Last year's rainfall can impact herbicide carryover problems. Diagnostic Versus Non-Diagnostic Symptoms Purple color in corn is NOT diagnostic. Purple color in corn is NOT diagnostic. To diagnose the problem, correctly identify diagnostic plant symptoms. Note the stage of growth when symptoms first became evident.
Many diseases occur only at certain growth stages.
Distinguish between primary and secondary stresses. Primary stress often brings on a disease response. Patterns can be regular, circular or semi-circular, scattered, irregular, or involve whole fields or units. A blend of seed that separated in the planter when small, denser seed settled to the bottom and were planted first Abnormal growth occurs across the field in regular pattern at about the same width. A strip the width of the sprayer, with a decreasing amount of injury, followed by several acres without injury.