20 October 2001

New strobs yield up

WHEN strobs were first introduced, the industry witnessed wheat yield potential shift up a gear. The exciting news is that new generation strobs can do better still, and the promise is confirmed by this years trials, according to agchem manufacturer BASF.

If pyraclostrobin, provisionally known as F500, passes all the hurdles of PSD approval, then growers might expect the new strob to give at least another 0.5t/ha over and above the best of the currently available strob programmes. All that, and top notch septoria eradication as well…

Its a bold claim, but with more than two years and 100 UK independent and distributor trials in its database, BASFs number crunching reveals that even in 2001 – an "extraordinary" season when establishment was difficult and disease pressure low – F500/epoxiconazole turned in 0.94t/ha extra yield over untreated. This was in a year when the best commercial strob applications managed just 0.75t/ha over untreated – still economically worthwhile but with a narrow margin, says BASFs Steve Waterhouse.

Convincing

In a more typical year, the strob yield boost would be a convincing 3.2t/ha over untreated, he says, with an F500/epoxiconazole programme pitching in at 3.8t/ha. If this performance level is achieved in practice, then the "to strob, or not to strob" debate should swing clearly in favour of treatment, if the F500 product is priced at a comparable level.

Curative action is a key strength for F500. Its better than Opus (epoxiconazole), or anything else currently on the market, suggests Mr Waterhouse. "Theres action on the fungal mycelium, which other strobs dont have. It can attack the fungus in its later, latent phase." Put F500 with epoxiconazole and together this mix becomes a formidable yield enhancer.

Like Landmark, F500 is likely to appear as a formulated mix with epoxiconazole, rather than as a straight strob, when its advantage over other existing strobs is less marked. "For anti-resistance objectives, wed prefer growers not to use a strob on its own, anyway," says Mr Waterhouse. "But having epoxiconazole increases the consistency of higher yield."

The curative action of the F500/epoxiconazole mix did suggest that it might be used to stretch fungicide timings. So BASF trials have explored the potential for using two spray treatments at GS31, and GS55 (first node and early ear). This worked well in trials in 2000 at Morley Research Centre, giving about 0.5t/ha more yield on Consort than a conventional GS32/39 programme.

However, Mr Waterhouse is not convinced that it would be wise to advocate this strategy as a general rule, and it certainly didnt pay off in the abnormal 2001 season, when the stretch programme didnt come out on top. Best timing with F500 in a repeat trial at Morley was GS31/39 this time. There was little difference between GS31 and GS32 treatments; the F500 worked well at both timings.

"We could not advise growers to wait, and not spray at flag leaf. It might lead to disaster, if you couldnt then get on. It seems the best tactic is to hit the disease when you can exploit the curative activity."

So its unlikely F500 will lead to any change in timing advice, which will remain as GS31/32, followed by flag leaf treatment at GS39. F500/epoxiconazole shows good activity on eyespot; the effect is at least on par with Landmarks, if not better, says Mr Waterhouse.

No varietal differences are emerging; F500 responsiveness does not appear to be linked to different resistance ratings.

THERES desiccation, and desiccation. In a demonstration potato crop of Maris Piper near Ramsey, Cambs, Pete Fryer (left) and Ian Black from distributor group Hutchinsons ponder the obvious success of treatment with new product Spotlight (carfentrazone-based), out on a limited trial basis this year.

"Most growers on this heavier land would already be using a two-spray approach, starting off with acid," says Mr Black. "Weve been looking at Spotlight for the second slot in the programme, because it is good at killing stems quickly."

The aim is to open up the canopy with the first desiccant treatment, typically, acid, Harvest or Reglone, which then allows the second application easy access to plant stems. Regrowth, and associated problems with extended crop growth and blight risk, must be avoided.

Spotlight is considered more environmentally friendly than acid; carfentrazone is highly active at low doses. There is no LERAP buffer zone requirement.

The Hutchinson trials aim to identify whether this new product would make an equally good T2 partner, to each of the other three at T1. Verdict so far: it looks good, says Mr Black – even with reduced water volumes. Standard recommendation is for 300 litres/ha through flat fan nozzles; these trials show equivalent desiccation when using 250 litres/ha through twin-cap nozzles, but this picture was taken just five days after application. "Wed like to look at angled application techniques in more detail," says Mr Black.