Thursday, August 14, 2008

What is wrong with Roundup?

Will pricing pressure act as a catalyst for change? Glyphosate prices rise.

One of the pressing issues for farmers is the price increase of farm inputs. Issues with the rise of Diesel have been well noted, however the increased cost of production have also been pushed by an increase in the cost of the most widely used herbicide Glyphosate, often still referred to by its original tradename Roundup.

Recent market forces have seen the price of Glyphosate effectively triple. Worldwide demand has increased triggered by increasing herbicide use in the developing world and the planting of genetically modified Canola in North and South America for use as biofuel. The Australian market is small in comparison to these larger markets. Global supply is not meeting up with demand and prices are rising. Last season in Australia the price of a 20Lt container of 360 gram per litre Glyphosate was just over $100. Currently the same product would cost $250-280.

McLaren Vale vineyard in August prior to bud burst (EL-4).

In vineyards under row weed management is necessary to conserve water, remove noxious weeds, and prevent growth into the vine canopy where weeds can contaminate the grape crop. Beginning in the 1970’s farmers moved from cultivation to control weeds and switched to the use of herbicides. The chief tool used was Glyphosate, a Group M herbicide. It was cost effective and its use became almost universal.

The current price increase has caused many to consider the way they use herbicide in their vineyard and take a much closer look at the efficiency of it use.

The increase in the cost of Glyphosate is not the only negative with its continuing use. Organic vineyard techniques are designed to replace herbicides due to their environmental effects. Organic and biodynamic farmers are particularly concerned with the effect of Glyphosate on soil micro-organisms. Glyphosate is seen as an undesirable product due to its effect on soil. Applications are considered to cause a reduction in the number of beneficial soil micro-organisms and arthropods. Studies show a reduction in the species that build humus, thus it contributes to the decline in soil organic matter (Cox, 1998).

When Glyphosate comes into contact with the soil, it rapidly binds to soil particles and is inactivated. Unbound Glyphosate is degraded by bacteria. This has the effect of ‘feeding’ bacteria which in turn limits the development of beneficial fungi in the soil. Bacteria generally break down nutrients in the soil, while fungi are of great benefit as they help improve soil structure and make nutrients better available to plants.
Glyphosate significantly reduces the activity of nitrogen-fixing bacteria. These bacteria transform soil nitrogen into forms that plants can use. Studies of Soybeans grown for nitrogen fixation showed a reduction in the number of rhizobium bacteria and the nitrogen they produce when Glyphosate was used for weed control (Lehmann and Pengue, 2000).

Another major issue with the widespread use of Glyphosate has been the development of herbicide resistant annual ryegrass (Lolium rigidum). Annual ryegrass is a commonly found across the south eastern Australia. In vine crops 13 sites have been officially documented as being Glyphosate resistant in South Australia and Western Australia (Preston, 2008). The majority of cases are not documented and problem is widespread. This is particularly the case in vineyards that were previously old orchards and received multiple Glyphosates without rotation to another herbicide group.

In the vineyard, Glyphosate resistant annual ryegrass populations generally begin to appear as a scattering of single plants or small patches of plants that have survived a Glyphosate application. After frequent herbicide applications these grass populations have evolved from being susceptible to being resistant to Glyphosate herbicides. The Ryegrass is not controlled by Glyphosate and multiplies becoming a weed.
Many farmers are finding ryegrass is becoming more of an issue and it has become a serious problem.

However negative issues revolving around the use of Glyphosate it is still the most widely used herbicide in viticulture. It is likely to continue to be in the foreseeable future. The increased cost of the product and environmental issues have highlighted how it when used it must be correctly and efficiently applied.

The effects of Glyphosate on soil micro-organisms can be minimised by rotation with other products or the adoption of organic techniques to limit its use. For organic growers, where the use of herbicides is not an option, cultivation has remained as the primary source of control. In many situations the heavy application of mulch can replace the need to use herbicides as frequently. As an added benefit mulches enhance vine productivity by limiting evaporation of water during summer.

Herbicide resistant ryegrass can also be controlled by organic techniques. Commercial trialling of under vine mowing is underway. Cultivation in sandy soils with ‘dodge’ plough remains common in the Blewitt Springs subregion of McLaren Vale and more vineyards may look to this modern variations of this technique.

Relative cost of usage for Glyphosate and alternative knockdown herbicides - July 2008.
Where herbicides need to be used alternative herbicide groups can be used to reduce the amount of ryegrass before it sets seed to continue another generation. In 2008 some new formulations have been developed to specifically target herbicide resistant ryegrass. The knockdown herbicides Amitrole, a group Sprayseed, Diquat and paraquat and combinations, Alliance a group L/Q herbicide of these actives represent a good option for where resistant ryegrass is a problem. Over a period of two to three years these Glyphosate alternatives can be used to eliminate the resistant ryegrass.

Higher Glyphosate costs are closing the price gap between Glyphosate treatment and using a pre-emergent herbicides as an alternative. Products like Stomp and Rifle, Group D herbicides with the active ingredient Pendimethalin, may come into wider use.

What is clear is with Glyphosate prices at an all time high, farmers need to get the best results they can. Families of adjuvant have developed to compliment Glyphosate. Ammonium Sulphate, Liase or Ammend, is used to soften water that contains high levels of calcium. In the many regions underground water and town water supplies are found to be high in calcium which limits the effectiveness of Glyphosate. Pulse is an aid to penetration of waxy plants; Goal, Striker, and Hammer/Spotlight, all Group G herbicides are used as spikes on hard to control weeds allowing lower rates of herbicide to be applied.

With a high cost the efficient application of Glyphosate is important. Any spray drift is a waste of money. Incorrect maintenance of spray equipment can lead to nozzle wear which wastes chemical. Incorrect spray calibration and pressure can lead to high proportion of small droplets which are prone to drift, or large droplets that splatter. Checking the efficiency of herbicide systems is always important, but with increasing production costs it is vital.

Industry analysts predict the price of Glyphosate will continue to rise, therefore adding to the increasing the cost of grape production. Increased production cost force alternatives to herbicide use to become commercially more widespread. Increased costs also focus on the correct use of Glyphosate in order to keep it a useful tool in farming production.



Cox, Carolyn. "Herbicide Factsheet: Glyphosate (Roundup)," Journal of Pesticide Reform, Vol. 18, No. 3 (Fall 1998, Updated October 2000)

Lehmann V. and Pengue W. (2000), Herbicide Tolerant Soybean: Just another step in a technology treadmill? Biotechnology and Development Monitor. September 2000.

Preston, C. (2005) Australian Glyphosate Resistance Register. National Glyphosate Sustainability Working Group. Online. Available

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