Sugar beet growers in England may have a new, non-chemical way of holding back the aphids that spread virus yellows. In an Adopt project run with Morley Farms in Norfolk, the British Beet Research Organisation (BBRO) grew an endophytic grass as an overwinter cover crop ahead of beet and counted only 0.3 aphids per plant in late May, against an average of five per plant where the farm's standard cover crop had gone before.

Endophytic grasses carry a symbiotic fungus that makes alkaloids which put insects off feeding. The variety in the trial is Barrier meadow fescue from CropMark Seeds, which contains the endophyte Epichloe uncinata and is already widely used in New Zealand to protect grazing pastures from root- and leaf-feeding pests. Earlier BBRO work had tried grinding the seed into a meal for the soil; the cover-crop route is the one now being tested on farm.

The method depends on timing and biomass. Dr Alistair Wright, BBRO's head of crop protection, says the grass must be established as soon as possible after cereal harvest, because the more biomass there is, the more the endophyte multiplies. Then the crop is deliberately damaged to mimic grazing: at Morley it was rolled in October and sprayed off with glyphosate in early winter, so that the plant ramps up alkaloid production in its own defence.

The beet was strip-tilled in March, leaving about 60 per cent of the dying grass undisturbed. As it breaks down, the water-soluble alkaloids leach into the soil and are taken up by the following crop. Leaf samples are being tested to confirm how much alkaloid the beet has absorbed, and virus yellows levels, yield and soil quality will be tracked through the season. "We also didn't see big colonies forming at all," Wright reports, which he thinks means the beet is less palatable and aphids stay for less time, transmitting less virus.

The system is not finished. Canopy growth was reduced this spring, which Wright puts down to broadcast fertiliser landing on the dying grass rather than reaching the beet — "an easy fix hopefully". The team is also watching whether the retained grass helps the harvester travel on Morley's compaction-prone clay loam, and what the following barley crop does.

Two other Norfolk farms are part of the project. Lugden Hill Farm near Docking is running strip trials on whether the grass reduces the plant-parasitic nematodes behind Docking disorder, and a farm at Brettenham near Thetford is testing whether seed of the grass can be produced in the UK.

Separately, BBRO plans a new A+ to S ranking of sugar beet varieties by projected yield loss to each of the three viruses in the virus yellows complex, drawing on two years of yield data from its Goliath inoculated-trial screening programme; three varieties on the current Recommended List carry a tolerance claim, rising to four in 2027. BASF is also developing a new aphid insecticide, dimpropyridaz (Axalion), which gave an average peak control of 88 per cent across 32 European sugar beet trials and which the company hopes to register in the UK within two years. Mike Abram reported for Farmers Weekly from the International Institute of Sugar Beet Research congress in Cambridge.

Source: Farmers Weekly