Fungicide Applications to Corn and the Potential for Positive Yield Responses
Written by Victoria Kleczewski, Lead Insect & Plant Disease Technical Manager for the FS Cooperative System
- The yield response to fungicide applications in corn depend on several factors conforming the disease
- Weather conditions such as temperature and humidity will drive pathogen development and spore
- Along with weather, the history of the field and farming practices can affect pathogen load and disease development
- Hybrids rated susceptible or moderately susceptible to grey leaf spot tend to be more responsive to fungicide applications than resistant hybrids
Although fungicide applications to corn around the VT to R1 growth stages result in the best yield protection, the magnitude of the response is affected by several factors. The growing environment, when conducive to fungal disease development, will be a key factor in driving yield responses. Weather conditions such as temperature and humidity will drive pathogen development and spore release. Temperature ranges ideal for disease development vary with the specific pathogen. For example, Northern corn leaf blight and Tar spot develop under cooler temperatures while Grey leaf spot and southern rust thrive in warmer conditions. However when it comes to moisture, high humidity environments seem to be the common ground for disease advancement. The yield response to fungicide applications tends to be higher under high moisture environments, where rainfall is prevalent during the late vegetative to early reproductive stages. The moisture factor is potentially the main reason why we see varying yield responses to VT fungicide applications across the region. Some areas had higher than average rainfall while others remained dry during the late vegetative and/ or through the reproductive stages of development. Along with weather, the history of the field and farming practices; continuous corn versus rotated fields, no-till or minimum till versus conventional tillage or fields with infested crop residue are all factors that can affect disease development.
Pathogen load along with a susceptible host crop can also affect yield responses to fungicides. Grey leaf spot is one of the most common diseases driving fungicide applications in corn across the region and different corn hybrids vary on their susceptibility/ resistance to this pathogen. Hybrids rated susceptible or moderately susceptible to grey leaf spot tend to be more responsive to fungicide applications and result in a positive yield response compared to moderately resistant or resistant hybrids. In fact, University recommendations will abstain from encouraging fungicide applications on resistant hybrids because grey leaf spot severity will most likely not build to damaging levels. However in situations when grey leaf spot is not the only fungal disease with the potential to damage yields, a fungicide application may still be of great benefit. A good example of this will be regions impacted by Tar spot, where a fungicide application during the early reproductive stages provided yield protection even in areas with little or no incidence of other fungal diseases. Just like for grey leaf spot, different hybrids vary on their susceptibility or resistance to Tar spot. However with Tar spot being a relatively new disease not much is known about the yield response of these hybrids to fungicide applications. For more information on disease management including fungicide and hybrid selection contact your local FS crop specialist.