24 July 2002

Stem-base diseases need more attention

By Andrew Blake

DONT automatically blame take-all for alarming whiteheads appearing in many wheats in the run up to harvest. They are much more likely to have been caused by stem-base diseases encouraged by T1 fungicide cuts, according to distributor Hutchinsons.

Eyespot, sharp eyespot and Microdochium nivale (formerly Fusarium nivale) foot rot account for about 80% of what many growers may mistakenly believe is take-all damage, says the firms Dick Neale.

He believes penny-pinching on apparently clean crops earlier in the season is largely to blame. "We couldnt persuade people to spend enough at GS31 and now the stem-base diseases are taking the potential away.

"We are seeing the result of a lot of early drilling, over-thick crops and not enough attention to stem-base diseases."

With foliar diseases, like septoria, there is always the chance of retrieving slipping control by raising product doses, says Mr Neale. "But once you get to GS37 and you have an inch of stem rotting with eyespot there is nothing you can do."

Growers financial losses could be compounded this autumn if they incorrectly opt for take-all seed treatments, he adds. "There is likely to be a lot of take-all dressing sold on the basis of what we are seeing now.

"Farmers must inspect their crops, dig up plants and wash the roots to see if the problem really is take-all. Walking stubbles is a good way to inspect for stem-base problems as affected areas tend to show up as bleached patches.

"The lesson to learn from this season is that you must start off with a dose that covers the worst scenario and all potential diseases. If you want to save money the time to do it is later. T1 is the least flexible time, even in a clean season."

This seasons experience makes applying an anti-fusarium seed dressing this autumn vital, believes colleague Colin Button. Some seed crops, especially in Kent, have been hard hit, and supplies of some new sought-after varieties like Solstice could be tighter than expected, he adds.

"If you are min-tilling, a dressing is even more important because the seed will be close to infected straw."

Dealing with stem-base diseases through seed dressings and T1 sprays involves careful product choices, the firms trials indicate.

Sibutol (bitertanol + fuberidazole) offers good fusarium protection for about £7.50/ha, explains Ian Black. Adding Latitude (silthiofam) clearly enhanced that protection in third crop Consort with better rooting and 50% more green leaf showing as the crop senesced. But at an average cost of £24/ha its addition could be hard to justify in the absence of take-all, he suggests.

Take-all competitor Jockey (fluquinconazole + prochloraz) at a similar price does have a significant effect on true eyespot, although there is no mention of it on the label, notes Mr Neale. "But it has no effect on sharp eyespot, so you have to be careful with T1 sprays. If you clear out all the eyespot and fusarium and apply something like Unix you can end up with a free-for-all for sharp eyespot."

Under those circumstances Amistar (azoxystrobin), which also offers some take-all control, combined with a triazole, would be the most appropriate choice for the T1, says the firms Andrew McShane.

Dont blame take-all for every poor plant in this years wheat, advises Dick Neale of distributor Hutchinsons. Eyespot and fusarium (inset), the legacy of inadequate T1 sprays, are often more to blame.

&#8226 Only 20% of whiteheads due to take-all.

&#8226 Eyespot, sharp eyespot & fusarium main culprits.

&#8226 Over-economising at T1 largely to blame.

&#8226 Fusarium treatment essential this autumn.

&#8226 Moisture conservation is vital for successful early cereal sowing. An inch of soil moisture is more valuable than the same amount of rain falling on a dry cloddy seed-bed.

&#8226 Tall hybrid wheat variety Hyno Esta is useful blackgrass competitor.

&#8226 Delayed T2 fungicide treatments can be rescued, but growers must be prepared to invest more heavily.

&#8226 Wheat growers still wasting cash on excessive seed rates for early sowing. Thinner Claire could save £10/ha on mildew control. But beware low seed rates if blackgrass troublesome.

&#8226 Money to be saved by better use of RB209 fertiliser advice, for example on nitrogen for wheat after oilseed rape.

&#8226 Cheap glyphosate herbicide is useful take-all management tool. Use it to kill host weed couch at every opportunity.