Commercially available foliar fungicides (Table 1) were evaluated for their impact on disease and yield responses. Under favorable conditions for disease development (i.e., wet and humid weather), foliar infections can cause premature leaf senescence, reduce photosynthetic capacity, and lower yields.

This trial was conducted at the Piedmont Research Station in Salisbury, NC, in a non-irrigated field. Corn hybrid ‘DKC59-82 VT2P 20 M PV1250+ B360 + EDC’ was planted on April 25 in 30-inch rows at a seeding rate of 139,000 seeds per acre. The experiment followed a randomized complete block design with four replications. Each plot measured 10 feet wide by 40 feet long and included four rows; only the center two rows were used for evaluation.

Xyway (15.2 fl oz/A) was applied in-furrow at planting in a 2×2 band. All other treatments were applied at the VT growth stage (July 1) using a CO₂-powered backpack sprayer calibrated to deliver 15 gallons per acre at 60 psi, using TJ-TT11002 nozzles spaced 30 inches apart. Gray leaf spot and other minor foliar diseases were rated on five ear leaves per plot on July 1, 15, and 31. The percentage of symptomatic leaf area was averaged for each plot. Plots were harvested on October 2, and yield was adjusted to 15.5% grain moisture.

Dry weather throughout the season was not conducive to disease development, and overall foliar disease pressure remained low (less than 5%). As a result, no notable differences in disease severity were observed among treatments throughout the season. Likewise, no significant yield differences were detected (Table 1), likely due to drought stress and limited disease pressure. Yield increases of 2.8 and 2.3 bushels/acre were observed with Aproach Prima and Veltyma, respectively, though these small gains are unlikely to offset the cost of treatment. All other fungicide treatments resulted in yield reductions compared to the untreated control, which may be attributed to the added stress of foliar applications under dry conditions.

Overall, foliar fungicides may not provide economic benefit in drought-stressed corn, as minimal disease pressure reduces the likelihood of a profitable return on investment. While some active ingredients may offer minor physiological benefits, university research has shown these effects rarely result in yield increases large enough to justify application costs. The best practice is to avoid fungicide applications when conditions are not conducive to disease development and when there is no evidence of disease presence.

Table 1. Yield response of Drought-Stressed Corn to Fungicides

^aYields (bushels /A) were determined by harvesting the 2 center rows of each plot on October 2, and converting plot yield (lb) using the test weight (lb) and grain moisture (%) for each plot. The final yield was adjusted to 15.5% moisture.

Additional resources on fungicide use in drought-stressed corn:

• Iowa State Extension
• University of Maryland
• Ohio State Research Poster
• University of Tennessee
• University of Wisconsin
• Crop Protection Network
• APSnet Feature Article