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Project Report No. 383
February 2006
Price: £4.50
Improving the deposition and coverage of fungicides on ears to
control Fusarium ear blight and reduce mycotoxin
contamination of grain
by
C S Parkin
1
, P C H Miller
1
, E S Powell
2
, J H Orson
2
, J Gill
2
N Magan
3
, and D Aldred
3
1
Silsoe Research Institute, Wrest Park, Silsoe, Bedfordshire, MK45 5HS
2
The Arable Group, Wymondham, Norfolk, NR18 9DB, UK
3
Cranfield University, Silsoe, Bedford, MK45 4DT, UK
This is the final report of a thirty-six month project that commenced in October 2002. The work
was funded by a contract for £166,168 from the Home-Grown Cereals Authority (Project No.
2743).
The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted
the research or written this report. While the authors have worked on the best information available to them,
neither HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered
directly or indirectly in relation to the report or the research on which it is based.
Reference herein to trade names and proprietary products without stating that they are protected does not
imply that they may be regarded as unprotected and thus free for general use. No endorsement of named
products is intended nor is it any criticism implied of other alternative, but unnamed, products.
CONTENTS
Page No.
ABSTRACT......................................................................................................................................... 1
SUMMARY.........................................................................................................................................2
1 INTRODUCTION .......................................................................................................................4
2 METHODS & MATERIALS ...................................................................................................... 7
2.1 Selection of test nozzles.......................................................................................................7
2.2 Spray deposit analysis..........................................................................................................7
2.3 Fungicide selection ..............................................................................................................8
2.4 Crop establishment, inoculation and spraying ..................................................................... 8
2.5 Mycotoxin extraction and analysis ....................................................................................10
2.6 Wind tunnel experiments 2003 ..........................................................................................11
2.7 Field trial 2003................................................................................................................... 12
2.8 Wind tunnel measurements 2004....................................................................................... 13
2.9 Field experiments 2004......................................................................................................14
2.10 Field experiments 2005......................................................................................................15
3 RESULTS .................................................................................................................................. 17
3.1 Wind tunnel experiment 2003............................................................................................ 17
3.2 Field experiment 2003 .......................................................................................................18
3.3 Wind tunnel experiment 2004............................................................................................ 22
3.4 Field experiment 2004 .......................................................................................................22
3.5 Field experiment 2005 .......................................................................................................23
3.6 Drop spectra measurements ...............................................................................................25
4 DISCUSSION ............................................................................................................................ 27
4.1 Results................................................................................................................................27
4.2 Implication for levy payers ................................................................................................31
4.3 Opportunities for further research...................................................................................... 31
5 CONCLUSIONS & RECOMMENDATIONS..........................................................................33
6 ACKNOWLEDGEMENTS....................................................................................................... 34
7 REFERENCES...........................................................................................................................35
1
ABSTRACT
Fusarium ear blight (FEB) infections in wheat can significantly reduce grain yield and produce mycotoxins
that are potentially harmful when consumed. Limits on the levels of mycotoxins found in grain are being
introduced. Fungicidal sprays need to not only control FEB but also reduce mycotoxin levels.
A three-year study aimed at developing techniques to both control FEB and reduce toxin levels was carried
out. Spray deposition from a range of application techniques was evaluated in the laboratory using a wind
tunnel and. Field experiments were carried out using established and emerging fungicides and commercial
field plots were inoculated with mycotoxin producing Fusarium species. Samples of ears were assessed for
FEB and analysed by HPLC techniques for trichothecene mycotoxins.
Deposition onto sensitive sites such as the spikelets was increased by angling nozzles and selecting an
appropriate spray quality. With some fungicides this could improve disease control. Recently-introduced
fungicides performed better than established fungicides. Application technique had no clear effect on
mycotoxin production.
Despite inoculation with mycotoxin-producing Fusarium sp., levels of disease established in the
experimental plots varied from year to year. Factors such as the naturally occurring Fusarium –
Microdochium complex and its variable response to fungicides appeared to mask any differences due to
changes in fungicide deposit. All grain samples analysed had mycotoxin levels below the forthcoming EU
standard of 1250 µg kg-1 for unprocessed wheat.
More reliable disease control will result from angling nozzles backwards. Medium spray quality or air-
included sprays may provide better control than fine sprays.
2
SUMMARY
A three-year study was carried out to investigate the settings and nozzle designs that increase deposition on
the ear and more specifically deposition onto the sites of FEB infection. The study aimed to identify spray
application techniques suited to UK conditions that could increase deposition onto FEB sensitive sites on the
ear and to select fungicides to provide both effective control of Fusarium sp. and reduced mycotoxin levels.
Because FEB control and its subsequent effect on mycotoxin levels is complex, only certain parameters were
considered in this research. Issues such as formulation chemistry, spray timing and volume application rate
were not considered. Particular attention was paid to the mycotoxins deoxynivalenol (DON) and nivaelenol
(NIV). A standardised volume rate of 150 l/ha was used throughout because it is representative of current
UK practice.
A series of wind tunnel experiments using a tray-grown crop were carried out in 2003 and 2004. These
experiments were used to explore the effect of different nozzle designs and configurations on spray
deposition to the ear. Deposition was measured by tracing dyes, fluorescent pigments and active ingredient.
The emphasis was on using angled nozzles and those that provided a range of spray qualities. Nozzles used
in tests during the project included conventional and air-induction flat-fan nozzles orientated vertically and
45° forwards and backwards. Conventional and air-induction hollow-cone nozzles were also used. An air
induction flat-fan nozzle angled at 10° (Amistar Az) was also tested.
Field experiments were carried out in 2003, 2004 and 2005 using different fungicides and application
systems selected using the results from the wind tunnel experiments. Treatments were applied to a crop of
winter wheat at mid-anthesis using a factorial design. All spray treatments were applied with adjustments to
speed and nozzle arrangements on the boom made when necessary to accommodate nozzle characteristics.
To help ensure the presence of ear diseases, the site was inoculated with known DON-producing Fusarium
sp. before fungicide application. Establishment of the fungi was encouraged by regular misting following
inoculation prior to fungicide application. Spray deposits on ears were measured in 2003 and 2004. FEB
control, mycotoxin production and yield were monitored throughout.
In 2003, field and wind tunnel data suggested a trend for a higher deposit on the back of the ear compared to
the front for all treatments, with deposits slightly higher on the front or the back of the ear from the Amistar
nozzle. This application system tended to give the highest yields in the field experiment for the three
fungicide treatments evaluated. Wind tunnel experiments using the fungicide tebuconazole as a tracer carried
out in 2004 showed good penetration of fungicide onto the rachis with the air-included hollow-cone and the
angled conventional nozzle showing the highest deposits. Similar measurements with samples from the field
experiment showed lower levels of tebuconazole penetrating the rachis. This could be due to differences
3
between the varieties or crop densities used in the field and the wind tunnel or to environmental conditions. It
was not possible to discern significant differences in tebuconazole deposition in the field caused by varying
application method, although the angled air-included spray had the highest deposit levels.
High levels of NIV were detected in 2003 and were thought to be due to the presence of F. poae affecting
individual plots for some treatments. In 2005, the results were similarly affected despite the increased
misting in that year and the more humid ambient conditions. However, lower temperatures and humidity
were encountered in 2004 and this appears to have reduced the levels of FEB infection and as a result
detectable levels of DON were not found. Detectable levels of DON were found in 2005 but with so few
samples showing contamination there was no clear relationship between application method and DON levels.
All samples were below 1250 µg kg-1.
Although fungicide deposits on ears can be manipulated by nozzle design and orientation, and under certain
circumstances deposit levels can be linked to disease control, the influence of application system on
mycotoxin production is far from clear. Factors such as the level of natural disease pressure, the Fusarium
sp. complex and its reaction to fungicides and crop meteorology appear to strongly influence mycotoxin
production even when experiments are carried out with irrigated crops inoculated by known DON-producing
strains.
Of the fungicide treatments evaluated in 2003, the full dose of Prosaro resulted in the lowest infection of
FEB and highest resulting grain yield. This was irrespective of application system used suggesting that for
this dose of fungicide, application system was less important. The Amistar + Folicur treatment appeared to
be more dependent on application system and, in particular, the Amistar nozzle tended to result in lower
infection of FEB and higher grain yield for this fungicide treatment.
The work has shown that more reliable disease control will result from angling nozzles backwards, and that
medium or air-included sprays may provide better control than fine sprays.
4
1 INTRODUCTION
In the UK Fusarium ear blight (FEB) on wheat is predominantly caused by F. culmorum but in some cases
by complexes of F. poae, F. avenaceum and F. graminearum and one Microdochium species M. nivale vars.
nivale and majus (formerly Fusarium nivale). Fusarium infection is of concern owing to the reduction in
crop yield that can result, with the extent of the loss being related to the species involved and the humidity
around the ear which affects the intensity of infection. Infection can also produce mycotoxins in grain that
are potentially harmful to humans and animals when consumed. In particular, F. culmorum is important as it
readily produces the mycotoxins deoxynivalenol (DON) and nivalenol (NIV) on ripening ears of cereals.
Because of concerns for human health, the EU has set maximum limits for mycotoxins found in cereal
products intended for human consumption. These limits will come into force in July 2006. For DON the limit
is 1250 µg kg-1 for unprocessed wheat.
The link between FEB control and mycotoxin levels is not simple. With naturally occurring infections, Ioos
et al. (2005) reported that treatments with tebuconazole, metconazole and azoxystrobin produced samples
that had high levels of the known DON and NIV producing F. graminearum and F. culmorum with low
mycotoxin levels and highly contaminated samples that were only lightly infected by those species. They
concluded that this was likely to be due to the several biotypes of Fusarium sp. reacting differently to
different fungicides. Inoculated field trials have also shown that the different members of the FEB complex
react differently to different fungicides. In a review of Fusarium mycotoxins Magan et al. (2002) reported
that field studies with tebuconazole and metconazole showed good control of FEB and reduced production of
DON, but azoxystrobin and related fungicides sometimes increased DON production. There is evidence to
suggest that because azoxystrobin controls Microdochium nivale, which does not produce mycotoxins, more
sites are available for the growth of Fusarium species that can produce mycotoxins. Also, low doses of
fungicide and environmental factors such as water stress are implicated in increased DON production.
It is clear that to suppress FEB using fungicides, sprays should be targeted onto the site of infection on the
ear. It is well known that angling spray nozzles can increase spray deposition onto cereal crops (Bryant et al.
(1984); Miller et al. (2002); Wolf et al. (2002)). What is not known are the settings and nozzle designs that
specifically increase deposition on the ear and more specifically deposition onto the sites of FEB infection.
Work by ARVALIS (Debroize, 2002) demonstrated increased control of FEB using two sets of fine spray
quality nozzles, one pointing forward, one back. However, recent work in Canada (Pilsner, 2000)
contradicted these findings with a single coarser spray providing better control.
In 2003 this three-year study was initiated to investigate the settings and nozzle designs that increase
deposition on the ear and more specifically deposition onto the sites of FEB infection. The project
5
consortium included Silsoe Research Institute, The Arable Group and Cranfield University, Silsoe. The study
aimed to identify spray application techniques suited to UK conditions that could increase deposition onto
FEB sensitive sites on the ear and to select fungicides that will provide both effective control of Fusarium sp.
and reduce mycotoxin levels.
Because FEB control and its subsequent effect on mycotoxin levels is complex, only certain parameters were
considered in this research. The interaction of the main parameters involved in FEB control and mycotoxin
production are shown in diagrammatic form in Fig. 1. Issues such as formulation chemistry, spray timing and
volume application rate were not considered. A standardised volume rate of 150 l/ha was used throughout
because it represents current UK practice.
Fig. 1. Interactions between the inputs and outputs involved in the control of FEB and
mycotoxins on wheat; shaded boxes indicate parameters under investigation in
this project.
The project objectives were:
1. To examine the total spray deposits on wheat ears achieved with a range of different application systems
so as to identify those systems that give relatively high total deposit on crop ears.
2. For systems that give a high level of deposit on crop ears, examine the distribution of this deposit so as to
identify those systems giving a higher level of uniformity of deposit particularly in the front/back
directions with reference to the direction of travel and the level of penetration of spray into the ear.
FEB Control
Infection
Fungicide
Dose
Ear Coverage
Timing DON
N
IV
N
ozzle design
Spray volume
N
ozzle orientation
Formulation
6
3. To conduct a series of plot trials over two cropping seasons with at least three different nozzle systems
identified from initial experimental work (to include a conventional reference system) and three different
fungicide mixtures in which the level of fusarium control was to be assessed. Assessments of spray
deposits would be made and plots taken through to yield.
4. To identify combinations of application method and fungicide mixture to maximise the control of
Fusarium sp., mycotoxins (as measured by DON and NIV).
5. To validate the performance of the recommended system in a series of field trials.
Some aspects of this work have been published (Powell et al., 2004; Parkin et al., 2006).
7
2 METHODS & MATERIALS
2.1 Selection of test nozzles
Nozzles were selected on the basis that they were likely to provide a range of sprays that could be
differentiated by measurement of deposit pattern, and/or biological effect. Some nozzles had a history of use
for fungicide ear washes, (e.g. Amistar Az nozzle) and others characterised a particular form of spray (e.g.
air-induction). Because deposition of spray onto ears is strongly effected by the angle of projection (Bryant
et al. 1984), the selection of nozzles included those mounted in twin-cap holders at 45° and designs such as
the Amistar AZ nozzle and hollow-cone nozzles where angled spray projection built-in to the nozzle design.
It was a requirement that the nozzles selected could be readily available to growers and used on current
sprayers without major modifications. The decision on each year’s test selection was based on the prior
experience gained from the previous year’s research and information on spray deposition available from
published and private sources. The nozzles chosen each year are presented in Sections 2.6 to 2.10.
To provide benchmark data on the performance of the nozzles selected, the drop spectra of the nozzles
selected were measured using a Malvern SprayTec laser drop size analyser. The SprayTec is capable of
measuring sprays with air-inclusions (Kippax et al., 2002) and is therefore suitable for evaluating air-
induction nozzles. The tests were carried out in the Silsoe Research Institute nozzle laboratory using standard
protocols. Measurements were made using a standard liquid (0.1% aqueous solution of Agral non-ionic
surfactant) and an x-y transporter to ensure adequate sampling of the complete spray pattern.
2.2 Spray deposit analysis
A key aspect of the project was the assessment of spray deposition onto ears or parts of ears. Spray
deposition was assessed using a variety of techniques; the technique chosen being based on its ability to
provide the level of resolution required. In this section we review the methods adopted. Further details of the
methods adopted are provided in the sections describing individual experiments.
Spray volume collected onto whole ears was assessed using a dye tracer technique. This is a technique that
has been used for some time by Silsoe Research Institute to establish spray deposition on natural surfaces.
The dye used, Green S (Merck Chemicals) is an approved food dye. It is easily recovered from biological
material and when used on cereals it does not suffer from background interference. Although the technique
has the advantage of providing a simple and relatively rapid method of assessment, it has the disadvantage of
not behaving as a fungicide particularly after the spray has impacted onto the ear. As a result it cannot be
used reliably to determine partitioning of the spray within the ear.
8
Although the front and rear spikelets were assessed separately using the dye tracer technique, most
measurements of spray partitioning within the ear utilised HPLC. Tebuconazole, a constituent of many
fungicide ear sprays, was used as the tracer with extraction made using a mixture of solvents. Using this
technique it was possible to determine the total volume deposited on the ear and the quantity deposited on
the rachis and spikelets. The technique was not rapid but it was able to provide more detail than the dye
tracer technique and it had the added advantage of using a commercially important fungicide.
Fluorescent pigment tracers were utilised as visual assessment technique in wind tunnel tests. This technique
provided images of spray deposits and assisted with the interpretation of analytical data from other
techniques. The technique was not used as a primary assessment tool.
2.3 Fungicide selection
The selection of fungicides was based on the requirement to include both existing and emerging products. In
2003 and 2004 field experiments included the then standard treatment of Amistar (azoxystrobin) and Folicur
(tebuconazole). In 2003 it was clear that several potentially important products were in development and that
they were likely to reach the market before the completion of the project. To ensure the results of this project
remained relevant following completion of this work, these compounds were incorporated into the field
experiment programme. It should be emphasised that this project did not aim to field test fungicides and the
results should not be taken as being indicative of the performance of individual fungicides.
2.4 Crop establishment, inoculation and spraying
It was necessary to grow wheat plants that could be used to assemble an artificial crop in the wind tunnel and
establish a commercial crop suitable for field experiments. For the wind tunnel experiments wheat (cv.
Claire) was grown outdoors in trays at Silsoe Research Institute within a commercial crop of wheat. The
trays then received the standard treatments applied to the commercial crop. However, because their roots
were restricted by the trays their head count was lower than a commercial crop (200 – 250 per m2) and they
required added irrigation to maintain vigour. Nevertheless, with careful selection the trays could be arranged
to provide a realistic spray target. An example of the tray grown crop is shown in Fig. 2.
9
Fig. 2. Tray grown wheat crop and spray transporter in Silsoe wind tunnel
For field experiments crops of winter wheat (cv. Napier) were grown at The Arable Group, Morley, Norfolk.
They were established using conventional approaches and treated with epoxiconazole plus chlorothalonil
(0.3 l Opus + 1.0 l/ha Bravo) at the second node detectable stage and trifloxystrobin plus epoxiconazole (0.8
l Twist + 0.4 l/ha Opus) at full flag leaf emergence. Plot size was 6 m wide x 24 m long to ensure that
reliable yields were obtained from the centre of the plot.
To help ensure the presence of ear diseases, the site was inoculated with Fusarium culmorum prior to the
experimental fungicide applications using inoculum produced by Cranfield University and applied by
sprayer in 2003 and 2004. In 2005 a mixture of F. culmorum and F. graminearum were used. The former
species is a well characterised DON and NIV producer (Hope et al., 2003)
and the latter was a know DON producer kindly provided by Dr. P. Jennings (CSL, York, U.K.). The spore
inoculum was grown on sterile moist wheat grain at 25°C for approx. 3 weeks prior to suspensions being
prepared and checked with a particle counter. The final concentration of spores used was 105 spores ml-1 of
F. culmorum in 2004 and 2005, and a mixture of 104 and 104 spores ml-1 of F. culmorum and F.
graminearum respectively. After application the control plots were analysed and the initial level of
contamination of the ears at anthesis was about 103 spores gram-1. This was analysed by homogenising 10 g
sub-samples in 90 ml of sterile water in a Colworth stomacher for 10 min. and serially diluting on malt
extract agar. The establishment of the fungi was encouraged by regular ‘misting’ using hollow cone nozzles
applying 800 l/ha water, each evening, for three days following inoculation prior to fungicide application.
Fig. 2 shows a typical misting application.
10
Fig. 3. Misting a wheat crop to promote Fusarium Ear Blight
The experimental fungicide treatments were applied at mid-anthesis and the experiments comprised a
factorial design. All field treatments were applied using a commercial scale farm sprayer (Fig. 3).
Fig. 4. Farm-scale application to experimental plots at Morley, Norfolk
2.5 Mycotoxin extraction and analysis
Analysis of DON and NIV was carried out using a modified method of that reported in Cooney et al. (2001).
Each sample was finely ground and mixed well. The samples were extracted by mixing with acetonitrile +
methanol (14:1; 40 ml), shaking for 2 hours and then filtering through Whatman No 1 filter paper. For
mycotoxin analysis a 2 ml aliquot was passed through a cleanup cartridge consisting of a 2 ml syringe
packed with a disc of Whatman No 1 filter paper, a 5 ml plug of glass wool and 300 mg of alumina/activated
carbon (20:1, 500 mg). The sample was allowed to gravity feed through the cartridge and the eluent
collected. The column was washed with a mixture of acetonitrile + methanol + water (80:5:15; 500 µl ), and
the combined eluate was evaporated with compressed air, at 50°C, to dryness and then re-suspended in
methanol + water (5:95; 500 µl ).
11
Quantification of DON and NIV was accomplished via HPLC, using a Luna C18 reverse phase column (100
mm x 4.6 mm, 5 mm particle size; Phenomenex) connected to a 4 x 3 mm guard column filled with the same
mobile phase. Separation was achieved using an isocratic mobile phase of methanol + water (12:88, v/v) at
1.5 ml min-1. Eluates (50 µl) were detected using a UV detector set at 220 nm with an attenuation of 0.01
AUFS. The retention time for DON was 13.3 minutes. Quantification was relative to external standards of 1
to 4 µg ml-1 in methanol + water (5:95) and the quantification limit was 5ng g-1. This method has been
described by Ramirez et al. (2004). Two replicates of all treatments were also subjected to full trichothecene
analysis using GC-MS in 2003 and 2004. In both years only DON and NIV were detected in the harvested
grain samples.
The relative amount of ear blight present in treatments was recorded about two weeks after fungicide
application and samples taken for mycotoxin analyses. The harvested grain samples were also examined for
the level of visible contamination with pink grains and contamination checked by plating on malt extract
agar and determining levels of Fusarium contamination. In 2003 and 2004 Taqman PCR was also employed
to examine the relative amounts of DNA of Fusarium species in the final grain samples using a method
developed by Waalwijk (2002).
2.6 Wind tunnel experiments 2003
An initial set of measurements assessing total ear deposits and deposits to the front and back of the ear was
carried out with nine different application systems (Table 1). The front of the ear was considered to be the
side that the spray liquid made contact with first when the spray boom was travelling forward.
12
Table 1. Details of application systems evaluated in 2003 wind tunnel experiments
Nozzle Description Spray
quality
Volume
Lurmark F110-03 Conventional flat fan nozzle Medium 150 l/ha
Amistar 10o angled back air induction
nozzle1 - 150 l/ha
2 x Lurmark F110-015
2 conventional flat fan nozzles
angled at 45o, one forward & one
back
Fine 150 l/ha
Delevan WRW2 Wide angle hollow cone nozzle Coarse 150 l/ha
Lurmark F110-015 Conventional flat fan nozzle angled
45o back Fine 150 l/ha
Lurmark F110-04 Conventional flat fan nozzle angled
45o back Medium 150 l/ha
D5-23 Hollow cone nozzle Fine 150 l/ha
Lurmark F110-04LD Pre-orifice flat fan nozzle Coarse 150 l/ha
Amistar 10o angled back air-induction
nozzle - 100l/ha
The tray grown crop was arranged in the tunnel to simulate a realistic canopy with guard trays surrounding
the tray to be treated. To determine deposition on the ear a spray liquid comprising 0.4% Green S tracer dye
and 0.1% Agral (surfactant) was used. For each treatment 10 ears were sampled, seven for whole ear
analysis and three to determine the amounts deposited on the front and back facing surfaces of the ears. The
concentration of recovered dye was measured using spectrophotometry. Visual assessments of deposit
patterns were carried out on four of the application systems that were selected for assessment in the field
(Table 2). The spray liquid for these experiments was a 2% suspension of Saturn Yellow fluorescent
pigment with 0.1% Agral.
2.7 Field trial 2003
A field experiment was established evaluating a range of fungicides and application systems. One of the
fungicide treatments evaluated was a development fungicide which was not yet commercially available and
was included in the project as a code only and evaluated at two doses. The application systems were selected
following visual assessments of deposit patterns from the initial wind tunnel experiments and selection was
such that the application systems were examples of current commercial practice or were likely to give a
range of spray deposition. Details of the fungicides, doses and application systems used are shown in Table
1 To date there is no agreed classification for air-induction sprays. A measure of spray quality can be estimated from
drop size (see Table 6) but this ignores differences in amount of air included.
13
2. All spray treatments were applied at a spray volume of 150 l/ha with adjustments to speed and nozzle
arrangements on the boom made when necessary to accommodate nozzle characteristics.
Table 2. Application systems and fungicides evaluated in the 2003 field experiment
Nozzles Fungicides
Lurmark/Hypro
flat-fan F110-03
0.3 l ha 1 Amistar (azoxystrobin 250 g l-1)
0.3 l ha-1 Folicur (tebuconazole 250 g l-1)
Amistar Az
angled air-induction nozzle
0.75 l ha-1 Prosaro2
(125 g l-1 prothioconazole; 125 g l-1 tebuconazole)
Lurmark/Hypro
F110-04 flat-fan angled nozzle
1.5 l ha-1 Prosaro
(125 g l-1 prothioconazole; 125 g l-1 tebuconazole)
Lurmark/Hypro
Hollow-cone D5-23
One hundred ears per plot were collected two weeks after spraying for visual assessment of FEB and analysis
of DON and NIV. Assessment of FEB was carried out on 10 randomly selected ears from the 100 ear
sample. For each sub sample, the area affected by FEB was assessed and expressed as a percentage of the
total area. Plots were harvested by replicate using a plot combine which used electronic weighing, moisture
and specific weight determination (Harvest Master HM-400 with Grain Gauge).
For each application system evaluated in the field trial a single plot was also treated with a Green S tracer
dye. These plots were located alongside the field trial. Total deposition on whole ears was measured using a
similar technique to the wind tunnel experiments.
2.8 Wind tunnel measurements 2004
A second series of experiments was conducted in the wind tunnel at Silsoe Research Institute laboratory in
2004 using a winter wheat crop (cultivar Claire) grown outdoors in trays. Measurements investigating
deposition onto spikelets and rachis were made using the fungicide tebuconazole (as Folicur applied at 1.0 l
ha-1) and HPLC. Each treatment was replicated three times and five ears were selected from each replicate.
Tebuconazole was recovered from the spikelets and rachis of each ear. Because the work carried out in 2003
had indicated that the form and location of the spray deposit on the ear may be important, angled spray
treatments with varying spray quality were tested. Details of the application techniques are given in Table 3.
2 When this product was applied it had not yet received approval and was not named. When reported (Powell et al.,
2004) it was coded as HGCA 1.
14
Table 3. Details of application systems evaluated in 2004 wind tunnel experiment
Application Nozzles Manufacturer Spray
quality
Volume
Conventional vertical flat-fan
nozzle 03F110VB Lurmark
Hypro medium 150 l ha-1
Flat-fan nozzle angled 45o
back 03F110VB Lurmark
Hypro medium 150 l ha-1
Flat-fan nozzles 45o twin cap 015F110VB Lurmark
Hypro fine 150 l ha-1
Flat-fan nozzles 45o twin cap 03F110VB Lurmark
Hypro medium 300 l ha-1
Air-induction nozzle 45o
back PJ-03 Sprays
International air-included 150 l ha-1
Hollow-cone air-induction
nozzle 80-025 HC Bfs/ Agrotop air-included 150 l ha-1
2.9 Field experiments 2004
In 2004 a field experiment was established at The Arable Group, Morley, Norfolk evaluating the application
systems selected following the wind tunnel and field experiments in 2003 and using different fungicides.
Application systems were selected to test the hypothesis that coarse spray directed to the ears would give
improved results3. This was based on the work carried out in 2003 and the work of Wolf et al. (2002).
Treatments were applied to a crop of winter wheat (cultivar Napier) at mid-anthesis and the trial comprised a
factorial design. Details of the fungicides, application systems used are shown in Table 4. All spray
treatments were applied at a volume rate of 150 l ha-1 using farm-scale sprayers to 6 m wide by 24 m long
plots. Adjustments were made to speed and nozzle arrangements to accommodate nozzle characteristics.
Two fungicidal treatments were used, azoxystrobin plus tebuconazole applied as Amistar (Syngenta) at 0.3 l
ha-1 plus Folicur (Bayer CropScience) at 0.3 l ha-1 and fluoxastrobin plus prothioconazole applied at 0.7 l
ha-1. This was known as the coded product Bayer (UK 187) but it is now sold as Fandango (Bayer
CropScience). The crop was established using conventional approaches and inoculated with a mixture of
Fusarium culmorum and F. graminearum five days before fungicide application. In 2003 the inoculum had
consisted solely of F. culmorum. The Fusarium mixture was adopted because it was considered to be more
representative of the infections currently found in Southern England.
As in 2003 the establishment of the fungi was encouraged by regular misting. The experimental plots were
monitored, sampled for yield and analysed for mycotoxins using the methods reported by Powell et al.
3 The air-included hollow-cone nozzle was not available for use in the field in 2004.
15
(2004).To determine deposition onto ears four samples, each of 10 ears, were taken from the plots where
tebuconazole was applied and subjected to a similar analysis to the wind tunnel samples.
Table 4. Details of application systems evaluated in 2004 field experiment
Description Nozzles Manufacturer Spray
quality
Spray
direction
Conventional flat-fan nozzle 03F110 Lurmark
Hypro medium vertical
Flat-fan nozzle 45o back 03F110 Lurmark
Hypro medium back
Flat-fan nozzles 45o twin cap 015F110 Lurmark
Hypro fine fore & back
Air-induction nozzle 10° back Amistar Syngenta air-
included back
Air-induction nozzle vertical PJ-03 Sprays
International
air-
included vertical
Air-induction nozzle 45o back PJ-03 Sprays
International
air-
included back
Hollow-cone nozzle D5-23 Lurmark
Hypro fine multi
2.10 Field experiments 2005
In 2005 a further field experiment using the same methodology was carried out using the applications set out
in Table 5. Because the emphasis for the experiments was to investigate application effects, a single
fungicide was selected. The fungicide chosen was prothioconazole/ tebuconazole applied at 1.5 and 0.7 l ha-1
as Prosaro (Bayer CropScience).
The crop was established using similar methods as in 2004 and inoculated with a mixture of Fusarium
culmorum and F. graminearum. The establishment of the fungi was again encouraged by misting but with an
increased frequency of application to maximise infection. The methods reported by Powell et al. (2004) were
used to assess FEB, yield and mycotoxin content.
16
Table 5. Details of application systems evaluated in 2005 field experiment
Description Nozzles Manufacturer Spray
quality
Spray
direction
Conventional flat-fan nozzle 03F110 Lurmark
Hypro medium vertical
Flat-fan nozzle 45o back 03F110 Lurmark
Hypro medium back
Flat-fan nozzles 45o twin cap 015F110 Lurmark
Hypro fine fore &
back
Air-induction nozzle vertical AI11003 Tee Jet air-
included vertical
Air induction nozzle 45o back AI11003 Tee Jet air-
included back
Hollow-cone nozzle D5-23 Lurmark Hypro fine multi
Flat-fan nozzles - two booms 015F110 Lurmark
Hypro fine fine
Hollow-cone air-induction 80-025HL Bfs/ Agrotop air-
included multi
17
3 RESULTS
3.1 Wind tunnel experiment 2003
The total ear deposits from each of the application systems evaluated are illustrated in Figure 5. The
differences in deposit between application systems were relatively small although there was a suggestion that
the highest deposits were achieved using the wide angle hollow-cone nozzle (WRW2) and the F110-015 and
F110-04 nozzles angled backwards. Many of the application systems resulted in a similar distribution of
deposit on the front and the back of the ear (Fig. 6) apart from the two F110-015 nozzles angled forward and
backwards and the single F110-015 nozzle angled backwards which resulted in higher deposits on the front
of the ear.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
F110-03*
Amistar*
2 x F110-015
WRW2
F110-015 back
F110-04 back*
D5-23*
F110-04LD
Amistar 100 l/ha
Application Method (150 l/ha unless stated)
Dye deposit on ears (µl/g)
Figure 5. Mean total deposits on wheat ears (µl g-1) from all application systems in the
wind tunnel experiments (* = application systems further evaluated in the
field trial)
18
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
F110-03*
Amistar*
2 x F110-015
WRW2
F110-015 back
F110-04 back*
D5-23*
F110-04LD
Amistar 100 l/ha
Application Method (150 l/ha unless stated)
Deposit on ear (µl/g)
Front
Back
Fig. 6. Mean deposit distribution on the front and back of wheat ears (µl g-1) from all
application systems in the wind tunnel experiments (* = application systems
further evaluated in the field trial)
3.2 Field experiment 2003
Fig. 7 shows the grain yield achieved from the range of application systems and fungicides tested. A full
dose of Prosaro (1.5 l ha-1) achieved the highest yield of grain with all of the application systems evaluated
and a clear dose response between the half and full dose of this fungicide was apparent. The grain yield
achieved by Prosaro was higher than the current standard treatment for FEB control, Amistar + Folicur,
particularly at the full dose. There was a trend for the three other application systems to result in higher
grain yield than the conventional flat fan-nozzle with a trend for the Amistar nozzle to give the highest yield
particularly when applying Amistar + Folicur or the full dose of Prosaro.
19
6.0
7.0
8.0
9.0
10.0
11.0
12.0
F110-03 Amistar F110-04 back D5-23 Untreated
Application (150 l/ha)
Grain yield (t/ha at 85% dm)
Amistar + Folicur
0.75 l/ha Prosaro
1.5 l/ha Prosaro
Fig. 7. Grain yield (t/ha at 85% dm) with three fungicide treatments and four
application systems in the field trial
Fig. 8 shows the percentage disease infection of FEB on wheat ears, two weeks after fungicide application. A
full dose of Prosaro significantly reduced the visible infection of FEB on ears with all application systems
compared to the untreated ears. The percentage disease infection was unexpectedly low on the untreated ears
and hence there were no significant differences between the reduced dose of Prosaro or Amistar + Folicur
with any of the application systems when compared to the untreated.
0
2
4
6
8
10
12
14
16
18
F110-03 Amistar F110-04
back
D5-23 Untreated
Application (150 l/ha)
% FEB infection
Amistar + Folicur
0.75 l/ha Prosaro
1.5 l/ha Prosaro
Fig. 8. Percentage infection of FEB on ears two weeks after spraying fungicides (error
bars show SEM)
Figure 9 shows the effect of treatments on relative amounts of biomass of F. culmorum present in the
harvested grain. The highest amount using quantitative PCR was present in the control. The least was present
20
in the nozzle treatments which were most effective and again confirms the effectiveness of the Prosaro
treatment at the higher (recommended) application rate.
0
50
100
150
200
250
300
350
400
450
F110-03 Amistar Az F110-04
back
D5-23 untreated
Application (150 l/ha)
DNA (pg / mg grain)
Amistar+Folicur
0.75 l/ha Prosario
1.5 l/ha Prosario
Fig. 9. The mean concentration biomass of F. culmorum in grain treated with different spray
systems and different fungicides in 2003
Fig. 10 shows DON and NIV levels for wheat ears two weeks after spraying. There was a trend for levels of
NIV to be generally higher than those of DON for most treatments but particularly for the backward angled
F110-04 nozzle and the hollow-cone nozzle applying Amistar + Folicur or 0.75 l ha-1 Prosaro. The levels of
DON observed were generally low for all treatments and unexpectedly there were very low levels (0.15 µg
kg-1) detected on the untreated ears.
0
100
200
300
400
500
600
700
F110-03, Amistar + Folicur
F110-03, 0.75 l/ha Prosaro
F110-03, 1.5 l/ha Prosaro
Amistar, Amistar + Folicur
Amistar, 0.75 l/ha Prosaro
Amistar, 1.5 l/ha Prosaro
F110-04 back, Amistar + Folicur
F110-04 back, 0.75 l/ha Prosaro
F110-04 back 1.5 l/ha Prosaro
D5-23, Amistar + Folicur
D5-23, 0.75 l/ha Prosaro
D5-23, 1.5 l/ha Prosaro
Untreated
Application (150 l/ha)
mycotoxin level (µg/kg)
DON
NIV
Figure 10. DON and NIV levels (µg/kg) on ears two weeks after spraying (error bars
show SEM)
21
The effect of treatments on DON and NIV in 2003 is shown in Figure 11. In both 2003 and 2004 GC-MS
showed that these were the only trichothecenes present. The levels of DON were lower than those for NIV.
Generally, based on these results there was very little effect of nozzle targeting on relative amounts of NIV
present in the harvested grain. There was some effect of the Prosario fungicide at the normal rate of
application with some nozzle treatments but there was no particular trend.
0
20
40
60
80
100
120
140
160
180
F-110-03 Amistar Az F110-04
back
D5-23 Untreated
Application (150 l/ha)
DON (µg/kg grain)
Amistar
0.75 l/ha Prosio
1.5 l/ha Prosario
0
1000
2000
3000
4000
5000
6000
F-110-03 Amistar Az F110-04
back
D5-23 Untreated
Application (150 /ha)
NIV (µg/kg grain)
Amistar
0.75 l/ha Prosio
1.5 l/ha Prosario
Figure 11. Effect of spray treatments and fungicide applications on content of DON and NIV
in harvested wheat grain in 2003; data is mean of GC-MS analyses.
22
3.3 Wind tunnel experiment 2004
The ear deposits of tebuconazole from each of the application systems evaluated in the wind tunnel in 2004
are illustrated in Fig. 12. Although the variability of deposits was high it appeared that significant amounts
of tebuconazole were detected on the rachis indicating that there was penetration into the ear. The data also
suggested that an angled medium quality spray and the air-included hollow-cone spray deposited more
fungicide on the ear.
0
5
10
15
20
25
30
35
F110 03
Vertical
F110 03
Angled
Back
F110 015
Twin Cap
F110 03
Twin Cap
300 l ha-1
AI Nozzle
Angled
Back
AI Hollow
Cone
Treatment
Tebuconazole (µg g
-1
)
Spikelets
Rachis
-1
Fig. 12. Mean total deposits on wheat ears from application systems in the wind tunnel
experiments in 2004 normalised to 150 l ha-1
3.4 Field experiment 2004
Deposits of tebuconazole from the field samples (Fig. 13) were lower than those from the wind tunnel but
this reflected the lower dose used. However, the proportion of chemical penetrating into the rachis was also
lower. Although deposits with each application system were broadly similar, unlike the wind tunnel data the
air-included angled spray produced the highest deposit.
23
0
2
4
6
8
10
12
14
16
18
F110 03 vertical
F110 03 angled back
F110 015 twin cap
Amistar nozzle
AI nozzle vertical
AI nozzle angled back
Hollow cone fine
Untreated
Treatment
Tebuconazle ( µg g
-1
)
Spikelets
Rachis
Fig. 13. Mean total deposits on wheat ears from application systems in the field
experiments in 2004 normalised to 150 l ha-1
Disease assessments following spraying showed that, unlike the 2003 season there was little FEB established
in the crop. Extraction of mycotoxins from ears showed that only NIV was present. With mean values 50-
100 µg kg-1 this was much less than the 400-600 µg kg-1 found in 2003. In harvested grain again only NIV
was present and at a maximum of 36 µg kg-1. Differences in yield could not be detected with any application
method.
3.5 Field experiment 2005
The field treatments in 2005 were scored for ear colour using a 1-5 scale. The results are shown in Fig. 14.
Although few significant differences were observed between treatments, fungicide dose appeared to have an
effect and the angled conventional nozzle (F110-03) at the higher dose rate produced a significantly better
score. Differences in yield could not be detected with either application method or fungicide dose. Samples
taken from the plots were found to be infected by ear blight at similar levels to 2003 (Fig. 13), although the
variability of the infection was greater making if difficult to observe any trends. However, plots where the
fungicide was applied with the angled air-induction nozzle and the air-induction hollow-cone nozzle had low
levels of infection. Despite Fusarium infection being established in the crop; only six of the 51 samples
showed detectable levels of DON. Where DON was present it was in the range 500 – 550 µg kg-1. As a
result, it was not possible to discern any relationship between DON levels and treatment. Levels of NIV were
higher (Fig. 14) but the high variability between replicate samples made it difficult to determine trends.
24
0
1
2
3
4
5
6
7
Conventional Nozzle
Single twin cap back
Twin Cap Fine
AI Back Single Twin
AI Hollow Cone
AI Nozzle vertical
Fine Spray vertical x2
Hollow Cone fine
Treatment
Score
Untreated
0.6 l ha-1
1.2 l ha-1
-1
-1
Fig. 12. Ear colour score for fungicide treatments in 2005; 1 = bright, 5 = dark; error
bar on the untreated plot represents the LSD
0
5
10
15
20
25
30
Conventional Nozzle
Single twin cap back
Twin Cap Fine
AI Back Single Twin
AI Hollow Cone
AI Nozzle vertical
Fine Spray vertical x2
Hollow Cone fine
Treatment
Ear blight (%)
Untreated
0.6 l ha-1
1.2 l ha-1
-1
-1
Fig. 14. Ear blight infection two weeks after fungicide treatments in 2005; error bars
represent the SEM
25
0
50
100
150
200
250
Conventional Nozzle
Single twin cap back
Twin Cap Fine
AI Back Single Twin
AI Hollow Cone
AI Nozzle vertical
Fine Spray vertical x2
Hollow Cone fine
Treatment
NIV (µg kg
-1
)
Untreated
0.6 l ha-1
1.2 l ha-1
-1
-1
Fig. 15. Nivalenol (NIV) levels in grain samples after fungicide treatments in 2005; error
bars represent the SEM
3.6 Drop spectra measurements
The drop spectra of the nozzles selected for use in the project are presented in Table 6. The hollow-cone
WRW nozzle could not be measured using the existing sampling arrangement in the nozzle laboratory
because of inherent sampling problems caused by the wide angle of the cone. The results show the wide
variation in drop spectra used for the experiments and confirm the spray quality descriptions used in Tables
1,3 4, and 5. The results also show the wide variation in drop size spectra that are obtained from air-
induction nozzles of a similar size emphasising the need for a classification of spray for air-included sprays.
26
Table 6. Drop spectra of nozzles used in wind tunnel and field experiments
Manufacturer Code Description Pressure Flowrate VMD4
bar l/min µm
Lurmark/Hypro 03F110 Reference nozzle 3 1.20 192.1
Lurmark/Hypro 015F110 Fine nozzle 3 0.91 177.1
Lurmark/Hypro 04F110 Coarse spray 2 1.30 226.2
Lurmark/Hypro 04F110LD
Pre-orifice
flat-fan 3 1.32 284.5
Lechler ID120-03
Air-induction
flat-fan 3 1.32 589.5
bfs/agrotop 80-025 HC
Air-induction
hollow-cone 3 0.97 447.7
Lechler TR 90-03 Fine hollow-cone 3 1.15 195.4
Syngenta Az
Air-induction
angled (150 l/ha) 4 1.17 294.8
Syngenta Az
Air-induction
angled (100 l/ha) 3 1.02 281.7
Sprays
International PJ-03 Air-induction
flat-fan 3 1.09 502.9
Spraying Systems D5-23 Fine hollow-cone 3 0.83 202.9
Delavan WRW Hollow-cone 3 0.80 n/a
4 Volume Median Diameter – 50% of the volume of the spray is in drops with diameter greater than this value.
27
4 DISCUSSION
4.1 Results
The results in 2003 indicated that variations in total ear deposits were relatively small for all the application
systems evaluated in the wind tunnel and many of the application systems also resulted in similar deposit
distribution between the front and the back of the ear. Of the four application systems that were further
evaluated in the field trial (as shown by * on Figs. 5 and 6), the deposit distribution on the front and the back
of the ear suggested a slight trend for a higher deposit on the back of the ear compared to the front for all
these treatments. The deposit patterns also suggested that for these four application systems, there was a
slightly higher deposit on both the front and the back of the ear from the Amistar nozzle, and this was the
application system that tended to give the highest yields in the field trial for the three fungicide treatments
evaluated.
Of the fungicide treatments evaluated in 2003, the full dose of Prosaro resulted in the lowest infection of
FEB and highest resulting grain yield. This was irrespective of application system used suggesting that for
this dose of fungicide, application system was less important. The Amistar + Folicur treatment appeared to
be more dependent on the application system and in particular the Amistar nozzle tended to result in lower
infection of FEB and higher grain yield for this fungicide treatment.
The high levels of NIV detected in 2003 are thought to be due to the presence of F. poae and F.avenaceum
which was also detected in the ears and is capable of producing relatively high levels of NIV. Similar
increases in NIV have been observed in trials at Harper Adams University College (Dr. S. Edwards, Personal
Communication). The presence of this fungus complicated the results by affecting individual plots for some
treatments (e.g. the backward angled F110-04 nozzle applying Amistar + Folicur and the hollow cone nozzle
applying the reduced dose of Prosaro) which resulted in high variation in the results.
The DON levels in 2003 were low for all treatments and the untreated ears and this is likely to be owing to
the lower than expected levels of infection of FEB caused by F.culmorum. DON levels for all treatments
were well below the proposed legislative limit.
It was concluded from the 2003 results that variations between the spraying systems evaluated appeared to
be relatively small, although these small differences in spray deposit could be more important when applying
some fungicides than others. This may be influenced by the mode of action of the fungicide and the
importance of targeting the spray deposit to the target and ability to reach the site of Fusarium infection may
vary between different fungicides. It may be that for some fungicides the target may not be the whole ear but
a specific part of the ear.
28
Wind tunnel experiments with tebuconazole carried out in 2004 showed good penetration of fungicide onto
the rachis with the air-included hollow-cone and the angled conventional nozzle showing high deposits.
Similar measurements with samples from the field experiment showed lower levels of tebuconazole
penetrating the rachis. This could be due to differences between the varieties or crop densities used in the
field and the wind tunnel or to environmental conditions. It was not possible to discern significant
differences in tebuconazole deposition in the field caused by varying application method although the angled
air-included spray had the highest deposit levels.
The high levels of NIV detected in 2003 were thought to be due to the presence of F. poae and F.avenaceum
producing relatively high levels of NIV and effecting individual plots for some treatments. It is likely that the
2005 results were similarly affected despite the increased misting and the more humid conditions. The lower
temperatures may also have had an influence on infection. Unlike 2004, detectable levels of DON were
found in 2005 but with so few samples showing contamination there was no clear relationship between
application method and DON levels. All samples were below 1250 µg kg-1.
It was clear from the results of the field experiments over the three years that, despite inoculation with DON
producing Fusarium sp., disease pressure and DON production were variable and this made determining
differences due to application method difficult. In 2003 it appeared that inoculation produced reasonable
disease pressure, but in 2004 using the same techniques produced little disease and no significant difference
between treatments. Because of these difficulties, the 2005 inoculation was carefully monitored and misting
increased in frequency. However, the natural variability of FEB between plots appears to have influenced the
results. Because the weather between inoculation and treatment is crucial to the establishment of disease, this
influence of weather was investigated. A summary of the Morley weather data is presented in Table 7.
Table 7. Summary weather data from Morley, Norfolk for the period between Fusarium inoculation
and fungicide spraying
Year
2003 2004 2005
Mean maximum temperature
(°C) 20.3 23.0 18.0
Mean % Relative humidity at
09:00hrs 80.8 74.0 86.6
Total rainfall (mm) 1.48 0.03 1.03
The data shows that during the crucial period between inoculation and spraying it was hotter and drier in
2004 than in 2003 and that in 2005 it was cooler and wetter than 2003. This may help explain why FEB
levels were lower in 2004 than in 2003 and why in 2005 there was significant natural variability between
plots. To illustrate this further the trends in Morley weather data are plotted in Figs 16, 17 & 18.
29
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8 9 1011121314
Day
Temperature (° C) / Rainfall (mm)
0
10
20
30
40
50
60
70
80
90
100
Relative Humidity % at 09:00 hrs
Rainfall
Max Temp.
Min Temp
Humidity
SprayingInoculation
Fig. 17. Meteorological data from Morley Research Centre during the 2003 field
experiment.
0
5
10
15
20
25
30
35
1234567891011121314
Day
Temperature (° C) / Rainfall (mm)
0
10
20
30
40
50
60
70
80
90
100
% Relative Humidity at 09:00 hrs
Rainfall
Max Temp.
Min Temp
Humidity
SprayingInoculation
Fig. 18. Meteorological data from Morley Research Centre during the 2004 field
experiment
30
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8 9 101112131415161718
Day
Temperature (° C) / Rainfall (mm)
0
10
20
30
40
50
60
70
80
90
100
% Relative Humidity at 09:00 hrs
Rainfall
Max Temp.
Min Temp.
Humidity
SprayingInoculation
Fig. 17. Meteorological data from Morley Research Centre during the 2005 field
experiment
The rainfall that occurred in between inoculation and spraying in 2003 and 2005 appears to have been crucial
in producing FEB. However, the cooler temperatures, particularly the overnight minimum, appear may be
linked to the increased variability of disease in 2005.
It therefore appears that although fungicide deposits on ears can be manipulated by nozzle design and
orientation, and that under certain circumstances deposit levels can be linked to disease control, the influence
of application system on mycotoxin production is far from clear. Factors such as the level of natural disease
pressure, the Fusarium sp. complex and its reaction to fungicides and crop meteorology appear to strongly
influence mycotoxin production even when experiments are carried out with irrigated crops inoculated by
known DON producing strains. Inoculation was done with levels of spores significantly higher than that
occurring naturally (106 spores/ml) with actual levels of at least 103 spores/gram of ear tissue present after
inoculation. The wetness periods at anthesis are critical to determining whether establishment and infection
occurs. This was conducive in 2003, but not so in 2004 when the weather after inoculation was dry. In 2005,
dry weather slightly delayed the application of the inoculum and fungicides although additional misting was
carried out. Establishment of ear blight was as good as in 2003. However, the infection was more variable
than in 2005 within plots which was shown by the larger standard errors. This is consistent with the
sometimes patchy nature of ear blight infection.
In terms of making recommendations for application systems, the work has shown it is likely that more
reliable disease control will result from angling nozzles backwards, and that medium or air-included sprays
may provide better control than fine sprays.
31
4.2 Implication for levy payers
The HGCA Nozzle Selection Chart (published in March 2002) recommends that in terms of efficacy, ear
sprays are applied by fine flat-fan spray nozzles. This advice is based on the conventional approach;
vertically projected sprays. Whilst the evidence from this project is not clear-cut it appears that a better
alternative would be to recommend the use of angled air-induction nozzles or angled medium quality sprays.
This approach would offer some advantages in terms of ear deposition and FEB control and it would also
have the advantage of improved drift control. Although air-included hollow-cone nozzles are relatively new
to the market, they also appear to offer advantages in terms of ears sprays.
Ear blight does not directly correlate with mycotoxin contamination. A range of variables, biological and
non-biological, interact to influence the levels of ear blight and the amount of mycotoxin contamination. The
disease pressure was high in 2003 and 2005. The levels of DON were low, but that of NIV were very high in
harvested grain in 2003 because of natural contamination with other Fusarium species in that year. The
important outcome of the project is that provided fungicides are applied at the recommended rate using the
best possible spraying systems then the risk from DON contamination can be minimised. Although
throughout the project the disease pressure in the treatment plots was low, even with inoculation by known
DON producing strains of Fusarium the 1250 µg kg-1 limit for DON was not exceeded by any of the samples
taken throughout 2003-2005. Best control was achieved at the recommended rates.
4.3 Opportunities for further research
It is clear that producing high and uniform levels of FEB in the field such that differences in control caused
by application can be determined remains a challenge. Even inoculating a crop with known DON producing
strains of Fusarium produced sufficient disease in 2003 and 2005 but not enough DON/NIV to be able to
distinguish effectively between treatments. In 2004 the adverse weather conditions resulted in poor
establishment in the field experiment. In the wetter but colder season in 2005 there was a lack of disease
uniformity and this caused difficulties. Further work on inoculation and the maintenance of FEB by
irrigation would assist future work on application techniques and also assist with the development of
techniques for fungicide selection. This could include work on assessing the influence of soil moisture on
FEB.
More detailed studies could be carried out in the wind tunnel with marked Fusarium strains (e.g. Green
Fluorescent Protein, mutants) in controlled studies to optimise application type directly on ripening ears
during the critical anthesis phase. This could further elucidate the complex interactions between spray
deposition, fungicides and control of different combinations of Fusarium species (e.g. F.culmorum,
F.graminearum, F.poae, F.avenaceum and mixtures of these) in different humidity regimes and lead to
32
further optimisation of spray application techniques. The influence of Microdochium – Fusarium interactions
on trichothecene production also requires further work.
33
5 CONCLUSIONS & RECOMMENDATIONS
Although fungicide deposits on ears can be manipulated by nozzle design and orientation, and that under
certain circumstances deposit levels can be linked to disease control, the influence of application system on
mycotoxin production is far from clear. Factors such as the level of natural disease pressure, the Fusarium
sp. complex and its reaction to fungicides and crop meteorology appear to strongly influence mycotoxin
production even when experiments are carried out with irrigated crops inoculated by known DON producing
strains.
In terms of making recommendations for application systems, this work has shown that it is likely that more
reliable disease control will result from angling nozzles backwards, and that medium or air-included sprays
may provide better control than fine sprays.
34
6 ACKNOWLEDGEMENTS
The authors of the report wish to recognise the contribution of many people involved in this work and thank
them for their input. Particular thanks are due to;
`
• the HGCA for funding the study and to the staff and members of the R&D Committee for their
helpful comments during the course of this project;
• staff at The Arable Group, particularly Marion Self who carried the statistical analysis of the
cropping data.
• staff at Applied Mycology Group, Cranfield University, particularly Ester Baxter and Carlos Pires;
• Dave Baker, John Power, and Andy Lane of the Chemical Application Group at Silsoe Research
Institute for their assistance with wind tunnel and field experiments;
• Colin Mitchell, Christine O’Sullivan and Paul Rooney of the Analytical Laboratory at Silsoe
Research Institute for their analysis of spray deposits.
35
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characteristics in wheat. Project Report No. 277, HGCA, London
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coverage of fungicides on ears to control Fusarium ear blight and reduce mycotoxin contamination
of grain. International advances in pesticide application, Aspects of Applied Biology 71:215-222
Ramirez ML, Chulze S, Magan N (2004). Impact of environmental factors on growth and deoxynivalenol
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coverage of fungicides on ears to control Fusarium ear blight and reduce mycotoxin contamination
of grain. International advances in pesticide application, Aspects of Applied Biology 71:215-222
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