Ontario growers losing the battle against nematodes

Farmers are losing control of a long-contained pest in Ontario’s soybean crop.

Soybean cyst nematode (SCN) is starting to develop resistance to the main control method used by farmers, said OMAFRA field crop pathologist Albert Tenuta at the Ontario Agriculture Conference last month.

It is not good news that one gene is responsible for around 95 per cent of soybeans’ resistance to SCN. The gene has protected crops for the better part of two decades, but it was inevitable that nematodes would evolve past a single method of control.

Nematodes can build up in the soil for five to 10 years before becoming an issue. But once the microscopic roundworms are established they are effectively impossible to remove and can cause yield losses as high as 25 per cent.

It’s much easier to control nematodes before they take over, Tenuta said. Resistant-varieties of seeds still work well against small populations of the nematode. Rotation is the other key: cycling out of soybeans denies the pest food and slows its population growth. But once the nematodes are in the field, they’re in there for good, he said.

The first, best step is to scout, he said. A classic sign of the nematode is yield losses in soybeans for no discernible reason. True to its name, it also leaves characteristic cysts on the roots of soybean plants.

An added incentive for growers to control the nematode is their concern over Sudden Death Syndrome. Sudden Death Syndrome is spreading and it tends to co-occur with the nematode. When in the same field, the two diseases exacerbate the problem.