Providing practical information to help you protect your farm from biosecurity risks

Untreated irrigation water: A clear biosecurity risk

July 30, 2014
Anthony Brandsema

Grower Anthony Brandsema is seeing the benefits of improved treatment of irrigation water. Photo: AUSVEG

Following a water-borne fungal outbreak in their north Tasmania glasshouse, brothers Anthony and Marcus Brandsema set about fine-tuning their irrigation system to minimise the risk of water-borne diseases, safe-guarding their income in the process.

More than 17 species of Phytophthora, 26 species of Pythium, 27 types of fungi, eight species of bacteria, 10 viruses, and 13 species of plant parasitic nematodes have been detected in water sources worldwide. Pathogens may be introduced via a number of sources, including sewage discharge and reuse, recirculated irrigation water, drainage from intensive livestock production systems and storm-water. 

“We discovered that we were getting a build-up of pathogens within the recirculated water and as a result we were exposing the rest of the crop to the pathogens and increasing the risk of spreading disease,” said Anthony Brandsema.

“We were just using hydrogen peroxide but we were never consistent with its use. Following the fungal outbreak we developed a system where we regularly make sure the recirculated water is being dosed with the correct amount of hydrogen peroxide,” he added.

Hydrogen peroxide is a natural oxidizing compound which eliminates pathogens as well as other organic material in the water. Used effectively, hydrogen peroxide is an effective defence against water-borne pathogens.

“In order to further limit the risk, and acting upon advice from agronomists and other growers, we also incorporated an ultraviolet (UV) water sterilisation system,” said Mr Brandsema.

UV light is absorbed by microorganisms and is capable of eliminating most fungi, bacteria and viruses. The UV steriliser acts as a secondary line of defence and should be used in combination with hydrogen peroxide dosing.

“The benefit is [increased] disease resistance and maximising our [production] capacity. We are now able to budget according to that and replicate each production year without being subject to the disease risk. We can budget and be confident knowing that we’re one risk less in our production,” said Mr Brandsema.

Irrigation water

Inadequate treatment of water can expose irrigated crops to an increased risk of infection by pests and diseases. Photo: AUSVEG

UV sterilisation and hydrogen peroxide dosing systems require significant investment, but Anthony says the risk posed by contaminated irrigation water justifies the investment.

“To remain viable we had to buy these pieces of equipment. Yes it was costly, but in the scheme of things the overall cost is not much. It’s about assessing the exposure to the risk and what measures to take to eliminate, not just reduce, the risk,” he said.

Many vegetable growers utilise multiple water sources to irrigate their crops. This increases the importance for early detection of water-borne pathogens, determining the pathogen load and assessing the overall risk this presents to crop health.

“We use the town supply as a backup and in our misting system, as well as collected roof water, and water from a storage dam which is pumped through the hydroponic unit. We routinely monitor pathogen loads and treat all water, other than the municipal supply which comes pre-treated,” said Mr Brandsema.

Anthony and Marcus are so impressed with the results of their UV sterilisation system that they are taking steps to increase its capacity, in an effort to end their reliance on the costly municipal water supply.

It is important that growers are aware of the risks presented by water-borne pathogens, and that they monitor their water supply and take precautionary measures to protect their farm.

Growers can contact the AUSVEG Biosecurity Officer, Dean Schrieke, on 03 9882 0277 for on-farm biosecurity advice.

Acknowledgement: This article was reproduced with the permission of AUSVEG