Crop rotation found not effective when fighting Pythium
With harvest winding down seed selection for next year’s growing season is currently on the minds of farmers across the state. There are so many traits and factors to consider when selecting varieties: what maturities should be planted where, soybean traits that are important in different soils types or even what seed treatments will ensure good stand from the start.
One of those seed treatments farmers should consider is a fungicide to fight Pythium, an Oomycetes pathogen that strongly affects early season stand establishment especially in areas with excessive soil moisture or low soil temperatures, said Jim Kurle, University of Minnesota Department of Plant Pathology Associate Professor.
Kurle recently finished a study on Pythium, which he said hadn’t been closely looked at for about 30 years, in which he discovered about 28 different species confirmed in Minnesota alone. Before, only three or four were known and studied. Kurle said this is key because now they can look for tools to fight all these species instead of just a few.
Unfortunately, Kurle found that a soybean and corn crop rotation is not an effective way to manage the pathogen since a number of Pythium species are pathogenic on both soybean and corn crops. But, there is hope for early-season stand establishment.
“So as part of the conclusion with our study, we looked at fungicides in seed treatments to protect against Pythium,” Kurle said. “And that looks really promising, especially with seed costs so high and growers needing an assured stand right from the start with the most effective seed treatments. We did find that Metalaxyl (the active ingredient in Apron for example) was effective on most types of Pythium and also a new fungicide, Ethaboxam, which was effective against many Pythium species.”
If farmers do identify a Pythium problem in any of their fields, Kurle said they should be considering one of these fungicides as part of their seed treatment this next spring. He said that because Pythium is very persistent in soils, it would take a longer period of rotation with other crops other than corn to make a large impact. This makes the effectiveness of rotation very limited.
“These findings lead into the next question: How do we deal with Pythium?” Kurle said. “There are a few ways. One would be to find other crops to mix into our rotations and the other would be to look for soybeans with genes that show resistance. This hasn’t really been done yet.”
Kurle said the barrier to resistance research in the past has been the many Pythium species that were not accurately identified until recently. With the new information, researchers can really focus in on looking for resistance to each particular Pythium type. Kurle said that looking for these varieties that are resistant or at least tolerant, having partial resistance, is the next step in finding tools for farmers to fight Pythium.
In fact, Kurle said research utilizing what was found in this study has already begun to find these varieties that are adapted to Minnesota. Their very first experiment is currently in their growth room.
But for the short term, Kurle’s advice to farmers for the coming season is to utilize the available seed treatments as stand insurance against Pythium since they have been found reliable.