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POPULATION DIVERSITY AND MANAGEMENT OF COMMON DANDELION
(Taraxacum officinale Weber) IN NO-TILLAGE CROPPING SYSTEMS

By

Aaron Scott Franssen

A DISSERTATION
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
Department of Crop and Soil Sciences

2004

 

 

ABSTRACT

POPULATION DIVERSITY AND MANAGEMENT OF COMMON DANDELION
(Taraxacum officinale Weber) IN NO-TILLAGE CROPPING SYSTEMS

By

Aaron Scott Franssen

Common dandelion has developed into a troublesome agronomic weed in
Michigan and the North Central Region. Widespread adoption of no-tillage
cropping practices and use of glyphosate-resistant crops is likely to have
contributed to the proliferation of this weed. This research was conducted to
evaluate population diversity of common dandelion and to identify herbicide
programs to control this weed in no—tillage cropping systems. Population diversity
was examined using morphological characteristics and genetic analysis to
determine if common dandelion collected from different geographical regions
exhibit phenotypic and genetic variability. Common dandelion was collected from
16 counties in Michigan and 11 additional states. A southern and northern field
nursery was established in Michigan near East Lansing and Chatham,
respectively. Overall, common dandelion grown at the East Lansing nursery were
larger and produced more seed than those at the Chatham nursery. Individual
collections that were larger and produced more seed at the East Lansing nursery
were also among the largest and most prolific at the Chatham nursery. Genetic
diversity of common dandelion collections established in the field nurseries was
evaluated using randomly amplified polymorphic DNA (RAPD) analysis. The

diversity of RAPD banding patterns observed suggest that there is a high level of

genetic diversity; however there was no apparent relation between genetic
similarity and geographical location. There does not appear to be a relation
between morphological characteristics and genetic similarity in the collections
examined. Field research trials were conducted on established populations of
common dandelion in no-tillage soybean and corn to identify strategies that
effectively control this weed. Glyphosate and 2,4-D ester were applied at typical
use rates at different preplant timings in the fall and spring, followed by
postemergence applications of glyphosate in glyphosate-resistant soybean.
When common dandelion control was evaluated at crop planting, glyphosate was
more effective than 2,4-D ester regardless of application timing. In addition, fall
applications of either herbicide were more effective than spring applications. A
sequential application of glyphosate either at the V3 or V6 soybean crop stage
was necessary to provide effective common dandelion control through soybean
harvest. Additional field trials were conducted to evaluate postemergence corn
herbicides for common dandelion control. Glufosinate and mesotrione applied
alone and in combination with atrazine were the most effective 28 days after
treatment. However, late-season plant regrth was observed with these
treatments. By 56 days after treatment, dicamba + diflufenzopyr was the most
effective treatment. In the absence of tillage, effective management of common
dandelion will include a combination of fall herbicide applications and sequential
treatment with postemergence herbicides. In addition, the high level of variability
observed with this species will make population specific management of common

dandelion unlikely.

ACKNOWLEDGEMENTS

I would like to thank my major advisor Dr. Jim Kells for all of his guidance
and for giving me the opportunity to attend Michigan State University to pursue
this degree. My sincere appreciation is extended to the members of my
committee, Dr. David Douches, Dr. Don Penner, Dr. Doo-Hong Min, and Dr.
Chris Difonzo for their time and effort with this project. I would especially like to
thank Dr. Douches for all of his technical assistance, and Dr. Penner for his
willingness to take the time to share his wealth of knowledge.

A very special thank you is in order for everybody that provided assistance
and friendship during my stay here at Michigan State University, especially
Andrew Chomas, Scott Bollman, Caleb Dalley, Corey Guza, Kathrin
Schirmacher, Eric Nelson, Trevor Dale, Brad Fronning, Adrienne Rich, Mark
Bemards, Jarrod Thelen and Kyle Thelen. I thank you all for your assistance both
solicited and unsolicited. My friendship with you will be with me wherever the
road may lead me.

And finally, but most importantly, to my family for all their support for all
these years. Thank you to my parents Richard and Anita for instilling in me desire
to strive at whatever I do. To my siblings Andrew, Nathan, and Courtney for their
encouragement and support. And to my wife Carin, for all her support and

understanding.

TABLE OF CONTENTS

LIST OF TABLES ............................................................................................... vii
LIST OF FIGURES ............................................................................................ viii
CHAPTER 1 ......................................................................................................... 1

EVALUATING COMMON DANDELION (Taraxacum officinale Weber)
POPULATION DIVERSITY USING MORPHOLOGICAL CHARACTERISTICS
AND DNA BASED GENETIC ANALYSIS.

ABSTRACT ................................................................................................ 1
INTRODUCTION ........................................................................................ 3
MATERIALS AND METHODS ................................................................... 5
Plant material .................................................................................. 5
Phenotypic variation among collections ........................................... 6
Genetic variation among collections ................................................ 7
Within-field genetic variation ............................................................ 8
Among-progeny genetic variation .................................................... 8

DNA extraction and RAPD analysis ................................................. 8
Comparison of plant size ............................................................... 10
Statistical analysis ......................................................................... 1 1
RESULTS AND DISCUSSION ................................................................. 12
Phenotypic variation among collections ......................................... 12
Genetic variation among collections .............................................. 14
Within-field genetic variation .......................................................... 17
Among-progeny genetic variation .................................................. 17
Comparison of plant size ............................................................... 18
LITERATURE CITED ............................................................................... 21
CHAPTER 2 ....................................................................................................... 30

CONTROL STRATEGIES FOR COMMON DANDELION (Taraxacum
officinale Weber) IN NO-TILLAGE CROPPING SYSTEMS

ABSTRACT .............................................................................................. 30
INTRODUCTION ...................................................................................... 32
MATERIALS AND METHODS ................................................................. 33
Effect of herbicide and application timing ...................................... 34
Effect of sequential applications .................................................... 35
Statistical analysis ......................................................................... 36
RESULTS AND DISCUSSION ................................................................. 37

TABLE OF CONTENTS (Cont’d)

Effect Of herbicide and application timing ...................................... 37

Effect Of sequential applications .................................................... 39
LITERATURE CITED ............................................................................... 44
CHAPTER 3 ....................................................................................................... 52

COMMON DANDELION (Taraxacum Officinale Weber) CONTROL WITH
POSTEMERGENCE HERBICIDES IN NO-TILLAGE GLUFOSINATE-
RESISTANT CORN (Zea mays L.)

ABSTRACT .............................................................................................. 52
INTRODUCTION ...................................................................................... 54
MATERIALS AND METHODS ................................................................. 55
Statistical analysis ......................................................................... 57

RESULTS AND DISCUSSION ................................................................. 57
LITERATURE CITED ............................................................................... 61
APPENDIX ......................................................................................................... 64

Appendix A1. Protocol for DNA extraction from common dandelion fresh
leaf tissue ................................................................................................. 65

Appendix A2. Reproductive Characteristics for common dandelion at East
Lansing and Chatham field nurseries in 2003. ........................................ 67

vi

LIST OF TABLES

CHAPTER 1

EVALUATING COMMON DANDELION (Taraxacum Officinale Weber)
POPULATION DIVERSITY USING MORPHOLOGICAL CHARACTERISTICS
AND DNA BASED GENETIC ANALYSIS.

Table 1. Location and site description Of common dandelion collections included
in the field nurseries Of for RAPD analysis ......................................................... 23

Table 2. Growth and reproductive characteristics for common dandelion at East
Lansing and Chatham nurseries ........................................................................ 24

Table 3. RAPD primers used to evaluate the genetic diversity between common
dandelion collections ......................................................................................... 25

Table 4. Matrix of genetic Similarity coefficients for RAPD analysis of 26 common
dandelion collections ......................................................................................... 26

Table 5. Comparison Of leaf area and dry weight of 9 collections Of common
dandelion grown in the greenhouse ................................................................... 28

CHAPTER 2
CONTROL STRATEGIES FOR COMMON DANDELION (Taraxacum Officinale
Weber) IN NO-TILLAGE CROPPING SYSTEMS.

Table 1. Application timing, application date, and average air temperature for
glyphosate and 2,4-D ester applications for common dandelion control ............. 45

Table 2. Yearly accumulation Of precipitation at the Michigan State University
CIarksviIle Experiment Station from 2001 thru 2003 ........................................... 46

CHAPTER 3

COMMON DANDELION (Taraxacum Officinale Weber) CONTROL WITH
POSTEMERGENCE HERBICIDES IN NO-TILLAGE GLUFOSINATE-
RESISTANT CORN (Zea mays L.)

Table 1. Trial location, Site description, and date of herbicide application for
common dandelion control with postemergence corn herbicides ....................... 62

Table 2. Control Of treated common dandelion 21 DAT and 56 DAT with
postemergence corn herbicides and corn yields ................................................ 63

vii

LIST OF FIGURES

CHAPTER 1

EVALUATING COMMON DANDELION (Taraxacum Officinale Weber)
POPULATION DIVERSITY USING MORPHOLOGICAL CHARACTERISTICS
AND DNA BASED GENETIC ANALYSIS.

Figure 1. Dendogram for RAPD analysis for 26 collections of common
dandelion .................................................................................................. 29

CHAPTER 2
CONTROL STRATEGIES FOR COMMON DANDELION (Taraxacum Officinale
Weber) IN NO-TILLAGE CROPPING SYSTEMS.

Figure 1. Common dandelion control at planting with preplant applications
of glyphosate, 2,4-D ester and tank mixture Of glyphosate plus 2,4-D ester
at 420 9 ae and 560 9 ae, respectively, as affected by application timing.
All treatments containing glyphosate were applied with 2% (w/v)
ammonium sulfate. Means within application timing with the same letter
are not Significantly different (a = 0.05) .................................................... 47

Figure 2. Common dandelion control at planting with glyphosate and 2,4-D
ester as affected by application timing. Glyphosate applied with 2% (w/v)
ammonium sulfate. Means with the same letter are not significantly
different (a = 0.05) .................................................................................... 48

Figure 3. Common dandelion control at soybean harvest with Single and
sequential herbicide applications as affected by application timing. All
treatments containing glyphosate were applied with 2% (w/v) ammonium
sulfate. Means within each graph with the same letter are not significantly
different (a = 0.05) .................................................................................... 49

Figure 4. Common dandelion plant densities at soybean harvest with
Single and sequential herbicide applications as affected by application
timing. All treatments containing glyphosate were applied with 2% (w/v)
ammonium sulfate. Means within each graph with the same letter are not
Significantly different (a = 0.05) ................................................................ 50

Figure 5. Soybean yield as affected by common dandelion control with
single and sequential herbicide applications as affected by application
timing. All treatments containing glyphosate were applied with 2% (w/v)
ammonium sulfate. Means within each graph with the same letter are not
Significantly different (a = 0.05) ................................................................ 51

viii

CHAPTER 1
EVALUATING COMMON DANDELION (Taraxacum Officinale Weber)

POPULATION DIVERSITY USING MORPHOLOGICAL CHARACTERISTICS
AND DNA BASED GENETIC ANALYSIS.

Abstract: Population diversity of common dandelion was examined using
morphological characteristics and genetic analysis. Seed from individual common
dandelion plants were collected from multiple counties in Michigan and several
states. Subsequent plants were established in field nurseries at Michigan State
University research stations near East Lansing and Chatham to determine if
common dandelion collected from different geographical regions exhibit
phenotypic variability. Overall, plants at the East Lansing nursery tended to be
larger and produce more seeds than those at the Chatham nursery. Individual
collections that were larger and produced more seed at the East Lansing nursery
were also the largest and most prolific at the Chatham nursery. Genetic diversity
Of common dandelion collections established in the field nurseries were also
evaluated using randomly amplified polymorphic DNA analysis. Nine random
primers amplified a total of 44 fragments that were polymorphic. Of the 26
populations screened, 24 were distinguishable from each other using the RAPD
analysis. The diversity Of polymorphic banding patterns Observed suggest that
there is a high level of genetic diversity in common dandelion in Michigan and the
other states. Genetic Similarity coefficients for all the populations evaluated

ranged from 0.25 to 1.00. There was no discrete separation between common

dandelion from Michigan and the other collections. A survey Of plants collected
from a single nO-tillage field in Michigan also revealed a high level Of diversity. An
additional study was conducted to verify the apomictic reproductive nature Of this
species. All progeny that were tested using the given random primers were
genetically similar to the maternal plant. There does not appear to be a visible
relation between morphological characteristics and the genetic similarity
examined here. A greenhouse study was conducted to determine if differences in
plant Size would be Observed between selected collections of common
dandelion. Nine collections of common dandelion were grown in the greenhouse
and the Size Of the plants compared 60 days after planting using leaf area and
dry weight. Differences in plant size were Observed; however collections that
were genetically similar did not necessarily Similar in size. With the high level Of
diversity documented in this study one could expect diversity in common

dandelion response to certain herbicides.

Nomenclature: common dandelion, Taraxacum Officinale Weber; red seeded

dandelion Taraxacum Iaevigatum L.

Index words: apomictic, phenotypic variation, RAPD analysis, genetic variation,

genetic similarity.

INTRODUCTION

Common dandelion (Taraxacum Officinale Weber) has developed into a
troublesome agronomic weed, especially in nO-tillage crop production in Michigan
and parts Of the United States. Putatively originating in west central Asia
(Richards 1970), this Species can be found world-wide, primarily concentrated in
temperate and cold regions (Solbrig and Simpson 1974). It was proposed that
common dandelion was originally introduced to the Americas via the Alaskan ice
bridge following the most recent ice age (Richards 1973). It is also presumed that
early European settlers reintroduced common dandelion as an ornamental used
to seed the roofs of sod houses to make them stand out on the prairie (Solbrig
1971; Stubbendieck et al. 1995).

Common dandelion, as it is collectively classified in the United States, is
comprised Of two similar Taraxacum species. Red seeded dandelion (T.
Iaevigatum) is virtually indistinguishable from T. officinale except for the red
coloration of the achene (GPFA 1996). Morphological and biochemical analysis
comparing these two species Showed no clear differentiation between them
(Taylor 1987). A more comprehensive genetic analysis Of ribosomal DNA (rDNA)
and Chloroplast DNA (CpDNA) supported this lack of a definite separation
between these species (King 1993). Furthermore, it has been argued that
morphological variation is by and large a response to the local environment
(Taylor 1987). For these reasons, T. laevigatum and T. Officinale are collectively

considered common dandelion here.

The genus Taraxacum is comprised of both sexual and asexual species.
Taraxacum Species that reproduce sexually are diploid (2n = 16), whereas the
asexual Species are triploid (3n = 24) and reproduce via agamosperrnous
apomictic seed production. The asexual species, which include T. Iaevigatum
and T. Officinale, are found primarily in North America where it is accepted that
they reproduce via apomixis. The result Of this apomictic mode Of reproduction is
progeny that are clones Of the maternal parent. Despite the potential for
populations in a given area to be genetically identical, differences in overall
fitness and isozyme Characterization have been documented (Solbrig and
Simpson 1974). Additional studies Of genotypic variation in rDNA have been
reported in asexual lineages Of common dandelion thought to be brought about
by somatic mutations (King and Schaal 1990).

DNA-based molecular markers, such as randomly amplified polymorphic
DNA (RAPD), are a powerful tOOl to examine genetic variation within a species
(Williams et al. 1990). An advantage of using RAPD markers over other DNA-
based markers (ie. SSR and AFLP) is that no prior knowledge Of the species
genome is required. Single Oligonucleotide primers Of arbitrary sequence are
used to randomly amplify segments Of template DNA. The simple presence or
absence Of an amplified DNA fragment represents a difference in the genome
that can be used to compare individuals. The use of RAPD analysis has been
utilized to examine genetic diversity in such weed species as leafy spurge
(Euphorbia esula L.) (Rowe et al. 1997), wild mustard (Sinapsis arvensis L.)

(MOOdie et al. 1997), and hemp dogbane (Apocyanum cannabinum L.) (Ransom

et al. 1998), as well as economically important Species such as tea plant
(Camellia SinensiS L.) (Jorge et al. 2003) and walnuts (Jug/an spp.) (Orel et al.
2003)

How genetic variation affects common dandelion management is currently
unknown. Therefore studies were conducted to understand genetic variation of
this Species to aid in future management strategies for this weed. The Objectives
of this research were to utilize RAPD analysis to 1) determine the amount of
genetic diversity Of common dandelion in Michigan and the United States, and 2)

identify unique populations Of common dandelion.

MATERIALS AND METHODS

Plant material

To examine the population diversity Of common dandelion, mature seed
(as indicated by the presence of white pappus) was collected from individual
plants from selected sites in 2001 (Table 1). Seeds were removed from the
flower receptacle and stored at 4 C until planting. Seed were planted in 1000 ml
pots filled with commercial potting soil1 and maintained in the greenhouse.
Seedlings were transplanted to individual 1000 ml pots filled with Spinks loamy
sand (sand, mixed mesic Psammentic Hapludalfs) with pH Of 6.8 and 2.4%
organic matter. Plants were maintained in the greenhouse until they were

transplanted to a field nursery.

Phenotypic variation among collections

Phenotypic variation Of common dandelion was examined by establishing
plants in field nurseries and Observing a number Of different morphological and
reproductive Characteristics. Common dandelion field nurseries were established
at two sites in Michigan. A southern and northern nursery was established at the
Michigan State University Agronomy Farm at East Lansing (42° N latitude) and
the Michigan State University Upper Peninsula Research Station near Chatham
(47° N latitude), respectively. Morphological differences were compared among
common dandelion collections from 12 counties in Michigan, 11 states, and a
collection Obtained from the Beal Botanical Garden at Michigan State University
that originated in Germany (Table 1). Single plants were randomly selected to
represent that population in which it was growing. Common dandelion plants
from agronomic fields and residential areas were selected for this analysis.

Common dandelion seedlings were established in the greenhouse and
transplanted into 0.6 by 0.6 m plots at the nurseries in the spring Of 2002. Plants
were irrigated weekly for the first month and with natural rainfall for the remainder
Of the experiment. Plants grew free Of competition by hand weeding around
established common dandelion plants. Characteristics Observed at each Of the
nurseries included winter survival, plant diameter, leaf Shape, leaf pubescence,
flowering date, growing degree days to flowering, total number of flowers
produced, and seeds produced per flower. Winter survival was determined by
Observing plants in the spring of the year following establishment in the field

nurseries. Plant diameter was recorded as the average of two perpendicular

measurements Of the common dandelion rosette. Leaf Shape was determined
using a scale from 1-5, where 1 represented a leaf with deeply lobed leaf
margins and 5 represented an entire leaf margin. Flowering date was recorded
as the day in which the first yellow flower was present on the individual plant.
Growing degree days were calculated using a 10 C base beginning on March 1,
2003. Total flower production was monitored weekly starting in May and
continuing until flower production declined approximately one month later. The
total number Of flowers produced each week was recorded, the mature flowers
were removed, and the seeds placed in paper envelopes. The number of seeds
produced per flower was determined by randomly collecting four individual
mature flowers per plant prior to seed dissemination. Mature flowers were dried

at 70 C for 24 h and stored at room temperature until the seeds were counted.

Genetic variation among collections

Genetic analysis Of common dandelion using RAPD analysis was
conducted to assess the amount Of genetic variation in this Species. Population
genetic diversity was examined for common dandelion collected from 16 counties
in Michigan, 9 states, and the collection from Germany (Table 1). Genomic DNA
was extracted from established plants in the common dandelion nursery at East

Lansing.

Within-field genetic variation

The genetic diversity Of common dandelion within a field population was
examined using eight established plants that were collected from a 0.5 ha area Of
a nO-tillage production field. Two plants were collected from each Of four 3 m by 9
m plots from a field near Elsie, Michigan that had been in a nO-tillage com-
Soybean rotation for 10 years. Entire plants (above and below ground biomass)
were randomly collected from each Of the four plots and maintained in the
greenhouse. Genetic analysis was conducted using the original plant collected

from the field.

Among-progeny genetic variation

The apomictic nature Of this species was examined by collecting mature
seeds from a Single flower and conducting the RAPD analysis on 10 Sibling
progeny and the maternal plant. Common dandelion seedlings were established
and maintained in the greenhouse for this analysis. Collections selected for this

evaluation included common dandelion from Michigan, Oregon, and Germany.

DNA extraction and RAPD analysis

Genomic DNA was extracted from the newest leaf material emerging from
plants growing either in the greenhouse or field nursery. DNA was extracted from
four 10 mm diameter leaf disks (approx. 45 mg fresh leaf tissue) using the
protocol described with the PUREGENETM DNA isolation kit2 (Appendix A1) and

stored in Tris-EDTA (TE) buffer (pH 7.0). DNA concentration was determined by

visual comparison with a known quantity of DNA mass ladder3 on an agarose gel
stained with 0.1 pg ml‘1 ethidium bromide. The presence Of an unidentified PCR
inhibitor required a 1:20 dilution (concentrated DNAzTE) Of DNA be conducted
prior to PCR amplification. This resulted in a DNA concentration Of less than 20
ng pl". The PCR primers utilized were 10-base pair (bp) random Oligonucleotides
from primer kit A“. Each PCR reaction was carried out in a 25 pl reaction volume
consisting Of 50 ng genomic DNA, 2.5 pg bovine serum albumin (BSA), 5.0 mM
MgCIz, 3.2 mM Tris-HCI (pH 8.4), 50 mM KCI, 0.2 mM each deoxynucleotide
triphosphate (dNTP), 1.2 mel 10 base pair (bp) Oligonucleutide primer, and 0.1
units Taq DNA polymerases. PCR reactions for each random primer were
conducted at least twice for each plant sample in a heated-bonnet thermal
cycler6 programmed for an initial denaturation temperature Of 94 C for 5 min
followed by 35 cycles of 1 min 15 sec at 94 C, 1 min 15 sec at 40 C, and 2 min at
72 C. The final cycle was followed by 3 min at 72 C, after which the temperature
was held at 4 C until gel electrophoresis. A 10 pl aliquot Of the PCR product was
loaded with DNA loading dye {50% glycerol, 0.25% bromophenol blue, 10 mM
Tris HCl (pH 8.0), 1 mM EDTA] onto a 2.0% (w/v) agarose7 gel stained with 0.1
pg ml'1 EtBr. Amplified products were resolved at 80 volts for 3 hr in a 1X Tris-
acetate (TAE) buffer (40 mM Tri-acetate, 1 mM EDTA). A 100 bp DNA ladder8
was used as a size reference. The gel was viewed and photographed on an
ultraviolet light box to confirm product amplification. Polymorphic PCR fragments
were scored as either present (1) or absent (0). Only those fragment length

polymorphisms that were repeatable and intensely amplified were scored.

Comparison Of plant size

A greenhouse experiment was conducted to compare plant sizes Of
selected common dandelion collections. Common dandelion from eight counties
in Michigan and one county in Illinois were selected for this experiment.
Collections were selected based on the results from the RAPD analysis. Plant
collections were selected to represent both genetically similar and dissimilar
collections. Mature seed was collected from the respective collections in the field
nursery and stored at 4 C until planted in the greenhouse. Common dandelion
seeds were planted 0.25 cm deep and seedlings individually transplanted to
1000 ml pots containing commercial potting mixture approximately 2 weeks later.
Greenhouse temperatures were maintained at 30/25 :I: 3 C (day/night) with 14:10
h (dayznight) photoperiod. Supplemental light intensity from sodium vapor lamps
provided a total midday light intensity of 1,000 pmol m'2 s‘1 photosynthetic photon
flux at plant height. Common dandelion plants were watered as needed and
fertilized with 50 ml Of N, P205, K20 (20%-20%-20%) at 20 ppm to promote
Optimum plant growth.

Comparison Of plant size for 9 common dandelion collections was
conducted 60 days after planting. Plant collections were compared by measuring
total leaf area and plant dry weight. Leaf area was measured with a transparent
belt conveyor accessory for a portable leaf area meterg. Dry weight was
determined for the above ground biomass; harvested plant material was dried at

70 C for 24 h.

10

Statistical analysis

Common dandelion collections were established in the field nurseries in a
randomized complete block design and each collection was replicated four times
at each Of the nurseries. Data were subjected to analysis of variance with SAS10
and means separated using Fisher’s Protected LSD (a = 0.05). Nursery by
collection interactions were significant; therefore data from each nursery location
were analyzed and presented separately.

Genetic similarity coefficients between common dandelion collections
were determined using Nei and Li’s (1979) calculation for qualitative data.
Dendograms for genetic distance were created using the unweighted pair group
method with arithmetic averages (UPGMA) cluster analysis. Genetic Similarity
calculations and dendograms were made using NTSYS-pc version 2.11L
software11 (Rohlf 2002). Collections were compared using calculated genetic
similarity coefficients where 0.00 indicated no similarity and 1.00 indicated that
the collections were identical.

The experiment to compare plant Size was conducted as a completely
randomized design. Each plant collection was replicated four times and the
experiment was conducted twice. Data were subjected to analysis Of variance
with SAS and means were separated using Fisher’s Protected LSD (a = 0.05).

Variances were determined to be homogenous, thus the experiments combined.

11

RESULTS AND DISCUSSION
Phenotypic variation among collections

Following the winter Of 2002-03 it was Observed that all Of the plants
established in the Chatham nursery survived, whereas mortality was Observed
for some collections in East Lansing. However, mortality was no more than one
plant from any collection. The one exception was the common dandelion
collection from Oceana CO. Michigan. AS a result it was dropped from the
analysis Of the East Lansing nursery. At the Chatham station in the Upper
Peninsula of Michigan, the mean annual snow fall is 380 cm. This snow cover
insulated the nursery, allowing these plants to survive the winter. The lack Of
snow fall and extreme cold temperature at the East Lansing nursery in 2002-03
may explain the common dandelion mortality and lower plant vigor in the 2003
growing season.

Some Of the characteristics measured, such as leaf shape and the
presences of pubescence on the leaf were variable between plants as well as on
an individual plant. Leaf Shape on an individual plant was highly variable,
resulting in difficulty identifying differences in leaf Shape between collections
(data not shown). Previous research using common dandelion leaf morphology
not only found leaf shape to be highly variable but also found that it was
influenced by the environment and even varied between seasons (Sturtevant
1886; Taylor 1987). The presence Of pubescence on the leaf surfaces appeared

tO be related to the age Of the leaf. Newly emerging leaf material for all of the

12

collections was typically pubescent. In contrast, the Older leaf tissue lacked
pubescence, regardless Of the collection (data not shown).

The common dandelion plants at the Chatham nursery were much smaller
in diameter compared with East Lansing (Table 2). A common dandelion
collected from Tolland CO. Connecticut was the largest in diameter at both East
Lansing and Chatham with 55 cm and 22 cm, respectively. At Chatham, common
dandelion from Hall CO. Nebraska was among the largest; however it was one Of
the smaller collections in East Lansing. The common dandelion collection from
Germany was the smallest in diameter at both Of the nurseries.

The date at which common dandelion began to flower was determined tO
be different at each Of the nurseries; however differences within the nurseries
were not apparent. The common dandelion collections at the East Lansing
nursery initiated flowering within 1 week Of each other beginning on May 1, 2003
at an accumulation Of 239 growing degree days (data not shown). This coincides
with previous research that classified common dandelion as a day-neutral plant
(Gray et al. 1973). At Chatham, flower initiation commenced approximately 3
weeks later.

There were no significant differences Observed in the total number of
flowers produced or the total number Of seeds produced per collection (Appendix
A2). However, there were differences Observed in the number Of seeds produced
per flower among collections (Table 2). Common dandelion in the East Lansing
nursery tended to produce more seeds per flower than at Chatham. Seed

production ranged from 106 to 230 seed per flower at Chatham and 123 to 304

13

seeds per flower in East Lansing. This difference in productivity is likely due to
the greater accumulation Of growing degree days at the East Lansing nursery as
compared to the Chatham nursery, which was located at a more Northern
latitude. At both nurseries, common dandelion from Baker CO. Oregon and
Cache CO. Utah were the most prolific producers Of seeds. The Alger CO.
collection, which was collected on the Chatham station itself, was one of the
more prolific plant collections at both of the nurseries. The common dandelion
collections from Hall CO. Nebraska and Germany were the least prolific at each

nursery.

Genetic variation among collections

Successful amplification of PCR products was dependent on the random
primer used. Of the 20 primers screened, 9 primers resulted in the amplification
of a DNA fragment. The nine random primers amplified a total Of 71 repeatable
DNA fragments, of which 44 were polymorphic (Table 3). The number Of
polymorphic fragments amplified per random primer ranged from 1 to 12. Of the
26 populations screened, 24 were distinguishable from each other using the
RAPD analysis. Common dandelion from Berrien and Calhoun counties in
Michigan were indistinguishable from each other.

The diversity Of RAPD banding patterns Observed suggest that there is a
high level of genetic diversity in common dandelion in Michigan and the other
states. Genetic similarity coefficients among all collections ranged from 0.25 to

1.00 (Table 4). Within Michigan, genetic Similarity ranged from 0.27 to 1.00.

14

There was no discrete separation among common dandelion collections from
Michigan and those collected from other states or Germany. However, common
dandelion from Michigan tended to be more similar to other Michigan collections
than with collections from the other states (Figure 1). Most of the Michigan
collections were grouped together in the dendogram, with a few Of the counties
appearing more closely related to common dandelion from other states.
Clustering Of collections within the dendogram indicate more similarity among
those collections than others outside the cluster. The amount of genetic variation
observed here is Similar to that Observed for other weed Species. For example,
RAPD analysis Of wild mustard (Sinapis arvensis) was found to be highly variable
(Moodie et al. 1997). In addition, analysis of wild mustard plants sampled over
two consecutive seasons showed different levels of population diversity,
suggesting the influence Of environmental variability. lsozyme analysis Of two
perennial species of snakeweed (Gutierrezia spp.) indicated a high level Of
diversity both within species and between species (Sterling and Hou 1997).
Common dandelion from three Michigan counties and two states were
identifiable with unique DNA banding patterns (data not Shown). The presence of
a single unique DNA fragment is associated with the collections from Stafford CO.
Kansas, Benton CO. Indiana, and Presque Isle and Clinton Counties in Michigan
using the random primers OPA-8, 9, 11, and 18, respectively. The absence Of the
675 bp fragment amplified by OPA—18 was unique to the Luce CO. collection.
Several additional collections shared either the presence or the absence of two

random DNA fragments (data not shown). A single 1000 bp random DNA

15

fragment amplified using OPA-18 was exclusive only to the collections from
Berrien, Calhoun, Hillsdale, and lngham Counties in Michigan.

Geographical location and genetic similarity did not appear to be related
when comparing common dandelion collections. Many of the Michigan
collections, which are in relatively close geographic proximity, tended to be
genetically similar. However, an exception to this trend included the lngham Co.
collection that was genetically more similar to Adams CO. Colorado (0.69) and
Benton CO. Indiana (0.69) than to any collection from Michigan.

The common dandelion from Presque Isle CO. Michigan, Stafford CO.
Kansas and Germany were identified from their seed color as red seeded
dandelion. NO RAPD polymorphisms were identified that were unique to red
seeded dandelion. Single polymorphic fragments from different random primers
were amplified that were unique to the Presque Isle CO. and Stafford CO.
collections. Random primer OPA-09 amplified a 450 bp fragment that was unique
to Stafford CO., whereas OPA-18 amplified a 650 bp fragment in the Presque Isle
Co. collection only. Random primer OPA-07 failed to amplify an 875 bp fragment
in either the Stafford CO. or Presque Isle CO. collections but did amplify a 1550
bp fragment in the Stafford CO. and Germany collections. The Stafford CO.
collection was genetically more similar to the collection from Germany than to
Presque Isle CO., 0.54 and 0.37, respectively. Common dandelion collected from
Stafford CO. and Germany were grouped together in the dendogram (Figure 1),

indicating they shared more unique DNA fragment length polymorphisms. The

16

Presque Isle CO. collection was more similar to other Michigan collections of T.

Officinale then the other two T. Iaevigatum collections.

Within-field genetic variation

The common dandelions that were collected from the nO-tillage production
field near Elsie, Michigan demonstrated a broad range Of genetic Similarity.
Coefficients of genetic similarity for the eight plants collected ranged from 0.30 to
1.00 (data not shown). Two of the plants were indistinguishable from each other.
A coefficient Of genetic Similarity of approximately 0.80 was calculated for three
of the collected plants from across the area. Plants that were collected from the
same 3 m by 9 m plots were not necessarily more related to each other. The
level Of diversity observed here is similar to that previously reported. Using
isozymes and plant growth competitiveness, Solbrig and Simpson (1974)
identified the presence of at least four common dandelion biotypes within an area

Of 0.01 ha.

Among-progeny genetic variation

RAPD analysis conducted on ten progeny from each of the three
collections selected did not reveal any genetic variation between the progeny and
the maternal plant using the 9 random primers. This Observation supports that
common dandelion is apomictic, at least with the individuals tested. King and
Schaal (1990) screened the rDNA Of over 700 progeny from 26 different parental

genotypes and Observed 42 plants with nonparental rDNA. This rate is higher

17

than what would be expected by mutation alone. Results from this study indicate

that a large number of individuals are needed to find genetic differences.

Comparison Of plant size

The nine collections in this experiment varied in their respective rate of
growth after 60 days. Overall the dry weights of the 9 common dandelion
collections ranged from 0.84 to 2.0 g per plant (Table 5). Total leaf area ranged
from 216 to 432 cm2. The Michigan collections from Alger, Monroe, and
Shiawassee Counties had the greatest leaf area and dry weights at the end Of
the experiment. Conversely, the collections from Berrien, Luce, and Newaygo
Counties in Michigan were the lowest in terms Of leaf area and dry weight. The
collection from Alger CO. demonstrated the greatest growth rate as measured by
leaf area and dry weight. This collection was genetically most similar to the
lngham Co. collection with a coefficient Of 0.61 (Table 4). These two collections
had similar leaf areas but were different in terms of dry weight. The collection
from Alger CO. was the least genetically Similar to the common dandelion from
St. Clair CO. and had a higher leaf area and dry weight (Table 5). The
Shiawassee CO. and Berrien Co. collections were genetically the most similar
(0.87) but differed in their growth rates. Conversely, the Vermillion CO. and
lngham CO. collections were the least genetically Similar (0.35) but were similar
in Size. The lack of an Obvious relation between genetic similarity and plant size
indicate that the polymorphisms identified were not associated with traits

influencing plant development.

18

The common dandelion collections in this analysis demonstrated a high
level of morphological and genetic variability. From the RAPD analysis we did not
identify distinctly unique biotypes of common dandelion. Similarity was Observed
between collections within a geographical region but there were no discrete
boundaries. Genetic similarity did not appear to be related to Similarity in
morphological characteristics. These characteristics measured in the common
dandelion nurseries are likely to be quantitatively inherited traits that are
controlled by more than one gene. In addition, the numbers of polymorphisms
used here to quantify the genetic diversity were insufficient to identify a relation
between phenotype and genotype.

The high level Of variability in common dandelion Observed in this
research could possibly be a result of the method Of seed dissemination in this
species. Mature seeds attached to white pappus are capable of long distance
travel, spreading the genetic diversity across a large area. In addition, common
dandelion become established across a wide range Of climates and geographical
regions, as is evident from its distribution throughout the world. And finally, the
high level Of genetic and morphological diversity Observed will make population-

Specific management of common dandelion unlikely.

Source Of Materials

1 Baccto, Michigan Peat Co, PO. Box 98029 Houston TX, 77098
2 Puregene DNA Isolation Kit, Gentra Systems, Minneapolis, MN 55441.

3 Low DNA Mass Ladder, lnvitrogen Life Technologies, Carlsbad, CA 92008.

19

4 Primer Kit A, Operon Technologies, Inc., Alameda, CA 94501.

5 Taq DNA polymerase, lnvitrogen Life Technologies, Carlsbad, CA 92008.
6 PTO-225 Peltier Thermal Cycler, MJ Research Inc., Waltham, MA 02451.
7 Agarose, lnvitrogen Life Technologies, Carlsbad, CA 92008.

8100 base pair ladder, lnvitrogen Life Technologies, Carlsbad, CA 92008.
9 Portable leaf area meter, Li-Cor lnc., Lincoln, NE 68504.

1° SAS version 8.2, SAS Institute, SAS Circle, Box 8000, Cary, NC 27512-8000.

1‘ NTSYS-pc ver. 2.11L software, Exeter Software, Setauket, NY 11733-2870.

20

LITERATURE CITED

GPFA (Great Plains Flora Association). 1996. Flora of the Great Plains.
Lawrence, KS: University Press Of Kansas. Page 1010.

Gray, E., E. M. McGehee, and D. F. Carlisle. 1973. Seasonal variation in
flowering Of common dandelion. Weed Sci. 21:230-232.

Jorge, S., M. C. PedrOSO, D. B. Neale, and G. Brown. 2003. Genetic
differentiation of Portuguese tea plant using RAPD markers. HortScience
38:1191-1197.

King, L. M. 1993. Origins Of genotypic variation in North American dandelions
inferred from ribosomal DNA and chloroplast DNA restriction enzyme analysis.
Evolution 47:136-151.

King, L. M. and B. A. Schaal. 1990. Genotypic variation within asexual lineages
Of Taraxacum Officinale. Evolution 87:998-1002.

MOOdie, M., R. P. Finch, and G. Marshall. 1997. Analysis Of genetic variation in
wild mustard (Sinapis arvensis) using molecular markers. Weed Sci. 45:102-107.

Nei, M. and W. H. Li., 1979. Mathematical model for studying genetic variation in
terms Of restriction endonucleases. Proc. Natl. Acad. Sci. USA, 76:5269-5273.

Orel, G., A. D. Marchant, J. A. McLeod, and G. D. Richards. 2003.
Characterization of 11 Juglandaceae genotypes based on morphology. chNA,
and RAPD. HortScience 38:1178-1183.

Ransom, C. V., D. D. Douches, and J. J. Kells. 1998. lsozyme and RAPD
variation among and within hemp dogbane (Apocynum cannabinum) populations.
Weed Sci. 46:408-413.

Richards, A. J., 1970. Eutriploid facultative agamospermy in Taraxacum. New
Phytol. 69:761-774.

Richards, A.J., 1973. The origin of Taraxacum agamospecies. Bot. J. Linn.
6:189-211.

Rohlf, F. J., 2002. NTSYSpc: Numerical Taxonomy System, Version 2.11L.
Exeter Publishing, Ltd.: Setauket, NY.

Rowe, M. L., D. J. Lee, S. J. Nissen, B. M. Bowditch, R. A. Masters. 1997.
Genetic variation in North American leafy spurge (Euphorbia esula) determined
by DNA markers. Weed Sci. 45:446-454.

Solbrig, O. T., 1971. The population biology of dandelions. Am. Sci. 59:686-694.

21

Solbrig, O. T., and B. B. Simpson. 1974. Components Of regulation of a
population Of dandelion in Michigan. J. Ecol. 62:473-486.

Sterling, T. M. and Y. Hou. 1997. Genetic diversity Of broom snakeweed
(Gutierrezia sarothrae) and threadleaf snakeweed (G. Microcephala) populations.
Weed Sci. 45:674-680.

Stubbendieck, J., G. Y. Friisoe, M. R. BOIiCk. 1995. Weeds of Nebraska and the
Great Plains. Lincoln, Nebraska: Nebraska Department Of Agriculture. pp. 176-
177

Sturtevant, E. L. 1886. A study Of the dandelion. Amer. Nat. 20:5-9.

Taylor, R. J., 1987. Population variation and biosystemic interpretations in weedy
dandelions. Bull. Torrey Bot. Club 114:109-120.

Williams, J. G. K., A. R. Kubelik, K. J. Livak, J. A. Rafalski, and S. V. Tingey.

1990. DNA polymorphisms amplified by arbitrary primers are useful as genetic
markers. Nucleic Acid Res. 18:6531-6535.

22

Table 1. Location and Site description Of common dandelion collections included
in the field nurseries for RAPD analysis.

 

Included in field Included in

. . . a
S'te Description nurseries genetic analysis

Collection Site

1 Alger CO. Ml dairy pasture X X
2 Berrien CO. MI NT agriculture X X
3 Calhoun CO. Ml NT agriculture X X
5 Clinton Co. Ml NT agriculture X
6 Hillsdale CO. Ml NT agriculture X X
7 lngham CO. Ml residential X X
9 lonia CO. Ml NT agriculture X X
12 IOSCO CO. Ml state park X X
13 Leelanau CO. Ml state park X
14 Monroe CO. Ml NT agriculture X X
15 Newaygo CO. Ml CT agriculture X X
17 Oceana Co. Ml fruit orchard X X
18 Presque Isle CO. Mlb state park X
20 Shiawassee CO. Ml CT agriculture X X
21 St. Clair CO. Ml CT agriculture X
22 Luce CO. Ml state park X X
23 YOIO CO. CA fruit orchard X X
26 Adams CO. CO SOd farm X X
27 Tolland CO. CT dairy pasture X X
28 Champaign Co. IL wooded area X

29 Vermillion Co. lL CT agriculture X X
30 Benton CO. IN CT agriculture X
31 Riley CO. KS CT agriculture X

32 Stafford CO. KSb ‘ CT agriculture X
33 Hall CO. NE residential X X
36 Baker CO. OR pasture X

37 Elk CO. PA road Side X

39 Cache CO. UT residential X X
40 Brazos CO. TX residential X X
42 Germanyb unknown X X

 

TAbbreviations: NT = nO-tillage; CT = conventional tillage.
Plants collected from these sites were identified as red seeded dandelion (T. Iaevigatum).

23

Table 2. Seed production and plant diameter for common dandelion at East
Lansing and Chatham field nurseries.

 

 

 

Number Of seeds Rosette diameter
Collection East Lansing Chatham East Lansing Chatham
— seeds per flower— —— cm

Alger CO. MI 275 200 42.2 15.6
Berrien CO. MI 232 208 37.8 20.6
Calhoun CO. MI 230 209 47.0 19.7
Hillsdale CO. MI 234 179 41.4 13.4
lngham CO. MI 230 202 37.4 24.1
lonia CO. MI 207 153 38.1 14.6
IOSCO CO. MI 206 148 52.1 19.1
Leelanau CO. MI 223 198 44.5 17.8
Monroe CO. MI 187 153 31.8 19.4
Newaygo Co. MI 152 153 40.3 14.3
Oceana CO. Ml" - 185 - 10.8
Shiawassee CO. MI 168 153 33.4 21.3
Luce CO. MI 183 142 36.2 11.5
YOIO CO. CO 173 132 31.7 17.8
Adams CO. CO 293 180 38.9 15.0
Tolland Co. CT 245 214 54.6 24.9
Champaign CO. IL 163 166 32.2 20.0
Riley CO. KS 212 230 38.8 16.5
Hall CO. NE 145 131 26.0 22.3
Baker CO. OR 304 222 38.5 19.4
Elk CO. PA 178 199 42.2 21.2
Cache CO. UT 261 215 35.6 14.9
Brazos CO. TX 168 145 33.0 21.3
Germany 123 106 22.0 12.2
LSD(0.05) 56 29 13.9 6.1

 

a Oceana County collection dropped from East Lansing nursery due to winter mortality

24

Table 3. RAPD primers used to evaluate the genetic diversity between common
dandelion collections.

 

 

RAPD Primer Sequence 5’ to 3’ NO. Of bands NO. polymorphic
OPA-03 AGTCAGCCAC 4 1
OPA-O4 AATCGGGCTG 14 8
OPA-07 GAAACGGGTG 10 8
OPA-08 GTGACGTAGG 12 1 1
OPA—09 GGGTAACGCC 5 2
OPA—10 GTGATCGCAG 6 2
OPA-1 1 CAATCGCCGT 3 2
OPA-18 AGGTGACCGT 10 6
OPA-19 CAAACGTCGG 7 4

Total 71 44

 

25

 

 

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27

Table 5. Comparison of leaf area and dry weight for 9 collections of common

dandelion grown in the greenhouse.

 

 

Collection Leaf areaa Dry weighta
cm3 9

Alger Co. MI 432 a 2.02 a
Berrien Co. MI 244 cd 0.84 c
lngham Co. MI 394 ab 1.56 b
Luce Co. MI 216 d 0.87 0
Monroe Co. MI 387 ab 1.79 ab
Newaygo Co. MI 266 cd 0.97 c
Shiawassee Co. MI 409 a 1.74 ab
St. Clair Co. MI 319 bc 1.57 b
Vermillion Co. IL 310 Do 1.51 b

 

a Means followed by the same letter within column are not significantly different according to

Fisher’s Protected LSD (o=0.05).

28

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29

CHAPTER 2

CONTROL STRATEGIES FOR COMMON DANDELION (Taraxacum officinale
Weber) IN NO-TILLAGE CROPPING SYSTEMS

Abstract: Common dandelion has developed into a troublesome agronomic
weed for no-tillage corn and soybean producers in Michigan and throughout the
North Central region. Field experiments were conducted on established
populations of common dandelion in 2001-02 and 2002—03 to evaluate the effect
of preplant herbicide applications and sequential herbicide applications for
efficacy on established populations of common dandelion. Preplant treatments of
glyphosate or 2,4-D ester were applied early fall, late fall, early spring, and late
spring. Glyphosate was applied at 420 9 ae ha'1 or 840 kg ae ha“; 2,4-D ester
was applied at 560 g ai ha'1 or 1120 g ai ha". A tank mixture of glyphosate plus
2,4-D ester was also evaluated at each of the preplant timings. Common
dandelion control was evaluated at the time of crop planting. For both glyphosate
and 2,4-D ester, the fall applications were more effective than the spring
applications. The late fall application of glyphosate at 840 9 ae was the most
effective treatment, with 80 percent control of common dandelion. A single
application of glyphosate or 2,4—D ester applied either in the fall or spring was not
sufficient in providing season long control of common dandelion. A subsequent
field experiment was conducted to evaluate the effectiveness of sequential

applications of glyphosate to provide season long control of common dandelion.

30

Sequential treatments of glyphosate following either glyphosate or 2,4-D ester

were effective in providing season-long control of common dandelion.

Nomenclature: Taraxacum officinale, TAROF, common dandelion; glyphosate,

N-(phosphonomethyl) glycine; 2,4-D ester, (2,4-dichlorophenoxy) acetic acid.

Key words: application timing, preplant treatment, sequential treatment.

31

INTRODUCTION

Common dandelion (Taraxacum officinale Weber) has developed into a
troublesome agronomic weed in Michigan and throughout the North Central
region of the US. Typically considered a problematic weed unique to forage
production and turf grass, the occurrence of common dandelion in no-tillage corn
and soybean production is becoming more common. The increased use of
herbicide-resistant crops in conjunction with the adoption of no-tillage cropping
practices has resulted in an environment conducive to the establishment of
common dandelion (Triplett and Lytle 1972).

Common dandelion is a simple perennial that possesses a large fragile
taproot that is used for carbohydrate storage and to acquire needed resources.
Tillage operations associated with conventional-tillage crop production are an
effective method of controlling perennial weeds such common dandelion
because tillage disrupts the establishment and development of the taproot
(Triplett 1985). Adoption of no-tillage cropping practices by crop producers has
occurred in response to environmental and economic incentives. Soil
conservation and reduced input costs are the primary drivers for this adoption
(Jasa et al. 1991). However, no-tillage cropping systems have a higher reliance
on herbicides for weed control (Koskinen and McWhorter 1986), often requiring
multiple herbicide applications to manage perennials (Buhler and Mercurio 1988;
Buhler and Proost 1990).

Non-selective herbicides, such as glyphosate, are widely used for

vegetation management prior to planting and postemergence in no-tillage

32

glyphosate-resistant cropping systems. A disadvantage of the use of glyphosate
as a preplant and postemergence treatment is the lack of residual soil activity
(Sprankle et al. 19753, 1975b). A consequence of the exclusive use of
glyphosate without the addition of soil applied residual herbicides is the potential
for weeds, including common dandelion seedlings, to emerge following the
glyphosate application. Glyphosate is effective in controlling many troublesome
perennial weeds (Davison 1972). However, common dandelion is often the one
weed not completely controlled. Furthermore, as common dandelion seedlings
become established, they become more difficult to control (T riplett et al. 1977).
The objectives of this research were to determine the effect of herbicide,
application timing, and sequential applications on control of established

populations of common dandelion in no-tillage cropping systems.

MATERIALS AND METHODS

Field experiments were conducted to evaluate control strategies for
common dandelion using glyphosate1 and 2,4-D esterz. Preplant treatments of
glyphosate and/or 2,4-D ester were applied at four application timings. Additional
experiments were conducted to evaluate sequential applications of glyphosate
following either glyphosate or 2,4-D ester. Initial applicationsof glyphosate or
2,4-D ester were applied preplant either in the fall or spring. Sequential
applications of glyphosate were applied postemergence in glyphosate-resistant

soybean.

33

Effect of herbicide and application timing

Experiments to evaluate preplant applications of glyphosate or 2,4-D ester
were conducted in 2001-02 and 2002-03 at the Michigan State University
Clarksville Experiment Station. Two identical experiments were established on
adjacent sites in both 2001-02 and 2002-03. Experiments were conducted on
sites with established populations of common dandelion that had been in a no-
tillage com-soybean rotation for 3 years. The soil at the experimental site was a
loam with pH 6.8 and 1.8% organic matter. Experimental sites were prepared by
removing the previous corn crop as silage approximately one month before the
initial fall applications. Plots measured 3 m wide by 9 m long. Herbicide
treatments were applied with a tractor mounted, compressed-air sprayer
calibrated to deliver 187 L ha'1 at 207 kPa through 8003 flat fan nozzles3.

Treatments of glyphosate or 2,4-D ester were applied at four application
timings prior to crop planting; early fall (EFALL), late fall (LFALL), early spring
(ESPRING), and late spring (LSPRING) (Table 1). Glyphosate and 2,4—D ester
were applied at typical use rates to evaluate common dandelion control.
Glyphosate was applied at 420 9 ae ha'1 and 840 9 ae ha"; 2,4-D ester was
applied at 560 g ai ha'1 and 1120 g ai ha". A tank mixture of glyphosate plus
2,4-D ester at 420 9 ae ha'1 and 560 9 ae ha", respectively, was also applied at
each of the four preplant timings. All treatments containing glyphosate were
applied with 2% (w/v) ammonium sulfate. Common dandelion control was

evaluated visually at crop planting and was recorded as percent control as

34

compared to the untreated; where 0 = no control and 100 = complete common

dandelion death.

Effect of sequential applications

Field experiments were conducted in glyphosate-resistant soybean to
evaluate the effectiveness of sequential applications of glyphosate following
initial applications of either glyphosate or 2,4-D ester. Experiments were
conducted in 2001-02 and 2002-03 at the Michigan State University Clarksville
Experiment Station as described above. Glyphosate-resistant soybean4 were
planted at a population of 494,000 seeds ha'1 in 19-cm rows, approximately 3
weeks after the initial spring application. In 2002-03, s-metolachlor5 was applied
preemergence over the entire study at 1424 g ai ha'1 for annual weed control. A
postemergence application of quizalofop-P-ethyl6 at 49 g ai he1 was applied with
non-ionic surfactant7 at 0.25% (v/v) for grass control in both 2001-02 and
2002-03.

Initial treatments of either glyphosate or 2,4-D ester at 840 9 ae and
1120 9 ae, respectively, were applied at two preplant application timings; fall and
spring. These application timings correspond with the LFALL and ESPRING
timings described above in Table 1. Sequential treatments of glyphosate at 840 9
ae were applied postemergence to glyphosate-resistant soybean at the V3 or V6
crop stage. The sequential application at the V6 stage of soybean was evaluated
in 2002-03 only. Common dandelion control was evaluated visually and common

dandelion plant density recorded at soybean harvest. Common dandelion density

35

was recorded as the number of plants per square meter. Soybean yield was
determined 2001-02 by hand-harvesting the middle 1.5 m of each 4.5 m long
plot. In 2002-03, the middle 1.5 m of each 9 m long plot was mechanically

harvested with a research plot harvester.

Statistical analysis

The herbicide and application timing experiment was conducted as a
randomized complete block design. Treatments were replicated four times for
each treatment and the experiment was conducted four times. Data were
subjected to analysis of variance with SAS8 and means separated using Fisher’s
Protected LSD (a = 0.05). Variances were determined to be homogenous and
the experiments combined.

The sequential application experiment was established as a split block
with four replications in 2001-02; the whole plot was the initial application and the
sub-plot was the sequential application. In 2002-03, the experiment was
conducted as a randomized complete block design with four replications. Data
were subjected to analysis of variance with SAS and means separated using
Fisher’s Protected LSD (a = 0.05). Data collected in 2001-02 and 2002-03 are

presented separately.

36

RESULTS AND DISCUSSION
Effect of herbicide and application timing

Significant differences in common dandelion control were observed
between herbicides and herbicide rates. Both glyphosate or 2,4-D ester at higher
rates were more effective than at lower rates at each of the four application
timings (Figure 1). Glyphosate applied at 840 9 ae was usually more effective
than 2,4-D ester at 1120 9 ae, regardless of application timing (Figure 2). The
most effective herbicide treatment to control common dandelion was the LFALL
application of glyphosate applied at 840 9 ae, resulting in 80 percent control. The
effectiveness of fall applications of glyphosate to control common dandelion has
been consistently demonstrated (Buhler and Mercurio 1988; Buhler and Proost
1990). At the same LFALL timing, 2,4-D ester at 1120 9 ae provided 58 percent
common dandelion control. The most effective application timing for 2,4-D ester
was the EFALL application timing which resulted in 60 percent control of
common dandelion. Glyphosate applied at the same timing was more effective
with 74 percent control of common dandelion. Glyphosate at the lower rate was
consistently more effective than 2,4-D ester at the lower rate at all application
timings (Figure 1).

Timing of the preplant application was as critical as the herbicide and
herbicide rate applied. For both glyphosate and 2,4-D ester, the preplant
applications in the fall were more effective than the spring applications (Figure 2),
despite the fact that temperatures at the time of application were lower in the fall

versus the spring, especially in 2001-02 (Table 1). Glyphosate applied at 840 g

37

ae provided 80 and 74 percent control at the EFALL and LFALL timings,
respectively. This same treatment at the ESPRING and LSPRING timings
resulted in only 65 and 55 percent control, respectively. A similar trend of
reduced control in the spring was also observed with 2,4-D ester (Figure 2).
Reduced control of common dandelion by spring treatments may relate to growth
patterns of the plant in the spring (Mann 1981; Rutherford and Deacon 1974).
Root tissue of common dandelion has the ability to generate new shoots (Mann
and Cavers 1979). Carbohydrates stored in the taproot are mobilized to the
above ground biomass of the plant during rapid vegetative growth in the spring.
Applications at this time result in insufficient herbicide translocation to the roots
for complete control.

Glyphosate or 2,4-D ester applied at the lower rates in the fall tended to
be more effective than the higher herbicide rates applied in the spring.
Applications of 2,4-D ester at 560 9 ae at the EFALL and LFALL timings provided
40 and 43 percent control, respectively (Figure 1). These treatments were more
effective than the ESPRING and LSPRING applications of 2,4-D ester at 1120 g
ae with 34 and 31 percent control, respectively. A similar trend was observed
with glyphosate for the spring applications. The LFALL application of glyphosate
at 420 9 ae was more effective than the LSPRING application of glyphosate at
840 9 ae.

Depending on application timing, 3 tank-mixture of glyphosate plus 2,4-D
ester at reduced rates was effective in controlling common dandelion.

Regardless of application timing, glyphosate applied at 840 9 ae was more

38

effective than the tank-mixture (Figure 1). At the LFALL application timing, the
tank-mixture was more effective than 420 9 ae of glyphosate. Common dandelion
control with the tank-mixture was more effective than 2,4-D ester at 1120 9 ae at
the LFALL, ESPRING, and LSPRING application timings. The tank-mixture was
as effective as 1120 9 ae of 2,4-D ester at the EFALL application timing. The
addition of 2,4-D ester to glyphosate did not antagonize common dandelion
control when applied at the EFALL, LFALL, and LSPRING application timing.
However, at the ESPRING application timing, the tank-mixture was less effective

than 420 9 ae of glyphosate.

Effect of sequential applications

A single application of glyphosate or 2,4-D ester either in the fall or spring
did not provide season-long control of common dandelion (Figure 3). However,
the addition of a sequential application of glyphosate following either glyphosate
or 2,4-D ester was effective in providing season-long control of common
dandelion. In both 2001-02 and 2002-03, glyphosate applied in the fall followed
by the sequential application at the V3 stage of soybean provided greater than 80
percent control. In 2002-03, similar control was observed with the fall application
followed by the sequential application at the V6 stage of soybean with 87 percent
control.

In 2001-02, the spring application of glyphosate followed by the V3 stage
of soybean provided 54 percent control. This was significantly lower than the

same treatment in 2002-03 with 97 percent control. This discrepancy in control

39

between years could be attributed to the lack of significant rainfall in 2002-03
following the spring application timing (Table 2). In 2002, the experimental site
received over 160 mm of precipitation from January thru April. This was
approximately 100 mm more than in 2003. The dry weather pattern reduced new
seedling germination and plant regrowth. The lack of new plant growth in
2002-03 is evident from the spring-only treatment of glyphosate that provided 75
percent control at harvest. This same treatment in 2001-02 provided only 20
percent control.

Treatment with 2,4-D ester followed by a sequential application of
glyphosate was also effective in controlling common dandelion, depending on the
timing of the initial application (Figure 3). In 2001-02, the fall application of 2,4-D
ester followed by glyphosate at the V3 stage of soybean provided 81 percent
control of common dandelion. However, the spring application of 2,4-D ester
followed by glyphosate at the V3 stage of soybean provided only 44 percent
control in 2001-02. Fall treatments were again more effective in controlling
established common dandelion. In 2001-02, the sequential application of
glyphosate at the V3 stage of soybean controlled newly emerged common
dandelion from the fall treatment. The initial spring treatment of glyphosate was
less effective, resulting in more established plants at the sequential application at
the V3 stage of soybean. These mature plants are more difficult to control than
seedling common dandelion (T riplett et al. 1977).

Similar to the sequential treatments of glyphosate in 2001-02 and

2002-03, a sequential treatment of glyphosate following 2,4-D ester in the fall

40

provided 81 and 80 percent control of common dandelion, respectively. Likewise,
the spring application of 2,4-D ester followed by glyphosate at the V3 stage of
soybean was less effective with only 44 percent control in 2001-02. This same
treatment in 2002-03 provided 80 percent control of common dandelion at
harvest. This differential response is likely a result of the extended period without
rainfall in 2002-03. Delaying the sequential application until the V6 stage of
soybean resulted in common dandelion control similar to the timing at the V3
stage of soybean regardless of timing of the initial application (Figure 3).

A single application of either glyphosate or 2,4-D ester applied in the fall or
spring was not effective in reducing plant densities as compared to the untreated
(Figure 4). However, the addition of a sequential application of glyphosate was
effective in reducing common dandelion plant densities. In 2001-02, the addition
of the sequential application of glyphosate at the V3 stage of soybean reduced
common dandelion plant densities as compared to the fall only treatment of
glyphosate. In 2002-03, delaying the sequential application until the V6 stage of
soybean significantly reduced common dandelion densities as compared to the
fall treatment of glyphosate. A sequential application of glyphosate following a
spring treatment of glyphosate did not reduce common dandelion densities in
either 2001-02 or 2002-03. A sequential application of glyphosate following 2,4-D
ester applied in the fall or spring was effective in reducing common dandelion
densities as compared to the initial treatment alone.

Timing of herbicide application had a significant effect on soybean yield. In

2001-02, the fall and spring applications of either glyphosate or 2,4-D ester did

41

not result in soybean yield greater than the untreated (Figure 5). In 2002—03, the
spring application of either glyphosate or 2,4-D ester resulted in soybean yield
greater than the untreated or the fall application of either herbicide. It is likely that
the lack of moisture that reduced weed seedling germination and regrowth in
2003 contributed to this observation. Soybean yields resulting from a fall
application of either glyphosate or 2,4-D ester followed by the sequential
application at the V3 stage of soybean were consistently among the highest in
both 2001-02 and 2002-03. Delaying the sequential application of glyphosate
until the V6 stage of soybean following the spring application of either glyphosate
or 2,4-D ester did not affect soybean yield as compared with the sequential
application at the V3 stage of soybean in 2002-03. However, delaying the
sequential application following the initial fall application of either glyphosate or
2,4-D ester did result in reduced soybean yield. Reduction of soybean yield
associated with the initial fall followed by the sequential application at the V6
stage of soybean is likely due to early-season competition from annual weeds not
controlled by the preemergence application of s-metolachlor.

It is apparent that established populations of common dandelion pose a
significant challenge to no-tillage crop producers. Common dandelion, when left
uncontrolled, has the potential to negatively impact soybean production. An
effective management strategy to control this weed includes field monitoring and
multiple herbicide applications. The lack of residual control associated with
glyphosate and 2,4-D ester makes sequential herbicide applications necessary to

achieve season-long control of common dandelion. An effective strategy to

42

control common dandelion in no—tillage crop production will include fall
applications of herbicides such as glyphosate followed by a sequential
postemergence application of glyphosate in glyphosate-resistant crops. The
timing of this postemergence application will depend on environmental conditions

and the presence of emerged weeds.

Source of Materials
1 Roundup UltraMAX, Monsanto Company, St. Louis, MO 63167.
2 2,4-D ester, Tenkoz lnc., Alpharetta, GA 30202.
3 Flat-fan spray nozzle, Spraying Systems Company, Wheaton, IL 60188.
4 DK 23-51, Dekalb Genetics Corp., Monsanto Company, St. Louis MO 63167
5 Dual ll Magnum, Syngenta Crop Protection, Inc. Greensboro, NC 27409.
6 Assure II, E. I. du Pont de Nemours and Company, Wilmington, DE 19898.
7 Activator 90, Loveland Industries Inc., Greeley, CO 80632.

8 SAS version 8.2, SAS Institute, SAS Circle, Box 8000, Cary, NC 27512-8000.

43

LITERATURE CITED

Buhler, D. D. and J. C. Mercurio. 1988. Vegetative management and corn growth
and yield in untilled mixed-species perennial sod. Agron. J. 80:454-462.

Buhler, D. D. and R. T. Proost. 1990. Sequential herbicide treatments for corn
(Zea mays) planted into mixed-species perennial sod. Weed Technol. 4:781-786.

Davison J. G. 1972. The response of 21 perennial weed species to glyphosate.
Proc. 11th Br. Weed Control Conf. Pages 11-16.

Jasa, P.J., D. P. Shelton, A. J. Jones, E. C. Dickey. 1991. Conservation tillage
and planting systems. Cooperative Extension Service, University of Nebraska-
Lincoln, Nebraska.

Koskinen, W. C. and C. G. McWhorter. 1986. Weed control in conservation
tillage. J. Soil Water Conserve. 41:365-370.

Mann, H. 1981. Common dandelion control with 2,4-D and mechanical
treatments. Weed Sci. 29:704-708.

Mann, H. and P. B. Cavers. 1979. The regenerative capacity of root cuttings of
Taraxacum officinale Weber under natural conditions. Can. J. Bot. 57:1783—1 791.

Rutherford, P. P. and A. C. Deacon. 1974. Seasonal variation in dandelion roots
of fructosan composition, metabolism, and response to treatment with 2,4-
dichlorophenoxyacetic acid. Ann. Bot. 38:251-260.

Sprankle, P. W. F. Meggitt, and D. Penner. 19753. Rapid inactivation of
glyphosate in the soil. Weed Sci. 23:224-228.

Sprankle, P. W. F. Meggitt, and D. Penner. 1975b. Adsorption, mobility, and
microbial degradation of glyphosate in the soil. Weed Sci. 23:229-234.

Triplett, G. B. Jr. 1985. Principles of weed control for reduced-tillage corn
production. Pages 26-40 in Weed Control in Limited Tillage Systems, A. F.
Weise, ed. Weed Sci. Soc. Am. Mongr. 2, Champaign, IL.

Triplett, G. B. and G. D. Lytle. 1972. Control and ecology of weeds in continuous
corn grown without tillage. Weed Sci. 20:453-457.

Tripplett, G. B. Jr., R. W. Van Keuren, and J. D. Walker.,1977. Influence of 2,4-D,

pronamide, and simazine on dry matter production and botanical composition of
an alfalfa-grass sward. Crop Sci. 17:61-65.

44

00:00:30 00.0.0000 3+. .000 >00 05 000 .8. .0 >00 00. .A T. 0.0000 00 05 00 0.30.0080. 0.0 00000>< m

 

 

 

9 N. 2 Bow .8 03.
: mm 8 Bow .2 .00....
2 N. 2 080 .0 0850.62
2 3 3 800 .0 .8900
0.. o F-

 

 

A0. «0.3.0.0000. :4.

00:00:30 .0 0.00

0 88 .8 09... 9.0% 23
mm «80 .0. .09.. 000% 2.00
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.0. 000000.300 0.00 0-0M 000 0.0000020 00.. 0.30.0000. 0.0 000.00 000 .0000 00:00:30 00.00 00:00:00.0. .: 0.00s

45

Table 2. Yearly accumulation of precipitation at the Michigan State University
Clarksville Experiment Station from 2001 thru 2003.

 

Annual precipitation

 

 

 

 

Month 2001 2002 2003
mm
January 19 7 3
February 64 34
March 14 49 35
April 67 78 22
May 136 104 122
June 67 66 50
July 23 47 60
August 103 71 92
September 78 25 45
October 143 45 29
November 48 53 173
December 34 22 21
Total 7—96— 5 370—

 

46

.300 u 0. .0000...0 2.0005090 .00 000 0000. 0000 0.... 5.3 00.0.. 0o..00..000 0.0:; 0000.2 0.0.50 00.00080 .23. £0 0....) 00:000
0003 0.0000020 00.0.0.000 0.000.000. ._< 00.00.. 00:00:30 >0 00.0000 00 .>.0>..000000 .00 m 000 000 00 m 00.. .0 00.00 0-...N 00.0
0.0000020 .0 00:00.0 0.00. 000 00.00 0-0.N 0.0000020 .0 000002.000 .00.0000 0:; 00:00.0 .0 .0008 0200000 coEEoO .. 0000...”.

3.00 0.0.N 00 0 0.0000020 00 m 00.00 0.} 00 0 0.0000020 00 m

 

 

 

 

8:: 00... 5.3.00. 0N0 0.00 8:: 00... xE-xc0. 0N0 000

 

 

 

 

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00

 

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00:

 

%) lonuoa uouepuep uowwoa

I

 

 

 

 

 

 

 

 

 

 

0°:

47

 

 

 

 

 

 

 

100
a I 840 9 ae glyphosate
b 1120 9 ae 2,4-D ester
= 80
.2
3 A
‘0’ of, so -
1“; 3
I-
5 ‘E 40 q
E 8
E
o 20 "
o _

 

 

LFALL ESPRING LSPRING

EFALL

Figure 2. Common dandelion control at planting with glyphosate and 2.4-D ester
as affected by application timing. Glyphosate applied with 2% (w/v) ammonium
sulfate. Means with the same letter are not significantly different (a = 0.05)

48

.600 n 0. .00.0...0 2.0005000 .00 0.0 .000. 0.000 00. 0...... 000.0
0000 0.0.0... 0000.2 0.0.30 E:.00EE0 3.5. $0 0...... 02.000 0.02. 0.0000020 00.0.0.000 0.000000... ._< .020... 02.02.000
>0 00.0000 00 002.02.000 00.20.00 2.000000 000 0.00.0 0...... .00200 0000.60 .0 .9008 02.00000 00.00.00 .0 0.00.".

00.0... 02.80000 .00.... 05:... 508.3% 0......

 

 

 

00.50 =0". 0:000 =0".

 

   
     

 

 

 

 

 

 

. 00.300
0.0000020 0. 0.0000020 n.
.800 n-v.~ . . 0.0000020

 

 

 

 

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. - -
HUM. V/Ir/A/é 1 0.0000020 0.
0> a 0n. n> 0. n... .8 a... .23 0.0.0 208002..

 

49

00...... 02.8.0...“ 0......

30.0 n 0. E0020 2.000....00.0 .00 0.0 .000. 00.00 00. 0...... 000.0 0000 0.0.0...
0000.). 0.0.30 0.200050 9.20 2.0 0...... 02.000 0.0.... 0.0000020 00.0.0.000 0.000.009. __< 00...... 02.02.000 >0 00.0000
00 000002.000 00.20.00 .00003000 000 0.00.0 0...... .00>.00 0000>00 .0 000.0000 .00.0 02.00000 00.00.00 .0 0.00.”.

00...... 02.8.0... .00....

 

 

 

 

 

0.0000020 0.
.200 9...“

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(z_ui squeld) Ausuep uouspuep uowuioo

50

 

 

w}; .  
“

    

 

Spri

 

 

 

Fall
Initial application timing

 

UNT

 

 

 

2001-02

 

 

fb glyphosate

glyphosate

 

 

 

Q

Spri

   
 

 

Fall
Initial application timing

 

UNT

 

 

 

 

 

 

affected by application timing. All treatments containing glyphosate were applied with 2% (w/v) ammonium sulfate. Means

Figure 5. Soybean yield as affected by common dandelion control with single and sequential herbicide applications as
within each graph with the same letter are not significantly different (a = 0.05).

(o pt 6») mark ueaqlios

51

CHAPTER 3
COMMON DANDELION (Taraxacum officinale Weber) CONTROL WITH
POSTEMERGENCE HERBICIDES IN NO-TILLAGE GLUFOSINATE-
RESISTANT CORN (Zea mays L.)
Abstract: Common dandelion has developed into a troublesome agronomic
weed for no-tillage corn producers. Measures to control common dandelion prior
to crop planting are not always effective. As a result, a postemergence herbicide
application is often required to reduce common dandelion competition with the
crop. Field experiments were conducted in 2002 and 2003 to evaluate 22
postemergence herbicide treatments for efficacy on established populations of
common dandelion in no-tillage corn. Postemergence herbicides were applied
when the corn was 5-6 collar. All herbicides were applied at labeled rates with
recommended adjuvants. At 28 days after treatment (DAT) the most effective
treatments included glufosinate, glufosinate + atrazine, mesotrione, and
mesotrione + atrazine, providing at least 76 percent control of common
dandelion. All other herbicide treatments at this time provided less than 40
percent common dandelion control. Common dandelion control was evaluated 56
DAT when regrowth of treated plants was observed for some herbicide
treatments. By 56 DAT, dicamba + diflufenzopyr was the most effective treatment
providing 83 percent control of common dandelion. In 2002, all herbicide
treatments, with the exception of flumiclorac, resulted in corn yields greater than

the untreated. Treatments that provided the greatest control of common

52

dandelion at 28 DAT also resulted in the greatest corn yield. None of the
postemergence herbicide treatments that were evaluated completely controlled
common dandelion. However; specific treatments were identified that effectively

reduced common dandelion competition with the corn crop.

Nomenclature: 2,4-D amine; 2,4-D ester; atrazine; bentazon; bromoxynil;
carfentrazone; clopyralid; dicamba; diflufenzopyr; flumetsulam; glufosinate;
halosulfuron; mesotrione; metolachlor; nicosulfuron; paraquat; primisulfuron;
rimsulfuron; sulfentrazone; thifensulfuron; Taraxacum officinale, TAROF,

common dandelion.

Abbreviations: AMS, ammonium sulfate; COC, crop oil concentrate; NIS, non-
ionic surfactant; UAN, 28% urea-ammonium nitrate; EPP, early preplant; PRE,

preemergence; POST, postemergence.

53

INTRODUCTION

Conservation tillage has become a widely accepted practice for both
environmental and economic reasons. By eliminating tillage, plant residue
remains intact on the soil surface, effectively reducing soil erosion by wind and
water movement. Economic benefits include reduced fuel and labor requirements
(Phillips et al. 1980; Jasa et al. 1991). Removal of tillage from the cropping
system also impacts the dynamics of weed populations present in the field. More
specifically, perennial weed species typically become more prevalent than
annuals (Triplett and Lytle 1972; Buhler et al. 1994). Populations of perennial
species are likely to increase in these systems because the lack of tillage allows
the plants to become established (T riplett 1985). And furthermore, as seedlings
of perennial species become established, they become more difficult to control
(Triplett et al. 1977). Effective weed control is the primary consideration for
adopting no-tillage (Koskinen and McWhorter 1986).

Common dandelion (Taraxacum officinale Weber) is a perennial weed
species that has developed into a troublesome weed problem that is unique to
no-tillage cropping systems. Common dandelion has been a concern primarily
associated with forage production, where it may contribute up to 30% of total dry
matter yield (Moyer 1989). Fortunately for forage producers, the presence of
common dandelion does not appear to be detrimental. In fact, common dandelion
appears to be high in forage quality (Dutt et al. 1977; Scheaffer and Wyse 1982).

However, common dandelion is not so benign in no-tillage corn production. We

54

have observed significant crop stress and yield reduction from common
dandelion competition in no-tillage corn (Franssen, unpublished).

The non-selective herbicide, glyphosate, is effective in providing common
dandelion control in no-tillage cropping systems. However, a postemergence
application with glyphosate is restricted to use in glyphosate-resistant corn
hybrids. Glufosinate is another non-selective herbicide that provides control of
many troublesome weeds when applied postemergence to glufosinate-resistant
corn hybrids. There are many additional conventional herbicides that provide
effective weed control in non-herbicide resistant corn production. As the
prevalence of common dandelion continues to increase in no-tillage crop
production, these herbicides need to be evaluated for common dandelion
efficacy. The objective of this research was to evaluate glufosinate as well as
several conventional postemergence corn herbicides for efficacy on established

populations of common dandelion in no-tillage corn.

MATERIALS AND METHODS
Field experiments were conducted on no-tillage crop production sites at
the Michigan State University Clarksville Experiment Station and at a commercial
production field near Elsie, MI in 2002 and 2003, respectively. The soil at the
Clarksville Experiment Station was a loam with 1.8 % organic matter and pH 6.8.
This site was in a no-tillage com-soybean rotation for 3 years. The soil at the
Elsie experimental site was a sandy loam with 2.8 % organic matter and pH 6.8.

This site was in a no-tillage com-soybean rotation for 10 years. The previous

55

year's crop for the Clarksville and Elsie experimental sites were com and
soybean, respectively. Descriptions of the trial sites are shown in Table 1.

Glufosinate-resistant corn hybrids“2 were planted at 69,200 seeds ha‘1 in
four row plots measuring 3 m wide by 9 m long. In both 2001 and 2002, paraquat
at 525 g ai ha'1 was applied early preplant (EPP) 7 days prior to planting to
remove common dandelion above-ground biomass and control winter annual
weeds. Annual weeds were controlled at the experimental sites using typical
application rates of the herbicides included in accordance with the commercial
herbicide label and current commercial practices. A preemergence (PRE)
treatment of s-metolochlor at 1424 g ai ha'1 was applied at planting. Common
dandelion control was evaluated using the postemergence (POST) herbicide
treatments listed in Table 2. All postemergence herbicides were applied when
com reached the 5-6 collar stage. Treatments were applied at the Clarksville and
Elsie experimental site on June 12, 2002 and June 22, 2003, respectively. At this
time, common dandelion above-ground biomass had fully recovered from.the
EPP paraquat treatment with an average diameter of 30-35 cm. Common
dandelion plant densities at the time of the postemergence applications were 6
and 3 plants m'2 in 2002 and 2003, respectively. Treatments were applied with a
tractor mounted, compressed-air sprayer calibrated to deliver 187 L ha‘1 at 207
kPa through 8003 flat fan nozzles3.

Common dandelion control from postemergence herbicides was evaluated
visually at 28 and 56 d after treatment (DAT). Common dandelion control was

recorded as percent control compared to the untreated; where O = no control and

56

100 = complete common dandelion death. In 2002 only, the middle two rows of
corn were harvested and the yields adjusted to 15.5 percent moisture. Due to
adverse dry weather conditions and competition from annual weeds, yield data

was not collected in 2003.

Statistical analysis

Twenty-two herbicide treatments plus an untreated control were arranged
in a randomized complete block design. Treatments were replicated four times
and the experiment was conducted twice. Data were subjected to analysis of
variance with SAS4 and means separated using Fisher’s Protected LSD (a =
0.05). Variances were determined to be homogenous and the experiments

combined.

RESULTS AND DISCUSSION

There was a difference in the rate at which common dandelion responded
to the herbicide treatments evaluated. Regrowth of treated plants reduced the
overall efficacy of some herbicide treatments that initially provided good control
of common dandelion. Also, herbicides that did not appear effective at earlier
ratings were more effective later in the season.

The most effective herbicide treatments at 28 DAT were glufosinate +
atrazine, mesotrione, mesotrione + atrazine, and glufosinate with 80, 77, 76, and
76 percent control, respectively (Table 2). Loux and Dobbels (2003) also found

mesotrione + atrazine effective for control of common dandelion when applied

57

preemergence in no-tillage corn. Atrazine applied alone provided only 23 percent
control. The pre-mixture of dicamba + diflufenzopyr provided 49 percent control.
All other treatments provided between 9 and 41 percent control of common
dandelion (Table 2).

By 56 DAT, significant regrowth of treated common dandelion was
observed for some treatments. Treatments of glufosinate, glufosinate + atrazine,
mesotrione + atrazine, and mesotrione, which were the most effective at 28 DAT,
provided only 63, 57, 57, and 54 percent control, respectively. At 56 DAT,
dicamba + diflufenzopyr provided the most effective control of common dandelion
with 83 percent control. The pre-mixture of atrazine plus dicamba provided 70
percent control. This treatment was more effective than either atrazine or
dicamba applied alone.

Herbicides with the same mode of action often provided similar control of
common dandelion. Treatments including the acetolactate synthase (ALS)—
inhibiting herbicides primisulfuron, rimsulfuron + thifensulfuron, nicosulfuron, and
halosulfuron provided similar control with 36, 34, 32, and 30 percent control,
respectively at 28 DAT (Table 2). At 56 DAT, nicosulfuron was the most effective
ALS-inhibiting herbicide with 55 percent control. The other ALS-inhibiting
herbicides were less effective. Similarities were also observed between
treatments that contained growth regulator herbicides. Dicamba, clopyralid, and
2,4—D ester provided similar control at 28 DAT. Common dandelion control with
2,4-D amine was as effective as 2,4-D amine and clopyralid. By 56 DAT,

common dandelion control had increased slightly and 2,4-D amine was as

58

effective as dicamba and 2,4-D ester. Clopyralid was the most effective growth
regulator herbicide at 56 DAT with 51 percent control. The protoporphyrinogen
oxidase (PPO)-inhibitors carfentrazone and flumiclorac were the least effective in
controlling common dandelion at both 28 and 56 DAT, neither providing more
than 13 percent control.

With a few exceptions, common dandelion control with pre-mixtures and
tank mixtures was generally similar to that of the individual herbicide components
alone. However, dicamba + diflufenzopyr was more effective than dicamba alone
at both 28 and 56 DAT (Table 2). Common dandelion control with primisulfuron +
dicamba at 28 DAT was as effective as primisulfuron or dicamba applied alone.
By 56 DAT, primisulfuron + dicamba was more effective than primisulfuron alone.
At both 28 and 56 DAT, Clopyralid + flumetsulam was as effective as Clopyralid
alone. The addition of atrazine in a tank mixture did not reduce common
dandelion control and in some instances it improved control (Table 2). At 28
DAT, dicamba + atrazine was as effective as dicamba alone. However, by 56
DAT, dicamba + atrazine was more effective than dicamba alone. Atrazine +
2,4-D ester was as effective as either 2,4-D ester or atrazine applied alone at
both 28 and 56 DAT.

All herbicide treatments, with the exception of flumiclorac, resulted in corn
yields greater than the untreated in 2002 (Table 2). Treatments that provided
effective control of common dandelion also resulted in the greatest corn yield.
Treatments that resulted in the highest corn yield include mesotrione + atrazine,

glufosinate, and glufosinate + atrazine with grain yield greater than

59

10,000 kg ha". Similar yield was observed with mesotrione, dicamba + atrazine,
and dicamba + diflufenzopyr with 9313, 9171, and 9133 kg ha", respectively.
Common dandelion can be managed in no-tillage corn with properly
selected postemergence herbicide. Although none of the treatments examined
here were effective in completely eliminating common dandelion, herbicide
treatments such as glufosinate, mesotrione, and dicamba + diflufenzopyr are
effective in suppressing common dandelion competition in no-tillage corn. No-
tillage producers that intensively manage this weed over several seasons will
ultimately reduce the presence of common dandelion in the soil seed bank. As
with many other perennial species, common dandelion seed has limited longevity
in the soil (Burnside et al. 1996). Effective management strategies for common
dandelion will require careful monitoring of production fields and combination of
herbicide applications. Weed control programs that include fall applications of
herbicides such as glyphosate or 2,4-D ester (Chapter 2) followed by
postemergence herbicide applications will likely be successful in reducing

common dandelion competition with no-tillage corn.

Source of Materials
1 NK 3030 corn hybrid, Syngenta Seeds Inc., Golden Valley, MN 55427.
2 N35-B8 corn hybrid, Syngenta Seeds Inc., Golden Valley, MN 55427.
3 Flat-fan spray nozzles, Spraying Systems Company, Wheaton, IL 60188.

4 SAS version 8.2, SAS Institute, SAS Circle, Box 8000, Cary, NC 27512-8000.

60

LITERATURE CITED

Buhler, D. D., D. E. Stoltenberg, R. L. Becker, and J. L. Gunsolus. 1994.
Perennial weed populations after 14 years of variable tillage and cropping
practices. Weed Sci. 42:205-209.

Burnside, O. C., R. G. Wilson, S. Weisberg, and K. G. Hubbard. 1996. Seed
longevity of 41 weed species buried 17 years in eastern and western Nebraska.
Weed Sci. 44:74-86.

Dutt, T. E., R. S. Fawcett, R. G. Harvey, and N. A. Jorgensen. 1977. Effect of
some perennial weeds on forage quality. Abstr., Weed Sci. Soc. Am. p. 57.

Jasa, P.J., D. P. Shelton, A. J. Jones, E. C. Dickey. 1991. Conservation tillage
and planting systems. Cooperative Extension Service, University of Nebraska-
Lincoln, Nebraska.

Koskinen, W. C. and C. G. McWhorter. 1986. Weed control in conservation
tillage. J. Soil Water Conserv. 41:365-370.

Loux, M. M. and A. F. Dobbels. 2003. Preplant herbicides for control of dandelion
in corn and soybeans. North Central Weed Sci. Proc. 58:44.

Moyer, J. R. 1989. Weed control during cicer milkvetch establishment and yields
in subsequent years. Can. J. Plant Sci. 69:213-222.

Phillips, R. E., R. L. Blevins, G. W. Thomas, W. W. Frye, and S. H. Phillips. 1980.
No-tillage agriculture. Science 208:1108-1113.

Sheaffer, C. C. and D. L. Wyse. 1982. Common dandelion (Taraxacum officinale)
control in alfalfa (Medicago sativa). Weed Sci. 30:216-220.

Triplett, G. B., Jr. 1985. Principles of weed control for reduced-tillage corn
production. Pages 26-40 in Weed Control in Limited Tillage Systems, A. F.
Weise, ed. Weed Sci. Soc. Am. Mongr. 2, Champaign, IL.

Triplett, G. B. and G. D. Lytle. 1972. Control and ecology of weeds in continuous
corn grown without tillage. Weed Sci. 20:453-457.

Tripplett, G. B. Jr., R. W. Van Keuren, and J. D. Walker. 1977. Influence of 2,4-D,

pronamide, and simazine on dry matter production and botanical composition of
an alfalfa-grass sward. Crop Sci. 17:61-65.

61

Table 1. Trial location, site description, and date of herbicide application for common
dandelion control with postemergence corn herbicides.

 

 

 

2002 2003
Location Clarksville Elsie
Years in no-tillage crop production 3 10
Previous crop corn soybean
Soil texture loam sandy-loam
Soil organic matter 1.8% 2.8%
Soil pH . 6.8 6.8
Early preplant application May 14 May 14
Preemergence application May 22 May 22
Postemergence application June 12 June 22
Corn height (cm)3 28 30
Corn stage (collars)a 5-6 5-6
Common dandelion height (cm)" 15 15
Common dandelion diameter (cm)° 30 35
Common dandelion density (plants m’")8 6 3

 

3 measurements taken at the postemergence application timing.

62

Table 2. Control of treated common dandelion 21 DAT and 56 DAT with postemergence
com herbicides and corn yields.

 

 

 

 

 

Controlg Yield
Herbicide treatmentab Rate 28 DAT 56 DAT 2002
9 ae ha'f % kg ha'1
Untreated control 0 0 2913
2,4-D amine 561 28 39 6920
2,4-D ester 561 28 31 7114
clopyralid 91 34 51 7467
dicamba+NlS+UAN 281 35 43 7708
halosulfuron+NlS+UAN° 35 30 26 6942
nicosulfuron+COC 35 32 55 7720
primisulfuron+COC 40 36 37 7684
carfentrazone+N IS 9 9 1 3 5284
flumiclorac+COCd 30 1 1 12 3809
bromoxynil 421 20 26 5785
atrazine+COC° 244 23 31 6300
bentazon 1 121 1 5 1 7 6940
mesotrione+COC+UAN 105 77 54 9313
mesotrione+atrazine+COC+UAN 105+281 76 57 1 061 3
glufosinate+AMS 351 76 63 1 0524
glufosinate+atrazine + AMS 351 +1 122 80 57 10310
atrazine+2,4-D ester 628+280 28 32 6029
atrazine+dicamba 1 121 +560 41 70 9171
primisulfuron+dicamba+N |S+UAN 26+126 39 58 8362
dicamba+diflufenzopyr+NIS+UANf 213+106 49 83 9133
clopyral id +flumetsulam+NlS+UAN 101 +34 32 43 6823
rimsulfuron+thifensulfuron+COC+UAN 12+6 34 1 9 8421
LSD(0.05) 7 17 1804

 

3 Abbreviations; AMS, ammonium sulfate; NlS, non-ionic surfactant; UAN, urea-ammonia
nitrate; COC, crop oil concentrate.

b Unless otherwise noted, adjuvants rates were; NIS at 0.25% (v/v); UAN at 2.5% (v/v); COC at
1% (v/v); AMS at 1.8% (w/v).

° UAN applied at 5% (v/v).

d coc applied at 0.6% (v/v).

°COC applied at 1.2 % (v/v).

fUAN applied at 1.25% (WV).

9 Data combined from 2002 and 2003.

63

APPENDIX

64

Appendix A1. Protocol for DNA extraction from common dandelion fresh leaf
fissue.

Cell Lysis

1.

2.
3.

Add 30 mg fresh leaf tissue (4 leaf disks) to a 1.5 ml microfuge tube. Grind
tissue to a fine powder with liquid nitrogen.

Add 300 pl Cell Lysis Solution + PVP. Vortex to wet the tissue.

Incubate cell lysate at 65 C for 60 minutes. After 30 and 60 minutes invert
tubes 10 times.

RNase Treatment

1.
2.

Add 1.5 pl RNase A Solution to the cell lysate.
Mix the sample by inverting the tubes 25 times and incubate at 37 C for 15-60
minutes.

Protein Precipitation

1.
2.
3.

Cool sample to room temperature.

Add 100 pl Protein Precipitation Solution to the cell lysate.

Mix the Protein Precipitation Solution uniformly with the cell lysate by
vortexing each tube at high speed for 20 seconds. Place sample on ice for
15-60 minutes.

Centrifuge at 16,000 x g for 3 minutes (14,000 rpm on EPPENDORF 5415C).
The proteins should form a tight, green pellet. If the pellet is not tight, incubate
on ice for 5 minutes and repeat Step 4.

DNA Precipitation

1.

99°!”

Pour the supernatant containing the DNA (leaving behind the precipitated
protein pellet) into a clean 1.5 ml microfuge tube containing 300 pl 100%
lsopropanol (2- -p.roponal)

Mix the sample by inverting gently 50 times.

Centrifuge at 16,000 x g for 1 minute. The DNA will be visible as a pellet that
ranges in color from off-white to light green.

Pour off supernatant and drain tube briefly on clean absorbent paper. Add
300 pl 70% Ethanol and invert tube several times to wash the DNA pellet.
Centrifuge at 16,000 x g for 1 minute. Carefully pour off the ethanol. Pellet
may be loose so pour slowly and watch pellet.

Invert and drain the tube on clean absorbent paper and allow to air dry for 10-
15 minutes.

DNA Hydration

1.
2.

Add 50 pl DNA Hydration Solution.
Rehydrate DNA by incubating sample for 1 hour at 65 C or overnight at room
temperature.

65

Appendix A1. (cont’d) Protocol for DNA extraction from common dandelion fresh
leaffissue.

Purifying Protein-Contaminated Samples

1.
2.

3.

Add 250 pl Cell Lysate Solution. Pipet up and down to mix. Be sure that the
sample in completely dissolved.

Add 100 pl Protein Precipitation Solution and vortex vigorously at high speed
for 20 seconds. Place sample on ice for 5 minutes.

Centrifuge at 16,000 x g for 3 minutes to pellet the protein. Repeat if
necessary.

Pour the supernatant containing the DNA (leaving behind the precipitated
protein pellet) into a clean 1.5 ml microfuge tube containing 300 pl 100%
lsopropanol.

Centrifuge at 16,000 x g for 1 minute to pellet the DNA. The DNA will be
visible as a small white pellet.

Pour off supernatant. Add 300 pl 70% Ethanol and invert tube several times
to wash the DNA pellet.

Centrifuge at 16,000 x g for 1 minute. Carefully pour off the ethanol.

Invert and drain the tube on clean absorbent paper and allow to air dry for 10-
15 minutes.

. Add 100uI DNA Hydration Solution. Allow DNA to hydrate at 65 C for 1 hour.

 

Note: Protocol modified from GENTRA Systems for isolating DNA from common
dandelion.

Cell Lysis Solution + PVP, 10 ml

1.

2.

3.

Add 200 mg (0.2 g) Polyvinylpyrrolidone (Sigma PVP-40) to 10 ml Cell Lysis
Solution (final concentration 20 mg/ml).

Incubate at 65°C for 5-10 minutes inverting occasionally until the PVP is
dissolved.

Cool Cell Lysis Solution + PVP to room temperature before using.

Store at room temperature.

66

Appendix A2. Reproductive characteristics for common dandelion at East
Lansing and Chatham field nurseries in 2003.

 

 

 

 

 

Number of flowers Total seeds produced
Collection East Lansing Chatham East Lansing Chatham
— no. per plant — no. per plant

Alger Co. MI 62 10 16920 2015
Berrien Co. MI 56 7 12888 1534
Calhoun Co. MI 118 8 27245 1718
Hillsdale Co. MI 37 6 8649 1088
lngham Co. MI 32 6 8342 1256
lonia Co. MI 64 8 13036 1192
losco Co. MI 28 5 7646 700
Leelanau Co. MI 66 12 14598 2381
Monroe Co. MI 33 9 6148 1408
Newaygo Co. MI 136 6 21147 895
Oceana Co. Mla ‘ 5 ' 925
Shiawassee Co. MI 52 15 9474 2328
Luce Co. MI 86 9 15731 1307
Yolo Co. CO 43 13 7797 1674
Adams Co. CO 29 6 8499 1057
Tolland Co. CT 69 8 16939 1659
Champaign Co. IL 59 12 9423 1991
Riley Co. KS 26 7 5029 1604
Hall Co. NE 28 9 4893 1244
Baker Co. OR 57 12 17049 2572
Elk Co. PA 71 10 12254 1982
Cache Co. UT 37 11 9326 2324
Brazos Co. TX 46 8 7609 1333
Germany 96 16 13333 1703
LSD(0.05) 48 5 10524 880
CV. 50 35 54 40

 

a Oceana County collection dropped from East Lansing nursery due to winter mortality

67

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