Date of this Version
Chapter in 2015 Crop Production Clinic Proceedings, University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources, pp. 163-168.
In years with conditions favorable for seedling disease and other disease there are typically concerns and inquiries about the cause(s) of symptoms in agronomic plants. Many of the questions focus on differentiating between plant injuries potentially caused by recent herbicide applications versus symptoms caused by plant pathogens. Chemical injury in row crops is caused by chemicals such as herbicides, fertilizers, fungicides, insecticides, growth regulators, and crop oils when they are applied individually, as a mixture, or together with adjuvants. If chemicals are applied incorrectly, plants may be damaged at any point during the growing season. Chemical injury can result from carryover in the soil, contamination of the spray tank, spray drift, or misapplication. Damage may even be realized with chemical applications when recommended application guidelines are followed if other environmental conditions are adverse, including low soil temperatures, high soil moisture levels, or if young plants are exposed to high levels of various fertilizers. Factors such as the mode of action of the chemical, application rate, growing conditions, and growth stage of the crop determine the extent of injury and symptom expression. Symptoms of chemical damage are diverse and include leaf lesions with burned, necrotic patches, wilting, damping off, and sometimes death of mature plants. These symptoms could easily be confused with those caused by various plant pathogens found throughout the state. In most instances management actions cannot be taken during the year of the injury once you are past the replant timing. Therefore, you will want to correctly identify what is causing any stand problems to aid with future management actions.