11 September 1998

Strobs might be saviour for winter barley crop

By Andrew Blake

RESULTS from East Anglian trials of modern fungicides in winter barley could help growers tempted to drop the crop justify its retention.

With set-aside increasing to 10% and many growers suggesting the crop has become too expensive to grow, the efficiency of disease control from strobilurin compounds offers fresh hope.

Untreated yields nearly doubled this season by using the latest chemistry, says Doug Stevens, Morley Research Centre cereals specialist.

Feed-back from Morley members in Norfolk and other areas unsuitable for consecutive wheats suggests the winter barley area is unlikely to decline much, says Mr Stevens. "One or two say they plan to put linseed in instead and grow more wheat. But rotationally most are locked into winter barley." But results from strobilurin trials could encourage growers, particularly of disease-prone varieties, elsewhere also to stick with the crop too, he says.

Contrary to an ADAS view that much of the strobilurins success is due to their physiological effects, Mr Stevens maintains their key function is keeping crops clean. "I attribute 90% of the added yield to disease control." But results depend largely on variety, he says.

In trials applying various fungicide programmes, net-blotch susceptible Gleam in particular responded very well to strob treatment. A full dose programme outstripped untreated output by 49-96% depending on site, he notes.

"But on Fanfare conventional fungicides came within spitting distance of the strobilurins, because we were dealing only with mildew and brown rust."

In HGCA-funded experiments on Puffin (see table), where net blotch severely affected the untreated crops upper leaves by mid- May, a two-spray Amistar (azoxystrobin) programme at first/second node (GS31/32) and early booting (GS41/43) gave yields far above the standard two-spray Sanction (flusilazole)/Corbel (fenpropimorph) control chosen three years ago.

"Where net blotch is the problem, Amistar gives levels of control just not available previously with conventional chemistry," says Mr Stevens.

"Some years ago we used to get quite reasonable control from triazoles, but there has been an erosion in their efficiency." Where rhynchosporium is the main concern, the strobilurin Landmark (kresoxim-methyl + epoxiconazole) can be as attractive as Amistar, he adds.

Clearly, applying costlier newer products, alone or as mixtures, must be warranted. Increasingly trial results are relayed to members in terms of margin over fungicide costs.

"A reasonable proportion of strobilurins can be justified, but using them at every timing does not always pay best. There are many opportunities to pick and mix new and old technologies to combine the strengths of each."

Applying strobilurins will not drastically affect the economics of producing the more disease resistant varieties, he says.

Where strobilurins should really score is in helping growers of specific varieties to continue producing them economically, he reasons. "Gleam is a typical example. It is the best option for malting on land affected by barley yellow mosaic virus." &#42

Puffin winter barley in HGCA Morley trial 1998

Yield Approx

(t/ha) 2 spray

cost (£)

Untreated 5.40 0

Sanction + Corbel

(0.4+0.5litres/ha) 6.04 65

Opus (1litre/ha) 6.87 56

Landmark (1litre/ha) 7.59 92

Amistar (1litre/ha) 8.26 76

Strobilurin fungicide effects on winter barley should encourage growers to stick with the crop, Morley Research Centre trials suggest.