The effectiveness is faltering for the gene that makes soybean varieties resistant to soybean cyst nematode (SCN). The gene is PI88788 and has been a 30-year veteran in 97% of the SCN-resistant soybean varieties. But Purdue nematologist Jamal Faghihi says it's not working as well as expected since failure was first noted in 2005.

He says Tennessee beans are no longer resistant; but Canadian beans are still resistant; and Illinois and Indiana beans are in between. He says farmers can switch to soybean varieties that contain Peking and CystX resistance genes. Both provide strong protection from SCN.

SCN is a yield-robbing, worm-like nematode that feeds on nutrients within a soybean plant's roots. The pest is linked to increased incidence of soybean sudden death syndrome. SCN-related yield losses can reach 50% in heavily infested fields.