Corn fields around the state, if not tasseling currently, will be soon. Soybeans are mostly in the R2 to R3 stages. Overall, disease pressure remains low with reports of gray leaf spot and bacterial leaf streak being found in corn and bacterial blight, septoria brown spot and phytophthora being found in soybeans. Insects reported include Japanese beetles, grasshoppers, and corn rootworm beetles.

The hot and humid conditions last week really pushed the crops along. The week also brought heavy rainfall to parts of the state – including areas in central Iowa getting 12+ inches over a 3-day period. Corn fields are starting to tassel, and soybeans are fully in the reproductive stages now. Bacterial leaf streak, Goss’s wilt, weed escapes, Japanese beetles, and adult corn rootworm beetles emerging are some of the issues observed by ISU extension field agronomists this past week.

In the next week or so, corn fields across Iowa will start to tassel and the buzz of crop dusters will no doubt join the buzz of insects. Research has consistently shown that the best time to apply a fungicide to manage foliar diseases, like tar spot, southern rust, northern corn leaf blight and gray leaf spot, is at tassel (VT) through milk (R3) stage. But do you really need to spray a fungicide? Fungicides protect yield potential by reducing foliar disease within the canopy.

Regional Update: