Plant health top tips - March: using precision spray tech to optimise weed control

In simple terms, precision spray technologies means using optical cameras and sensors to identify individual weeds or patches within fields and applying high rates of herbicide to prevent seed set.

Initially this technology was used primarily in fallow fields to clean up patches of weeds that escaped summer fallow sprays. Growers who have adopted this technology are reporting savings of up to 90 per cent on their herbicide costs as they are only spraying 10-15 per cent of the field. Therefore, this also means they are using 90 per cent less water. If you are applying herbicide as a blanket application, you are spraying 85-90 per cent bare ground. For growers this is inefficient and expensive.

Precision spray technologies have allowed us to undertake site specific weed management and patch management within fields, adding important tools to the Integrated Weed Management package that is the Herbicide Resistance Management Strategy (HRMS). Precision sprayers have evolved from the adoption of precision agriculture in the 1990s. Growers for many years have been using GPS to segment fields and produce yield maps. As technology has developed and computer processing power improved, growers are now able to access variable rate fertiliser, high resolution aerial imagery, soil maps and weed detection systems in real time.

The evolution in weed sensing technology is now allowing growers to identify not only green on brown differences, but green on green. Initially weed sensing sprayers were used to control weed escapes in fallows (green on brown), however in the past two years improvements in detection, computer analysis and machine learning is allowing weeds to be detected within crop (green on green).

This ability to incorporate site specific management into otherwise homogeneous fields is allowing growers to manage issues in a targeted manner, reducing input costs and potentially reducing the risk of developing herbicide resistance from broadacre applications of products such as glyphosate. By identifying patches of weeds within fields or fallows, growers can apply high rates of herbicide with different modes of action without the increased cost of applying these products across the whole fields. Precision spraying has the potential to improve the management of herbicide resistant and hard-to-kill weeds by using herbicide mixtures at higher rates that would be otherwise too expensive as a blanket application.

One added benefit in the use of precision sprayers in fallow situations is the potential to reduce the risk of off target damage from summer applications of herbicides. Summer fallow sprays can produce significant levels of potentially drift-able product (environmental loading) as large numbers of growers are spraying within the same window. Using precision sprayers to target patches will reduce the amount of product in the environment.

The issues of off target damage to susceptible crops is placing pressure on agriculture and the social license to continue applying pesticides. The use of precision spray technology will reduce herbicide use and provide greater control for applicators. Growers can now use precision sprayers to reduce pesticide input and limit the threat of residues appearing in grain and other products.

Therefore, it is in the interests of the industry and farmers to not only be seen to be doing the right thing but to look at technologies that will enable a reduction of pesticide use while maintaining or increasing profitability.

A good summary of the pros and cons of precision sprayers is available on the WeedSmart website.

Perhaps the next big step is to implement this technology onto autonomous platforms that can operate independently from the grower. This is the focus of new research in Australia and overseas.

For more information, please contact CottonInfo’s Weed Management Technical Lead, Eric Koetz.