- Pythium species cause one of the most harmful diseases in corn and soybeans.
- Protection against seedling disease can lead to higher yields through plant retention.
- At locations where plant stand was significantly different, Vayantis® seed treatments showed higher yield as a result of increased final plant stands.
IntroductionStand establishment is one of the most important yield contributing factors. Many things can limit stand establishment, but seed and seedling diseases can reduce stand by:
- Reducing root development
- Impeding water and nutrient uptake
- Slowing seedling growth
- Causing seedlings to die in severe cases of infection
Pythium fungi overwinter as oospores in the soil and plant material. Pythium fungi are known as “water molds” because they thrive in wet soils. These fungi are also active over a wide range of temperatures, including activity in cooler soils of early planted fields. Symptoms include stunted, chlorotic growth that may resemble nitrogen deficiency, drought-induced wilting, inconsistent plant size or leaf stage and brown root tissue (Figure 1).1
2020 Trials
Golden Harvest® Agronomy In Action research trials established at 8 testing sites were designed to investigate the effectiveness of seed treatment in reducing the effects of Pythium damage. Specifically, a primary objective was to understand if adding either ethaboxam or picarabutrazox, a seed treatment coming soon which will be marketed as Vayantis seed treatment, can provide additional levels of protection against Pythium greater than that already provided by CruiserMaxx® Corn 500. 2 of the 8 trials established were lost to a late season derecho in 2020 (Figure 2). All trial plots were inoculated with Pythium at the time of planting to improve chances of disease presence to see treatment differences. CruiserMaxx® Corn 500 with Vibrance® seed treatment, a combination of 1 insecticide and 5 fungicides, was applied as a control as well as with either ethaboxam or Vayantis treatments to understand differences in performance. Trials were replicated 4 times in a randomized complete block design using the same hybrid across all treatments at each location. Plant vigor, emerged plants and plant uniformity data were collected at locations. Yield, moisture and test weight were recorded with a research combine at the time of harvest.
Results
Final plant stands varied across locations, likely as planting and growing environments were variable early in the growing season. Measurement of early season uniformity, percent of plants at least one growth stage behind the majority of plants, was similar across all locations except Clay Center, KS. Roughly 47% and 39% of the CruiserMaxx Corn 500 with Vibrance alone and with ethaboxam were at least 1 leaf stage behind other plants, respectively. Uniformity was greatly improved when Vayantis was included in the treatment, with only 1.6% weak plants observed (Graph 1).![]()
Bridgewater, SD, Sac City, IA, Clinton and Oregon, IL, had no significant differences in final plant stand or yield. Both Seward, NE, and Clay Center experienced significant stand reductions from Pythium. Adding either ethaboxam or Vayantis improved final plant stands at these locations. The final plant stands of the Vayantis treatment were significantly greater than both ethaboxam and the control. Of the locations where stand loss occurred, on average, adding ethaboxam increased plant stands by 3,400 plants/A whereas adding Vayantis increased plant stands by more than 9,000 plants/A (Graph 2).
The combined stand reduction and lack of plant uniformity at Clay Center and Seward unsurprisingly resulted in yield differences among treatments. Although not statistical, ethaboxam increased yield by 8.3 bu/A, whereas adding Vayantis statistically increased yields by 32 bu/A (Graph 3). At the locations not observing plant emergence or uniformity differences, there was still a small numerical yield advantage of 4.7 and 2.6 bu/A when adding Vayantis and ethaboxam, respectively (Graph 4).
Summary & Discussion
Results from these locations suggest that adding a second mode of action for Pythium control may help preserve plant stand and uniformity in cases where Pythium disease risk is high. Improved yield potential is also likely by improving plant stands and uniformity in growth.
3 key elements must be available for disease to be present and impactful:
If 1 is missing, plant disease will not occur. Typically, the impact of Pythium on corn plant stand has been minimal due to the effectiveness of active ingredients in current seed treatment packages that address this specific disease. However, as we continue to see shifts in Pythium species and their sensitivity to current seed applied fungicides, it will be even more important to add a second mode of action, such as Vayantis, to current seed treatment packages.
Management practices to create less favorable environments for Pythium development and to protect corn seedlings include:
Installing drainage in wetter areas to reduce water-logged soils.
Holding off planting immediately before any extended cool and wet weather forecast.
Planting when soil conditions are warm and favorable for seed germination and growth.
For more information on protecting your corn from Pythium development, contact your local Golden Harvest Seed Advisor.
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References:
1 Broders, K., P. Lipps, P. Paul and A. Dorrance. 2007. Characterization of Pythium spp. associated with corn and soybean seed and seedling disease in Ohio. Plant Disease 91(6): 727-735