The ideal time to apply a fungicide to corn to achieve maximum yield response and optimum disease control is the short window between tassel emergence (VT) and blister stage (R2). Though most fungicides applied on tasseled corn include both curative and preventative active ingredients, fungicides are far more effective at preventing disease infection than they are at stopping disease after plants have been infected. Many leaf diseases can take seven to ten days before lesions appear after infection, therefore waiting to see visible signs of disease is not always recommended, especially on disease sensitive hybrids when conditions are favorable for disease infection. If you elect to wait on fungicide treatment, a later treatment will still be effective at stopping disease progression. These later treatments can also improve plant standability at harvest time, but positive yield responses to offset treatment costs will be more difficult to obtain.
When conditions are favorable for fungal disease development, all fungicides routinely deliver a positive return on investment, but not all fungicides perform equally. Over the past few seasons, the newest fungicide active ingredients on the market contain multiple sites of action and are consistently delivering higher yields. These newer fungicides have improved disease control and longer lasting residual over brands that are just a few years old.
Aside from disease prevention and treatment, fungicides also help mitigate plant stress including heat and drought that occurs during pollination through grain fill. Fungicides provide no protection against Goss’s Wilt and Bacterial Leaf Streak infections. However, a fungicide may be recommended to offset the plant stresses these diseases create.
Tassel time fungicide treatments are also a good time for some tank mixing with insecticide for silk and ear damaging pests including Western Bean Cutworm, Rootworm Beetles, and Japanese Beetles. It is not recommended to add insecticide when not needed, so a thorough scouting of a field for these insects before application must be made.
Over time fungicide has been a great way to protect yield. The correct product and timing will consistently increase yields and profits. Norder Supply agronomists continue to evaluate new fungicide options and can help find the right fit for your farm.