Fungicide Becomes Hot Topic as Diseases Appear in Corn

Well-known plant breeder declares it the year of gray leaf spot.

Published on: Jul 27, 2009

Scouting fields last week, Dave Nanda found two significant things in corn- significant European corn borer infestation in a few field, and an early outbreak of gray leaf spot that was noticeable in several fields in central Indiana.


In fact, one field on the irrigated farm that was used for Corn Illustrate plots two years ago is sporting significant amount of gray leaf spot on one particular hybrid. And while you might think the fungus is developing because irrigation adds humidity, this field has yet to be irrigated this season. Adequate to more than adequate rainfall has kept it well watered so far this year. Apparently, this particular hybrid is highly susceptible to the disease.


Nanda, a plant breeder with 40 years of experience, a crops consultant for Corn Illustrated and also president of Bird Hybrids, Tiffany, Ohio, viewed the plots recently. While most of the lesions haven't coalesced, which means they haven't grown together yet, they are numerous, especially on the lower leaves.


The real threat to yield occurs if conditions remain favorable for gray leaf spot later in the season, Nanda notes. Lesions that lead to death of leaves above the ear leaf became stressful, and have the potential to significantly lower yields. That's simply because if too much leaf area is destroyed, the plant doesn't have enough manufacturing capacity left to produce as many sugars for conversion to starches, protein and oil that would deliver maximum yield.


The knee-jerk reaction might be to spray fungicides immediately. However, Nanda says that could be a mistake. Experiences of many over the past two years indicate that spraying fungicide, depending on which one it is, before tasseling, can cause injury to the developing ears. Nanda prefers that pollination is complete, not just underway, to avoid damage. The best bet is to consult the label, or have your dealer consult it, to make sure you spray in a timely fashion, but not so early that you risk injury in ear development,. The injury that can result from spraying too early is sometimes called arrested ear development.


"We will have a plot here at our former Corn Illustrated field," Nanda insists. "The farmer will have the application of fungicide applied aerially at the right time."


In fact, he's lined it up through a special program with the Shelby County Co-op, Shelbyville, Ind. If he wants to spray it, he simply gives them the nod and the field will be aerially sprayed. There is no penalty if he decides not so spray. Meanwhile, the applicator and co-op staff are checking for possible environmental hazards in the area, such as a neighbor's swimming pool or a specialty crops.


Considerable dollars are hanging in the balance either way, form not treating if it's needed and treating if it isn't.