Direct feeding by free-living nematodes could be causing greater yield loss in potato crops at lower population numbers than previously thought, a Scottish Agricultural Colleges’ researcher believes.
Andy Evans’ research has shown direct feeding by free-living nematodes cause potatoes to put more resources into root production at the expense of top growth.
Laboratory experiments indicated that tuber development in potatoes grown in soils without a nematode population produced tubers much faster than those grown in soils with nematodes, he said. “That definitely has an impact on yield.”
The next step would be to quantify how population size affected yield loss, he said. Traditionally it has been thought that growers didn’t need to worry about direct feeding, particularly with populations smaller than 100 nematodes in 250g of soil.
“But we’re finding at lower populations than that root weight is increasing at the expense of top growth [and affecting yields],” he said.
That could have implications for control, particularly as numbers of nematodes had increased by 300% over the past decade. “It might be that growers who have a negative tobacco rattle virus test result, but have high nematode populations might still find it worthwhile to putting a nematicide in furrow at planting, because there’s nothing you can do after that.”
Why have free-living nematode numbers exploded?
The banning of “nasty” soil pesticides, such as gamma-col in cereals, had contributed to the 300% increase in free-living nematodes, Dr Evans suggested.
“They were probably keeping nematode numbers down incidentally, but numbers have probably exploded because there is nothing nasty being applied to soils between potato crops.
“We’re also seeing problems with nematodes in cereals and carrots. They’re a hidden menace.”