Pre-emergent herbicides (i.e. Atrazine) are usually applied in early spring. Post-emergent products (i.e. Atrazine, Glyphosate and 2,4-D) are applied in June through early July. Herbicides are rarely applied aerially.
Glyphosate is the most commonly used herbicide in Iowa. Glyphosate is classified as low to very low in toxicity when inhaled or applied to skin. Eye and skin irritation have been reported, though typically in cases where the exposure resulted from mixing the concentrated product. Inhalation of spray mist may cause oral or nasal discomfort and throat irritation. Worker restricted-entry interval: 4 hours
Atrazine is common in both agricultural and non-agricultural settings; approximately 75% of the field corn acreage in the US is treated with atrazine. It is slightly to moderately toxic to humans, potentially causing skin rashes and irritation of the mucus membranes when inhaled as well as moderate to severe eye irritation. Worker restricted-entry interval: 12 hours.
2-4, D is a broadleaf weed control agent used in both agricultural and non-agricultural settings. Inhalation of 2,4-D may cause coughing and upper-respiratory discomfort. Dermal absorption is poor, but dermal exposure may cause skin irritation. 2-4,D is highly toxic when ingested. Worker restricted-entry interval: 48 Hours