Will it pay to apply a fungicide? That’s the million-dollar question for farmers looking to boost production on a limited budget. The honest answer is, it depends. At a time when every input dollar matters, here are some tips to help maximize your profitability on fungicide applications.
Each year brings different environmental conditions, which is why most fungicide sales are made in-season. But knowing the risk factors that can make your fields more susceptible to disease helps focus your scouting efforts.
- Tillage and crop rotation. Fungal spores overwinter in soil and plant debris left behind with conservation tillage practices. Generally, these fields contain more fungal spore populations, thus increasing the likelihood of disease when conditions are favorable for infection. Fields with limited crop rotation are also at a higher risk for disease infection.
- Seed genetics. Review seed choices when you’re trying to prioritize fungicide applications with limited input dollars. Most seed guides will rate a seed hybrid or variety based on its susceptibility to disease infection. While this serves as a good reference, keep in mind that usually these ratings are based on visual observations and don’t take into account actual yield responses. Hybrids and varieties that are more susceptible to disease are usually more responsive to a fungicide application. Thus, you’ll get a better return on your investment if you focus your fungicide dollars there.
- Seed placement. While choosing the right genetics is important, you need to go one step further and make sure you’re placing the right genetics on the right acre. For example, low-lying areas that hold moisture are more prone to disease and would be well-suited for a hybrid with more disease resistance. Keep notes of disease pressure by field so that you have a historical record of what to expect depending on environmental conditions. Survey your fields AND your genetics to make sure you’re placing the right seed on the right acre to limit disease risk.
- Environmental conditions. One of the biggest risk factors (and one that is largely out of your control) is weather conditions. Most fungal diseases thrive in moist, warm conditions. If you’ve had an extended period of wet weather, it’s a good idea to start scouting for diseases. If the future forecast is hot and dry there’s a good chance disease progression will halt and a fungicide application may not be necessary.
Know When to Pull the Trigger
Once you’ve surveyed your risk factors, it’s time to pencil out whether a fungicide application will be profitable. With low commodity prices, you’ll need to see higher yield responses from your fungicide application to make it profitable.
A meta-analysis of data gathered from 2002 to 2009 across 14 states in the Corn Belt showed average yield increases of 1 to 4 bu/ac when foliar fungicides were applied when disease pressure was low (less than 5% of the ear leaf infected with disease between R4 and R6 growth stages). In this scenario, the probability of not breaking even on a fungicide application was greater than 70 percent for a wide range of application costs and grain prices. Over the test period, even at the highest grain price of $7 per bushel and with the lowest fungicide application cost of $16.20 per acre, there was a 25, 44, 41, and 65% chance of the yield increase being insufficient to cover the cost of applying pyraclostrobin, propiconazole plus trifloxystrobin, propiconazole plus azoxystrobin, and azoxystrobin active ingredients, respectively, when disease severity was low. This data suggests that a foliar fungicide application is unlikely to be profitable when disease pressure is low, and yield expectation is high.
The graphs below show the probabilities of not breaking even on fungicide cost for the four common active ingredients listed above based on various corn prices and application costs over the study period. The left column of graphs shows probabilities when disease pressure is low, while the right column shows probabilities of not breaking even when disease impacts more than 5 percent of the ear leaf at the R4 to R6 growth stage.
Source: Meta-Analysis of Yield Response of Hybrid Field Corn to Foliar Fungicides in U.S. Corn Belt (Phytopathology, 2011)
If you decide a fungicide application is likely to be profitable based on your analysis, it’s time to consider application timing. In corn, the ear leaf and leaves above generate 75 to 90 percent of the carbohydrates for grain fill. So, you’ll generally get better yield response when you wait until VT to R1 to apply a fungicide in corn. For soybeans, waiting until the beginning of flower to the beginning of pod formation (R1 to R3) will give you the best return on investment based on university and seed company data.
Adding the right tank mix partners can make your fungicide work harder. More leaf coverage means you’ll get better plant protection. Adding the right adjuvant to your tank mix helps deliver more active ingredient deeper into the canopy where many fungal diseases start. Adjuvants can also help products spread and stick on leaf surfaces, resulting in better plant coverage. Relative to the cost of a fungicide application, adding an adjuvant is a small investment that can result in big yield advantages.
Think about other tank mix partners that might make sense with your fungicide application. For example, insecticides can help control pests that are vectors for plant diseases. Consider adding micronutrients to your tank mix if supplemental fertilization is needed based on tissue sampling results. Always consult product labels to ensure compatibility and spray limitations.
What’s This All Mean?
The bottom line is that applying a fungicide isn’t a black and white decision. There are many variables to consider before it makes economic sense, especially with depressed commodity prices. Consider your seed’s genetics, environmental conditions, production practices and field history to help guide smart decision making. If disease pressure is low and your hybrids and varieties are more resistant to disease, data shows it probably won’t be profitable to apply a fungicide. On the other hand, if you’ve planted more susceptible seed varieties and disease pressure starts early and is heavy, you might see a substantial yield advantage by protecting plant health.
But, just throwing any fungicide in the tank and spraying it on a field won’t cut it. A smart application starts with choosing the right fungicide, applying it at the right time and adding the right tank mix partners to improve overall plant health. Work with your local agronomic advisor to help pencil out best and worst case scenarios based on the cost of fungicide application and disease risk factors.
1. Meta-Analysis of Yield Response of Hybrid Field Corn to Foliar Fungicides in the U.S. Corn Belt. P. A. Paul, L. V. Madden, C. A. Bradley, A. E. Robertson, G. P. Munkvold, G. Shaner, K. A. Wise, D. K. Malvick, T. W. Allen, A. Grybauskas, P. Vincelli, and P. Esker. Phytopathology 2011 101:9, 1122-1132