Attention to detail critical in beating moulds
STRIKING the delicate balance between using too little and too much is imperative where post-harvest fungicides are concerned.
That message was emphasised by E.E. Muir & Sons’ post-harvest consultant Craig Wooldridge, based at Renmark, South Australia, at the Citrus Australia Tech Forum and Field Day.
Craig shared results from a series of industry-led surveys, conducted by South Australian Research and Development Institute’s (SARDI) Peter Taverner and supported by E.E. Muir & Sons, that tracked fungicide resistance in five large packing sheds and coolrooms in the Riverland and Sunraysia regions. The project found that mould spore loads and resistance generally rose throughout the season.
Craig said excessive use of fungicides could breach maximum residue limits in export destinations such as Japan (where not only the government but also individual retailers set specific requirements).
Applying too little, on the other hand, resulted in poor control and contributed to allowing fungicide-resistant pathogens to evolve, he said. Populations were not killed outright so surviving organisms were able to develop increasing levels of tolerance in each generation.
Speaking after the forum, E.E. Muir & Sons’ national post-harvest product manager, Lee Duffy, said inadequate fungicide application and substandard hygiene and sanitation could be caused by many factors.
“It might be that packers are not seeing evidence of a mould problem, or they’re looking to reduce costs by minimising their inputs so they’re actually not using enough of the product.
“Perhaps they don’t need an extended period of control, or they just don’t implement the correct practices, procedures and rates, or the temperature of the fruit or the drench isn’t where it needs to be, or there’s an error in the pH of the drench solution – possibly caused by other treatments – or in the contact time. The different types of product all have different formulations.”
He recommended two relatively new products, Scholar and Philabuster, as ideal alternatives to long-established favourites.
In summing up, Lee said:
- Sanitation and hygiene were crucial, not only in pack sheds but at every step along the chain – for packers this meant both cleaning down and sanitising daily (with particular emphasis pack lines and coolrooms)
- Product efficacy relied on correct techniques and rates being used
- Fungicides must be rotated (ideally with a change in routine for between two and four weeks during part of the season) rather than used continually
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