9 July 1999

Identify your adjuvant aims

TO get the most from spray adjuvants be sure you know what you want them to do, particularly when working with the latest fungicides.

"If you are to benefit from using an adjuvant you must know what you want to achieve," said Duncan Webb, spray application specialist at IACR Long Ashton.

Poor product retention but good uptake may give the same result as good retention and poor uptake. "What you want is good retention and good uptake."

To achieve that note how a wheat plant changes as it gets older. At GS10-15 the leaves have undamaged wax and present an open canopy. By GS 37-39 the wax is damaged, but the canopy remains fairly open. By flag leaf the wax is often very damaged and the canopy has closed in.

Tests show that spray droplets can bounce off a plant at GS 10, but at flag leaf the damaged wax holds on to the drops. With the current interest in ensuring strobilurin fungicides are evenly distributed in the wax of the cereal plant that knowledge could be very helpful, Mr Webb noted.

Trials undertaken as part of a MAFF funded project at Long Ashton have shown that tallow amine based adjuvants give a consistently better retention of product, while silicones can make it spread and actually run off a non-retentive leaf surface. Rainfastness tends to be enhanced by some of the oil-based products.

The effectiveness of aqueous formulations, such as plant growth regulators, can be enhanced by using appropriate adjuvants. But the presence of emulsifiers in a tank mix including fungicides often improves their effectiveness without more adjuvant. "Some formulations are already as good as you can get," Mr Webb said.

commented.

ADJUVANT CHOICE

&#8226 Know what you want to achieve.

&#8226 Good product retention and uptake target.

&#8226 Many factors interact.

&#8226 Some formulations already as good as you can get.

&#8226 More independent trials results available to aid choice.

ADJUVANT CHOICE

&#8226 Know what you want to achieve.

&#8226 Good product retention and better uptake target.

&#8226 Many factors interact.