23 May 1998

German wheat ban

OUTBREAKS of a rare type of stinking smut or bunt in German wheat crops has led China impose a general export ban for German wheat.

  So-called dwarf bunt was identified for the first time after many years in organically-grown wheat crops in the federal states of Baden-Wurttemberg and Bavaria last year. Identification of dwarf bunt in non-organic farms quickly followed. However, on the conventionally-farmed units that were affected, it was found that seed dressing had been badly carried out, or done with unsuitable substances.

  The Chinese Ministry of Agriculture has sent a deputation to Germany to investigate the spread of the disease and control measures being taken. The ban is unlikely to be lifted this year, but both governments are now discussing control methods acceptable to both countries so that wheat trading can recommence as soon as possible.

DUTCH scientists have isolated a fungus (Ulocladium atrum) which will biologically control botrytis. It is harmless to crops but, like botrytis, feeds from dead vegetation, including diseased leaf tissues.

Spores of the competitive antagonist fungus are sprayed on a crop, which establish themselves and then, if and when botrytis starts multiplying in the crop, competes for food. This decreases spore production, spreading power of the disease.

  The botrytis antagonist was chosen because it can survive in field conditions, even on living green foliage, for a matter of weeks. It can also withstand cold and lengthy dry periods.

    The Dutch scientists believe this biological method of fungus control will work with other necrotrophic crop fungi such as septoria in cereals.

French-based DuPont de Nemours has approval to sell its cereal fungicide Harvesan (carbendazim + flusilazole) for use against cercospora leaf spot in sugar beet in France and Germany. It is a disease rarely found here, but causes significant yield losses elsewhere in Europe.

  The product is also effective against ramularia in beet. DuPont claim marked increases in sugar yield per hectare.

CONVENTIONAL ploughing has the most damaging effect on earthworms, confirms newly-released research in Germany.

  Worm counts taken in fields that had been ploughed every year for 15 years averaged 50g/sq m of worms. On land that had undergone minimal cultivations such as grubbing and power harrowing over the same period, the average weight of worms present was more than double -100-110g/sq m.

  Worms thrived best where direct drilling had been employed every year. In such cases the worms weighed-in at an average 200g/sq m.

Although the trials did not go on to compare relative yields, the scientists say that fertility was considerably higher in fields with the highest worm populations.

AMARANTH, the native South American high-protein grain crop, will be encouraged on Austrian farms because of increasing demand for food products made with the nut-flavoured corn.

  Present grain amaranth types are more suitable for south European climates, but efforts are being made to select for hardier lines since the crop is increasingly popular with farmers in the Continental-climate east of the country. There, demand for the grain in muesli, cakes and pastries far exceeds local supply.

  The grain types, including Amaranthus caudatus and A hybridus, have a high-lysine protein content running from 10% to 17%. Austrian farmers have learned that no nitrogen dressings should be given for the crop as it lodges easily. To avoid frosts, sowing takes place after mid-May at up to 2 kg/ha (1.8lb/acre).   The plants grow to about 2m (6ft 6in) in height and are harvested – increasingly by combine – when half the grain has achieved ripeness – usually early September. Yield: 1 to 3t/ha (8 cwt to 24 cwt/acre).

Mechanical weeding between the rows is the only method of weed control.