More than two years on from the banning of chlorpropham (CIPC) in potato production in the UK, a natural alternative, developed from the oil in orange peel, has firmly established itself in the market.

The alternative in question is ARGOS® from UPL, a ‘natural product containing pure, food grade orange oil with d-limonene as the active ingredient’. It 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.

ARGOS is a ready-to-use product and 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.

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. 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.

“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,” said Jonathan Kemp of Mercian Ltd who used ARGOS last season. “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 first and second applications.

“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.”

ARGOS is applied at a rate of 100ml per tonne of potatoes and a 21-day minimum interval must be observed between applications. The frequency of multiple applications is dependent on the susceptibility to sprouting. For best results carry out regular inspections to spot the break of dormancy. Although much larger sprouts have been successfully controlled, the best control and shortest intervals come from timing the fog to when 20% of tubers have the ‘white points’ of new sprouts visible.

Fans should run for 24 hours prior to fogging with the relative humidity controls switched off. Fans should deliver a uniform movement of air to all parts of the store during fogging and steps should be taken to avoid jetting of the air flow or short-circuiting leading to over or under dosing.

ARGOS can be applied up to nine times a season and be used right up to just 48 hours before leaving storage. It can also be used in boxed or bulk situations, in all varieties for chipping, crisping and fresh markets, and is flexible for use in a programme with other sprout suppressants such as following field applied maleic hydrazide. The ARGOS fog is light and dry and readily reaches all parts of the store. The vapour disappears within a few days and produces no taint or smell on the treated potatoes or store structure.