Natural take-all control under spotlight again
TAKE-ALL levels in wheat have been trimmed at IACR-Rothamsted by artificially inoculating plots with a naturally occurring soil fungus.
The fungus, a species of Phialophthera known as lobed hyphopodia, has been known as a weak pathogen of cereal roots for some time, says researcher Richard Gutteridge. By competing with the take-all fungus it can help delay its development.
"We first isolated lobed fungi in the mid 1970s. But it was rare at the time so it was put on the back burner."
New research into their effects has been stimulated by the imminent arrival of take-all control fungicides and the apparent build up of the lobed fungus in UK soils over the past decade. "In Australia they are already trying to use it to coat seeds as a form of biological control," says Mr Gutteridge.
In the latest MAFF funded work researchers bulked the various fungi on oat grains and applied these to plots to create different infection pressures.
Initial results suggest that to achieve significant control through artificial inoculation, the take-all competitor must be in place well before the disease starts to build up.
That the Phialopthera has no detrimental effect on output was confirmed last year in spring wheat. Untreated plots, where the natural take-all score on a 0-300 scale was just one, and those receiving the lobed competitor, yielded 7t/ha (2.8t/acre). Plots artificially inoculated with take-all scored 187 and produced only 5.8t/ha (2.3t/acre).
Sampling this year in the following winter wheat with naturally progressing take-all found the effect of the added Phialopthera had apparently worn off with both treated and untreated plots having about 28% plants with take-all.
But where Phialophthera had again been inoculated, only 12.6% of plants showed signs of take-all.
Where extra take-all was added to the winter wheat, 59% of plants were affected, and adding the competitor at the same time had no useful effect. But where the winter crop followed Phialopthera-treated spring wheat the level was only 40%.
"These results emphasise the need to have the Phialopthera there at the start of the sequence," says Mr Gutteridge.
Decline in wild is unaffected
NEW take-all control seed treatment MON65500, which recently gained emergency approval as Latitude in Eire, has shown no signs of interfering with natural decline of the disease, says Monsanto.
The company is working on a computer model to help UK growers predict and manage the disease in their rotations and decide where best to use the product when it is expected to be launched here next year.
So far the company has discovered no evidence that the chemical affects biological control fungi such as Phialophthera, says UK technical team leader David Leaper.
"To date we have seen no detrimental effect. But we need to increase our data base."
One of the main assumptions of the new Farm Model is that it takes no account of natural take-all decline, he admits.
The software takes into account factors such as rotation, climate, soil type, sowing date and the predicted yield recovery from MON65500 to provide a detailed take-all risk assessment field by field.
The program makes rotational suggestions to boost gross margins, and growers will also be able to choose from a range of pull-down menus to explore the predicted outcome of a wide range of "what-if" scenarios, both on individual fields and on crop rotations across the whole farm.
Yield data on MON65500 for the model comes from 200 trials from 1994-97.
As well as showing where best to use the seed treatment, the model also highlights when it is inappropriate to apply it, for example on wheat following a sugar beet/beans sequence, says the firms Jonathan Griffin.
"We see it as a tool giving growers a good analysis and understanding of gross margins across the farm by field and crop, to improve decision making."
Main aim now is make the software, which will probably be made available on CD-Rom, which is more user-friendly, says developer Gregory Ong. *
IACR centre set to be axed
IACR-Long Ashton, due to celebrate 100 years of farming research in 2003, could be closed the same year.
According to a report in Research Fortnight, the Bristol-based unit, which employs about 200 staff and has a 100ha (250-acre) farm, is to become a casualty of a recent Biotechnology and Biological Sciences Research Council review.
Mixed performance and the need for large capital investment to update facilities are expected to mean that Institute of Arable Crops Research will be concentrated at Rothamsted, Herts.
Recent work at IACR-Long Ashton included integrated crop management. *
A SEPTORIA surge in wheats is on the cards after recent wet weather, warns BASF.
"Septoria is turning out to be the disease of the season," says the firms John Peck. With disease levels already at record levels in many areas the effectiveness of ear protecting sprays will be crucial in determining profitability, he warns.
Many T2 sprays were applied quite early and could be running out of steam, so correct T3 timings and contents are doubly important. Strobilurins alone will not control established disease, particularly septoria, he notes. "A combination with an effective triazole is the key to success." *
Seed test price up
DESPITE strong opposition from plant breeders and merchants MAFF has increased official seed testing fees by an average of almost double the rate of inflation and in one case 88%.
The move comes despite cost savings at NIAB secured by MAFF and detailed consultation. "UKASTA is very disappointed that the ministers have gone ahead with this decision without looking at all the consequences," says UKASTA seeds manager, Paul Rooke. *
SUPPLEMENTARY aid from the EU for growing Durum wheat in the UK is £118.60/ha (£48/acre), not as published last week (Arable, p63). *