The addition of an adjuvant helps ensure thorough coverage of stain removal products onto kiwifruit prior to harvest but selecting the right adjuvant for the job is important.

Du-Wett Stainless, from UPL NZ Ltd, is a specialised, low water volume adjuvant which complements stain removers to help get kiwifruit stain-free and ready for picking faster.

Formulated for use with low pH water stain removal products, including New Zealand industry preferred sprays Kiwilustre® LF and Kiwi Stainoff LF, Du-Wett Stainless helps deposit these sprays evenly across the fruit to allow the stain remover to work effectively.

UPL NZ Adjuvant Product Manager David Lingan says the lactic acid in the stain removal products is very effective at dissolving stains and it’s essential to wet the entire fruit with good spray coverage for a thorough job to be achieved.

Conventional super-spreaders are not suited to working in the low pH environment of a water stain remover, which are typically around pH 3. 

“This acidic environment breaks down most surfactants or wetting agents,” David says. “In contrast, Du-Wett Stainless is stable in these acidic environments, allowing the stain remover to be evenly spread across the fruit by the spray unit.”

David says Du-Wett Stainless increases spray deposition and overall coverage on treated fruit by at least five to ten times1 that of standard non-ionic adjuvants. “The addition of Du-Wett Stainless can make a big difference to how successful fruit stains are removed.”

The characteristic dark stains on kiwifruit are caused by tannins from kiwifruit foliage and vines dripping onto fruit after heavy dew, fog, rain or overhead irrigation.

“While these don’t impact kiwifruit quality, they are considered a cosmetic defect, which limits the saleability of the fruit in many market places. The presence of stains typically results in downgrading or even rejection at your packhouse.”

Kiwifruit, particularly green kiwifruit (Hayward), is difficult to wet effectively. Green kiwifruit are covered in very dense ‘hairs’ called trichomes.

“This furriness means that any water or spray just tends to sit on top of the trichomes and not reach the fruit skin. Du-Wett Stainless breaks that surface tension to provide even spread of the liquid being sprayed onto the fruit. This helps ensure your spray effectively spread across the fruit surface.”

Du-Wett Stainless also provides value for money by ensuring the stain remover is placed where it’s able to do the intended job.

Other benefits of using the low water volume super-spreader include fruit drying more quickly after spray application, allowing harvest to start sooner, and the fact it requires around one-third of the usual water volume to be used in the spray unit.

“The ability for the stain remover plus Du-Wett Stainless combo to work effectively in lower water volumes fits with increasing sensitivities around water use. 

“The lower total volume of spray means application is completed in less time, which also reduces machinery and labour costs with faster application time, less re-filling of tanks and travelling back and forward between blocks and your refill site. 

“Any tool that enables an important orchard job to be completed using less diesel and fewer total hours while still achieving an effective result is worth considering if you’re not already using it.”

The low water volume capabilities of Du-Wett Stainless also means there’s less water being applied to vines. Fruit dries faster after spraying, allowing harvesting to start sooner.”

For more advice about using Du-Wett Stainless, talk with your local Fruitfed Supplies Technical Horticultural Representative. 
¹Trial references Agrivet 2008, Te Puke; Agrivet 2009, Katikati; Fruitfed Supplies FSEXP90809-17 2008, Katikati.