DUPONT WILL stand by growers finding crop damage after spraying its new SX formulations of spring sulfonylurea broad-leaved weedkillers, if the new, quicker washing out procedure has been followed correctly.

So says the firm”s Steve Cranwell. “The method has been tested extremely thoroughly, including in worst-case scenarios.”

That includes trials with washings sprayed on to sugar beet by consultant Simon Fisher of Armstrong Fisher. “The sprayer was left standing overnight, prior to washing out, which from customers” experiences is the worst-case scenario.” Washings were recovered after the first and second water rinsings using both SX and DF formulations, as well as after a full All Clear Extra washout, as previously advised. “There was a big difference between the two formulations,” says Mr Fisher. “Using washings from just one rinse with the DF formulation, you could see leaf senescence and older leaves flat on the deck, a tell-tale sign of sulfonylurea damage, after just 14 days.

“That got steadily worse, and after eight weeks there was also obvious damage with that formulation on the plot sprayed with double rinse washings [ie the new shorter sulfonylurea washout method], though there was none where the full All Clear Extra method was used.

“Yet there was no damage at all where the SX formulation was used.” That should increase growers” confidence that non-target crops and weeds are safer from accidental contamination, he says.

On a mixed rotation farm, that is good news, suggests Agrovista”s Mark Hemmant. “Using the SX brand will mean less risk to growers of sugar beet and pulses.”

The new washout method, which eliminates the need to completely fill the tank with water and leave it standing for 15 minutes, has environmental benefits, adds Mr Fisher.

“The key aspect is the reduced water need. That could be crucial with the Water Framework Directive coming in.”

It also saves time. “Often crops are not sprayed at the optimum time in the spring. Saving 90 minutes on washing out could mean spraying an extra 10ha or more a day.”

But it is essential that growers read sulfonylurea labels, warns Mr Cranwell. “The washout is specific to SX formulations.”

DuPont is replacing many of its older DF formulations with SX, including Ally (metsulfuron-methyl), Quantum (tribenuron-methyl) and Harmony M (metsulfuron-methyl + thifensulfuron-methyl).

“If the SX products are tank-mixed with other products the washout should be the most stringent required by any one,” he adds.

That is why DuPont still advocates using All Clear Extra.

Agrovista”s advice is to use All Clear Extra regardless of whether the SX formulation has been used, says Mr Hemmant.

mike.abram@rbi.co.uk