Orange is the new knack


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21 November 2022
One year after UK introduction, those who have experimented with orange oil fogging issue their verdicts.

MORE than two years on from the banning of chlorpropham (CIPC) in potato production in the UK and following extensive research and development on a global scale, a natural alternative, developed from the oil in orange peel, has been finding favour within the potato market.

ARGOS® from UPL, is a natural product containing pure, food grade orange oil with d-limonene as the active ingredient. The manufacturing process is very straightforward – the oil is extracted from whole oranges by vacuum distillation without the need for heat or solvents. The result is a product that is 100% food grade orange oil and about as sustainable as you can get and as such could be considered the future of potato sprout control. The product was launched last Autumn in the UK but has been sold for two seasons in the Netherlands, Belgium, and France, where it has achieved a high market share.

A ready-to-use product, it is applied as a hot fog through fogging machines operated by specialist contractors using suitable temperature-controlled fogging equipment. The fog machine puts the oil into a vapour state which then removes the sprouts by rapidly desiccating the soft growing points on the tubers.

This storage season there was massive variability between crops in the UK. Some had decent hydration while others were very drought-stressed, with little or no irrigation. These tubers have very low natural dormancy and low or zero MH residues, leading to an early start to storage fogging programmes in many cases.

Some crops had secondary growth in the field, chain tuberization and very small tubers which tend to have lower MH residues even in a good season. Residue testing for MH will greatly help to predict future sprout control requirements and should help when loading stores and managing the timing of the fogging operations. When yields are low, there will be a temptation to mix in the same store varieties with different dormancy/MH loading but this could lead to issues timing the fogging operation correctly.

Inspections should be made regularly and carefully so that break of dormancy is spotted instantly, and the ARGOS is applied at the ideal timing of 20% of tubers at the very first ‘white points visible’ stage, according to the manufacturer. This will lead to a quicker sprout kill and longer intervals between applications – saving money in the long run. It claims much longer sprouts have been well controlled by ARGOS, particularly if they are thin and quick growing and whilst this may be necessary this season in droughted and low MH crops, the best timing is still at the first signs of dormancy break.

When ARGOS was launched in October last year stores were already full which meant that in several cases there was very little space to fog into and the fog was hitting the potatoes directly. This should be avoided this season by leaving a good space around the fogging port so that ARGOS can develop a good quality light, dry fog before it is drawn into the boxes, the manufacturer adds. Growers should be aware that the fogging efficiency of the new products can be affected by stores which are either too full or part empty. With sky high energy costs there will be a temptation to switch off fans early, but it is very important that the cooling and curing period is completed before fogging begins.

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Jonathan Kemp of Mercian Ltd, a major supplier to the UK crisping industry, used ARGOS last season. He said: “We started last season expecting only to apply BIOX-M but we were keen to try ARGOS oil to compare products so we purchased the latest Synofog 2HV hot fogger adapted for use with ARGOS. Flowrates are similar for both products, 25-30 l/hour, although application times can be longer for ARGOS with a higher use rate (100 ml/T vs 60-90 ml/T).

"Once the products have been applied, the stores are closed up for between 36 and 48 hours. This timeframe has been reduced from last season’s 72 hours. We apply both products in an identical way - same application timing, same fogging equipment and store closed for the same amount of time - and have found them both to work in a very similar way. ARGOS has the advantage in box stores as it seems to be more mobile and has improved the effectiveness in the corners of the stores which BIOX-M failed to reach. In bulk stores, both work really well and future ARGOS applications could have a reduced rate to cut application times and cost.

"We are still learning about re-application intervals, but our initial findings are that they are very similar i.e., 30-35 days between 1st and 2nd applications. In the 2020/21 season, we only had BIOX-M for sprout control for crisping potatoes and, after a nervous start, we soon realised it would work successfully. Now that we have an alternative option, we feel confident that we can manage sprout control through to July.

"A word of warning - make sure the ARGOS fog isn’t hitting the crop in large quantities because it will scorch or burn the potatoes. We fogged many stores last season and experienced crop damage issues in just two. We feel confident with our current knowledge it will not happen again.”

Tim Kitson, an independent potato storage consultant, storage expert and Potato Solutions Ltd Director, also has extensive experience with Argos.

"Over the last season ARGOS fitted very well into my storage management. The product shows good efficacy in store and controls sprouting within a specific range," he said. "With the new oil sprout suppressants, good air flow is fundamental to provide that full coverage of a contact kill. Moisture, condensation, and damp refrigeration coils can cause ‘crop scorch’. Refrigeration coils on certain units are narrow, so cooling and fall out has been seen on the tops of crops. 

"All these risks I reduce by good store practices before and during applications. Certain varieties and stores had a field MH application followed by only one application of ARGOS and left the store in April without sprouting. Fry colour is unaltered during the season which for certain end users is critical. Where my customers require a minimal harvest interval for flexible marketing it fits well. The ability to ‘sit and wait’ for movement rather than proactively treat, can also be advantageous and save money in shorter term storage. I will continue to use ARGOS again this season and be mindful as with any chemical of its usage."

*More details on this feature are included in the January issue of Potato Review. Click here to receive a copy.

Orange is the new black ...
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