach.

Developed by the AHRI, RIM has recently been updated with GRDC support. The new RIM version is available to download for free from the AHRI website ( The software includes both strategic and tactical weed control methods.

Integrating ryegrass biology, agronomy and economics, RIM allows the user to observe the predicted effects of ‘what-if’ scenarios on ryegrass plant and seed populations, crop yields, and paddock economic returns over a 10-year period.

AHRI researcher Myrtille Lacoste, who developed the new RIM package, says RIM is a convenient way to test the profitability of ryegrass control methods before putting actual dollars at risk.

Key features of RIM

  • It evaluates the efficacy and profitability of ryegrass
    control methods in broadacre cropping systems on
    a per-hectare and paddock basis over a 10-year period.
  • It provides a choice of seven crop and pasture
    enterprises – winter wheat, barley, canola, legume
    crop and three types of pastures.
  • It incorporates 44 strategic and tactical field operations
    including cultural, chemical and mechanical methods
    such as time of sowing, herbicide choice, sowing rate
    (crop competition), grazing, crop sacrifice, crop topping,
    and harvest weed seed control (chaff cart, narrow
    windrow burning, Harrington Seed Destructor and direct
    baling system).
  • It enables users to customise the program using specific
    paddock details or use default settings based on an
    average southern-Australian grain production system.
  • It shows changes in ryegrass plant and seed densities
    over time, as well as the competition burden on crops.
  • It offers the possibility to compare the results of two
    strategies or two different situations.
  • It provides economic outputs including yearly gross
    margins, long-term economic return and budget allocation
    for weed control.
  • It allows settings, graphs and results to be saved,
    exported and printed for easy reference.

Computer simulations enable us to assess future scenarios so that we can make better decisions in the present. RIM won’t replace your expert judgement, but it will give you one more piece of evidence so that you can make important management changes with increased confidence,” Ms Lacoste says.

RIM helps growers tackle questions such as:

  • What combination of control options and rotations will provide the best overall weed management system in the long term?
  • How much could herbicide resistance cost me and how can I maintain my income if I am not able to rely on some herbicides into the future?
  • To what extent can I diversify my weed management system and remain cost efficient?
  • What is the economic value of tactical methods such as green manuring or mouldboard ploughing for controlling weeds?
  • Is it worth investing in harvest weed-seed-control machinery and, if so, under what circumstances will it be economic?

Users choose from seven crop and pasture enterprises and more than 40 field operations to build, evaluate and compare 10-year cropping and ryegrass management strategies.

More information:

Myrtille Lacoste
08 6488 7872,

To register your interest for RIM workshops or for more information visit, or email

Download RIM and its user manual and video for free from:

GRDC Project Code UA00124

Region West