Pest Control · May 2025 · 6 min read
Early identification of crop diseases can mean the difference between a minor yield drag and a devastating loss. Knowing what to look for at each growth stage helps you make timely management decisions and protect your investment.
Gray leaf spot appears as rectangular, grayish-tan lesions bounded by leaf veins, typically showing up after tasseling in humid conditions. Northern corn leaf blight produces long, cigar-shaped gray-green lesions on lower leaves first. Common rust presents as small, cinnamon-brown pustules on both leaf surfaces. Scout fields weekly from V8 through grain fill, paying extra attention to continuous-corn fields and susceptible hybrids.
Sudden death syndrome (SDS) causes interveinal chlorosis and necrosis on upper leaves while the stem pith remains white. White mold appears as fluffy white mycelium on stems during canopy closure in cool, wet years. Frogeye leaf spot shows circular lesions with gray centers and dark brown margins. Timely fungicide applications at R3 can help manage foliar diseases when conditions favor infection.
Fusarium head blight (scab) causes premature bleaching of individual spikelets during flowering, often with a salmon-pink discoloration at the base. Stripe rust forms yellow-orange pustules in stripes along leaf veins and spreads rapidly in cool, moist weather. Septoria leaf blotch produces irregular tan lesions with dark pycnidia visible under a hand lens. Fungicide timing at flag leaf emergence is critical for protecting yield potential.
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