Northern Corn Leaf Blight (NCLB) has become a disease that impacts all corn growers to some extent. The disease has been moderate to severe over the last ten years or so. We had a reprieve in 2016 because of the unusually dry conditions.
Disease resistance in hybrids is variable. The disease organism is continually evolving to overcome partial plant resistance. There are nearly 20 fungicides from two chemical families that are labeled for control of NCLB. The majority of efficacy testing has been done in the Midwest. In NY, CCE and industry rely on that information for our recommendations.
In the spring of 2017, I received grant support from the NY Corn and Soybean Growers Association to compare the performance of pre and post tassel fungicide applications in corn for control of NCLB. There were three cooperating farms in our region and an additional site managed by extension colleague, Aaron Gabriel in Washington County in Eastern NY.
The 2017 field study was designed to measure forage quality and compare impacts on yields from early-vegetative and post tassel fungicide treatments for control of NCLB. Yield results will be used to compare cost of fungicide application with value of yield gained. This study provided data to help define the relative benefits of early and late season fungicide application to protect yield and impact quality.
The three fungicides that were used in this study were Affiance, Priaxor and Headline Amp. All have two ingredients providing mixed modes of action. Affiance and Priaxor are said to have 30 days of systemic activity. The early application timing, when corn is still vegetative, can be combined with post emergence weed control, allowing us to evaluate if it will give adequate season-long protection. Headline Amp is rated “very good” for control and is the fungicide used by many custom applicators.
Affiance and Priaxor were applied in the V4-V6 stage. Affiance and Headline AMP were applied post tassel. There were 5 treatments including the untreated control, with 3 repetitions per farm.
In addition to pathogen control, these fungicides are promoted for offering “plant health” benefits even in the absence of disease pressure. Mid-west Corn Belt trial results have been mixed related to the economic returns associated with plant health benefits as well as yield gains. In about 50% of the studies, the yield potential protected by fungicides is more than the cost of the fungicide application.
In 2017 we had very low incidence of NCLB. Most treatments had less than 1% incidence. In a year with minimal disease pressure from NCLB, our data from 4 cooperating farms found that yields among farm were statistically significantly different but the treatments were not. Forage samples were collected and analyzed for each treatment. We found no statistically significant impact on forage quality for any of the components tested.
The complete project report is available on our website: https://nydairyadmin.cce.cornell.edu/uploads/doc_587.pdf