Date of Award

Spring 2014

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Agronomy

First Advisor

James Camberato

Second Advisor

Robert Nielsen

Committee Member 1

Corey Gerber

Committee Member 2

Kiersten Wise

Abstract

The use of fungicides on corn has recently increased as a result of higher grain market prices, changes in cropping practices, higher disease incidence and severity, and the availability and marketing claims of new fungicides. Some of the marketed potential "plant health(TM)" benefits include improved tolerance to drought and heat, improved N utilization, and increased stalk strength. Previous studies have displayed delayed canopy senescence, changes in water use efficiency, and reduced ozone damage in controlled environments. Foliar fertilization has also increased in popularity in recent years due to an increase in grain prices, manufacturer claims, and product availability.

Large-scale field experiments were conducted at three locations in 2012 and five locations in 2013 representing different soil types and growing conditions to evaluate the effectiveness of treatments and timing (V5, R1, V5+R1) of two QoI fungicides and two fungicides containing both QoI and DMI active ingredients. Foliar fertilizer containing N and B was applied at the V5 growth stage. Multiple measurements were conducted throughout the growing season to determine the effects of several common foliar xvi fungicides and a foliar fertilizer on different indicators of plant health. Measurements included disease assessments, leaf surface temperature, crop canopy reflectance, chlorophyll meter values, green leaf area below the earleaf, and stalk strength assessments. At the end of the growing season, grain yield and moisture content were estimated with a commercial harvester and calibrated yield monitor and grain was analyzed for nutrient concentration.

The foliar fertilizer had essentially no effect on the plant parameters measured and no effect on grain yield at any of the locations. The most consistent effect of foliar fungicides on the plant parameters measured was disease control. No fungicide effects were observed on leaf surface temperature or crop canopy reflectance. Small and inconsistent effects were observed with foliar fungicide applications made at R1 on chlorophyll meter values, the number of green leaves below the earleaf, and stalk strength (push test). Fungicides applied at V5 increased grain yield 13% of the time, and fungicides applied at R1 increased grain yield 50% of the time. Overall, the effects of fungicide applications at R1 were greater than those from applying fungicides at V5, and two applications of fungicides did not affect overall plant health or grain yield more than one application made at R1. Based on these data from the 2012 and 2013 growing seasons, applications of foliar fertilizer or foliar fungicides at the V5 growth stage were not beneficial. Applying foliar fungicides at R1 inconsistently improved some indicators of plant health and grain yield.

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