Variety Selection/seed treatments key to managing soybean pathogens
“We’ve got several key pathogens including Phytophthora root rot, soybean cyst nematode, seedling diseases, and frogeye leaf spot, all of which can be managed with variety selection and the use of seed treatments in some instances,” said Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center.
When it comes to managing Phytophthora root and stem rot, variety selection with the right resistance package is key, said Dorrance. Many single genes are no longer effective or are beginning to erode in their resistance.
“The Rps1a gene is no longer effective, and the Rps1c and Rps1k genes about 10 years ago were about 50 percent effective and they continue to erode,” said Dorrance. “It’s important to pick a variety with a resistance gene, but that particular resistance gene is not going to work in every location in the field or in all fields.”
In addition, previous Ohio State research has shown that Phytophthora populations in Ohio soybean fields are adapting to plants carrying single Phytophthora root rot resistant genes, such as Rps1a, Rps1b, Rps3a and Rps6.
“We really need to pay attention to the Phytophthora package in any given variety,” said Dorrance. “Phytophthora root rot is the single biggest threat to soybean production in the poorly drained soils. Reduction in yield from the disease can range anywhere from five to 30 bushels per acre depending on the resistance package in the variety.”
Dorrance encourages growers to also look to partial resistance for Phytophthora in soybean varieties.
“High levels of partial resistance to Phytophthora root rot help maintain yields across disease pressures and disease locations,” said Dorrance. ““Partial resistance varieties can be very effective, sometimes having a 30 percent difference in yields compared to soybean plants that have no resistance to Phytophthora at all, depending on the disease pressure.”
When it comes to soybean cyst nematode, Dorrance encourages growers to test their field first to determine whether or not SCN is even present.
“Take an Integrated Pest Management approach. If you don’t know if you have SCN in your field then don’t plant an SCN-resistant variety,” said Dorrance. “The main reason is that SCN will adapt.”
If a field does contain SCN, Dorrance recommends growers work with their seed company to find the right genetic cross in the variety, especially if the current variety being used isn’t working as well as it should be.