My Thoughts Fungicide Spray Program Economics Thoughts

Written by: David Langston

I hear a lot of people complaining about the cost of growing peanuts versus contract prices. Maybe that’s a topic among growers most years across commodities? Growers have more control over input costs than contract prices, so I tend to focus on what can be controlled.

Peanuts are a little different than other agronomic (field, row) crops in that they must be sprayed with fungicides multiple times to obtain acceptable yields. Choosing which fungicides to use and how many times they’re applied has a direct effect on net returns.

Two fungicide-by-variety trials were conducted each year in 2022 and 2023 through a collaboration between Dr. Maria Balota and myself. The objective was to evaluate the effect of different fungicide programs across five popular Virginia-type peanut varieties to determine whether fungicide inputs could be reduced depending on the variety selected.

The varieties evaluated (subplots) were Bailey II, Emery, NC 20, Sullivan, and Walton.

The fungicide programs (main plots) included:

• Full Program – Miravis + Elatus (60 & 90 days after planting), Provost Silver (90 & 105 DAP), and Bravo (120 DAP) – approximately $135 per acre.
• Advisory Program – Bravo (2 applications), Provost Silver (2 applications), and Omega 500 (1 application) – approximately $90 per acre.
• Leaf Spot Only Program – Bravo (3 applications) and Provost Silver (2 applications) – approximately $63 per acre.

There were no significant yield differences among varieties during either year. However, differences among fungicide programs were significant.

Net value for each fungicide program was calculated using a contract price of $540 per ton. Net return was determined by subtracting the value of the untreated check from the value of each fungicide program.

In both years, the program designed to control only leaf spot produced the highest yields and the greatest net return per acre because its overall cost was lower than the other two programs.

Neither the Full Program nor the Advisory Program statistically improved yields over the untreated check during 2022, likely because extremely dry weather limited disease development. As a result, net returns for both programs were relatively low, particularly since fungicides targeting Sclerotinia blight were applied even though disease pressure remained low.

Weather conditions during 2023 were much more favorable for disease development, and both leaf spot and Sclerotinia blight were present at both trial locations. Higher disease pressure improved net returns for both the Full and Advisory Programs. However, because of their higher fungicide costs, both programs still produced lower net returns per acre than the less expensive Leaf Spot Only Program.

Overall, the Leaf Spot Only Program would have generated greater profits for growers in both years.

The risk of Sclerotinia blight was low at both trial locations during 2022. In 2023, only one of the two locations experienced conditions favorable for higher Sclerotinia blight pressure, resulting in differences in disease severity among fungicide programs. However, disease onset did not occur until September 1, which was too late in the season for Sclerotinia blight to reduce yields enough to significantly impact overall profitability.

Across all four trials conducted over the two-year period, all three fungicide programs performed similarly in controlling leaf spot despite large differences in program cost.

These results suggest that lower-cost leaf spot programs can provide the greatest economic return, particularly since leaf spot affects substantially more peanut acreage than Sclerotinia blight. In years when Sclerotinia blight develops earlier in the season, fungicide programs targeting that disease would likely provide greater economic benefit in fields with a history of severe losses.

In North Carolina and South Carolina, where southern stem rot is more common, fungicide recommendations and disease management strategies differ considerably from those typically used in Virginia.