After a very wet start to the growing season, diseases are beginning to show in corn throughout the state. Gray leaf spot will begin as small rectangular blocks of a tan color surrounded by jagged edges of brown. As the disease progresses, the spots will extend between veins to long lesions of gray, tan, and brown.
Scout's Report 7/1: European corn borer feeding begins in Indiana
Northern Corn Leaf Blight lesions are commonly referred to as the spots shaped like cigars. These lesions show up as a tan and olive green color on the leaves and will cross over veins, unlike GLS lesions. Both diseases are probable due to the humid conditions and moderate temperatures. NCLB in particular prefers cooler temperatures.
These lesions will appear in the lower leaves first and make their way up the plant after tasseling. Management of GLS and NCLB needs to be based on growth stages for each field that is infected. Spraying a fungicide after pollination is the best option for control of disease. Sidestep stress to the plant by waiting to spray until pollination is complete. The stress of spraying around tassel time can limit the pollination and leave some kernels unfertilized.
European corn borers are still eating at non-GMO crops. The insects can damage plants and move on to the next ones down a row, leaving behind a damaged still tassel wrapped in the whorl. Controlling the spread of these borers is a very timely task. Catching the egg masses is key and spraying an insecticide before they have a chance to burrow down into the stalks is critical.
Nitrogen loss has devastated many growers across the state, especially in the northern regions. With over saturated soils, roots are struggling to find nutrients and oxygen. Some fine roots have resorted to reaching the soil surface to find oxygen. The yellow areas of fields with shorter and stunted plants are the result of excessive water for an extended period of time. These areas are likely to fall further behind in maturation and hurt final yields.
Scout's Report, 6/24: Stink bug damage and yellow leaves for Indiana corn
The traps throughout north central Indiana have shown some European corn borer moth flight action. Check Purdue Entomology and Agronomy updates for more information.
Look for my findings again next week.
Kettler is a senior at Purdue University. She is scouting this summer for Beck's Hybrids, Atlanta, Ind. She works with Ben Grimme, Kris Johnson, and Beck's agronomist, Denny Cobb.