Northern corn leaf blight

Late-season diseases pose a significant threat to corn’s yield potential, and without the proper precautions and vigilance, they can sneak in undetected. Growers should be especially mindful during the R1 silking phase. This critical stage sets the tone for harvest, as the number of kernels are determined and maximum plant height is achieved during this growth stage.

From Flowering to Grain Fill

During the R1 stage, flowering begins as each potential kernel develops its own silk, a process that can be disrupted by adverse weather conditions and stress, such as drought. Silks remain active until pollinated and kernels form, but silks that fail to emerge mean fewer kernels to fill. Once pollination is complete, the plant turns its focus to grain fill. Full, unfurled leaves allow for maximum photosynthesis, helping ears fill to their full potential. According to Purdue University Extension, green matter from the ear leaf to the top of the plant is responsible for about 60% of the photosynthesis required to fill the ear.

Purdue University Extension also maintains that a stress-free grain fill period can maximize the yield potential of a crop, while severe stress during grain fill can cause kernel abortion or lightweight grain and encourage the development of stalk rot. This stress can come from many directions. Weather stress is a big issue, as drought stress impacts the plant’s ability to function, while hail and wind destroy green matter surface area, impacting their ability to feed the ear. Diseases such as Northern corn leaf blight, gray leaf spot, rust and tar spot can also cause serious damage to plant health as depicted in these images from our Grow More™ Experience site in Slater, IA.

Prepare to Protect

With stakes this high, a well-timed fungicide application during the R1 growth stage is a strategic move. Wally West, agronomy service representative based in SD, says that R1 is the sweet spot for fungicide applications, providing the best return on investment even in the absence of disease by providing additional plant-health benefits.

Plus, the effects of environmental stress can have compound effects. For example, consider weather damage to leaves. This damage decreases the amount of green tissue for photosynthesis, but it can also provide a direct route for pathogens, especially stalk rots or ear molds, to infect plants and compromise yield potential. In situations like these, fungicide applications can have a large positive effect.

West elaborates in this video from the Iroquois, SD, Grow More Experience site.

Two products we recommend for corn at the R1 growth stage are Miravis® Neo and Trivapro® fungicides. Miravis Neo helps crops produce more bushels more often with 3 active ingredients – propiconazole, azoxystrobin and ADEPIDYN® technology – to deliver superior plant-health benefits and improved preventive and curative control of key diseases. Trivapro combines broad-spectrum preventive and curative disease protection against key foliar corn diseases with longer-lasting residual control for optimal protection from application to harvest.

With a proven fungicide in place during the R1 growth stage, corn will be well-protected from common diseases lurking in fields and well-equipped to manage through stress from Mother Nature.

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