Location: Agroecosystems Management ResearchTitle: Effects of fungicide seed treatments and a winter cereal rye cover crop in no till on the seedling disease complex in corn
|ACHARYA, JYOTSNA - Iowa State University|
|Moorman, Thomas - Tom|
|LENSSEN, ANDREW - Iowa State University|
|ROBERTSON, ALISON - Iowa State University|
Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2018
Publication Date: 9/7/2018
Citation: Acharya, J., Bakker, M.G., Moorman, T.B., Kaspar, T.C., Lenssen, A.W., Robertson, A.E. 2018. Effects of fungicide seed treatments and a winter cereal rye cover crop in no till on the seedling disease complex in corn. Canadian Journal of Plant Pathology. 40(4):481-497. https://doi.org/10.1080/07060661.2018.1506503.
Interpretive Summary: Cover cropping is a valuable conservation practice that reduces sediment and nutrient losses from agricultural systems and improves soil quality. However, farmers using cover crops need to adjust management to minimize risks and maximize benefits of this practice. For example, the risk of seedling disease may be higher for corn planted following a winter rye cover crop, compared to corn planted following a winter fallow. However, several different types of micro-organisms can cause corn seedling diseases and these diseases may occur in some years or fields whether or not a rye cover crop is present. One approach to managing these corn seedlings diseases has been to use fungicide seed treatments. A number of different fungicides are available and these fungicides have different active ingredients that have varying degrees of effectiveness against different pathogens. Because cover cropping is a relatively new practice in corn rotations, it is important to identify which fungicide seed treatments are most effective with this management practice. Additionally, by testing different fungicides with active ingredients that are more effective against particular seedling pathogens we will be able to identify which micro-organisms may be most important in causing corn seedling disease following rye cover crops. We performed a series of experiments in which corn seeds were given fungicide seed treatments with different active ingredients and were planted either following a rye cover crop or no cover crop. Our experiments confirmed the potential of rye cover crops to elevate disease pressure on corn seedlings when conditions are cold and wet. Among several potential corn seedling pathogens, organisms belonging to Clade B of the genus Pythium appear to be most important in causing corn seedling disease after rye cover crops. We also found that seed fungicides that contained the active ingredient metalaxyl were the most effective. This information may lead to more targeted and effective management strategies that reduce the cost of cover cropping by minimizing disease risk in the following corn crop. The impact of this research is that farmers, extension personnel, crop advisors, and NRCS conservationists will be able to use and manage cover crops more effectively, which will lead to more cover crop adoption, less risk to corn yield, and more environmental benefits.
Technical Abstract: Seed treatments with active ingredients targeted to different fungal and oomycete genera were used to study root infection in corn planted after winter rye or a winter fallow. Controlled environment experiments tested corn seed treated with the following fungicides: (i) metalaxyl, pyraclostrobin, fludioxonil, ipconazole, and sedaxane, to reduce infection by Pythium, Fusarium, and Rhizoctonia solani (treatment ALL); (ii) metalaxyl alone, to reduce Pythium (P); (iii) metalaxyl and pyraclostrobin, to reduce Fusarium and Pythium (FP); (iv) pyraclostrobin, fludioxonil, ipconazole and sedaxane, to reduce Fusarium and R. solani (FR); and (iv) non-treated seed control (NT). Complementary field trials compared the ALL seed treatment against non-treated seed (NT), with and without rye. Under cold and wet environmental conditions, winter rye negatively affects corn seedling growth and increases seedling root disease and Pythium incidence. In general, seed treatments improved seed germination and seedling growth (P < 0.05) under controlled environment conditions. Seed treatments active against Pythium spp. (i.e. P, FP, and ALL) reduced radicle disease index scores (P < 0.01) compared to FR and NT. Similarly, Pythium spp. recovery rates from corn seedlings following rye were lower with P, FP, and ALL seed treatments, although only in 1 of 2 Runs. Seed treatment effects were not evident on the recovery of Fusarium spp. In the field, no benefit of fungicide seed treatment was detected on corn seedling growth or root disease incidence following rye, although mesocotyl disease incidence was reduced with fungicide treatment in 2014. These results suggest that Pythium species play a major role in the corn seedling disease complex following a winter rye cover crop. Management of corn in a system with winter rye cover crops should explicitly consider Pythium spp.