Project title
Outdoor flowers: evaluation of a herbicide to replace
Dosaflo for volunteer potato control in gladiolus
Project number:
BOF 65
Project leader:
Cathy Knott
Report:
Final report, March 2009
Previous report:
None
Key staff:
Cathy Knott
Location of project:
Winchester Growers, Surfleet, S. Lincs
Project coordinator:
Andrew Ellis, Poplar Farm, Old Fendyke, Sutton St.
James, Spalding, Lincs. PE12 0HE,
Date project commenced:
1 March 2008
Date project completed:
31 March 2009
Key words:
gladiolus, outdoor, weed control, crop quality, herbicide
replacement, Dosaflo (metoxuron), volunteer potatoes,
Sumimax (flumioxazin), Defy (prosulfocarb), Alpha
linuron (linuron)
Whilst reports issued under the auspices of the HDC are prepared from the best available
information, neither the authors nor the HDC can accept any responsibility for inaccuracy or
liability for loss, damage or injury from the application of any concept or procedure
discussed.
The contents of this publication are strictly private to HDC members. No part of this
publication may be presented, copied or reproduced in any form or by any means without
prior written permission of the Horticultural Development Company
The results and conclusions in this report are based on an investigation conducted over a
one-year period. The conditions under which the experiments were carried out and the
results have been reported in detail and with accuracy.
However, because of the
biological nature of the work it must be borne in mind that different circumstances and
conditions could produce different results. Therefore, care must be taken with interpretation
of the results, especially if they are used as the basis for commercial product
recommendations.
 2008 Agriculture and Horticulture Development Board
AUTHENTICATION
We declare that this work was done under our supervision according to the procedures
described herein and that the report represents a true and accurate record of the results
obtained.
Catharine Knott
Private Herbicide Consultant
Signature ............................................................
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Date
[Name]
[Position]
[Organisation]
Signature ............................................................
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Date
Report authorised by:
[Name]
[Position]
[Organisation]
Signature ............................................................
............................................
Date
[Name]
[Position]
[Organisation]
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Date
 2008 Agriculture and Horticulture Development Board
CONTENTS
Page
Grower Summary
Headline
1
Background and expected deliverables
1
Summary of the project and main conclusions
2
Financial benefits
6
Action points for growers
7
Science section
Introduction
8
Materials and Methods
9
Results and Discussion
11
Conclusions
14
Technology transfer
16
Appendix 1
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 2008 Agriculture and Horticulture Development Board
Grower Summary
Headline

Potential alternative herbicides screened to control volunteer potatoes in gladiolus
crops were not as effective or crop-safe as Dosaflo (metoxuron), which is no
longer available.

Sumimax (flumioxazin) at 100 ml/ha killed small volunteer potato shoots and gave
some suppression of larger plants however it caused slight damage to gladiolus
leaves.
Background and expected deliverables
Crops of gladiolus are often grown in the same rotation as potatoes.
In the past Dosaflo
(metoxuron) was used for suppression of volunteer potatoes in gladiolus (and carrots)
but it was not supported in EC 91/414 Review of pesticides- it can no longer be used.
If potato volunteers are not controlled they are a reservoir for potato blight infection.
The
cost of removal by hand-pulling or with selective application of glyphosate by hand could
be prohibitive. Potato volunteers in crops of gladiolus reduce yields. Importantly, flower
quality is affected because the stem becomes weak by excessive elongation, trying to
outgrow potatoes.
Some herbicides can cause damage and also affect quality.
Sumimax
(flumioxazin) applied post-emergence appeared to have potential for suppression of
volunteer potatoes in vegetable trials but it caused some damage to lilies in project BOF
58.
Sumimax controls other broad-leaved weeds (e.g. mayweeds) but not knotgrass.
It
has foliar contact and soil residual activity and is less effective on weeds in dry
conditions. The objective of the project is:

To find a post-emergence herbicide that controls volunteer potatoes to replace
Dosaflo.

To evaluate in one trial post-emergence application timing and dose rates of
Sumimax for safety to gladiolus.
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 2008 Agriculture and Horticulture Development Board

To evaluate a tank-mix of Defy (prosulfocarb) + Linuron that has proved useful
for volunteer potato control in carrots.
2
 2008 Agriculture and Horticulture Development Board
Summary of the project and main conclusions
Herbicide treatments: a ‘+’ denotes a tank-mix, ‘&’ followed by
Herbicide
g a.i./ha
L or ml/ha
-
1. untreated
Applied when
stage#
Gladiolus
at
2
leaf
2. Sumimax
3. Sumimax
4. Defy + Alpha Linuron 50SC
15
30
2000 + 325
50ml
100ml
2.5 L + 0.65 L
30
100ml
Applied 20 days after Gladiolus at 2
leaf stages
5. Sumimax
Applied when Gladiolus at 2 leaf
stage and 20 days after 2 leaf stage
6. Sumimax & Sumimax
15 & 15
# most volunteer potatoes emerged at this stage
50ml
& 50ml
The trial was in a commercial crop of gladiolus cv. Velvet Moon at Surfleet near Boston,
South Lincolnshire, on light silt loam soil.
Potatoes were grown in rotation with gladiolus
at this site. The gladiolus corms were planted 15cm below the soil surface in double
ridges.
The trial treatments were not replicated. Standard herbicide tank-mix Jupiter 40
CIPC (chlorpropham 400 g/L EC) + Alpha Linuron 50SC (linuron 500g/L SC) at 6.0
+ 1.0 L/ha applied after planting and pre-emergence of the crop, controlled all weeds
except potato volunteers.
Windy weather delayed the spraying date for the second
applications until 19 June.
Crop safety
Crop tolerance of gladiolus to herbicides assessed on several dates; score:0 plant death, 7
acceptable damage, 10 no damage ; (.percentage damage on total leaf area of the
plant)
Herbicide
L or ml/ha
Gladiolus GS:
1. untreated
-
13 June
30 June
16 July
29
July#
2-3 L
(% damage)*
5 L
(%damage)
6-7 L
9L
10
10
10
10
9 (1%)
7 (10%)
5 (30%)
9.5 (0.5%)
8 (8%)
6 (15%) st
10
10
9 st
Applied when Gladiolus at 2 leaf stage (31 May)
2. Sumimax
50ml
8 sc sp
3. Sumimax
100ml
6 sc sp
4. Defy + Linuron 50SC 2.5 L + 0.65 4 severe bl
L
Applied 20 days after Gladiolus at 2 leaf stages (19 June)
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 2008 Agriculture and Horticulture Development Board
5. Sumimax
100ml
-
5 (25%)
4 (30%)
4
5 (20%)
5
Applied when Gladiolus at 2 leaf stage and 20 days after 2 leaf stage
6. Sumimax & Sumimax 50ml
& 50ml 8 sc, sp
6 (10%)
bl bleaching; sc scorch; sp white spotting; st stunting, GS growth stage, L leaves
*. #On 29 July scores excluded leaves 1 and 2
Assessments made on the 13th of June showed that damage from Defy + Linuron was
unacceptable.
Sumimax 100 ml/ha caused white spotting mainly on the second leaf and
the leaf margins were scorched. Damage was less severe from the 50 ml dose of
Sumimax (treatments 2 and 5).
On the 30th of June new growth, i.e. leaves 3, 4 and 5, appeared normal and
unaffected by previous herbicide applications (treatments 2, 3, 4 and 6) hence the %
area affected decreased.
Defy + Linuron caused the most severe damage and the
bleached ends of leaf 2 died, Sumimax spotting and slight scorch was less severe.
On the 16th and 29th of July Defy + Linuron appeared to cause slight stunting. There was
slight yellowing of leaf tips and margins on L4 and L5 on 21 August – perhaps from soil
leaching after heavy rainfall and root uptake of Linuron.
Herbicide effects on the first 2 leaves do not reduce quality because leaves at the base
of the plant are never included in the cropped stem.
Gladioli were at 3-4 leaf stage on 19 June when the later applications of Sumimax
(treatments 5, 6) were made. Visible damage to the larger leaf area was more severe
than from early sprays and was unacceptable (30 June assessment). Leaves that were
erect caught less spray than those that were horizontal.
On 16 July damage had
increased on the second leaf, and leaves 3 and 4 were also affected by the follow-up
application of Sumimax 50 ml/ha.
Damage from Sumimax 100 ml/ha applied late was
more severe than the earlier application because a larger leaf area suffered white leaf
spotting/streaking on leaves 2, 3 and 4.
Assessments on 29 July showed that leaves
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 2008 Agriculture and Horticulture Development Board
that emerged after herbicides were applied were undamaged but leaf spotting, streaking and
leaf tipping effects from all herbicide treatments were still visible and remained until
cropping on 21 August.
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 2008 Agriculture and Horticulture Development Board
Sumimax 100 ml/ha applied on 31 May at 2-leaf stage of the crop, 13 days after treatment
Defy + Alpha Linuron 50 SC (2.5 + 0.65) L/ha applied on 31 May at 2-leaf stage of the
crop, 13 days after treatment
Sumimax 100 ml/ha applied at 4-leaf stage of the crop, damage 11 days after treatment
Volunteer potato control
Volunteer potatoes were at an advanced growth stage when the first herbicide treatments
were applied on 31 May. Most potatoes were large: 5-7 shoots per plant, c. 40 cm tall,
60 cm across with flower buds.
All of the herbicide treatment killed 100% of the foliage on small potatoes.
Only the Defy
and Linuron treatment gave >90% control of potato foliage of large potatoes but even with
this treatment 4 weeks after application re-growth was noted.
None of the herbicide
treatments prevented tuber formation.
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 2008 Agriculture and Horticulture Development Board
Percentage foliage killed of small (S) or large (L) volunteer potato shoots; score for
control (0 no control as untreated, 7 acceptable control, 10 complete control)
Herbicide
L or ml/ha
1. untreated
0
8 June
13 June
30 June
30 June
S
L
S
L
S
L
score
0
0
0
0
0
0
0
Applied when Gladiolus at 2 leaf stage Applied 20 days after Gladiolus at 2 leaf stages (31 May)
2. Sumimax
3. Sumimax
4. Defy + Linuron 50SC
50ml
80
100ml
90
2.5 L + 0.65 100
L
25
50
90
100
100
100
50
80
90
100
100
100
st
3
st
6
re-gr 9
-
-
100
50
5
100
80
6
Applied 20 days after Gladiolus at 2 leaf stages (19 June)
5. Sumimax
100ml
-
-
Applied when Gladiolus at 2 leaf stage and 20 days after 2 leaf stage
6. Sumimax & Sumimax
st stunted; re-gr regrowth
50ml
& 50ml 80
25
100
60
Cropping: maturity, harvestability, quality and vase-life
It is possible that the early, most damaging treatments (3 and 4) Defy + Linuron and
Sumimax 100 ml/ha caused slight delay of flowering.
The most damaging herbicide, Defy
+ Linuron, appeared to reduce crop height in comparison with other treatments.
The length of cropped gladiolus stems was 80 – 85 cm according to the market
specification.
Velvet Moon was a late-maturing very tall variety, and seven lower leaves
remained on the plant after cropping. This meant that for this cultivar any damage from
application of herbicide at growth stages 4-leaf stage (treatments 5 and 6) did not spoil
quality but this may not apply to short early varieties.
The two bottom leaves are not
included in the cropped stem of gladiolus thus leaf damage from the early applications
when the gladioli were at 2- leaf stage would not affect quality.
There was negligible difference in vase-life and quality between samples of treated and
untreated gladiolus.
Herbicide
treatments
did
not
appear
to
affect
the
gladiolus
corms.
No
grow-on
experiments were done but no defects were observed on samples from plots.
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 2008 Agriculture and Horticulture Development Board
Conclusion

Gladioli have an erect growth habit and are poor competitors with volunteer
potatoes. Early removal of competition from potatoes will increase yield and quality.
All herbicides caused some damage in the form of leaf scorch, bleaching or
spotting to the gladiolus crop and all killed small potato shoots.

An early application of Sumimax at 100 ml/ha applied at 2-leaf stage of gladiolus
was the safest treatment and would remove competition early although some handpulling may be needed where the control of large potatoes is incomplete.
The
lower dose was inadequate.

Defy + Linuron (2.5 + 0.65) L/ha caused very severe damage initially, and was
not safe to gladiolus although it gave the best foliar suppression of volunteer
potatoes damaging 90% of the leaf area of large potatoes..
The weed control
programme with Linuron pre-emergence used on this crop (total 1.65 L/ha) would
exceed the 1.2 L/ha dose rate permitted on any crop after December 2008.
Linuron products have now been revoked for use in ornamental plant production.

There will be a SOLA approval for Sumimax for use in ornamental plant production.
Defy can be used in ornamentals under the Long Term Arrangements for Extension
of Use for non-edibles. These arrangements are under review and in future a
SOLA will be needed.
Use of Linuron in ornamental plant production has been
revoked there is no SOLA or LTAEU.
held applications will still be excluded.
A SOLA is being re-assessed, but handDefy alone will not control volunteer
potatoes.
Status of the herbicides used in this project in 2008 (as at November 2008)
Product
name
a.i. and formulation
Marketing
company
EC
Review
UK Approval
Sumimax
Flumioxazin 300 g/L
EC
Prosulfocarb
800
g/L EC
Interfarm
Annex 1
Syngenta
Annex 1
Ornamental plant production
SOLA
LTAEU
Defy
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 2008 Agriculture and Horticulture Development Board
Alpha
Linuron 500 g/L SC Makhteshim
Annex 1
No SOLA#, no LTAEU.
Linuron
Revoked for ornamental plant
50SC
production
# to be re-assessed; LTAEU Long Term Arrangements for Extension of Use; SOLA Specific Offlabel Approval
Financial benefits
Weeds, including volunteer potatoes, in gladiolus crops reduce yields and interfere with
picking. Importantly, flower quality is reduced because the stem becomes weak by
excessive elongation, trying to outgrow the weed.
If volunteer potatoes are not controlled they can act as a reservoir of potato blight
infection posing a risk to potato crops on the farm and gladiolus crops will be unpopular
on rented land. The cost of removal by either hand pulling or using selective application of
glyphosate by hand is expensive. Some herbicides can cause damage and also affect
quality.
This trial aimed to maintain or improve the cost-effectiveness of producing cut-flowers of
gladiolus in UK crops by identification of a crop-safe, effective herbicide alternative to
Dosaflo used by growers of gladiolus but lost in the EC Pesticide Review.
Sumimax could be useful to remove competition from potatoes early but it may not be as
effective or as safe as Dosaflo.
Some hand labour may be needed as well.
Action points for growers

Sumimax applied at 100 ml/ha no later than 2-leaf stage of gladioli caused
acceptable damage (white spotting and scorch) and did not reduce quality because
the bottom leaves will be discarded from the cropped stem.
of potatoes and cause severe damage to large ones.
It will kill small shoots
It could be useful to remove
competition early but it may not be as effective as Dosaflo and some hand labour
may still be needed.
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 2008 Agriculture and Horticulture Development Board

Defy + Linuron (2.5 + 0.65) L/ha was more effective on potatoes in this trial but
was too damaging to gladiolus.

There are no on-label approvals for Sumimax in flowers or ornamentals but there will
be a SOLA for ornamental crop production.
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 2008 Agriculture and Horticulture Development Board
Science Section
Introduction
The demand for UK cut flowers is increasing, and the production of flowers in the field
provides an opportunity for UK growers. The lack of technical information for weed control
with herbicides in cut-flower species was addressed in projects BOF 51 and 51a, in lily in
BOF 58 and in gladiolus (a member of the Iridaceae family) in 2007, BOF 51b but
there were no volunteer potatoes in these trials. Crop protection companies cannot justify
the cost of the development and approval for herbicides for minor crops such as outdoor
flowers.
Crops of gladiolus are often grown in the same rotation as potatoes.
In the past
Dosaflo (metoxuron) was used to suppress of volunteer potatoes in gladiolus (and
carrots) but it was not supported in the 91/414/EEC review process and it can no
longer be used.
If potato volunteers are not controlled they are a reservoir for potato
blight infection.
The cost of removal by hand-pulling or with selective application of
glyphosate by hand-held weed wipers could be prohibitive. Potato volunteers in crops of
gladiolus reduce yields. Importantly, flower quality is affected because the stem becomes
weak by excessive elongation, trying to outgrow them.
Some herbicides can cause
damage and also affect quality.
‘Volunteer’ potatoes included in a herbicide screen in vegetables (HDC project FV 256 in
2006), flumioxazin
(coded 212H) gave good suppression of potatoes. A different
formulation as product Sumimax (flumioxazin) caused some damage to lilies in project
BOF 58.
Sumimax controls other broad-leaved weeds (e.g. mayweeds) but not
knotgrass.
It is less effective on weeds in dry conditions. Work in gladiolus is reported in
‘Evaluation of flumioxazin and other herbicides for Weed Control in Gladiolus’ (Richardson
& Zandstra, Weed Technology Vol 20, No 2 394-398). There was a project BOF 51b
in 2007 on weed control in gladiolus, but volunteer potatoes were not included and neither
11
 2008 Agriculture and Horticulture Development Board
was flumioxazin.
Following work with Defy (prosulfocarb) in tank-mix with Linuron for
potato control in carrots, a treatment with Defy + Linuron was also included.
Overall aim of the project:
To maintain or improve the cost-effectiveness of producing cut-flowers of gladiolus in UK
crops by identification of a crop-safe, effective herbicide alternative to Dosaflo for control of
volunteer potatoes .

To evaluate Sumimax, a possible alternative to Dosaflo, applied post-emergence at
different dose rates and timing for volunteer potato control and crop safety in
gladiolus.

To evaluate Defy + linuron as a treatment for control of volunteer potatoes.
Materials and methods
Status of the herbicides used in this project in 2008 (as at November 2008)
Product
name
a.i. and formulation
Marketing
company
EC
Review
UK Approval
Sumimax
Flumioxazin 300 g/L
EC
Prosulfocarb
800
g/L EC
Linuron 500 g/L SC
Interfarm
Annex 1
Syngenta
Annex 1
Ornamental plant production
SOLA
LTAEU
Defy
Alpha
Makhteshim
Annex 1
No SOLA#, no LTAEU.
Linuron
Revoked for ornamental plant
50SC
production
# to be re-assessed; LTAEU Long Term Arrangements for Extension of Use; SOLA Specific Offlabel Approval
There are no on-label approvals for Sumimax (or Linuron formulations or Defy) in flowers
or ornamentals.
The Long Term Arrangements for Extension of Use (LTAEU) for non-
edibles are under review and in future SOLAs will be needed.
Sumimax for use in ornamental plant production.
There will be a SOLA for
Defy can continue to be used in
ornamentals under the Long Term Arrangements for Extension of Use for non-edibles.
Applications of Linuron products have been revoked for ornamentals.
It cannot be used
under LTAEU and a SOLA was not granted. It is possible that low dose-rates could be
re-assessed but hand-held applications are excluded.
Defy alone will not control volunteer
potatoes.
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 2008 Agriculture and Horticulture Development Board
The
trial
was
in
a
commercial
crop
of
gladiolus
at
Surfleet
near
Boston,
South
Lincolnshire, on light silt loam soil (ADAS classification) typical of the South Lincolnshire
area where gladiolus are grown.
Potatoes were grown in the same rotation as gladiolus.
Gladiolus, cultivar Velvet Moon (deep red/purple), was planted 15cm below the soil
surface in double ridges.
Standard herbicide Jupiter 40 CIPC (chlorpropham 400 g/L
EC) + Alpha Linuron SC (Linuron 500g/L) at 6.0 + 1.0 L/ha applied after planting
and pre-emergence of the crop, controlled all weeds except potato volunteers. Treatments
were applied with an Azo precision plot sprayer, delivering 200 L/ha water volume through
Lurmark flat fan nozzles 02F110 at 1.9 bar pressure to give fine spray quality.
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 2008 Agriculture and Horticulture Development Board
Herbicide treatments; ‘+’ denotes tank-mix,’&’ denotes followed by
Herbicide
g a.i./ha
L or ml/ha
-
1. untreated
Applied when
stage#
Gladiolus
at
2
leaf
2. Sumimax
3. Sumimax
4. Defy + Alpha Linuron 50SC
15
30
2000 + 325
50ml
100ml
2.5 L + 0.65 L
30
100ml
Applied 20 days after Gladiolus at 2
leaf stages
5. Sumimax
Applied when Gladiolus at 2 leaf
stage and 20 days after 2 leaf stage
6. Sumimax & Sumimax
15 & 15
# most volunteer potatoes emerged at this stage
50ml
& 50ml
The trial treatments were not replicated. Gladiolus corms (cv. Velvet Moon) were planted
in two ridges per plot.
Plot size was two ridges wide 1.54m x 6m length.
Several volunteer potatoes emerged but there were no broad-leaved or grass weeds.
The dates of field operations and spray applications are given in Table 1.
Windy weather
delayed the spraying date for the second applications until 19 June (intended on 14 June,
14 d after the first 31 May application).
Table 1.
Diary of field operations and spray applications 2008
Date
2008
Operation
3 April
31 May
Planted
Treatments
2,3,4,6
Post-emergence
19 June
Treatment 5, 6
post-emergence
19 August
Commercial
cropping began
Trial flowers
cropped
21 August
Weather
Growth stage
Gladiolus
Growth stage untreated
volunteer potatoes
Temp 16°C (20°C
later); RH 53%; cloud
cover none; soil damp;
rain 22.6mm 1-3 June
Temp 19°C; RH 35%;
cloud cover 30%; soil
wet; rain 20-21 June
7.4mm
1½ - 2 leaves
a few just
emerged,
Small 1-2 shoots plants
15cm tall 20cm across;
Large 5-7 shoots plants
40cm tall, 60cm across.
All large 3-7 shoots
some at crop height,
most plants 40cm tall,
60 cm across
3-4 leaves,
crop 60cm tall
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 2008 Agriculture and Horticulture Development Board
The single plots were not yielded.
The following assessments were made:

Crop and weed stage of development at the time of treatments

Crop tolerance (i.e. phytotoxic symptoms) assessed at intervals after each herbicide
application using the scores given below:
Crop
Tolerance score
% Phytotoxicity
0
1
2
3
4
5
6
7
Complete kill
80 – 95% damage
70 – 80% damage
60 – 70% damage
50 – 60% damage
40 – 50% damage
25 – 40% damage
20 – 25% damage (considered unlikely to cause reduction in yield or quality at
cropping)
10 – 20% damage
5 – 10% damage
No damage (as untreated controls)
8
9
10

% green leaf area of potatoes (identified by labels as small and large) damaged
after each application.

Digs of a few potatoes/plot to establish effect on tubers compared with untreated
potatoes.

Crop damage symptoms recorded and Gladiolus corms examined for damage.

Flowers were cropped at commercial cropping stage when two buds per stem
showed colour, and cropping date recorded.

Vase-life under standard conditions.
Results and Discussion
Crop safety
The first applications were on 31 May. Two days later gladiolus treated with Defy +
Linuron (2.5 + 0.65) L/ha had suffered severe scorch and by 8 June the ends of
leaves were bleached on all plants.
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 2008 Agriculture and Horticulture Development Board
Table 2. Crop tolerance of gladiolus to herbicidesscore (0 plant death, 7 acceptable
damage, 10 no damage) assessed on several dates. The percentage damage on total leaf
area of the plant is shown in parentheses
Herbicide
L or ml/ha
Gladiolus GS:
1. untreated
-
13 June
16 July
(%damage)
6-7 L
29 July
2-3 L
30 June
(% damage)*
5 L
10
10
10
10
9 (1%)
7 (10%)
5 (30%)
9.5 (0.5%)
8 (8%)
6 (15%) st
10
10
9 st
4 (30%)
4
5 (20%)
5
9L
Applied when Gladiolus at 2 leaf stage (31 May)
2. Sumimax
50ml
8 sc sp
3. Sumimax
100ml
6 sc sp
4. Defy + Linuron 50SC 2.5 L + 0.65 4 severe bl
L
Applied 20 days after Gladiolus at 2 leaf stages (19 June)
5. Sumimax
100ml
-
5 (25%)
Applied when Gladiolus at 2 leaf stage and 20 days after 2 leaf stage
6. Sumimax & Sumimax 50ml
& 50ml 8 sc, sp
6 (10%)
bl bleaching; sc scorch; sp white spotting; st stunting, GS growth stage, L leaves
On 29 July scores excluded leaves 1 and 2
Damage from Defy + Linuron (Treatment 4) was unacceptable: on 13 June 30-50% of
total leaf area on all plants was bleached.
(Table 2).
Damage was mainly on the second leaf
Sumimax 100 ml/ha (Treatment 3) caused white spotting mainly on the
second leaf on 50% of plants and the leaf margins were scorched, overall the damage
was 20% of leaf area of the plant, damage was less severe from the 50 ml dose
(treatments 2 and 5) affecting 20% of plants.
On 30 June new growth, i.e. leaves 3, 4 and 5, appeared normal and unaffected by
previous herbicide applications (treatments 2, 3, 4 and 6) hence the % area affected
decreased.
Defy + Linuron caused the most severe damage and the bleached ends of
second leaves died.
Sumimax spotting and scorch was less severe.
Defy + Linuron appeared to cause slight stunting observed on 16 and 29 July. There was
also yellowing of leaf tips and margins on L4 and L5 on 21 August – perhaps from soil
leaching and root uptake of linuron after heavy rainfall.
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 2008 Agriculture and Horticulture Development Board
Herbicide damage wasstill apparent on the first 2 leaves on the 21 August (at harvest)
but this did not reduce quality because leaves at the base of the plant are never included
in the cropped stem.
Gladioli were at the 3-4 leaf stage on the 19 June when the later applications of
Sumimax (treatments 5, 6) were made. Visible damage to the larger leaf area was more
severe than from early sprays and was unacceptable on the 30 June assessment. Leaves
that were erect caught less spray than those that were horizontal.
On 16 July, damage
had increased on the second leaf, and leaves 3 and 4 were also affected by the followup application of Sumimax 50 ml/ha (Treatment 6).
Damage from Sumimax 100 ml/ha
(Treatment 5) applied late was more severe than the earlier application because a larger
leaf area suffered white leaf spotting/streaking on leaves 2, 3 and 4.
Assessments on 29 July showed that leaves that emerged after herbicides were applied
were undamaged but leaf spotting, streaking and leaf tipping effects from all herbicides
were still visible and remained until cropping.
Volunteer potato control
Volunteer potatoes were at an advanced growth stage compared with the gladiolus crop
when the first herbicide treatments were applied on 31 May. Most potatoes were large: 57 shoots per plant, c. 40 cm tall, 60 cm across with flower buds; a few were small 1-2
shoots per plant, 15 cm tall and 20 cm across.
Table 3. Percentage foliage killed of small (S) or large (L) volunteer potato
shootsscore for control (0 no control as untreated, 7 acceptable control, 10 complete
control)
Herbicide
L or ml/ha
1. untreated
0
8 June
13 June
30 June
30 June
S
L
S
L
S
L
score
0
0
0
0
0
0
0
Applied when Gladiolus at 2 leaf stage Applied 20 days after Gladiolus at 2 leaf stages (31 May)
2. Sumimax
3. Sumimax
4. Defy + Linuron 50SC
50ml
80
100ml
90
2.5 L + 0.65 100
L
25
50
90
100
100
100
50
80
90
100
100
100
st
3
st
6
re-gr 9
-
-
100
50
Applied 20 days after Gladiolus at 2 leaf stages (19 June)
5. Sumimax
100ml
-
-
5
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 2008 Agriculture and Horticulture Development Board
Applied when Gladiolus at 2 leaf stage and 20 days after 2 leaf stage
6. Sumimax & Sumimax
st stunted; re-gr regrowth
50ml
& 50ml 80
25
100
60
100
Defy + Linuron (2.5 + 0.65) L/ha had a quick effect on potatoes -
80
6
on 8 June, eight
days after the first application the small shoots were dead and 90% of the leaf area of
large potatoes were scorched. Sumimax caused damage in the form of leaf crinkling and
black/brown leaves and stem. Sumimax at 100 ml/ha had greater effect than 50 ml
particularly on the large potato plants.
On 13 June, all small potato shoots were dead on treatments 2, 3, 4 and 6 (Table 3).
Defy + Linuron had more effect on the large potatoes than Sumimax but there was some
re-growth of the large potatoes later on 30 June. On untreated plots a few potatoes were
as tall as the crop 60 cm, and ground cover was approximately 70%.
On 30 June on untreated plots, potato plants were 50-60 cm tall, 65 cm across and
ground cover was 100%, the gladioli were 60-70cm tall and above the potatoes.
The
application of Sumimax at 100 ml at the second timing (treatment 5) caused potato
damage similar to the earlier application (treatment 3) and it also killed the flowers.
Potatoes treated with the split dose of Sumimax (treatment 6) were severely stunted.
Potatoes
were
also
stunted
where
Sumimax
was
applied
earlier
at
50
or
100ml
(treatments 2 and 3) with a 50% reduction compared with untreated potatoes.
The most effective treatment for volunteer potato control was with Defy + Linuron (2.5 +
0.65) L/ha.
On 16 July, potatoes were removed by hand from all plots in error. The labels remained
and potatoes were dug from each plot.
None of the herbicides had prevented tuber
formation.
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Cropping: maturity, quality and vase-life
A few stems of gladioli cv. Velvet Moon on the trial area were ready for cropping on 19
August.
It is possible that the early, most damaging treatments (3 and 4) Defy + Linuron and
Sumimax 100 ml/ha caused slight maturity delay at flower cropping stage on 21 August.
The most damaging herbicide Defy + linuron appeared to reduce crop height in comparison
with other treatments.
The length of cropped gladiolus stems was 80 – 85 cm according to the market
specification.
Velvet Moon was a late-maturing very tall variety, and seven lower leaves
remained on the plant after cropping. This meant that for this cultivar any damage from
application of herbicide at growth stages 4-leaf stage (treatments 5 and 6) did not spoil
quality but this may not apply to short, early varieties.
However for all gladiolus types,
the two bottom leaves are not included in the cropped stem thus leaf damage from the
early applications when the gladioli were at 2- leaf stage would not affect quality.
Samples were cropped (5 per plot) on 22 August when two buds per stem were
showing colour, for vase-life tests. The stems were held in cold store for 24h before
vase-life assessment in water containing bulb flower food. There was negligible difference
in vase-life between treated and untreated gladiolus.
Herbicide treatments did not appear to affect gladiolus corms i.e. no defects were observed
on samples from plots, although the corms were not grown on.
Conclusions
Gladioli have an erect growth habit and are poor competitors with volunteer potatoes. Early
removal of competition from potatoes will increase yield and quality. In addition, herbicides
are more effective on small potato shoots and in this trial all treatments gave 100%
control.
Sumimax, Defy and Linuron all have contact and soil residual activity.
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In the past Dosaflo (metoxuron) was used for suppression of volunteer potatoes in
gladiolus (and carrots).
It was not supported in the EC 91/414 Review of pesticides
and it can no longer be used.
volunteer potatoes.
Dosaflo was very safe to gladiolus and effective on
In this trial the potato plants were large when treated and the
herbicides tested here may not offer a complete answer to volunteer potato control.
All
herbicides tested caused some damage in the form of leaf scorch, bleaching or spotting to
the gladiolus crop and all killed small potato shoots.
Herbicides only affected leaves that had emerged at the time of application.
For all
gladiolus types, the two bottom leaves are not included in the marketed stem, thus leaf
damage from the early applications when the gladioli were at 2-leaf stage would not
reduce quality.
For tall, late maturing varieties such as Velvet Moon tested in this trial,
later applications might not spoil quality, provided the cropped stem length specified did not
include any damaged lower leaves but this will not apply to short-stemmed, early varieties.
However, potato shoots usually emerge at the same time as the crop and early removal
of potatoes will increase yield and quality as demonstrated for lilies (HDC trial, BOF 58).
In addition, herbicides are more effective in controlling small potato shoots and in this trial
all treatments gave 100% control,
An early application of Sumimax at 100 ml/ha applied at 2-leaf stage of gladiolus was
the safest treatment and would remove competition early although some hand-pulling may
be needed later where the control of large potatoes is incomplete.
Damage was
acceptable in the form of white spotting and leaf scorch. The lower dose was inadequate.
Defy + Linuron (2.5 + 0.65) L/ha caused very severe damage initially and it may have
delayed maturity and reduced crop height.
It was not safe to gladiolus. In this trial it
gave the best foliar suppression of volunteer potatoes - 90% of the leaf area of large
potatoes were damaged although there was some re-growth later. Linuron has been reregistered at a total dose-rate of only 600 g a.i./ha/year i.e. 1.2 L/ha of a 500 g/L
formulated product.
Defy alone without Linuron does not suppress volunteer potato foliage.
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 2008 Agriculture and Horticulture Development Board
The weed control programme with Linuron pre-emergence used on this crop (total 1.65
L/ha) would exceed the 1.3 L/ha dose rate permitted after December 2008. There are
other pre-emergence alternatives for this soil type such as Stomp + Sencorex. (BOF
51b).
There are no on-label approvals for Sumimax (or Linuron formulations or Defy) in flowers
or ornamentals.
The Long Term Arrangements for Extension of Use (LTAEU) for non-
edibles are under review and in future SOLAs will be needed.
There will be a SOLA for
flumioxazin for use in ornamental plant production, Defy can continue to be used under
LTAEU and a SOLA is being sought.
revoked for ornamentals.
Applications of Linuron products have now been
It cannot be used under LTAEU and a SOLA was not granted.
It is possible that low dose-rates could be re-assessed.
Technology transfer
Article on results from the 2008 trial has been submitted for HDC News.
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Appendix 1
Sumimax 100 ml/ha applied on 31 May at 2-leaf stage of the crop, 13 days after
treatment
Defy + Alpha Linuron 50 SC (2.5 + 0.65) L/ha applied on 31 May at 2-leaf stage of
the crop, 13 days after treatment
Sumimax 100 ml/ha applied on 19 June at 4-leaf stage of the crop, damage 11 days
after treatment.
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