Unknown worm plague hits barley crops

An unknown worm plague has hit barley and wheat crops in the Northern Cape and the Free State, causing large-scale damage. The plague was discovered in early November and at the time of going to press more than 1 000ha of barley had been affected.

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Irrigated crops from the Vaalharts and Prieska areas in the Northern Cape to Viljoenskroon in the Free State have been affected. Most of the damage has occurred on barley crops, but wheat lands have also been damaged. The worms eat the wheat and barley ears and, sometimes, the leaves. They are 2cm to 3cm long.

Dr Goddy Prinsloo, an entomologist at the Agricultural Research Council (ARC’s) Small Grain Institute in Bethlehem, said, “The scale of the damage varies between the areas. In Barkly West the damage is at 25% so far, while farmers in Vaalharts have reported 50% damage to their crops.”

He said the worm has yet to be identified, so it’s difficult to decide which insecticide to use against it. The ARC has collected samples of the pupae to identify the moths once they hatch. “Not much can be done until the worms have been identified. Some farmers have taken a chance and used bollworm insecticides, which seem to have stopped the damage. But this is a risk as it isn’t registered for this use,” said Dr Prinsloo.

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“The worms take about 10 days to work through a land. If farmers don’t keep inspecting their crops for damage, the worms could go unnoticed until it’s too late.”One Vaalharts farmer inspected his crops on 25 October and found no damage. But three weeks later, the worms had infested his whole crop. –

For more information, contact Dr Prinsloo at 082 875 3401.