Evaluation of High Input vs.

Low Input Corn (Zea mays L.)

Production Systems

K. Bradley, B. Hibbard, L. Sweets, & W. Bailey

University of Missouri

Objectives1. To determine the effects of

various one- and two-pass herbicide programs on grass and broadleaf weed control and corn yield.

2. Determine the effects of near-isogenic corn hybrids containing stacked insect protection traits or no insect protection traits on European corn borer and corn rootworm damage and corn yield.

3. Determine the effects of pyraclostrobin application on end-of-season disease incidence and severity and corn yield.

Experiments to Evaluate High-input vs. Low-input Corn Production: Factors Evaluated

1. Near-isogenic “Stacked” Corn Hybrids– RR– RR/ECB (Cry 1a protein)

– RR/ECB/RW (Cry 1a and Cry 3Bb proteins)

2. Herbicide Programs– Full rate PRE only (3 qt Lexar)

– Full rate PRE fb glyphosate (3 qts Lexar fb 22 ozs Rndup)

– Full rate PRE fb conv trtmt (3 qts Lexar fb 3 ozs Callisto + 1 pt Aatrex)

– Half rate PRE fb glyphosate (1.5 qt Lexar fb 22 ozs Rndup)

– Half rate PRE fb conv trtmt (1.5 qt Lexar fb 3 ozs Callisto + 1 pt Aatrex)

– 1-pass POST for RR corn (3.6 pts Halex + 1 pt Aatrex)

– 1-pass POST for conv corn (2 ozs Callisto + ¾ oz Stdfst + 1 qt Aatrex)– Untreated

3. Fungicide Application– Fungicide at Tasseling (Headline @ 6 oz/A)

– No Fungicide

Materials and Methods: 2 trials conducted each year from 2007-2009

(+corn rootworm and -corn rootworm)

Near-isogenic corn hybrids no-till planted in early- to mid-May at 28,700 seed/A

Individual plots arranged in a split-plot design with 4 replications:– main plot= corn type (RR, RR/ECB, or RR/ECB/RW)

– subplot= herbicide strategy

All pesticide applications made with a CO2-powered backpack sprayer delivering 15 gpa with XR8002 flat fan nozzles

Materials and Methods

• Predominant weeds across trials:

– Common Cocklebur– Common Ragweed– Common Waterhemp– Morningglory spp.– Prickly Sida– Barnyardgrass– Fall Panicum– Giant Foxtail– Large Crabgrass– Yellow Foxtail

• Weed density by species was determined in 2, ½ m2 quadrats within each plot soon after tasseling

Results

Weed Density at Tasseling

Herbicide Strategy

Grass

Weeds

Broadleaf

Weeds

Total

Weeds

---------------- # / m2 ----------------

1-pass PRE Only 9 bc 8 b 17 b

Full rate PRE fb Glyphosate POST 3 ef 4 cd 7 c

Full rate PRE fb Conventional POST 6 cde 1 e 7 c

Half-rate PRE fb Glyphosate POST 4 def 3 d 7 c

Half-rate PRE fb Conventional POST 7 cd 1 e 8 c

1-pass POST Glyphosate w/Residual 2 f 4 cd 6 c

1-pass POST Conventional w/Residual 11 b 5 c 16 b

Untreated 39 a 16 a 55 aaMeans followed by the same letter are not different, P<0.05.

Influence of Herbicide Programs on Total Weed

Density at Tasseling across Six Sites, 2007- 2009

Herbicide Strategy Corn Yield

--- Bu/A ---

1-pass PRE Only 130 bc

Full rate PRE fb Glyphosate POST 135 ab

Full rate PRE fb Conventional POST 132 abc

Half-rate PRE fb Glyphosate POST 137 a

Half-rate PRE fb Conventional POST 128 c

1-pass POST Glyphosate w/Residual 137 a

1-pass POST Conventional w/Residual 118 d

Untreated 104 eaMeans followed by the same letter are not different, P<0.05.

Influence of Herbicide Programs on Corn Yield

across Five Sites in Missouri, 2007- 2009

Conclusions:Influence of Herbicide Strategies on Weed Control and Yield

1-pass PRE only and the 1-pass

conventional POST w/residual

herbicide strategies resulted in higher

weed densities at tasseling than any of

the remaining strategies evaluated

Highest corn yields occurred with:

− Half-rate PRE fb glyphosate POST

− Full rate PRE fb glyphosate POST

− Full rate PRE fb conventional POST

− 1-pass POST glyphosate w/residual

ConclusionsWeed Management Strategies

Across six site-years, similar weed control and corn yield was achieved with a full rate PRE fb POST conventional herbicide program compared to programs containing glyphosate and the RR trait. However, the use of glyphosate and the RR trait resulted in more strategies that provided optimal weed control and corn yield than conventional herbicide strategies and thus allowed more flexibility in the weed management program.

Influence of Insect Resistance Traits in Near-Isogenic

Corn Hybrids on Tunneling and Tunnel Length Caused

by European Corn Borer Across Four Sites, 2008-2009

ECB Damagea

Near-isogenic

Corn Hybrid Tunnels

Tunnel

Length

-- #/plant -- --- mm ---

RR 0.20 a 5.50 a

RR/ECBb 0.05 b 0.29 b

RR/ECB/RWc 0.05 b 0.29 baMeans followed by the same letter are not different, P<0.05.bContains the Cry1A protein for European corn borer control.cContains both the Cry1a and Cry 3Bb1 proteins for European corn borer

and rootworm control.

Influence of Insect Resistance Traits on Root Damage Caused by Corn Rootworm Across

Three Sites in Missouri, 2007-2009

Rootworm Damagea

Near-isogenic

Corn Hybrid 2007 2008 2009

---------------- Avg./plantb ----------------

RR 0.44 b 0.035 a 0.56 a

RR/ECB 0.55 a 0.028 ab 0.49 a

RR/ECB/RW 0.10 c 0.019 b 0.06 baRoot damage assessed using a linear 0-3 root damage scale.bMeans followed by the same letter are not different, P<0.05.

Influence of Insect Resistance Traits on Corn Yield Across Five Sites, 2007-2009

Near-isogenic Corn Hybrid Corn Yielda

------ Bu/Acre ------

RR 125 b

RR/ECBb 130 a

RR/ECB/RWc 127 abaMeans followed by the same letter are not different, P<0.05.

bContains the Cry1A protein for European corn borer control.

cContains both the Cry1a and Cry 3Bb1 proteins for European

corn borer and rootworm control.

Conclusions:Influence of Insect Protection Traits on Insect Injury & Yield

ECB injury was significantly reduced with RR/ECB and RR/ECB/RW hybrids compared to RR alone (data not shown)

CRW damage was lowest in the RR/ECB/RW hybrid in 2 out of 3 site-years

Across 3 site-years, CRW injury was not sufficient to cause yield reductions in RR/ECB/RW compared to RR or RR/ECB hybrids

Ultimately, will producers have any choice in the future when it comes to “stacked” insect protection events?

Influence of Headline Fungicide Application on Gray Leaf

Spot and Common Rust Severity 6 Weeks After

Application Across Four Sites, 2008-2009

Treatments

Gray Leaf

Spot

Common

Rust

--------------- %a ---------------

Headline @ Tasseling 0.41 b 0.07 b

No Headline 4.05 a 1.57 a

aMeans followed by the same letter are not

different, P<0.05.

Influence of Headline Fungicide Application

on Corn Yield Across Five Sites, 2007-2009

Treatments Corn Yielda

------ Bu/Acre ------

Headline @ Tasseling 131 a

No Headline 124 b

aMeans followed by the same letter are not

different, P<0.05.

Influence of Headline Fungicide Application on Relative Chlorophyll Content of Corn Leaves

Across Four Sites in Missouri (2008-2009)

Corn Leaf Position

Treatments Ear Leaf Ear Leaf -2

----- Chlorophyll (%) a -----

Headline @ Tasseling 42.5 a 36.0 a

No Headline 43.7 a 36.3 a

aMeans followed by the same letter are not

different, P<0.05.

Conclusions:Influence of Fungicide Application on Disease Severity & Yield

Application of Headline decreased gray

leaf spot & common rust severity, but

levels in untreated were <5%

Across 5 site-years, all herbicide

strategies, and hybrids, Headline

increased corn yields by 7 Bu/A.

At a selling price of $4/Bu, this yield

increase would provide a net return of

approximately $8.00/A (year-to-year

variation in Headline price and corn

market value will determine ultimate

return to grower).