Eyespot decisions

18 June 1999




Broad spectrum lock-on strob is on the way

Technical innovation is the

life-blood of arable farming.

Here we preview the latest

product messages at Sprays

& Sprayers from event

organiser Novartis

A NEW strobilurin fungicide, which locks on to crops to provide a much broader spectrum of disease control than currently available products, is just over the horizon at Novartis.

"F279, the code name for trifloxystrobin, has a unique combination of modes of action," says Neil Waddingham. "We call it mesostemic power. Not all strobs act in the same way."

Most of the new chemical bonds strongly into the waxy surfaces of wheat and barley plants to provide an extremely long lasting barrier to all the common foliar diseases, he explains. Very small, but significant amounts also vaporise to redistribute themselves among the crop.

Last, about 3% seeps into the plant tissue. That is nothing like the 32% with another strob, kresoxim-methyl, says Mr Waddingham. "F279 is not systemic in the true sense of the word. But even that amount is sufficient to give excellent control of deep-seated rusts and septoria."

Unlike available strobs, azoxystrobin and kresoxim-methyl, trifloxystrobin protects against all the main wheat and barley disease except eyespot.

Various formulations are under development. In a Novartis winter wheat two-spray programme trial an epoxiconazole/F279 mix outyielded epoxiconazole alone by over 1.5t/ha (0.6t/acre).

Its worth spending to beat blackgrass

SPEND more on blackgrass control and reap the benefits, urges herbicide specialist Mike Lickman.

Hawk (clodinafop-propargyl + trifluralin) costs about £4/ha (£1.60/acre) more than a typical ipu + partner alternative. But even on a 7.5t/ha (3t/acre) crop with wheat as low as £60/t it makes economic sense to adopt the more expensive approach, he calculates.

Hawks 98% control of 100 plants a sq m (an average blackgrass population) leaves 2/sq m which will give 6 heads a sq m. There is no yield loss at that level."

By contrast the 87% average control from ipu leaves 13 plants a sq m and 50 heads a sq m. "That equates to a 5% yield loss. That is about 0.4t worth £24. Add the cost of over-spraying maybe a fifth of the area and the bill comes to £29/ha."

Even at 30/sq m the margin from Hawk is likely to be £5/ha more than from ipu. "And that ignores any knock-on effect on weed seed banks which is equally important for overall crop management."

Best against wild oats

WILD oats are UK agricultures most competitive weed, being nearly three times as yield-robbing as cleavers and 16 times worse than blackgrass.

With industry-leading control and a price 25% lower than last year Topik (clodinafop-propargyl) should be the product of choice, even where hand-roguing has been considered an economic alternative to spraying before, says Novartis Andrew Cottrell.

It takes two or three man hours a hectare to rogue even the lowest populations, he says. As labour costs increase, chemical control will become increasingly viable for even the more marginal wild oat infestations.

Topiks key advantage over competitors is its consistency, he maintains. In 274 UK trials in 1993-98 it gave 95% control 95% of the time. In 176 trials with fenoxaprop (as in Cheetah) control was 95% only 85% of the time, he says.

"Clodinafop achieved 99% control in no less than 83% of cases. Fenoxaprop managed the same level in only 70%."

Know lodging cause for top control

BETTER understanding of the causes of cereal lodging help explain why Moddus (trinexapac-ethyl) can be so much more effective than chlormequat alone in preventing flat crops and boosting yield, says Novartis Andrew Cottrell.

Crops go down when they can no longer support their own weight, and they do so for several reasons, he says. They may be too tall, their stems may be too weak, or their roots may fail to hold them.

"If the most important factor is likely to be rooting you will need to adopt one approach. If it is stem strength you will require another." Crop height can be significant, especially in barley, but is rarely the whole story in wheat. "You cannot judge the effectiveness of a growth regulator by height reduction," he stresses.

One of the biggest influences on lodging is variety. But NIABs standing power ratings do not explain why one variety is less likely to end up flat than another.

To find answers Novartis has spent two years, with Harper Adams Agricultural College researchers, measuring wheat root systems and stem strengths as well as the forces needed to topple plants. That knowledge makes it easier to apply the most appropriate growth regulator strategies.

60 company trials show the extra £5/ha spent replacing 1.25 litres/ha of chlormequat by 0.2 litres/ha of Moddus is worthwhile every time, even in the absence of lodging, with wheat at £80/t. In lodging years the extra rewards are much higher, switching from straight product to the Moddus/chlormequat mix generating an extra £90/ha.

Eyespot decisions

FOUR in five wheat crops are unlikely to merit spraying against eyespot.

But with yield losses of over a third possible in the rest, predicting those likely to benefit is vital. Novartis has drawn up a new guide to calculate the risk by assigning a score to each of the key factors :

&#8226 Drilling date.

&#8226 Cultivation.

&#8226 Rotation.

&#8226 Soil type.

&#8226 NIAB resistance rating.

These are summed to give a total which scores the crop as low, medium, high or very high risk. &#42


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