10 May 2002

Adjuvants raise flag leaf spray performance

CEREAL growers striving to get the best from T2 fungicides, especially those applying reduced water volumes, cannot afford to dismiss the role of adjuvants, says Agrovista.

But make sure that function has been fully field-proven, advises the firms technical manager Mark Palmer.

Five years of field development work with Transcend, a US spray additive made by sister company Helena, highlights the products value in enhancing the performance of certain less systemic cereal fungicides, he says.

"We have tested it in over 50 trials with various fungicides and it certainly doesnt work with them all."

However, three years results from using it in 200 litres/ha applications of triazole-based T1 and T2 treatments show mean yield increases of 0.29t/ha and 0.47t/ha respectively, says Dr Palmer.

"It seems to work best with fungicides based on epoxiconazole and other triazoles and with the less systemic strobilurins like Ensign, Landmark and Mantra. We have seen similar effects with the translaminar/mesosystemic types like Twist and Opponent.

"Its less effective with the more systemic Amistar and Acanto."

Last seasons work with Transcend, a patented formulation of organo-silicone, methylated vegetable oil and other surfactants, highlights its ability to make the protection from fungicides sprayed at lower water volumes more uniform, he says.

The applications, to Claire and Consort winter wheat threatened mainly by Septoria tritici, were made in only 100 litres/ha of water through conventional flat fan nozzles.

Added at a rate of 0.25% to a mix of 0.35 litres/ha of Ensign (kresoxim-methyl + fenpropimorph) and 0.75 litres/ha of Eclipse (epoxiconazole + fenpropimorph) Transcend boosted yields by an average of 0.4t/ha, he says.

"At a cost of £2/ha for the adjuvant and with wheat at £55/t thats about a 10:1 financial return, based on two years worth of trials data."

Much of the benefit is thought to come from the adjuvant offsetting the otherwise poorer fungicide distribution from the lower water volume.

"We are not suggesting you can reduce chemical doses by using the adjuvant. In the past a lot have been sold in this way.

"We are trying to overcome the snake-oil image that these sorts of products have and address scientifically a market which has been over-sold, over-stated and over-claimed."

Many more growers are switching to 70-100 litres/ha.

The key with all such products is that they should be backed by sound information showing how and where they work and where they are inappropriate, he says. &#42

&#8226 US-made patented spray additive.

&#8226 Increases low volume reliability.

&#8226 Most suited to non-systemic fungicides.

&#8226 More work needed on latest strobs.