Archive Article: 1997/07/05

5 July 1997




In defence of

adjuvants

In Adjuvant Angst (Crops w/e 7 June) Dr Stuart Wale appears to add to, rather than clarify, the confusion surrounding the products. He begins by saying that the only sure thing about using adjuvants to bolster reduced rate pesticides is "that the results will be inconsistent…"

The same comment could be made about most pesticides. Take triazole fungicides. It is recognised that one particular triazole may be strong on rusts, while anothers strength is septoria.

But no-one dismisses the whole group as inconsistent. In the same way all adjuvants cannot be dammed with such sweeping statements.

The trial which Dr Wale cites to make his point shows that all four adjuvants tested gave an improvement over fungicide alone.

The best, Slippa, increased yield by 0.6t/ha – more than the fungicide alone achieved. If this was a fungicide trial the conclusion would be that the Slippa/ Folicur treatment was best. Instead, Dr Wale chooses to make the point that there is wide variation in adjuvant performance.

Large number

Another cause of Dr Wales angst with adjuvants is the large number of products available – 251 authorised in April this year, many identical ingredients under different trade names. It is no different from pesticides, where dozens of identical products can be found for older, well-established products.

In the UK, the adjuvant position is comparatively simple. There are 15 active ingredients used, five of which are unique. A detailed overview can be obtained in a poster produced by, and free from, Interagro UK.

As for the old chestnut of all the necessary adjuvants are already included or specifically recommended on the label…..

Following pioneering work by the now defunct, Weed Research Organisation, it became common practice to add ethoxylated tallow amine with half rate glyphosate and so achieve considerable savings without impairing performance.

More recently, the manufacturers of Cheetah conceded that adding mineral oil to half rate product was as effective as full rate alone. This must have saved Britains farmers millions of pounds in blackgrass control.

I would also suggest Dr Wale reads what Dr J M Green of Du Pont had to say in a recent paper entitled: "Specifying adjuvants for pesticides."

In his opening summary he states: "Adjuvants are essential for the performance of many fungicides, insecticides and herbicides."

He adds: "Adjuvant use is growing because adjuvants are often the best way to reduce pesticide rates and to increase efficacy."

His paper concluded: "Adjuvants fit prominently into the current themes of reducing pesticide rates, costs and any perceived unwanted environmental and toxicological effects."

Adjuvants are vital tools as the industry embraces Integrated Crop Management. Their performance-enhancing effects allow older, but more environmentally benign products such as sulphur to be used with greater effect.

Two trials, conducted by the Scottish Agricultural College in 1995 and 1996, which fit this theme have been overlooked by Dr Wale. Commissioned by Interagro, these trials show that adding Slippa to sulphur gave mildew control on spring barley equal to the standard morpholine and triazole programme.

There is a wealth of information building up to overcome the adjuvant angst. However, I would agree with Dr Wale that we need more information still.

Our industry is made up of small companies. The combinations of pesticides and adjuvants that could be tested is almost limitless, our funds are not.

Is there a case for those levy bodies charged with conducting research and development to look further at the potential benefits adjuvants could bring on the crops they represent?

Should organisations such as SAC and ADAS be looking further into this area for the benefit of their customers?

In an era when Britains arable farmers are looking at severe reductions in their margins, the ability to get the benefits of some of the latest pesticide technology for considerably reduced input costs must be an attractive proposition that is worthy of a detailed look.

Richard Newman,

Technical director, Interagro (UK) 2 Ducketts Wharf, Bishops Stortford, Herts


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