26 February 1999

Spin-off with GMbeet

APHIDS could be less of a problem in genetically modified herbicide tolerant sugar beet, according to work at IACR-Brooms Barn.

Herbicides are currently applied before beet reaches the two-leaf stage, but GMHT varieties can be treated later, allowing weeds to develop further.

In trials where weed control was delayed until the 8-10 leaf stage the resulting insect population had far fewer damaging peach potato aphids.

The cause could be greater competition from non-damaging aphids, or more predators and parasites, notes IACR entomologist Alan Dewar. Insecticide use could be cut as a result, he suggests.

But leaving the beet crop unsprayed until the 8-10 leaf stage also caused a yield drop. "There is a good potential for manipulating weed and insect populations with this technology. But we have to fine-tune the timing," says Dr Dewar.