Project title Evaluation of potential alternatives for … title Evaluation of potential...
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Project title Evaluation of potential alternatives for weed control in asparagus following the loss of herbicides (continuation of project FV 372)
Project number: FV 372a Project leader: Philip Langley, Agronomist, Sandfields Farms Ltd,
Luddington, Warks, CV37 9SJ Email: [email protected]
Report: Final Report, 15/2/13 Previous report none Key staff: Marc Willis, SGS UK Ltd Philip Langley, G’s, Sandfields Farms Location of project: 1. Pre-emergence sites – A - Bidford,
Worcestershire, B - Great Ellingham, Norfolk 2. Post-emergence sites – C - Salford Priors, Worcs, D - Ombersley, Worcestershire
Project coordinator: Philip Langley, Sandfields Farms Ltd., Manor Farm,
Luddington, Warwickshire CV 37 9SJ Date project commenced: 01 March 2012
Date project completed: 28 Feb 2013 Key words:
Asparagus, herbicides, Callisto (mesotrione), HDC H17, Sencorex WG, Stomp Aqua (pendimethalin), Gamit, HDC H16, Flexidor, Lentagran, Lentagran + wetter, pre-spear-emergence, post-emergence, fern
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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
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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. P Langley Agronomist Sandfields Farms Ltd Signature ............................................................ Date ............................................ Report authorised by: [Name] [Position] [Organisation] Signature ............................................................ Date ............................................
Contents
Page
Grower Summary 1 Headline 1 Background 1 Project aims and objectives 1 Summary of the project and main conclusions 2 Financial benefits 5 Action points for growers 5 Photographs 6 Science section 12 Introduction 12 Materials and Methods 13 Results and Discussion 16 Technology transfer 26 Appendix 27
© Agriculture and Horticulture Development Board 2013. All rights reserved - 1 -
GROWER SUMMARY
Headlines
Applied pre-emergence of spears:
There is flexibility in reducing Callisto dose rate in mixtures. HDC H17 gave good initial control
of groundsel and black nightshade. Gamit 36 CS would be a useful addition for groundsel and
cleaver control at this timing and residue data generation will be investigated.
Applied post-emergence of spears:
Sencorex WG and Lentagran applied alone as split doses can be safe to the crop and effective
for small weeds. Mixtures may be required for larger weeds but young crop safety can be an
issue.
Background
Weeds in asparagus crops reduce yield and quality of spears, delay maturity and increase
harvest costs. Nettles and thistles deter pickers. Some herbicides can cause damage and also
affect quality. Crop Protection Companies cannot justify the cost of the development and
approval process for herbicides for minor, high value crops such as asparagus. There are 9
selective herbicides for broad-leaved weed control in asparagus, all of them SOLAs (now
referred to as EAMUs - extension of authorisation for minor uses). No herbicides are, or are
likely to be, authorised for use during the harvest period.
Asparagus is grown for up to 10 years and frequent use of the limited range of herbicides has
led to a build-up of weed species that may escape control. Weed seeds are exposed where
pickers disturb soil. A survey in 2004 by the Asparagus Growers Association showed that
thistles, nettles, field bindweed and fat-hen were frequently occurring weeds and black
nightshade, groundsel and cleavers were the most serious problems. In 2010 groundsel with
partial resistance to Sencorex (metribuzin) and possibly Goltix (metamitron) was identified.
In 2010 HDC Project FV 372 identified: Callisto (mesotrione), HDC H17 as potential
alternatives. When applied pre-emergence of spears, both controlled groundsel and black
nightshade. Callisto now has a SOLA but further work on dose rates is needed. An application
for an EAMU has been requested for HDC H17 and further information on weed control would
be useful.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 2 -
Cleavers control is a problem. Gamit 36 CS (clomazone) can only be used post-harvest and
before the start of fern growth. An application pre-spear emergence is needed but the effect on
quality (potentially bleaching) is not known, but there are no residues data at this timing.
Lentagran (pyridate) controls cleavers and fat-hen and has a SOLA for post-harvest use but
information on dose rates and timings is required.
This project aims:
To provide a wider range of herbicides so a weed control strategy using different
herbicides at different timings and years could avoid build-up of certain weed species
and also avoid herbicide resistance.
The specific objectives are:
To further evaluate alternative new herbicides identified in FV 372 in 2010 (Callisto, HDC
H17), Gamit 36CS (clomazone) and HDC H16 applied pre-emergence of spears for crop
tolerance and weed control.
To evaluate Lentagran (pyridate) post-harvest at different timings and dose rates for
crop tolerance and control of fat-hen, nightshade and cleavers.
Summary of the project and main conclusions
Herbicide screening trials in 2012 were in established commercial crops (Site A, sandy loam,
and B, loamy fine sand), and newly planted crowns (Site C, sandy clay loam and D, sandy
loam).
Pre-emergence trials
Herbicide Treatments (applied in 200 l/ha water volume) Herbicide Product Active Ingredient Product l or
kg/ha
1 untreated - 2 Callisto mesotrione 1.5 l 3 Callisto mesotrione 1.0 l 4 Callisto mesotrione 0.5 l 5 Callisto + Sencorex WG mesotrione + metribuzin 0.75 l + 0.75 kg 6 Callisto + Stomp Aqua mesotrione + pendimethalin 0.75 l + 3.3 l 6a Sencorex WG + Stomp Aqua metribuzin + pendimethalin 0.75 kg + 3.3 l
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Herbicide Product Active Ingredient Product l or kg/ha
7 Gamit 36 CS clomazone 0.25 l 8 Gamit 36 CS + Sencorex WG Clomazone + metribuzin 0.25 l + 0.75 kg 9 Gamit 36 CS + Callisto Clomazone + mesotrione 0.25 l + 0.75 l 10 HDC H17 HDC H17 4.0 l 11 HDC H17+Sencorex WG HDC H17 + metribuzin 4.0 l + 0.75 kg 12 HDC H16 HDC H16 4.0 l 13 Sencorex WG + Flexidor metribuzin + isoxaben 0.75 kg + 1.5 l
Treatment 6 applied at site B, and 6a applied at site A
Crop Safety
Soils were dry at application in mid-late March, followed by wet conditions in April.
There was no observed crop damage at Site B. At Site A during fern growth, there was slight
stunting and chlorosis from the double rates of Gamit + Callisto and HDC H17 + Sencorex WG,
with a lesser effect from HDC H16. All these symptoms had grown out by full fern development
in mid-July.
Weed control
Site A – the main weed species were groundsel, black nightshade and chickweed which began
to emerge in the untreated plots not long after application.
Site B – main species groundsel, mayweed and cleavers. Perennial weeds (marestail and
thistle) affected one corner of the trial area, making assessments difficult in a few plots.
Callisto – all rates gave good control of groundsel, nightshade, mayweed and chickweed during
the harvest period, but with a more variable rate response at Site A. The highest 1.5 l/ha rate
generally gave the best control and persistence, although mayweed control was not maintained
through to the later assessment. However, the 1.0 and 0.5 l/ha rates were also effective, but
may lack persistence to the end of harvest when used alone.
Callisto mixes – adding Sencorex WG improved groundsel control over the lower rates of
Callisto at Site A, but less so at Site B. This may reflect a decline in the efficacy of metribuzin at
Site B where it had been used more widely in the crop (3-4 years) compared to Site A (1 year).
The grower had also noticed a drop in efficacy with metribuzin in the trial field.
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Persistence of mayweed control was markedly improved with the addition of Sencorex WG or
Stomp Aqua.
Nightshade control also appeared to benefit from the addition of Sencorex WG so that 0.75 l/ha
Callisto in mixture was equal to the 1.5 l/ha rate alone.
Adding Gamit improved the level and persistence of groundsel control, added a significant
degree of cleaver control (80%+), but no benefit on nightshade or mayweed.
Gamit – applied alone confirmed good activity on groundsel, chickweed and mayweed, slightly
poorer control of cleavers than expected (63%), and no effect on nightshade.
Cleaver control appeared to be improved in mix with both Callisto and Sencorex WG, although
these are not effective when used alone.
Gamit + Callisto was one of the best overall mixes in the two trials.
HDC H17 – the trials confirmed good activity on nightshade, groundsel, chickweed and
mayweed, with some control (55%) of cleavers. However, overall activity and persistence was
improved with the addition of Sencorex WG.
HDC H16 – this was reasonably effective on groundsel, nightshade and cleavers, but lacked
persistence. Activity was better on mayweed and chickweed. If this is to be pursued, further
work would be required looking at mixtures with HDC H16 to establish any benefit.
Of the standard treatments included, Sencorex WG + Flexidor was surprisingly effective on
nightshade through the harvest period, and slightly better overall than Stomp Aqua + Sencorex
WG (Site A only).
Sencorex WG + Flexidor also gave better control of groundsel, as would be expected from the
history of use of metribuzin, at Site A (90%+) compared to Site B (73%).
© Agriculture and Horticulture Development Board 2013. All rights reserved - 5 -
Post-emergence trials
Herbicide Treatments (applied in 200 l/ha water volume) Herbicide Product Active Ingredient Dose product l/ha Timing
1 untreated - - - 2 Sencorex WG metribuzin 0.5 kg T1 & T2 3 Lentagran pyridate 2.0 kg T1 4 Lentagran pyridate 1 kg & 1 kg T1 & T2 5 Lentagran + Logic oil pyridate + oil 1 kg + oil & 1 kg + oil T1 & T2 6 Lentagran + Sencorex WG pyridate + metribuzin 1 kg + 0.5 Kg T1 & T2
T1 = early fern, weeds small T2 = 10 days after T1
Crop Safety
All treatments were safe to the crop at Site D. At Site C there was initially slight (but acceptable)
chlorosis from all treatments. This persisted and worsened only with the Lentagran + Sencorex
WG mix to give marginal crop safety by the later assessment in early August. This site had been
treated earlier (June rather than July) and the fern may have been softer/less waxed compared
to the second site (a small commercially treated area of Lentagran + Sencorex WG in June also
showed no crop damage to the fern of a newly planted crop).
Weed control
Site C: main weeds mayweed, annual nettle, shepherds purse, black nightshade, fumitory,
pansy, annual meadow grass and sow thistle.
Sencorex WG – gave excellent control of all weeds at the early assessment, with only some re-
growth of nightshade and sowthistle by early August. The addition of Lentagran gave no
additional benefit.
Lentagran – a split dose application was more effective than a single early treatment, especially
on nightshade. The addition of oil gave little improvement overall, but may help with mayweed
control.
Site D: main weeds sow thistle, fat hen, knotgrass, black nightshade.
Weeds were larger at the first application compared to Site C, and all treatments struggled to
give adequate control.
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Sencorex was again the best product, but with the larger weeds required the addition of
Lentagran to achieve any significant level of control.
All Lentagran treatments were poor overall.
Herbicides: Current Approval Status of products in the trials (January 2013)
Herbicide active ingredient Product and formulation Company Authorised use on asparagus?
isoxaben Flexidor 125 125g/l SC Landseer SOLA (was voluntarily withdrawn, now on EU list approved actives)
clomazone Gamit 36 CS 360 g/l CS Belchim SOLA post-harvest, not pre-emergence of spears
pendimethalin
Stomp Aqua 455g/L CS BASF
SOLA
metribuzin Sencorex WG 70% w/w WDG or use the new SC
Interfarm Bayer
SOLA
mesotrione Callisto 100 g/l SC Syngenta SOLA
HDC H16 - - No
HDC H17 - - No
pyridate Lentagran WP 45% w/w Belchim SOLA
Financial benefits
Without suitable herbicides, asparagus production costs could be prohibitive. Safe and effective
alternatives to herbicides lost as a result of the EC Review have been found and this will benefit
the industry.
Labour savings, and the high cost of hand-weeding would be avoided.
New actives could provide growers with alternatives for weed control.
A wider range of herbicides for this perennial crop will enable a weed control strategy using
different herbicides at different timings and years to avoid build-up of certain species and
also avoid herbicide resistance (groundsel resistance has already been identified in some
crops where there has been repeated use of metribuzin, with the potential for cross-
resistance to metamitron).
Residues data and EAMUs will need to be sought and this may involve additional costs,
although it may be possible to obtain residues data for asparagus from another country.
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Action points for growers
Pre-emergence herbicides
There is some flexibility in reducing the dose rate of Callisto, especially when used in
mixture. Mixtures will improve the range of weeds controlled and persistence through the
harvest period. Reducing the dose when used alone may result in inadequate weed control.
HDC H17 again gave good initial control of groundsel and black nightshade, but appeared
less persistent in these trials compared to FV 372 in 2010. The addition of Sencorex WG
improved control.
Gamit appeared crop safe in these trials when used pre-emergence and would be a useful
addition for groundsel and cleaver control at this timing. A request has been made to HDC
for an EAMU (SOLA) and for the residue trials to be done. Residue tests carried out in the
trials showed no detection of clomazone at early spear emergence.
HDC H16, whilst crop safe, does not appear to offer any particular advantage over other trial
or existing products. It may be a consideration if there are problems gaining new approvals
or there are other product losses. If data is available for asparagus, it would be worth
including in future trials in mixtures to establish its efficacy.
The lack of persistence with some treatments/weeds may have been due to the high rainfall
in April and May, although residual herbicides tend to work better with good levels of soil
moisture compared to a dry year.
Post-emergence herbicides
Sencorex WG applied alone as a split dose can give good control of a broad range of
weeds, providing weeds are still small at application. The addition of Lentagran may help
control larger weeds, but may also result in some crop damage to young fern
Lentagran applied as a split dose can be effective and safe to the crop, the addition of oil
does not compromise crop safety and may help on some weeds. However, application to
larger weeds may give poor results.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 8 -
Gamit + Callisto
Untreated
Site A – pre-emergence, May 2012
© Agriculture and Horticulture Development Board 2013. All rights reserved - 9 -
Site C – weeds at second application
12/6/12
Site C – crop 8 days after second
application 20/6/12
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Site C Post-emergence -
28/7/12
untreatedSencorex +
Lentagran
Lentagran
2kg/ha
Sencorex split
© Agriculture and Horticulture Development Board 2013. All rights reserved - 11 -
Site D Post-emergence,
Sencorex + Lentagran
Site D Post-emergence,
untreated
© Agriculture and Horticulture Development Board 2013. All rights reserved - 12 -
SCIENCE SECTION
Introduction
Weeds in asparagus crops reduce yield and quality of spears, and compete with fern growth.
Nettles and thistles deter pickers. Some herbicides can cause damage and also affect quality.
Popular herbicides simazine, terbacil and diuron have been lost as a result of the Pesticide
Review 91/414/EEC and can no longer be used. There may be further losses under the new
Regulation EC 1107/2009 where criteria will be hazard-based. At product re-registration stage
herbicide dose rates may be reduced and this will reduce efficacy. Crop Protection Companies
cannot justify the cost of the development and approval process for herbicides for high value but
minor, crops such as asparagus. There are a number of selective herbicides remaining for
asparagus, most of them EAMUs, but all have limitations either on timing or weed spectrum. No
herbicides are, or are likely to be, authorised for use during the harvest period.
Asparagus, a perennial crop is grown for up to 10 years and frequent use of the limited range of
herbicides has led to a build-up of weed species that may escape control, and where weed
seeds are exposed when pickers disturb the soil surface. A survey of growers in 2004 by the
Asparagus Growers Association showed that thistles, nettles, field bindweed and fat-hen
occurred frequently and black nightshade, groundsel and cleavers were the most serious
problems. However, since then new approvals (Dow Shield etc. (clopyralid) for thistle control,
Goltix 90 etc. (metamitron) for groundsel, Centium etc. (clomazone) for cleavers, Callisto
(mesotrione) for groundsel and Lentagran (pyridate) EAMUs) have alleviated the problems to
some extent, but season long weed control remains a challenge both during harvest and the
fern stages.
Limitations and problems with current approvals are:
Metamitron and clomazone are only authorised for post-harvest use on established
crops.
Growers suggest that black nightshade and groundsel control remains very difficult.
In 2010 groundsel with partial resistance to Sencorex (metribuzin) was identified with
cross resistance to Goltix (metamitron) possible.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 13 -
Newly planted crops have the additional problem of not being able to top-up the residual
herbicide at the end of harvest compared to an established crop.
The aims of this project are to:
To further evaluate alternative new herbicides identified in FV 372 in 2010 (Callisto, HDC
H17), Gamit 36CS (clomazone) and HDC H16 applied pre-emergence of spears for crop
tolerance and weed control.
To evaluate Lentagran (pyridate) and Sencorex (metribuzin) post-harvest at different
timings and dose rates for crop tolerance and control of fat-hen and cleavers.
This could provide a wider range of herbicides so a weed control strategy using different
herbicides at different timings and years could avoid build up of certain weed species and
resistance problems. Herbicide screening trials in asparagus were therefore conducted to
establish potential treatments for weed control and crop safety. Trials in asparagus, cv. Gijnlim,
were conducted at two sites for one year. Target weeds were: groundsel, Polygonums, fat-hen
and small nettle at Site 1; groundsel and black nightshade at Site 2. Candidate herbicide
treatments were selected on the basis of known effectiveness and safety in other crops and
information from other EU Member States.
Materials and methods
Herbicides: Current Approval Status of products in the trials (January 2013)
A single-year trials programme over 4 sites. Plot yields not recorded.
1. Herbicide screening trials (four replications, 3 single rate, one double rate (sprayed twice) to
give extra crop safety information in complete randomised blocks) in asparagus were
conducted to establish potential treatments for weed control and crop safety. Target weeds
pre-emergence of spears: cleavers, groundsel, black nightshade; post-fern and fern stages in
a new crop: cleavers, groundsel, fat-hen and fumitory. Controls were provided by additional
untreated plots.
2. Trial A and B at 2 sites: herbicide treatments pre-spear emergence in an established crop in
its final year (to avoid crop destruction for 5 years after unauthorised treatments applied)
© Agriculture and Horticulture Development Board 2013. All rights reserved - 14 -
Trial C and D at 2 sites: herbicide treatments early fern and post-fern in a new crop.
Standard pre-spear emergence treatment applied overall.
Plots were 8 m long in trials A and B and 6 m long in trials A and B, all 1.5 m wide - asparagus
was grown in ridges with 1 ridge per plot.
Larger plots were used for pre-emergence site where the crop was in its last year of production
– old crops are likely to be patchier, so this approach provided more assessable plants for crop
safety.
Herbicide treatments were applied using a precision sprayer as directed by the label or in 200
litres water per ha.
Herbicide Treatments
Pre-emergence trials (applied in 200L/ha water volume)
Herbicide Product Active Ingredient Product l or
kg/ha
1 untreated - 2 Callisto mesotrione 1.5 l 3 Callisto mesotrione 1.0 l 4 Callisto mesotrione 0.5 l 5 Callisto + Sencorex WG mesotrione + metribuzin 0.75 l + 0.75 kg 6 Callisto + Stomp Aqua mesotrione + pendimethalin 0.75 l + 3.3 l 6a Sencorex WG + Stomp Aqua metribuzin + pendimethalin 0.75 kg + 3.3 l 7 Gamit 36 CS clomazone 0.25 l 8 Gamit 36 CS + Sencorex WG Clomazone + metribuzin 0.25 l + 0.75 kg 9 Gamit 36 CS + Callisto Clomazone + mesotrione 0.25 l + 0.75 l 10 HDC H17 HDC H17 4.0 l 11 HDC H17+Sencorex WG HDC H17 + metribuzin 4.0 l + 0.75 kg 12 HDC H16 HDC H16 4.0 l 13 Sencorex WG + Flexidor metribuzin + isoxaben 0.75 kg + 1.5 l
Treatment 6 applied at site B, and 6a applied at site A No double rate applied at site B
© Agriculture and Horticulture Development Board 2013. All rights reserved - 15 -
Post-emergence trials (applied in 200L/ha water volume)
Herbicide Product Active Ingredient Dose product l/ha Timing
1 untreated - - - 2 Sencorex WG metribuzin 0.5 kg T1 & T2 3 Lentagran pyridate 2.0 kg T1 4 Lentagran pyridate 1 kg & 1 kg T1 & T2 5 Lentagran + Logic oil pyridate + oil 1 kg + oil & 1 kg + oil T1 & T2 6 Lentagran + Sencorex WG pyridate + metribuzin 1 kg + 0.5 Kg T1 & T2
T1 = early fern, weeds small T2 = 10 days after T1 No double rates applied at site C
Assessments
Crop tolerance (phytotoxicity) was scored, at appropriate intervals after applications. Damage
symptoms and effects such as bleaching, distortion, etc. were recorded together with weed
control scores, and % weed cover per plot.
Application details
Pre-emergence sites
Site A Bidford on Avon, Warks, B50 4AU B Great Ellingham, Attleborough, NR17 1AG
Soil type Sandy clay loam Loamy fine sand Application: Pre-em Pre-em Date: 21/3/12 27/03/2012 Method: Spray, med flat fan, 50cm spacing Spray, med flat fan, 50cm spacing Placement: Soil Soil Air Temp C: 13.2 21.9 Rel. Humidity %: 63 46.2 Wind Speed: 0.8 m/s 0.9 m/s Soil Temp C: 7.8 15.1 Soil Moisture: Slightly moist Slightly dry Next Rainfall: 22/3/12 – 2.5mm 28/03/2012
Crop and Weed Information at Application Crop Stage Pre-emergence Pre-emergence Crop coverage % 0 0 Weeds no emerged weeds no emerged weeds
© Agriculture and Horticulture Development Board 2013. All rights reserved - 16 -
Post-emergence sites
Site C Salford Priors, Worcs, WR11 5UU D Droitwich, Worcs, WR9 0JL
Soil type Sandy loam Sandy loam Application: Post-em 1 Post-em 2 Post-em 1 Post-em 2 Date: 1/6/12 12/6/12 27/03/2012 Method: Spray, med flat
fan, 50cm spacing
Spray, med flat fan, 50cm spacing
Spray, med flat fan, 50cm spacing
Spray, med flat fan, 50cm spacing
Placement: Foliar Foliar Foliar Foliar Air Temp C: 19 12 15 17.5 Rel. Humidity %: 86 79 72 87 Cloud Cover: 100 100 40 85 Wind Speed m/s 0 1.2 0 0.5 Soil Temp C: 12.5 13 18 18.5 Soil Moisture: dry wet wet normal/moist Next Rainfall: 2/6/12 14/6/12 6/7/12 16/7/12 Dew present: no no no no
Crop and Weed Information at Application
Site C Salford Priors, Worcs, WR11 5UU D Droitwich, Worcs, WR9 0JL
Crop Stage early fern fern fern fern Crop height cm 45 50 110 120 Crop coverage %
5 7 35 40
Weeds field pansy 3 cm
scentless mayweed 8 cm common nettle
6 cm shepherds purse
4 cm black nightshade
1 leaf
field pansy 3 cm
scentless mayweed 8 cm
common nettle 6 cm
shepherds purse 4 cm
black nightshade 1 leaf
scentless mayweed 20 cm
smooth sowthistle 110 cm fat hen 30 cm
black nightshade 35 cm
field sowthistle 20 cm
cleavers 20 cm
Knotgrass 15 cm
scentless mayweed 25 cm
smooth sowthistle 130 cm fat hen 45 cm
black nightshade 35 cm
field sowthistle 50 cm
cleavers 20 cm
Knotgrass 15cm
Results and Discussion
Pre-emergence trials
Crop Safety (Table 1) Soils were dry at application in mid-late March followed by wet conditions in April.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 17 -
There was no observed crop damage at Site B. At Site A during fern growth, there was slight
stunting and chlorosis from the double rates of Gamit + Callisto and HDC H17 + Sencorex WG,
with a lesser effect from HDC H16. All these symptoms had grown out by full fern development
in mid-July.
Weed control (Tables 2 and 3)
Site A – the main weed species were groundsel, black nightshade and chickweed which began
to emerge in the untreated plots shortly after application
.
Site B – main species groundsel, mayweed and cleavers. (Perennial weeds (horsetail and
thistle) affected one corner of the trial area, making assessments difficult in a few plots).
Callisto – all rates gave good control of groundsel, nightshade, mayweed and chickweed during
the harvest period, but with a more variable rate response at Site A. The highest 1.5 l/ha rate
generally gave the best control and persistence, although mayweed control was not maintained
through to the later assessment. The 1.0 and 0.5 l/ha rates were also effective, but may lack
persistence to the end of harvest when used alone.
Callisto mixes – adding Sencorex WG improved groundsel control over the lower rates of
Callisto at Site A, but less so at Site B. This may reflect a decline in the efficacy of metribuzin at
Site B where it had been used more widely in the crop (3-4 years) compared to Site A (1 year).
The grower had also noticed a drop in efficacy with metribuzin in the trial field.
Persistence of mayweed control was markedly improved with the addition of Sencorex WG or
Stomp Aqua.
Nightshade control also appeared to benefit from the addition of Sencorex WG so that 0.75 l/ha
Callisto in mixture was equal to the 1.5 l/ha rate alone.
Adding Gamit improved the level and persistence of groundsel control, added a significant
degree of cleaver control (80%+), but no benefit on nightshade or mayweed.
Gamit – applied alone confirmed good activity on groundsel, chickweed and mayweed, slightly
poorer control of cleavers than expected (63%), and no effect on nightshade.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 18 -
Cleaver control appeared to be improved in mix with both Callisto and Sencorex, although these
are not effective when used alone.
Gamit + Callisto was one of the best overall mixes in the two trials.
HDC H17 – the trials confirmed good activity on nightshade, groundsel, chickweed and
mayweed, with some control (55%) of cleavers. However, overall activity and persistence was
improved with the addition of Sencorex WG.
HDC H16 – this was reasonably effective on groundsel, nightshade and cleavers, but lacked
persistence. Activity was better on mayweed and chickweed. If this is to be pursued, further
work would be required looking at mixtures with HDC H16 to establish any benefit.
Of the standard treatments included, Sencorex WG + Flexidor was surprisingly effective on
nightshade through the harvest period, and slightly better overall than Stomp Aqua + Sencorex
WG (Site A only).
Sencorex WG + Flexidor also gave better control of groundsel, as would be expected from the
history of use of metribuzin, at Site A (90%+) compared to Site B (73%).
© Agriculture and Horticulture Development Board 2013. All rights reserved - 19 -
Table 1 Sites A & B – Pre-emergence Crop Damage (0-10, 0 = no damage, 10 = crop dead)
Damage symptoms - stunting, chlorosis
Site A, Warwicks
B, Norfolk
Date 23/4/12 16/5/12 21/7/12 11/04/12
25/04/12
09/05/12
22/06/12
Crop GS spears spears fern spears spears spears fern
Days after application
33 56 122 15 29 43 87
Treatments Rate/ha single rate
double rate
single rate
double rate
single rate
double rate
single rate
1 Untreated 0 0 0 0 0 0 0 0 0 0
2 Callisto 1.5lt 0 0 0 0 0 0 0 0 0 0
3 Callisto 1lt 0 0 0 0 0 0 0 0 0 0
4 Callisto 0.5lt 0 0 0 0 0 0 0 0 0 0
5 Callisto+ Sencorex WG
0.75lt + 0.75kg 0 0 0 0 0 0 0 0 0 0
6 Callisto+ Stomp Aqua
0.75lt + 3.3lt na na na na na na 0 0 0 0
6a Sencorex WG + Stomp Aqua
0.75lt + 3.3lt 0 0 0 0 0 0 na na na na
7 Gamit 0.25lt 0 0 0 0 0 0 0 0 0 0
8 Gamit+ Sencorex WG
0.25lt + 0.75kg 0 0 0 0 0 0 0 0 0 0
9 Gamit + Callisto 0.25lt + 0.75lt 0 0 0 2.0 0 0 0 0 0 0
10 HDC H17 4lt 0 0 0 0 0 0 0 0 0 0
11 HDC H17 + Sencorex WG
4lt + 0.75kg 0 0 0 1.0 0 0 0 0 0 0
12 HDC H16 4lt 0 0 0.7 0.0 0 0 0 0 0 0
13 Sencorex WG + Flexidor
0.75kg + 1.5lt 0 0 0 0.0 0 0 0 0 0 0
© Agriculture and Horticulture Development Board 2013. All rights reserved - 20 -
Table 2 Site A (Warwicks) – Pre-emergence weed control (% control, untreated = % ground cover of weed)
Date 16/5/2012 21/7/2012 16/5/2012 21/7/2012 16/5/2012 16/5/2012 21/7/2012
Crop GS spears fern spears fern spears spears fern
Weed Black nightshade Groundsel Chickweed all
Weed GS 1-2 leaf 50cm 3-5 lf, 4cm 30cm 1-4cm
Days after application 56 122
56 122 56 56 122
Treatment Rate/ha
Mean all weeds
Mean all weeds
1 Untreated 4 17 4 27 1 3 22
2 Callisto 1.5lt 83 90 91 87 93 89 88
3 Callisto 1lt 77 73 77 27 100 84 50
4 Callisto 0.5lt 86 80 87 60 69 81 70
5 Callisto+ Sencorex WG
0.75lt + 0.75kg
90 88 87 77 100 92 83
6 Callisto+ Stomp Aqua
0.75lt + 3.3lt na na na na na na na
6a Sencorex WG + Stomp Aqua
0.75lt + 3.3lt 85 91 85 73 100 90 82
7 Gamit 0.25lt 0 0 99 90 100 66 45
8 Gamit+ Sencorex WG
0.25lt + 0.75kg
77 23 98 88 100 92 56
9 Gamit + Callisto
0.25lt + 0.75lt 99 75 99 94 100 99 85
10 HDC H17 4lt 94 80 91 57 100 95 68
11 HDC H17 + Sencorex WG
4lt + 0.75kg 96 92 96 85 100 97 88
12 HDC H16 4lt 79 30 82 33 100 87 32
13 Sencorex WG + Flexidor
0.75kg + 1.5lt 95 82 99 90 100 98 86
© Agriculture and Horticulture Development Board 2013. All rights reserved - 21 -
Table 3 Site B (Norfolk) – Pre-emergence weed control (% control, untreated = % ground cover of weed)
Date 25/04/2012 09/05/2012 22/06/2012
mean groundsel
11/04/2012 22/06/2012 22/6/2012
mean all weeds 22/6/12
Crop GS spear spear fern spear fern fern
Weed Groundsel Mayweed Cleavers
Weed GS flower buds 1st flower senescing 7 leaf
buds visible flower
Days after application 29 43 87 15 87 87
Treatment Rate/ha
1 Untreated 30 64 24 39 1 3 6 33
2 Callisto 1.5lt 94 93 81 89 94 59 0 47
3 Callisto 1lt 94 94 81 90 94 55 0 45
4 Callisto 0.5lt 94 86 76 85 93 33 0 37
5 Callisto+ Sencorex WG
0.75lt + 0.75kg
94 91 85
90
95 95 38
73
6 Callisto+ Stomp Aqua
0.75lt + 3.3lt
94 88 68
83
94 98 20 62
6a Sencorex WG + Stomp Aqua
0.75lt + 3.3lt
na na na
na
na na na na
7 Gamit 0.25lt 84 81 75 80 89 23 63 53
8 Gamit+ Sencorex WG
0.25lt + 0.75kg
83 76 71
77
95 99 90 87
9 Gamit + Callisto
0.25lt + 0.75lt
94 93 86
91
91 64 83 78
10 HDC H17 4lt 76 68 74 73 91 87 55 72
11 HDC H17 + Sencorex WG
4lt + 0.75kg
83 78 84
81
94 99 70 84
12 HDC H16 4lt 85 76 75 79 91 90 75 80
13 Sencorex WG + Flexidor
0.75kg + 1.5lt
75 66 76 73 93 79 0 52
© Agriculture and Horticulture Development Board 2013. All rights reserved - 22 -
Post-emergence trials
Crop Safety (Table 4)
All treatments were safe to the crop at Site D. At Site C there was initially slight (but acceptable)
chlorosis from all treatments. This persisted and worsened only with the Lentagran + Sencorex WG
mix to give marginal crop safety by the later assessment in early August. This site had been treated
earlier (June rather than July) and the fern may have been softer/less waxed compared to the second
site (a small commercially treated area of Lentagran + Sencorex WG in June also showed no crop
damage to the fern of a newly planted crop).
Weed control (Tables 5 and 6)
Site C – main weeds mayweed, annual nettle, shepherds purse, black nightshade, fumitory, pansy,
annual meadow grass and sow thistle.
Site D – main weeds sow thistle, fat hen, knotgrass, black nightshade.
Site C
Sencorex WG – gave excellent control of all weeds at the early assessment, with only some re-growth
of nightshade and sowthistle by early August.
The addition of Lentagran gave no additional benefit.
Lentagran – a split dose application was more effective than a single early treatment, especially on
nightshade. The addition of oil gave little improvement overall, but may help with mayweed control.
Site D
Weeds were larger at the first application compared to Site C, and all treatments struggled to give
adequate control.
Sencorex was again the best product, but with the larger weeds required the addition of Lentagran to
achieve any significant level of control.
All Lentagran treatments were poor overall.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 23 -
Table 4 Sites C & D – Post-emergence Crop Damage (0-10, 0 = no damage, 10 = crop dead)
Site Site C Site D
Date 20/6/2012 3/8/2012 15/7/2012 1/8/2012 21/8/2012
Days after application
T 1 19 63 10 27 47
T 2 8 52 0 17 37
Treatments Rate/ha Timing
1 Untreated 200l water 0 0 0 0 0
2 Sencorex WG 0.5kg T1 & T2 1.8 0 0 0 0
3 Lentagran 2kg T1 0.5 0 0 0 0
4 Lentagran + Logic oil
1kg + 1.5l/ha T1 & T2 0.8 0.5 0 0 0
5 Lentagran 1kg T1 & T2 0.8 0.75 0 0 0
6 Lentagran + Sencorex WG 1kg + 0.5kg T1 & T2 1.6 3 0 0 0
T1 – early fern, T2 – 7-10 days after T1 Damage symptoms - stunting, chlorosis
© Agriculture and Horticulture Development Board 2013. All rights reserved - 24 -
Table 5 Site C (Salford Priors) – Post-emergence weed control. Early assessment (% control, untreated = % ground cover of weed)
Date 20/6/2012
Days after application
T 1 19
T 2 8
mean all
weeds
Weed mayweed nettle shepherds
purse black
nightshade fumitory pansy
Weed GS 20cm 15cm 10cm 10-15cm 20cm 5cm
Treatments Rate/ha Timing
1 Untreated 200l water 9.5 3.8 1.5 2.3 1.5 0.6 19
2 Sencorex WG 0.5kg T1 & T2 100 100 100 100 100 100 100
3 Lentagran 2kg T1 95 95 78 88 90 25 78
4 Lentagran + Logic oil
1kg + 1.5l/ha T1 & T2 99 96 98 100 100 63 93
5 Lentagran 1kg T1 & T2 95 98 100 98 100 38 88
6 Lentagran + Sencorex WG
1kg + 0.5kg T1 & T2 100 100 100 100 100 100 100
Site C – Post-emergence weed control. Late assessment (% control, untreated = % ground cover of weed)
Date 3/8/2012
Days after application
T 1 63
T 2 52 mean all
weeds Weed mayweed nettle annual meadow
grass black
nightshade sow thistle
Weed GS flower 70cm Flower flower/seed 70-80cm
Treatments Rate/ha Timing
1 Untreated 200l water 15 8 6 16 9 54
2 Sencorex WG 0.5kg T1 & T2 100 100 100 91 94 97
3 Lentagran 2kg T1 80 63 0 70 93 61
4 Lentagran + Logic oil
1kg + 1.5l/ha
T1 & T2 98 85 0 73 100 71
5 Lentagran 1kg T1 & T2 79 86 0 88 100 70
6 Lentagran + Sencorex WG
1kg + 0.5kg
T1 & T2 100 100 100 90 100 98
T1 – early fern, T2 – 7-10 days after T1
© Agriculture and Horticulture Development Board 2013. All rights reserved - 25 -
Table 6 Site D (Ombersley) – Post-emergence weed control. Early and late assessment (% control, untreated = % ground cover of weed)
Date 1/8/12
mean all
weeds
21/8/12
mean all
weeds
Days after application
T 1 27 47
T 2 17 37
Weed
field sowthistle
fat hen knotgrass
black nightshade fat hen knotgrass
black nightshade
Weed GS flower
end fl e. flower full flower
seeds form. full flower
seeds form.
Treatments Rate/ha Timing
1 Untreated 200l water 4.7 1.7 43.3 3.7 53.4 3.3 52 6 61
2 Sencorex WG 0.5kg T1 & T2 60 20 15 2 24 5 22 0 8.9
3 Lentagran 2kg T1 15 8 2 2 7 10 0 9 6.33
4 Lentagran + Logic oil
1kg + 1.5l/ha T1 & T2 20 13 2 9 11 7.7 3 3.3 4.57
5 Lentagran 1kg T1 & T2 8 7 3 3 5 10 0 3.3 4.43
6
Lentagran + Sencorex WG 1kg + 0.5kg T1 & T2 100 28 48 4 45 80 78 36.7 65
T1 – early fern, T2 – 7-10 days after T1
© Agriculture and Horticulture Development Board 2013. All rights reserved - 26 -
Technology transfer
Project update to Asparagus Growers Association, 18 February 2013. HDC News article Presentation to growers at AGA agronomy day, June 2013.
© Agriculture and Horticulture Development Board 2013. All rights reserved - 27 -
Appendix 1 Weed species in trials
Latin name Common name
Capsella bursa-pastoris Shepherd’s purse Chenopodium album Fat-hen Equisetum arvense Horsetail Fumaria officinalis Fumitory Galium aparine Cleavers Matricaria sp Mayweed Poa annua Annual meadow-grass Polygonum aviculare Knotgrass Senecio vulgaris Groundsel Solanum nigrum Black nightshade Sonchus arvensis Field sowthistle Stellaria media Chickweed, common Urtica urens Small nettle Viola arvensis Field pansy