Roundup Ready canola is resistant to glyphosate but glyphosate can only be applied from the 2-6 leaf stage to avoid serious yield penalties. As yield penalties are associated with the lack of ryegrass control on emergence, it is recommended to incorporate the residual grass herbicide trifluralin when sowing to gain long term grass control. Not only does this create additional costs, but also for many farmers, this negates the reason for growing canola as a break crop to avoid chemicals commonly used in alternative rotations as glyphosate and trifluralin are commonly used on cereal crops.

The remaining broadleaf weeds are controlled by one or two applications of glyphosate at 621gm/ha (similar to 1.38L/ha of glyphosate 450) between the two to six leaf stage. This narrow time-frame window of approximately two to four weeks after sowing will prove difficult as farmers are busy sowing other crops or there may be delays caused by unsuitable weather. If multiple germination of canola occur, it will be difficult to apply glyphosate in this time frame as it could be either too late or too early for a percentage of the crop.

As there is no residual broadleaf control on the canola crop, it is likely that late emergence of wild radish and wild turnip will occur. These weeds are closely related to canola and there is no post-emergent herbicide available to control them. Severe infestation will lead to yield penalties and a weed burden that will carry to following crop rotations. If wild radish or wild turnip is found in the harvested sample of canola, it can lead to price penalties and rejection of the product as it affects the quality and taste of canola oil.

Farmers growing GM and neighbours surrounding farmers that grow GM must apply an additional chemical to glyphosate to ensure they have controlled unwanted glyphosate tolerant volunteer canola.

As part of the resistance management plan, farmers must remove glyphosate as a knockdown chemical in following rotations. As there are limited choices for alternatives, farmers will use either tillage or the more toxic chemical, Sprayseed. As most farmers have already adopted minimal tillage practices for environmental purposes, it is a backward step to reintroduce tillage. The chemical Sprayseed (paraquat/diquat) is considered one of the worst to apply, as it is common for farmers to get headaches, hallucinations and blood noses from only a light inhalation of fumes. It is also not as effective for weed control as glyphosate, particularly if there is the buildup of stubble residue that is common with minimal tillage practice.

Farmers may object to following the resistance management plan that could create an extremely serious problem with the development and spread of glyphosate resistant weeds due to overuse of the chemical and survival of plants that have a natural resistance to glyphosate. Glyphosate is the most important chemical available to Australian farmers and development of resistance to glyphosate will have a serious impact on the economics of farming.

The first independent and regulated National Variety Trials showed GM Roundup Ready hybrids yielded less than non-GM triazine tolerant and Clearfield varieties. Four GM RR varieties (3 hybrids, one non-hybrid) were compared to 24 non-GM varieties. The best of GM in Victorian trials was 0.73t/ha compared to 0.82t/ha for non-GM and the worst yield of GM was 0.5t/ha. In New South Wales the best yield of GM was 1.15t/ha while the best yield for non-GM was 1.26t/ha.

The weed control cost of applying trifluralin and glyphosate on GM Roundup Ready compared to triazine used on non-GM TT crops is higher. The cost of Roundup Ready seed and seed use is very high. In 2008, the additional costs included a "half price" stewardship fee of $500/farm; a "discounted" $10.20/tonne user fee proponent to be deducted in an end point royalty and approx. $43.50/ha additional for seed if sown at 3kg/ha. In order to pay for technology use a considerable increase in yield is required. In Canada, the price of GM technology has increased by 600% since introduction in 1996. It is illegal to save and replant seeds and each year, the farmer is bound by Monsanto’s contract.

GM Roundup Ready canola is only a weed control tool but weed control is very limited. As no increase of yield is available while costs are far higher the expected economic loss associated with growing GM Roundup Ready canola is significant.

Invigor canola is resistant to glufosinate ammonium but this herbicide does not control radish or turnip at all. As there is no post emergent radish control available, it is unlikely that farmers with a radish or turnip problem can grow this crop. As there is no residual weed control offered with glufosinate ammonium, it is likely that additional post emergent weed control is required.

The recommended rate of application of Liberty herbicide is 2kg/ha at the 2-4 leaf stage with a top up application 7 days to 10 days later. This narrow-window spraying regime would be difficult to incorporate in a busy seeding schedule. Limited data is available for Invigor crops but in 2002, Bayer Cropscience estimated costs of glufosinate ammonium at $18/litre (equating to $72/ha). Considering the limited weed control offered, it is unlikely farmers will be prepared to pay these additional costs.