Exploit strobs to reduce variable and fixed costs

9 February 2001

Exploit strobs to reduce variable and fixed costs

By Andrew Swallow

GROWERS could save themselves far more on sprays by adjusting inputs to varieties and using new chemistry to fine-tune timings, says Morley Research Centre.

That was one of the key messages from HGCA-funded work presented to Morley members at last weeks winter conference at Stowmarket.

"You need to vary the dose according to the variety. Look at the NIAB list and use that information," says Morleys Ben Freer. "And strobilurins give extra flexibility in timing over and above the old conazoles."

That is echoed by Morley director Jim Orson. "Exploit the strobs to decrease variable costs or fixed costs, or even both if you are clever. It is frustrating that the average fungicide saving on a resistant variety is only 7%."

Simply by driving faster, or cutting the volume of application, growers could cut the dose rate on resistant varieties by 33% without even changing the tank-mix, he suggests.

The second year of an HGCA trial at the Norfolk research centre highlights the opportunities for savings. Using Landmark (epoxiconazole + kresoxim-methyl) or Mantra (epoxiconazole + kresoxim-methyl + fenpropimorph) on Riband or Claire respectively, plots were sprayed at GS32 at either half or full rate.

Then a second application was made, at full rate, with the timing ranging from a traditional T2 at GS39, through to a late T2 at GS55.

"You can imagine two umbrellas of protection being pulled apart. We are stretching the gap," says Mr Freer.

With the generally disease resistant variety Claire, yields gradually increased the later the second application was made, and the half-rate T1 hardly reduced yield. Hence the best margin over fungicide and application cost was achieved with the sprays at the maximum interval, 31 days, for the second year running.

In contrast to 1999 results, Riband responded similarly. But that was a quirk of the season, as disease pressure was low between the T1 and delayed T2 sprays.

"There was a lot of disease pressure late on but we had a dry spell in May," comments Mr Freer. That meant even on the septoria susceptible Riband delaying the T2 increased yield.

But unlike the Claire, maximum margin was achieved using a three-spray programme including 1.0 litre/ha Opus (epoxiconazole) plus 1.0 litre/ha of Bravo (chlorothalonil) at GS31.

Make use of varietal differences to cut costs, says Morleys Ben Freer. Strobilurin chemistry means there is more flexibility with timings.

Mind the gap with strobs

Yield (t/ha) (half-rate T1) (full-rate T1)

RIBAND plus Landmark.

15 8.96 9.13

21 9.27 9.31

26 9.73 9.94

31 10.09 10.16

CLAIRE plus Mantra

15 10.31 10.24

21 10.26 10.32

26 10.48 10.37

31 10.66 10.64