More than 200 soybean varieties that resist soybean cyst nematode (SCN) have been made available for the 2003 growing season, but you should still monitor SCN populations says Ohio State University (OSU).

Of the new resistant varieties, all but four originate from the same resistant source, telling OSU plant pathologist Anne Dorrance that eventually varieties from PI88788 will no longer be effective against the pest.

Dorrance says the barrier between SCN and certain resistant soybean varieties is already crumbling in limited areas of Ohio and will likely continue as SCN populations adapt to varieties that carry the PI88788 resistance.

"I think what growers don’t understand is that resistance does not mean a complete resistance. The way resistance is measured to Soybean Cyst Nematode is by how many females reproduce compared to the susceptible check," says Dorrance. "There will still be females reproducing on that resistant line, developing nematodes that eventually will develop and appetite for that particular resistant variety.

The best way for growers to determine whether they should plant a susceptible variety or a non-host crop is to test their soils for egg populations.

Though PI88788 has been the main stay of soybean cyst resistant lines for the past decade, Dorrance says that growers should be keeping their eye out for the development of new lines that carry resistance, suck as ‘Peking’ and ‘Hartwig’.