Fungicide seed treatments reduce infection of maize by soil-borne Fusarium species and thereby contribute to improved photosynthesis

Maize seed treated with either Cruiser Extreme+ 250 [fludioxonil (2.5 g ai/100 kg seed) + azoxystrobin (1 g ai/100 kg seed) + thiamethoxam (62.5 g ai/100 kg seed) + mefenoxam (2 g ai/100 kg seed)] or a premix of Vortex+-Trilex+ FL-Allegiance+ FL [ipconazole (2.5 g ai/100 kg seed)+ trifioxystrobin (10 g ai/100 kg seed) + metalaxyl (28 g ai/100 kg seed)], was planted at Southeast Research Farm, Crawfordsville, Iowa and Northeast Research Farm, Nashua, Iowa. Fungicide seed treatments effects on early season growth and physiology were evaluated by assessing incidence of Fusarium species colonization, chlorophyll fluorescence (CF) (estimate of photosynthetic performance) 14, 28 and 52 days after emergence (dae). Plant height was assessed at 28 and 52 dae. The most prevalent species isolated at both locations were F. graminearum and F. subglutinans, followed by F. verticillioides at Nashua and F. proliferatum at Crawfordsville. Photosynthetic performance, as measured by CF, decreased with increased incidence of Fusarium species at 28 and 52 dae (Nashua, r super(2) = -97, r super(2) = -0.74; Crawfordsville, r super(2) = -0.71, r super(2) = -0.81, respectively). Cruiser Extreme+ 250 seed treated plants had the highest (P < 0.05) CF values and lowest (P < 0.05) incidence of Fusarium species colonization at both locations at 52 dae. CF measurements positively correlated with plant height measurements (Nashua r super(2) = 0.64; Crawfordsville r super(2) = 0.57) at 52 dae.