project title evaluation of potential alternatives for … title evaluation of potential...

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-

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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.


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


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.


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%).


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.


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.


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.


Gamit + Callisto

Untreated

Site A – pre-emergence, May 2012


Site C – weeds at second application

12/6/12

Site C – crop 8 days after second

application 20/6/12


Site C Post-emergence -

28/7/12

untreatedSencorex +

Lentagran

Lentagran

2kg/ha

Sencorex split


Site D Post-emergence,

Sencorex + Lentagran

Site D Post-emergence,

untreated


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.


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)


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


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


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



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


smooth sowthistle 110 cm fat hen 30 cm

black nightshade 35 cm

field sowthistle 20 cm

cleavers 20 cm

Knotgrass 15 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.


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.


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%).


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


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


0.75lt + 0.75kg

90 88 87 77 100 92 83


0.75lt + 3.3lt na na na na na na na


0.75lt + 3.3lt 85 91 85 73 100 90 82

7 Gamit 0.25lt 0 0 99 90 100 66 45


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


4lt + 0.75kg 96 92 96 85 100 97 88

12 HDC H16 4lt 79 30 82 33 100 87 32


0.75kg + 1.5lt 95 82 99 90 100 98 86


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


0.75lt + 0.75kg

94 91 85

90

95 95 38

73


0.75lt + 3.3lt

94 88 68

83

94 98 20 62


0.75lt + 3.3lt

na na na

na

na na na na

7 Gamit 0.25lt 84 81 75 80 89 23 63 53


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


4lt + 0.75kg

83 78 84

81

94 99 70 84

12 HDC H16 4lt 85 76 75 79 91 90 75 80


0.75kg + 1.5lt

75 66 76 73 93 79 0 52


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.


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


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


Table 5 Site C (Salford Priors) – Post-emergence weed control. Early assessment (% control, untreated = % ground cover of weed)

Date 20/6/2012


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


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


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


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


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


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


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


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.


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


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


Technology transfer

Project update to Asparagus Growers Association, 18 February 2013. HDC News article Presentation to growers at AGA agronomy day, June 2013.


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

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