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How long are disinfectant products effective for?

Quaternary ammonium (QA) products have been shown to kill fungal spores that cause Panama disease. Our researchers have been investigating the longevity of three QA products that contain 120g/L of the active ingredient, didecyl dimethyl ammonium chloride. The QA products evaluated included Sporekill®, Steri-max® and Path-X™, at a 1% (1200ppm) solution.

So what did we do?

The QA products were placed in plastic storage containers outside (with the lids kept on) and exposed to field conditions (e.g. sunlight and temperature) for a period of 12 months. The high level (0-1500ppm) QA test strips were used as indicators to test the solutions on a regular basis, and at 4, 8 and 12 months intervals.  At these intervals, small samples of the solutions were collected and inoculated with fungal spores of Panama disease race 1.

QA disinfectant samples placed outdoors and exposed to field conditions.
Testing of QA disinfectants.

So what was the outcome?

The results showed that after 12 months exposure to sunlight, temperature and humidity, all three QA products were still effective at killing spores that cause Panama disease race 1. Testing at 12 months indicated a reduction in the concentration (using the test strips) for some of the QA products, particularly Path-X™. Despite the potential reduction, no colony growth was detected when samples of the three QA products were inoculated with spores of Panama disease race 1 in the lab. This result indicated that the products were stable, even after 12 months exposure to field conditions.

Test strips used to test concentration of disinfectants 12 months after exposure to outdoor conditions.
Image on left shows growth of 800+ fungal colonies recovered from control (water no disinfectant). No fungal growth was recovered from disinfectant solutions (image on right).

Good news for growers...

QA disinfectants used in infrastructure such as spray shuttles, that isn’t contaminated with soil and organic matter, will be effective for an extended period of time even when exposed to field conditions. However, always remember to schedule regular testing of your disinfectant solutions to ensure they are effective. This can be achieved by using easy-to-use test strips.

For more information about this work contact the better bananas team: betterbananas@daf.qld.gov.au or 13 25 23

This research is part of the Fusarium Wilt Tropical Race 4 – Biosecurity and Sustainable Practices project (BA14013). This project is funded by Hort Innovation, using the banana research and development levy, co-investment from the Queensland Department of Agriculture and Fisheries and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.