Iowa soybean farmers have a powerful tool available in the fight against soybean cyst nematode, but researchers say how farmers use that tool now could determine how effective it remains in the future.
Peking resistance has become increasingly available in soybean varieties and is providing strong control of SCN. However, Iowa State University nematologist Greg Tylka says farmers should be careful not to repeat what happened with PI 88788, the resistance source that has dominated the soybean industry for decades.
Tylka has evaluated resistant soybean varieties for yield and SCN control at Iowa State for more than 30 years. That has allowed him to watch how SCN populations have responded to PI 88788 over time.
PI 88788 provided very good control when it was first widely used, but repeated reliance on the same resistance source allowed SCN populations to gradually adapt. Tylka says Peking provides another effective option, but its success also creates a reason for caution. He believes SCN could overcome Peking more quickly than it did PI 88788 if farmers rely too heavily on it.
That makes rotation an important part of preserving both resistance sources.
University of Nebraska plant pathologist Dylan Mangel says farmers already have an important tool for reducing SCN populations because corn is a non-host crop. During soybean years, he says growers should also avoid repeatedly planting varieties with the same source of SCN resistance.
Mangel says even when a Peking variety is not available with the other characteristics a farmer needs, growers can still avoid repeatedly planting the exact same PI 88788 variety. The goal is to avoid putting the same selection pressure on an SCN population year after year.
Farmers are also gaining more choices as additional Peking varieties become available. Tylka says Iowa State University maintains an annually updated list of SCN-resistant soybean varieties with support from the Iowa Soybean Association.
At the time of the Farm Progress Show interview, Tylka said about 20 percent of the varieties on the Iowa State list used Peking resistance, while roughly 80 percent relied on PI 88788. The resource includes hundreds of soybean varieties and identifies characteristics including herbicide tolerance and the source of SCN resistance.
The increased availability of Peking does not mean PI 88788 no longer has a place in SCN management. In fact, Tylka says using Peking can help make PI 88788 more effective.
A rotation that includes corn and Peking-resistant soybeans can reduce SCN populations before a farmer returns to a PI 88788 variety. That gives the older resistance source a lower nematode population to contend with rather than repeatedly exposing a high SCN population to PI 88788.
Protecting both resistance sources is especially important because researchers do not currently see another widely available option ready to take their place.
For Iowa soybean farmers, the message is not to abandon PI 88788 in favor of Peking. Instead, researchers want growers to take advantage of having two resistance sources and use them strategically.
Rotating corn with soybeans, alternating between Peking and PI 88788 and avoiding repeated use of the same resistant varieties can help reduce SCN pressure while extending the useful life of the tools farmers currently have.
Peking may provide farmers with an important advantage against SCN today, but preserving that advantage will depend on avoiding the same pattern of repeated use that allowed the pest to gradually overcome PI 88788.
The post Protecting Peking key to Iowa SCN management appeared first on Iowa Agribusiness Radio Network.
