Vodic Za Korovske Biljke

Managing weeds inarable rotations – a guide

Summer2010

Incorporating latest WRAG guidelines

2 Managing weeds in arable rotations – a guide

Introduction

The EU Sustainable Use Directiveaims to encourage greater use ofIntegrated Crop Management. Forweed control, the challenge is tointegrate crop choice/rotation, drillingdate, cultivation method, herbicideuse, resistance management andenvironmental protection.

These issues are also inter-related,for instance a range of different cropspecies widens both chemical andcultural opportunities to control grassand broad-leaved weeds.

Properly managed weed controlthrough a rotation can reduce costswhilst limiting the build up ofresistance, maintaining yields,protecting water quality andenhancing biodiversity.

Weed control has always beenchallenging but has become evenmore difficult because:

– herbicide availability has declined,– there are no new modes of

herbicide action currently available,– herbicides are being found in

water and– herbicide resistance is increasing.

Improving weed management means:

– Getting the most out of culturalcontrol and maximising herbicideperformance.

– Keeping weed populations lowfor good weed and resistancemanagement.

– Planning weed control across thefull rotation as this is nowessential.

Weed management

Weed control is vital for high yields of good quality crops and to preventthe spread of pests and diseases, eg ergot. But with fewer activeingredients, a need to protect water and manage herbicide resistance,the weed challenge must be managed across the rotation.

Weed control is more than just using herbicides. Many factors determineweed incidence and effective weed management in arable crops requiresintegration of them all:

– Crop choice and rotation– Managing the weed seedbank– Cultivations– Drilling date– Crop competition– Herbicide choice, application and timing– Recent weed control strategies– Weather– Agronomist/farmer perceptions.

The aim of this publication is to provide a practical guide for farmersand agronomists that brings together recent research to allow improvedweed management through a rotation dominated by autumn-sown crops.

This guide is different because ittreats resistance managementas an essential part of rotationalweed management.

Therefore, the Weed ResistanceAction Group Guidelinestogether with practicalinformation on cultural controland herbicide use are fullyintegrated within thispublication.

See pages 13–17.

Managing weeds in arable rotations – a guide 3

4 WeedbiologyKnowing your weeds and their biology is essential. TheEncyclopaedia of Arable Weeds (www.hgca.com/awe)provides important additional information.

6 Managing the seedbankUnderstanding the seedbank is at the heart of betterweed management. Cultivation strategies can beoptimised to reduce weed numbers, while managementcan be more predictive and preventative.

7 CultivationCultivation is not just about crop establishment, it alsochanges weed populations. The extent of seed burial andmixing influences weed numbers. The gap from harvestto drilling gives different opportunities and benefits.

8 Crop choiceCrops and their sequence in the rotation determine theweeds present and the opportunities for control. Adiversity of crops enables a range of practices andherbicide options. Including autumn and spring sowncrops within a rotation increases the range of weedspecies and reduces overall numbers.

9 DrillingdateDrilling date influences weed emergence and the windowfor weed control – a key time for many managementoptions. Intensity of crop competition is also influencedby drilling date.

10 Optimising herbicide timingThe right product applied at the right time with thecorrect spray quality maximises control from a herbicide.Often a sequence of herbicides is required.

11 Protectingwater qualityFollowing industry best practice guidelines to preventherbicides reaching water courses is a vital part ofmaintaining the range of products for weed control.

12 Effective herbicide applicationApplication techniques, weather conditions, nozzle choiceand spray volumes all affect herbicide performance.

13 WRAGGuidelinesIt is vital to minimise the risk of herbicide resistance. Thisrequires a combination of cultural and herbicide control.Know your risks through sampling and assess herbicideperformance. Follow the latest WRAG guidelines.

18 Weedmanagement in practiceCase studies of how farmers across the UK are changingtechniques to meet their weed challenges together withsuggested improvements.

23 Further information

Weed management toolboxPage

germinating GS111 true leaf

GS144 true leaves

GS21Start of tillering

GS31 Stem extension


Weedbiology–understanding weeds improves theirmanagementCrop competitionThe damage weeds cause depends on:

– weed species– weed density– competitive ability of the crops– growth stage when weeds

compete.While some weeds are highlycompetitive, others pose little threatand may be valuable to wildlife.Weeds can delay ripening andharvesting, eg cleavers in oilseedrape, or impair produce quality, egvolunteer potatoes in peas (Table 1).

*Threshold for 5% reduction in winterwheat yield.

Based on Blair, Cussans and Lutman (1999)

Table 1: Toleranceof commonarableweeds inwinterwheat

Population Weedtolerated* (Species in italics(plants/m²) have a high feed

value to birds)

0 barren brome, black-grass, cleavers,couch, Italian rye-grass, meadowbrome, wild-oat.

Up to 20 charlock, mustard,mayweed, oilseedrape, poppy, thistle.

20-49 black-bindweed,white campion,chickweed, fat hen,forget-me-not,redshank.

50-99 annual meadowgrass, crane’s-bill,fool’s parsley,fumitory, groundsel,knot-grass, red dead-nettle, scarletpimpernel, sow-thistle, speedwell.

Over 100 field pansy, parsley-piert, venus’s-looking-glass, wild onion.

WeedgerminationWeeds emerge at different times and the interaction between weed andcrop growth is important. Most problems occur when weeds and cropsemerge at the same time. Being able to predict when a weed germinatescan help determine the most appropriate control methods.

Weedsize and cropgrowth stageSmall weeds are generally easier to control (Figure 1), but very small weedsmay be less easy to kill with herbicide due to small areas of spray contact.

Non-chemicalweed controlNon-chemical techniques are increasingly important to reduce weed numbersand the need for herbicides, so reducing the risk of resistance developing.However, increasing the number of species increases biodiversity (Table 2).

+++ high, ++ moderate, + low, ( ) limited experience*from Lutman and Moss (2009)

Table 2:Non-chemical options forweed controlPotential to: Example

Decrease Increase number Black-grassnumbers of species control in wheat*

Spring crop +++ +++ 80%

Fallow +++ ++ 70%

Plough +++ + 67%

Delayed drilling ++ ++ 30%

Higher + (+) 30%seed rates

Competitive + (+) 22%variety

Mechanical (+) (+)weed control

Minimising weed (++) (++)seed dispersal

germinating cotyledon 2lf 4lf 6lf 8lf 25mm (1”)

weedgrowth stage

Figure 1: Easeof control declines asweedsgrow

Largerweeds causehigher yield loss

Easeofcontrol


Table 3:Germinationperiodsof commonweedsTiming Common weeds

Early spring common orache,spring wild-oat.

Mid spring black-bindweed, blackmustard, charlock,cock’s-foot, fat-hen, fool’sparsley, hedge mustard,hemp-nettle, knot-grass,pale persicaria,redshank,volunteer oats.

Late spring black nightshade,scarlet pimpernel,sun spurge.

Early autumn annual nettle, cleavers,with common poppy,spring flush couch, forget-me-not,

groundsel, mayweed,red dead-nettle, thistles,volunteer barley,volunteer oilseed rape,volunteer peas,volunteer wheat.

Autumn barren brome, meadowbrome.

Mainly black-grass, commonlate autumn field-speedwell, Italian

rye-grass, loose silkybent, venus’s-looking-glass, volunteer beans,wild-oat.

All the year annual meadow-grass,common chickweed,crane’s-bill, field-speedwells, fumitory,groundsel, red dead-nettle, mayweed,shepherd’s-purse,smooth sow-thistle.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Germination over 20%under 5% 5%-20%

For more information on the biology of weeds, see:The Encyclopaedia of Arable Weedswww.hgca.com/awe


Soil contains many weed seeds –the ‘seedbank’. This increases anddecreases as both weeds and cropsset and shed seeds. Weed seeds arespread within fields by the combinespreading straw at harvest and bycultivations.

Weeds emerge each year, generallyonly from the top 5cm. Cultivations stirup the seedbank burying freshly shedseed and bringing seed, from lowerdown the profile, to the surface.Depending on species, some buriedseed will become dormant and survivefor many years, some will germinate,some decay and some will be eatenby wildlife eg birds and insects.

ImportedweedseedsMost of the seedbank comes fromlocal weeds, but some seeds may beimported on machinery or in crop seed.Manure and slurry applications mayspread weeds from hay or bedding.Composting, drying manure or storingit for over eight weeks reduces the risk.Sewage sludge may contain weedsdepending on how it is processed.

DepthofweedseedsWeed seeds are distributed throughoutthe soil profile, but usually only emergefrom the top 5cm; those buried deeper,apart from a few larger seeded species,eg barren brome and cleavers, seldomemerge. This is a key point whenplanning weed control strategies.

Weed seeds are not viable for everand have a natural death rate (Table 4).

To reduce the weed seedbank– Encourage weeds to germinate

by changing crop type,cultivation timing and drillingdates.

– Prevent weeds from settingand shedding seed.

It is not necessary to count weed seeds in a soil profile, germinating weedsin an untreated area give a good indication of weed infestation.

Changing rotation to reduce the weed seedbankThe Weed Manager programme (Project Report 388) can predict weedseedbank levels through a rotation and has been used to derive Figure 2and evaluate suggested improvements in the case studies (pages 18–22).

Table 4:Weed seed longevityLongevity Grasses Broad-leaved weeds

Under 1 year soft brome, rye brome, barren volunteer sunflowerbrome, volunteer cereals and oats and linseed

1–5 years perennial rye-grass, black-grass, winter wild-oat chickweed, crane’s-bill, creeping thistleand mayweed

Over 5 years wild-oat, loose silky bent, Italian rye-grass, black bind-weed, charlock, common poppy,orache and many others speedwells and volunteer rape

Managing the seedbank– theheart of all goodweed control

Cultivation

Crops

plough

SBns

non-invert

WW

non-invert

WW

plough

WW

non-invert

WOSR

non-invert

WW

Amendedrotation

Cultivation

Crops

plough

WBns

non-invert

WW

non-invert

WW

non-invert

WW

non-invert

WOSR

non-invert

WW

Initial black-grasslevels high

Plough

Spring beans

Very high

Low

SBns = spring beans WBns = winter beans WOSR = winter oilseed rape WW = winter wheat

Year 1 Year 2 Year 3 Year 4 Year 5 Year 6

Wee

dse

edb

ank

Basicrotation

In year 2 changing to a spring crop significantlyreduces the seedbank and this is reduced furtherby ploughing before the second wheat in year 4.

Figure 2:Howchanging crop type, cultivation anddate in aheavy landrotation affects black-grass


Stubble cultivationShallow cultivation, immediately afterharvest can stimulate weed seedgermination, especially barren bromeand volunteer cereals. For best effectsoil must be moist. However,cultivations prevent mammals andbirds eating weed seeds. Stubblecultivation reduces annual meadow-grass.

Primary cultivationsApart from stubble cultivation, the‘primary’ cultivation is the first one toprepare soil for the next crop.

Cultivations may be classified intofour groups (Table 5) and are abalance between bringing older seedfrom depth and burying newly-shedseed.

PloughPloughing is unique as it inverts soil,burying 95% of freshly-shed seed to15-20cm, but brings up 35% of oldseed. Subsequent cultivations aremore shallow so buried seed is notdisturbed. Most weeds germinatefrom seeds shed in previous seasons.

Deep till and shallow tillNon-inversion tillage mixes the upperlayer to a set depth. Germinatingweeds are a mix of newly-shed seeds

and those from previous seasons.About half the seed is buried belowgermination depth and 10% of oldseed returns to the surface.

No-tillWith no-till, including Autocasting,the soil is only cultivated by the drill.Weed seeds are predominantly in thetop 3cm, but some smaller seedsmove down soil cracks.

OtherSubcasting, using a subsoiler ormodified cultivator, results in freshly-shed seed falling down cracks butwith little soil mixing. Using discsleads to more mixing – equivalent todeep or shallow till.

Cultivation–changesweedpopulation asmuchas cropestablishment

Cultivation After harvest Plough Deep till Shallow till No-till

Soil Inversion Deep Little No mixingmovement

Cultivations Over 5cm, Over 5cm Under 5cm Nonedepth inverted

Example Plough Discs over 5cm Discs under 5cm No-till drill

Many old seeds Fewer old seeds Very few old A few seedsbrought to brought to surface, seeds brought may changesurface, most some new to surface. Few layers.new seeds buried. seeds buried. seeds added to

the seedbank.

Weed Generally Has little effect Keeps weed Keeps weedcontrol reduces weed on weed seeds in top 5cm seeds in top 5cm

populations. populations. of soil where they of soil where theycan germinate. can germinate.

Table 5: Cultivationoptions andeffect onweed seedbank

5cm

30cm

Soil depth


Crop choice– the essential buildingblockof anyweedmanagement strategy

Crop choiceChoice of crop affects many things,including the time of drilling, the typeand timing of cultivations and therange of herbicides available. Somecrops compete better than otherswith weeds (Table 6).

RotationsThe ideal rotation should include a balance of different crops. The aim is toprovide an economically successful sequence which breaks pest and diseasecycles, improves weed control, prevents erosion with crop coverand improves nutrient cycling and soil condition.

Table 6: Comparisonof spring- andautumn-drilled crops

*Ranging from ++++ high to + low BLW = broad-leaved weed(s) Pre-em = pre-emergence

Number of Competition Benefits Disadvantagesherbicide with weeds*activesavailable*

Winter sown Well suited to heavy soils. Usually higher yielding. Provides overwinter crop cover.

Cereals

Wheat ++++ +++

Barley ++++ ++++

Oats +++ ++++Rye +++ ++++

Broad-leaved crops

Beans ++ ++

Oilseed rape ++ ++++ Herbicides with no known Cannot delay drilling. Mostresistance available. BLW control must be pre-em.

Volunteers can be a problem.

Spring sown Spreads workload. Changes weed species and numbers. Good for biodiversity. Less suited to heavy soils.

Cereals

Barley ++++ ++++

Wheat ++++ +++ Minimise cultivations on lightsoils if drought is a problem.

Triticale +++ +++

Oats +++ ++++ Difficult to control grass weeds.

Rye +++ ++++

Broad-leaved or other crops

Beans ++ ++ Late sowing can lead to a lateharvest.

Peas ++ + Delayed sowing reduces yield.

Oilseed rape ++ ++++ Few herbicide options.Susceptible to drought at drilling.Volunteers can be a problem.

Sugar beet +++ +++ Multiple low dose systems High capital investment. Poorlyfor weed control. Can be competitive initially. Very latemechanically weeded. harvest.

Potatoes ++ +++ Can use non-specific High capital investment.herbicides. Good competitor Can leave volunteers.with weeds.


Theeffect of delayeddrillingon specificweedsBlack-grassUnderstanding dormancy and the effect of weatherand soil conditions is important (Table 7). Weatherduring ripening determines black-grass dormancy.Low dormancy occurs in warm, dry conditions andseeds will grow rapidly if moisture is not limiting.In some years black-grass germinates as the cropripens. Conversely, cold wet weather leads to highdormancy and delayed black-grass emergence fromseed shed in the current season.

Drilling date

Annualmeadow-grassDelayed drilling has little effect.

Italian rye-grassSeed dormancy is short-lived and mostseed emerges by November. Delayeddrilling reduces populations.

MaximisingcropcompetitionA crop’s ability to compete is aproduct of seed rate and drilling date.Lower rates leave more space forweeds to establish but early drillingmeans crops have longer for tilleringand so are more competitive thanthose drilled later.

Crop establishment declines incereals drilled after mid-October,seed rates should be increased tomaintain yield. Late emerging weedsare less competitive and producefewer seeds.

The window for drilling winter barleyis narrower than for winter wheat. Alow vernalisation requirement meansbarley is less suited to very earlydrilling while yield declines rapidlywhen drilled after mid-November.

Variety choice affects cropcompetition. Some cereal varietiesreduce the competitive effect ofweeds by over 30%.

Table 7: Dormancy andmanagement of black-grassHigh dormancy Low dormancy

Pre-harvest No effect. Check and treat if black-glyphosate grass is emerging inapplication wet conditions.

Black-grass More protracted, 90% emergence 90% emergence 30emergence 60 days after drilling. days after drilling.

Cultivations Plough – unless low weed Non-inversion.populations.

Drilling Early encourages crop competition. Delay for maximumweed emergence.

Pre-em Use robust mixture with a Apply immediately afterherbicide herbicide residual component. drilling.

Post-em Could be delayed but add a Apply early, once mostherbicide residual if applied early. germination is complete.

– has amajor effect onweed species andnumber

The interval between harvesting onecrop and drilling the next is important,as a non-selective herbicide can beused on emerged weeds. Delayingdrilling increases the time availablefor weed control but it can reducesubsequent crop competiveness,although increased seed rate canhelp compensate.

All emerged weed seedlings shouldbe killed before drilling, ideally with anon-selective herbicide. Cultivations,especially in moist soils, will not kill

seedlings and surviving plants will belarger and more difficult to control.

Where possible wait for a weedflush before drilling. Drill fields withlow weed populations first, leavingthose with high grass weed burdensuntil last.

Weather conditionsDry weather between harvest anddrilling minimises weed emergence,but crops will not emerge either.

BromesShallow cultivate barren and greatbrome seeds to bury them as soon aspossible after harvest unless choppedstraw provides good seed cover.Meadow, soft and rye brome seedsare usually under ripe and burialimmediately after harvest enforcesdormancy. Leave seeds to ripen forone month before cultivating.Brome emerges quickly in moist soiland dormancy has little effect onemergence. Wait until brome hasemerged and spray off withglyphosate pre-drilling.

Wild-oatDelayed drilling allows a longer periodfor predation and seed germination.


Herbicides form a large part, typically 20-30%, of the variable costs associatedwith producing a crop. Product labels and technical support can providegrowers with information to optimise herbicide effectiveness, but generalprinciples apply to all crops (Table 8).

Optimising herbicide timing

Table 8:Optimisingherbicide timing in autumn-sowncrops – factors to considerHerbicide Aim Mode of Advantages Disadvantagestiming action

Pre-drilling Encourage weed Contact Can use non-selective Early drilling shortens timegrowth. Control herbicides, which reduce for weeds to emerge and beweeds from resistance risk. controlled.harvest to drilling.

At drilling Apply before crop Residual Prevents weed establishment. Poor weed control whereor weeds emerge Essential building block of seedbed quality is poor or(pre-em), within grass weed control; only seedbeds are dry. Crop seed24-48hrs of drilling. effective timing for some depth, or soil cover, can be anControl weeds until species/herbicides. Limited issue with some herbicides.end of winter. resistance to pre-em herbicides.

Autumn/winter Control later Residual Weeds visible to identify Control more difficult if weedsgerminating weeds Contact which aids product choice. are large. Soils can be too wet.or escapees from Stressed crops. Large croppre-emergence canopies. Beware coldtreatments. Target temperatures which can reduceweeds when small. efficacy of some herbicides.

Spring Control spring Contact Weed spectrum visible. Large weed size. Sometimesgerminating weeds. Some too late for certain species.Tidy up winter residual Target crop growth stage isescapees. missed.

Pre-harvest Control late Contact Ideal timing for perennial Few species at correct growthgerminating and weeds. stage. Some weed seed set.perennial weeds. Some crop market restrictions.

– to improve effectiveness and increase value

Cereal herbicidesEffective grass weed control isessential in rotations with autumnsown crops. Mixtures (severalproducts applied together) orsequencing/stacking (severalproducts applied in close succession)are more effective at controllinggrass weed populations thanindividual products. Pre-emergenceoptions are less affected byresistance and should form a keypart of a cereal herbicideprogramme.

Black-grassRecent research shows flufenacetis a key active in programmes buta further 2-4 actives are necessaryto achieve good control. Commerciallyacceptable control is more likelywhere untreated populations areunder 100 heads/m2.

Annual meadow-grassHerbicides are necessary to controlthis weed as it germinates throughoutthe season and cultural methods havevery little effect. Both pre-emergenceand post-emergence strategies can bevery effective.

Barren, or sterile, bromeCultural methods, eg ploughing anddelayed drilling, can give good controlotherwise a sequence of pre- andpost-emergence herbicides isnecessary.

Oilseed rapeherbicidesSpring herbicide options are limitedin oilseed rape and weed controldecisions need to be made priorto drilling.

Establishment methods and weedspresent affect control options:

– where cleavers and/or poppy arepredicted, a robust pre-emergencetreatment – based on metazachlor– is required. Rape seed must bewell covered by soil to a depthof 15mm.

– for black-grass and other grassweeds, herbicides such aspropyzamide are more effectiveafter no, or very shallowcultivation. Where deepercultivations are used adding agraminicide (‘fop’ or ‘dim’) willimprove the level of control.


The importance of keeping pesticides out of water courses is increasing. EUand UK water quality legislation may affect or restrict use of several herbicides,particularly those used extensively, as well as those used at high rates andapplied at times of year when drains may be running or there is potential forrun-off to watercourses. The result of new legislation could be restrictions onrate and/or timing, with product withdrawal as a last resort.

A small number of approved pesticides are detected regularly in surface water(Table 9). Herbicides can enter water in a wide range of ways:

Stores hold concentrated chemicals; afire or leak can have a huge impactdownstream.Drips or spills of concentratedchemical at sprayer filling canwash offconcrete or hardcore into drains andwater courses.Over-sprayingwatercourses iscareless and jeopardises aquatic life andwater quality.Drift concerns neighbours and canharmaquatic life andwater quality.Drain flow is themainway herbicidesleave the field in thewintermonths.

Herbicides attached to soil particles, orin drainagewater, enterwater courseswhen drains are flowing.Surface run-off carrying soil andpesticides can occur onmost soils andslopes after heavy rain and can bechannelled by tramlines.Cleaning sprayers produces largequantities of dilute pesticidewhich caneasily reach drains if poorlymanaged.Disposingof pesticide containers byburial is illegal and can cause long-termdamage towater quality.

Keypoints(For herbicides in Table 9)– Establish grass buffer strips

of at least 6m wide besidewatercourses, or use a 5mno-spray zone.

– Do not spray when heavy rain orsnow is forecast within 48 hoursof application; or when soil isvery wet or drains are running orare likely to run.

– Only spray in suitable settledweather, preferably when soil ismoist.

– Do not spray when soil is dry andcracked.

– Do not apply the aboveherbicides if the fields have beenmole drained or sub-soiled belowplough depth/layer.

– Minimise dose rate if possible.– Take care when filling or

emptying the sprayer.– Wash sprayer in the field and

park under cover.– Pressure, or triple wash and drain

pesticide containers beforestoring them under cover toawait disposal by a wastedisposal contractor.

Protecting water quality

Table 9: Some herbicides detected in water and best practice to avoid risk

Maincrop(s)

Bestpractice

metazachlor

Oilseed rape

Apply from pre-emto early post-em ofweeds to moist soil.

Apply in latesummer/earlyautumn.

Max dose of 1000gai/ha every 3rd yearin same field.

propyzamide or carbetamide

Oilseed rapeBeans

Apply to cold, moist soils(not saturated).

Avoid use if drains are flowing orlikely to flow in the near future.

clopyralid

CerealsOilseed rape

Apply when weedsare actively growing.

Avoid use if drainsare flowing orlikely to flow inthe near future.

chlorotoluron

Cereals

Apply from pre-em toweeds at 1-3 leaves tomoist soil.

mecoprop-P

CerealsGrassland

Apply when a fullcrop canopy ispresent and nomore than 50%bare ground.

Straight mecopropcannot be appliedto cereals between1 October and1 March.

For detailed guidanceon protecting water qualityand responsible pesticide use

www.voluntaryinitiative.org.uk

– essential to protect theproduct choice available

Extracted from H2OK? Water Protection Advice for farmers and advisers – 2009/10available from the Voluntary Initiative website


Herbicide performanceApplication technique can significantly affect herbicide performance,particularly for small weeds early in the season. Consideration should begiven to:

– timing of the application

– high levels of deposit of active substance

– the right droplet size

– controlling spray drift.

Optimum timing is important. Where weather conditions limit available spraydays, high work rates are necessary but must be balanced against the risk ofspray drift.

SpraydepositsSmall weeds are particularly challenging targets, especially grass weedsbecause of their vertical structure.

The highest deposits on target weeds result from reducing both applicationvolume and droplet size. Using lower volumes (around 100-150l/ha) is generallymore effective than volumes of 200l/ha and higher.

Some horizontal movement of droplets is necessary to ensure adequatedeposition on small grass weeds. Angling nozzles is one way to createhorizontal velocities which increases active ingredient deposition on smallvertical targets.

Droplet sizeFor many herbicides, finer quality sprays are more reliable than coarser sprays.Often air-induction nozzles giving the smallest droplet sizes perform as well asmedium-fine conventional sprays (Figure 3).

ControllingdriftFine sprays are likely to lead to the highest drift. Applications where little cropcanopy exists to absorb spray will also increase risk of drift. The lower theboom, the less the drift. Maintaining the correct boom height throughout thespray operation is essential. Wind speed has an important, but smaller, effecton drift.

WeedsizeLarge, rather than small, weeds aremore suitable for treatment with airinduction nozzles, particularly thosegiving the smallest droplet sizes,which can still significantly reducedrift compared with conventionalnozzles.

FormulationWater-soluble liquid formulations witha high level of surfactants – such asglyphosate – may also increase spraydrift so additional precautions forcontrolling drift may be necessary.

Increasing work rateReducing water volume from 200 to100l/ha, achieved by changing nozzlesize, gives an estimated 40%increase in work rate for a 24m boomon a 3000 litre self-propelled sprayer.Increases in work rate can also beachieved by increasing forward speedand boom width. However, fasterforward speeds and wider boomsmay require increased boom height.This increases the risk of drift as doesspraying reduced volumes throughsmaller-sized conventional nozzles.

It is essential to comply with productlabels and the Code of Practice forusing plant protection products.

Effective herbicide application–correctwater volumeanddroplet size improve efficacy

Nozzle style Air induction Conventional

Spray droplet size Small droplet Large droplet Fine Medium Coarse

Pre-and early post-emergence

Grass weeds - 3 leaves or fewer �

Grass weeds - more than 3 leaves

Broad-leaved weeds - up to 2cm across �

Broad leaved weeds - 2-5cm across �

Broad leaved weeds - more than 5cm �

Non-selective (eg glyphosate) �

�

�

Figure 3:Matchingnozzles toweed challenge

=Acceptable

=Preferred

=Best for drift control�

Remember– Check carefully any restrictions

on mixing or sequencingherbicides.

– Avoid treating in waterloggedor frosty conditions or if crop issuffering nutrient stress.

– Most residual herbicides workpoorly in soils of high organicmatter content (over 5%).

– Residual herbicides requiremoisture and an even seedbedfor good control.

– Heavy rain after application canmove herbicides down the soilprofile away from the weedgermination zone.

– In no-till established cropswhere crop seed is not coveredwith soil, wait until the crophas established before applyingherbicides.

Optimisingweed controlstrategies for herbicideresistancemanagementMany of the most active herbicides(eg ALS and ACCase inhibitors)pose a very high resistance riskbecause they are affected by targetsite resistance and, in most cases,enhanced metabolism resistance too.It is essential to utilise strategies tolimit resistance to these herbicides,especially now that fewer, lower riskherbicides are available. Herbicideresistance is an irreversible process –it does not disappear or decline ifherbicides cease to be used. Thismeans more use of non-chemicalmethods to reduce dependence onherbicides, maximising the benefitfrom pre-emergence herbicides andensuring effective use and timing ofremaining post-emergence products(Table 10).

Non-chemical control methodsto reduce reliance on herbicidesSee page 6 – 9 for more details.Non-chemical methods cannotreplace herbicides on most farms,but reduced reliance on herbicideswill be necessary both from apractical (increasing resistance,lack of new herbicides) andpolitical (complying with newEU legislation) aspect.Pre-emergence herbicides– Reduce the overall weed

population and the need for higherrisk post-emergence products.

– Flufenacet, pendimethalin,prosulfocarb and triallate are allaffected by enhanced metabolismresistance, but generally only to alimited extent.

– Products or programmes basedon combinations of these activeingredients usually give usefullevels of control. Resistance tothese herbicides does not appearto build up rapidly.

– Valuable in any integratedresistance management strategy,especially for grass weeds.

Post-emergence herbicidesPlace less reliance on high resistancerisk post-emergence herbicides.– The ACCase (‘fops’, ‘dims’, ‘dens’)

and ALS inhibitors (egsulfonylureas) are prone toresistance, and their regular useis associated with a high risk ofherbicide resistance, andconsequently poor weed control.

– To avoid, or delay, resistancedevelopment, do not rely on eitherclass as the main weed control insuccessive crops.

– Use these herbicides, in mixtureand/or sequence with lower riskmodes of action, to help reduceweed populations. However, thiswill not prevent further selectionfor resistance.

– Remember, there are restrictionson the sequential use of bothACCase and ALS inhibitors –introduced to reduce herbicideresistance risk.

– Using mixtures and sequences isa sensible approach, but it is bestconsidered as a strategy to delay,rather than prevent, resistance.

– Where possible, use lowerresistance risk post-emergenceherbicides in the rotation,eg propyzamide and carbetamide,in oilseed rape.

Table 10:Herbicide resistance risk factors

Agronomic factor Lowest risk Highest risk

Cropping system Good rotation of spring Continuous winter cerealsand autumn crops

Cultivation system Annual ploughing Continuous non-ploughing

Control method Cultural only Herbicides only

Herbicide use Different modes of action Single mode of actionthroughout therotation

Weed infestation level Low High

Resistance incidence None in vicinity Identified locally in similarcropping systems

The Weed Resistance Action Group(WRAG) website contains many usefuldocuments and references. This includesthe WRAG guidelines and an up-to-datelist of herbicide modes of action.

www.pesticides.gov.uk/rags.asp?id=714

Minimise resistance risks–maintain product effectivenesswith an integrated approach

13

‘Herbicide resistance is the inheritedability of a weed to survive a rate ofherbicide that would normally kill it.’

Resistance mechanismsHerbicide resistance, first identifiedin black-grass in 1982, also affectswild-oat, Italian rye-grass and, morerecently, common chickweed, commonpoppy and scentless mayweed.

Herbicide resistance occurs throughselection of plants that surviveherbicide treatment. With repeatedselection, resistant plants multiplyuntil they dominate the population.Three main types of resistance arepresent in UK grass-weed populations(Table 11). In broad-leaved weeds,only ALS target site resistance hasbeen confirmed.

These WRAG guidelines bring togetherthe latest research and field experienceto help UK farmers and advisors:

– prevent resistant weed populationsdeveloping

– manage existing resistantpopulations

– prevent the spread of herbicideresistant weeds.

Recent research has highlighted thekey factors that can contribute tobetter integrated weed managementstrategies.– Increase use of non-chemicalcontrol methods to reducereliance on herbicides.Non-chemical methods cannotreplace herbicides on most farms,but reduced reliance on herbicideswill be necessary.

– Make greater use of pre-emergence herbicides. Thesereduce the overall weed populationand the need for higher risk post-emergence products. Resistanceto the pre-emergence herbicidesused for grass-weed control tendsto be only partial and builds uprelatively slowly, so they appear tobe a lower resistance risk thanmost post-emergence options.

– Place less reliance on highresistance risk post-emergenceherbicides. The regular use ofACCase (‘fops’, ‘dims’, ‘dens’) andALS inhibiting herbicides (egsulfonylureas) is associated witha high risk of herbicide resistance.Do not rely on either class as themain means of grass-weed controlin successive crops. Wherepossible, use lower resistancerisk post-emergence herbicides inthe rotation, eg propyzamide andcarbetamide, in oilseed rapeand beans.

– Use mixtures and sequences toreduce the threat. Using higherresistance risk herbicides inmixture or sequence with lowerrisk modes of action, will helpreduce weed populations.However, this will not preventfurther selection for resistance.Remember, there are restrictionson the sequential use of bothACCase and ALS inhibitingherbicides – introduced to reducerisk of herbicide resistance.

– Monitor herbicide performance inindividual fields. Resistance canvary considerably between and,to a lesser extent, within differentfields. Management strategiesneed to take account of thisinter-field variation. Closemonitoring of variations in herbicideperformance, both within andbetween fields, can act as an earlywarning of potentially greaterproblems ahead.

– Carry out regular testing forresistance.While the factorsresponsible for the evolution ofherbicide resistance are wellestablished, predicting the riskat an individual field scale isimprecise. Consequently, actualtesting of seeds or plants fromfields provides a more robustindicator of the degree of herbicideresistance. This needs to be doneregularly, at least once every 2-3years, if changes in resistance areto be detected reliably.

Managing herbicide resistance

Table 11: ResistancemechanismsEnhanced metabolism ACCase target site ALS target siteresistance (EMR) resistance (ACCase TSR) resistance (ALS TSR)

Results in herbicide detoxification and Blocks the site of action specific to Blocks the site of action ofis the commonest resistance mechanism ‘fop’ (eg Topik, Falcon), ‘dim’ (eg Laser) sulfonylurea (eg Atlantis) andin grass weeds in the UK. It affects most and ‘den’ (eg Axial) herbicides in related herbicides (eg Broadway Star,herbicides to varying degrees, but only in grass weeds. It only affects these Attribut) in grass and broad-leavedsevere cases results in complete loss of groups of herbicides, but can result weeds. It only affects this group ofcontrol. Tends to increase slowly. in very poor control. Can increase rapidly. herbicides but can result in poor

control. Currently less common thanACCase TSR, but is increasing.

NB All three resistance types can occur independently, in different plants within a single field, or even within the same plant.

– goodpractice is vital to preserveproduct effectiveness

Key factors formore sustainable resistancemanagement


15

Detectingherbicide resistanceEarly detection is very important. Symptoms of herbicide resistance are:– A gradual decline in control over several years.– Healthy plants beside dead plants of the same species.– Poor weed control leading to discrete weed patches.– Poor control of one susceptible species when other susceptible species are

well controlled.

Testing for herbicide resistanceHave a test carried out on seed or plant samples if you suspect resistancecould be developing. Good sampling methodology is important if results areto be credible (Table 12). Seed samples are best collected in mid-July.– Preferably collect samples while control levels are still good overall. Do not

wait until herbicides fail totally, as by then resistance management optionswill be much more limited.

Discuss sample collection and testing options with your adviser or cropprotection supplier.

Monitor the success of resistancemanagement strategies– Keep accurate field records of cropping, cultivation and herbicide use, and

control achieved.– Monitor herbicide performance critically within individual fields to detect any

progressive loss in herbicide efficacy which can act as an early warning ofpotentially greater problems ahead.

– Test specific fields regularly every three years – either those with a knowndegree of resistance or where there is a high risk of resistance developing.

Unit of assessment Consistency Implication for sampling

Patches Good One sample is likely to berepresentative of that patch.

Within fields Good/variable Collect seed from a number of patchesacross the field.

Between fields Variable Consider carefully how to approachsampling and be prepared to takesamples from several fields oneach farm.

Farms Variable Do not rely on the results at one farmto predict those of another.

Table 12: Sample areas for resistance

Herbicide resistanceThe threat of herbicide resistancecontinues to increase due to:

– increasing use of higherresistance risk herbicides(ACCase and ALS inhibitors,eg Atlantis)

– loss of lower resistance riskherbicides (eg trifluralin andisoproturon)

– lack of herbicides with newmodes of action

– trend towards more non-inversion tillage which favoursgrass weeds

– dominance of autumn-sowncereals and oilseed rape inarable rotations.

Rapid and effective tests ofherbicide resistance are available

Sensitive

Resistant

Monitor herbicide resistance– regular testing andassessment are essential tomaintain control


Herbicide resistance in individual weeds

Black-grass(Alopecurus myosuroides)the major resistanceproblem in England

Resistance first found 1982

Cases confirmed over 2,500

Number of counties 31

– Resistance to mesosulfuron +iodosulfuron, introduced intothe UK in 2003 as ‘Atlantis’,has been confirmed on over250 farms in 21 counties. ALStarget site resistance wasconfirmed in many resistantpopulations, althoughenhanced metabolism alsoposes a big threat.

– Use of high resistance riskALS and ACCase inhibitingherbicides in mixtures andsequences with lower riskmodes of action increases theoverall level of weed control,but does not preventresistance increasing.

It is now accepted that some degree of resistance occurs in virtually allfields in England sprayed regularly with herbicides to control black-grass.

– Resistance can reduce theefficacy of all currently availablepre-emergence herbicides, butusually only to a limited degree.Flufenacet appears the leastaffected herbicide. Resistancealso appears to increase moreslowly compared with thepost-emergence ACCase andALS inhibiting herbicides.

– Non-chemical control methodscan give useful, if modest, levelsof control of black-grass. Greateruse of non-chemical controlmethods will reduce thedependency on herbicides, andso reduce the risk of resistance.

Italian rye-grass(Lolium multiflorum)an increasing threatthroughout the UK


Cases confirmed over 300


Resistance status: Enhanced metabolism – common

Target site resistance to ‘fops’, ‘dims’ and ‘dens’ –occurs, but less commonly than in black-grass

Target site resistance to ALS inhibitors – suspected

– Resistance to diclop-methyl(eg Hoegrass) and tralkoxydim(eg Grasp) was found on 70%of farms in a survey of fieldsin England. Resistance tocycloxydim (eg Laser) andpinoxaden (eg Axial) was foundless commonly (<20% farms).

– Resistance was mainly due toenhanced metabolism,although ACCase target siteresistance was also detected.Resistance to ALS inhibitingherbicides is likely to increase.

Resistance is widespread, but is currently less problematic than with black-grass. Resistance poses an increasing threat due to over-reliance on highresistance risk herbicides (ACCase and ALS inhibitors).

– Rye-grass produces more seedsper plant than black-grass, and isat least as competitive, so highlevels of control are needed

– Most plant emergence (94%)occurs in the autumn, fromOctober to December. Autumnemerging plants produce about23 times as much seed as springemerging ones.

– Weed control should be focusedon autumn rather than springtreatments.

Findings from recent research studies


Resistance status: Enhanced metabolism – very widespread

Target site resistance to ‘fops’, ‘dims’ and ‘dens’ –widespread

Target site resistance to ALS inhibitors – increasing

17

Commonwild-oatandwinterwild-oat(Avena fatua and Avenasterilis ssp. ludoviciana)a limited, but widespreadproblem


Cases confirmed over 200


Resistance status: Enhanced metabolism confirmed

Target site resistance tends to be specific to the‘fop’ herbicides

Target site resistance to ALS inhibitors – not yetconfirmed in the UK

– Herbicide-resistant wild-oatappear to be a relativelylimited problem in the UKand have not increased aspredicted. This is surprising,as resistant wild-oats are anincreasing problem in someother countries (eg Canada,Iran) where there is highdependence on ACCase andALS inhibiting herbicides.

– Wild-oats are self pollinatedand so resistance cannot be

Currently, resistance tends to be more localised than with black-grass andrye-grass. Resistance continues to pose a threat due to over-reliance onhigh resistance risk herbicides (ACCase and ALS inhibitors).

spread by pollen. This may be whyresistant wild-oats tend to occur indiscrete patches. Preventingresistant patches spreading shouldbe a top priority.

– In contrast to black-grass andrye-grass, ACCase target siteresistance tends to be morespecific to ‘fops’, with ‘dims’ and‘dens’ often remaining effective.

Broad-leavedweeds – chickweed,commonpoppyandscentlessmayweedStellariamedia,PapaverrhoeasandTripleurospermuminodorum

Chickweed Poppy Mayweed

Resistance first found 2000 2001 2002

Cases confirmed 15 11 1

Number of counties 11 7 1

Comment Mainly a problem Limited problem, Limited problemin Scotland and but a bigN. Ireland potential threat

Resistance status: Enhanced metabolism – not found in broad-leavedweeds in the UK

Target site resistance to ALS inhibitors – confirmedin all three species

NB: ACCase resistance is irrelevant as these herbicides are not active on broad-leaved weeds

– Resistance is mainly confinedto ALS inhibiting herbicides(eg sulfonylureas such asmetsulfuron-methyl) in allthree species, with alternativemodes of action givingcomplete control.

– Alternative herbicides whichgive good control of ALSresistant populations include

Although resistance has only been detected in these three species in theUK, worldwide experience shows that resistance could evolve in manyother broad-leaved weeds too, so vigilance is required.

fluroxypyr (eg Starane 2) onchickweed and ioxynil+bromoxynil(eg Oxytril CM) on poppy andmayweed.

– Resistance to mecoprop inchickweed has been confirmedin England in the past, and issuspected to occur in Scotland,but the extent of the problemis uncertain.




Chris BaileyKnapwellCambridgeshire

“A cover cropbefore spring

beanspreventsNloss andgives awidewindow for

black-grasscontrol”

180haHanslope clay

Problemweeds:Highly resistant black-grass.Patches of wild-oat.Typical range of broad-leavedweeds including crane’s-bill.

Rotation:1. Winter wheat2. Winter oilseed rape3. Winter wheat4. Spring beansSometimes includesa 2nd wheat.

Cultivation and timing

Current practice

No-till establishment of oilseed rapeKeeps weeds rooting at soil surface for a very high level of control frompropyzamide.

Sprayout black-grass patchesWhere black-grass populations are high and autumn herbicides have hadlittle effect, spraying out black-grass with a non-selective herbicide minimisesseed return.

Suggested improvements

Delaywinterwheat drillingChris mainly sows early and uses non-inversion techniques in his rotation.At present, black-grass control is adequate but the weed seedbank is buildinggradually. To reduce this, late sowing in the 1st wheat after oilseed rape allowsfor increased use of a non-selective herbicide, while ploughing before springbeans reduces the weed seedbank further.

Later sowings can maintain this lower seedbank.

Cultivation

Basicrotation

non-invert

WOSR

non-invert

WW

non-invert

WW

non-invert

SBns

non-invert

WW

non-invert

WW

Plough

Very high

Low

WW = winter wheat WOSR = winter oilseed rape SBns = spring beans


Delay drilling

Current practice Suggested improvements

Wee

dse

edb

ank

Crop Soil movement Cultivation timing Drilling

Winter wheat Disc and tine Soon after harvest End Septemberafter springbeans

Winter oilseed None – Seed broadcast intorape wheat before

harvest

Winter wheat Disc or tine Soon after harvest End Septemberafter OSR

Spring beans Disc October March

Weed management in practice 1


AndrewCraggRomney MarshKent

“Spring croppingis not attractive inthe short-termbutoffersmany long-termbenefits”

560hasilty clay loam

Problemweeds:Black-grass(ALS resistance confirmed).Crane’s-bill and cleavers increasedin recent years.Sow-thistle and charlock inoilseed rape.Hedge mustard in peas.

Rotation:1. Winter wheat2. Winter wheat3. Winter oilseed rape4. Winter wheat5. Winter wheat6. Vining peas


Current practice

Inclusionof a spring cropPloughing and a wide window for weed control with non-selective herbicidesgive high levels of black-grass control and a herbicide-free spring crop.

Controlled traffic systemImproved soil structure and oilseed rape establishment.


Ploughing and later drilling to reduce theblack-grass seedbankPloughing down black-grass before spring peas results in fewer seeds in thegermination layer. Ploughing before wheat in year 3 would lead to an initialdecrease in black-grass. (Delaying sowing from October until early Novemberwould increase the effect much more). Ploughing in year 3 also reduces thevolunteer OSR seedbank. A pea crop and October sowing of the final wheatcrop maintains the lower black-grass seed bank.

Cultivation

Basicrotation

non-invert

WOSR

non-invert

WW

non-invert

WW

non-invert

WW

plough

VP

non-invert

WW

Delay drilling

Plough

Very high

Low

WW = winter wheat WOSR = winter oilseed rape VP = vining peas



Wee

dse

edb

ank


1st winter Disc At drilling Late Septemberwheat

2nd winter Mainly disc or Soon after harvest Octoberwheat some plough

OSR Loosening and power As early as possible Early Augustharrow

Vining peas Plough and press Early autumn April-May



RichardDaveyChalgroveOxon

“Rather thanhaving apoorly

establishedbreakcrop it’s betterto haveno crop

at all”1,150ha

Light sandy loam toheavy clay

Problemweeds:High levels of highly resistantblack-grass.

Rotation:1. Winter wheat2. Break3. Winter wheat4. Break

Soil type and topographydictate break crops which includewinter beans, winter and springoilseed rape.


Current practice

Promptherbicide applicationResiduals applied within 24 hours of drilling.

Stale seedbedShallow cultivation after harvest encourages black-grass to chit. If moisture isadequate, then deeper cultivations used for a better chit.

Delayedwheat drillingDelaying drilling until early October enables weed control via stale seedbed.


Use fallows to reduce soil seedbankRichard does not want to plough and is not keen on spring cropping due toestablishment problems. While controlling weed numbers in his crop, hiscurrent practice has not reduced the black-grass seedbank.

A possible change may be the use of later sowing and fallows. A Novembersowing in year 3 begins to reduce the seedbank. A fallow in year 4 causesa further large reduction.

Cultivation

Basicrotation

non-invert

WOSR

non-invert

WW

non-invert

WW

non-invert

WBns

non-invert

WW

non-invert

WOSR

Fallow

Delay drilling

Very high

Low

WW = winter wheat WOSR = winter oilseed rape WBns = winter beans



Wee

dse

edb

ank


1st winter Disc and tines Soon after harvest End Septemberwheat

Winter beans Disc and tines Soon after harvest End October

Winter Disc and tines Soon after harvest 3rd week Augustoilseed rape



PhilipMortimerMaidenheadBerkshire

“Changing fromwinter to spring

oats hashelped toachievebetterblack-grass

control”397haHeavy clay and silty clay loam

Problemweeds:Suspected resistant black-grass,annually rogued wild-oat,crane’s-bill.

Rotation:1. Winter wheat2. Winter oilseed rapeSpring beans or spring oatsgrown to break up the rotation.


Current practice

Broadcasting rapebehind combineheaderKeeps weed seeds on soil surface to maximise control from propyzamide.

Spring croppingMaximises periods for non-selective herbicides to control germinatingblack-grass.

PloughingBuries short-lived seeds to decrease seedbank levels.


Reduce resistant black-grass seednumbers in theupper soil layerPhilip’s target rotation is to alternate winter wheat and rape. He usually usesminimum tillage, but will plough if black-grass levels seem to be getting toohigh. An alternative is spring cropping after ploughing which provides a longerperiod for winter weed control. This reduces seed in the germination layer forfuture years.

Cultivation

Basicrotation

non-invert

WOSR

non-invert

WW

plough

WW

non-invert

WOSR

non-invert

WW

non-invert

WOSR

Plough and plantspring beans

Non-invert

Very high

Low

WW = winter wheat WOSR = winter oilseed rape



Wee

dse

edb

ank


Winter wheat Disc and flat lift Soon after harvest October

Winter oilseed None – Broadcast behindrape combine header

Spring beans/ Plough Early autumn Marchoats



GraemeNeillNr Arbroath, Angus

“Resistantchickweed is

controlledbeforedrilling andby

usingmixtures ofherbicides”

262haSandy loam

Problemweeds:ALS-resistant chickweed,common field-speedwell, annualmeadow-grass, cleavers.

Rotation:1. Potatoes2. Winter wheat/spring barley3. Winter wheat4. Spring barley5. Winter oilseed rape5. Winter wheat


Current practice

Usingnon-inversion tillage in firstwheats after potatoesVolunteer potatoes are becoming less of a problem in the rotation due toincreased predation.

Usinga rangeof active ingredients to control chickweedALS-resistant chickweed is not widespread on the farm. Chickweed seed ispersistent in the seedbank and multiplication rates are high.

Suggested improvement

Controlling chickweed seedbanks in theupper layer of soilChickweed seeds survive for over five years, so it is important after ploughingto leave the old seeds at depth and not disturb them. Seed return is managedby stale seedbeds before drilling, and all subsequent seeds are left on thesurface. Spring barley crop allows a long period to control emerging chickweedas they emerge over winter.

Current practice Suggested improvement

Cultivation

Basicrotation

plough

WBar

plough

WW

plough

WOSR

wellmixed

WW

rotovate

Potatoes

plough

WW

Spring barley

Very high

Low

WW = winter wheat WBar = winter barley WOSR = winter oilseed rape


non-inversion

Wee

dse

edb

ank


Potatoes Plough and stone separator November/December April

Winter wheat Deep till Late End September orSeptember/October later

Winter barley Plough Early September Early September

Spring barley Plough December March

Winter oilseed Plough August August/Septemberrape



Further information

HGCA publications and details ofHGCA-funded projects are allavailable on the HGCA website– www.hgca.com and the CropOracle CD.

Guides andTopicSheetsManaging and preventingherbicide resistance in weeds.HGCA (2003) G10.

Enhancing Arable Biodiversity– six practical solutions forfarmers. HGCA (2007) G35.

The Encyclopaedia of ArableWeeds. HGCA (2009) G47.www.hgca.com/awe

Topic Sheet 24 (1999).Dormancy and persistence ofvolunteer oilseed rape.

Topic Sheet 100 (2007).Effective, sustainable Italianrye-grass control in winter cereals.

Information Sheet 02 (2008).Pre-harvest glyphosate applicationto wheat and barley.

Information Sheet 03 (2008).Herbicide-resistant black-grass:managing risk with fewer options.

Information Sheet 06 (2009).Control of ALS-resistant chickweedand poppy in cereals.

Information Sheet 07 (2009).Identification and control of bromegrasses.

Information Sheet 09 (2009).Oilseed rape herbicides and waterprotection.

Project ReportsProject Report 266 (2001).Strategies to control wild-oats andreduce the risk of selecting forherbicide resistance.

Project Report 370 (2005).Cost-effective weed control incereals using vision-guided inter-rowhoeing and band spraying systems.

Project Report 381 (2006).Improving crop profitability by usingminimum cultivation and exploitinggrass weed ecology.

Project Report 388 (2006).Development and validation of'Weed Management SupportSystem' (Weed Manager).

Project Report 404 (2006).Collection and dormancy testing ofblack-grass seed.

Project Report 408 (2007).Spray behaviour and efficacy ofherbicides and fungicides applied towheat at reduced volumes.

Project Report 416 (2007).Sustainable Arable Farming For anImproved Environment (SAFFIE).

Project Report 421 (2007).Developing an effective strategy forthe sustainable control of Italian rye-grass (Lolium multiflorum).

Project Report 466 (2010).Integrated management ofherbicide resistance.

Research Review 57 (2006).Review of HGCA-funded weedresearch (including LINK projects)1994-2005.

Research Review 62 (2007).Spatially variable herbicideapplication technology;opportunities for herbicideminimisation and protection ofbeneficial weeds.

Research Review 65 (2007).Pre-harvest glyphosate for weedcontrol and as a harvest aid incereals.

Research Review 70 (2009).Pesticide availability for cereals andoilseeds following revision ofDirective 91/414/EEC; effects oflosses and new research priorities.

Research Review OS2 (1991).Weeds in oilseed crops.

OngoingProjects

Project RD-2006-3336.Dormancy in grassweeds.

Project RD-2006-3341.New strategies to autumn grassweed control in cereals and oilseedrape.

Project RD-2006-3343. Maximisingthe control achieved by soil appliedherbicides.

Project RD-2008-3605.New approaches to weed controlin winter oilseed rape.

Project RD-2009-3652.Improving oilseed rape cropsfor effective weed control.

Other reportsBlair A, Cussans Jand Lutman P (1999).Biological framework fordeveloping a weed managementsupport system for weed controlin winter wheat: weed competitionand time of weed control. BrightonConference Weeds, BCPC,753-760.

Lutman P and Moss S (2009).The management of weeds inwinter cereals: the role of cropagronomy. Research Review forSyngenta, 56pp.

AcknowledgmentsThis guide, funded by HGCA as a knowledge transferproject, was written by Dr Sarah Cook and James Clarke,ADAS; Dr Stephen Moss, Rothamsted Research andDr Clare Butler-Ellis and Ron Stobart, NIAB TAG; assistedby Dr Ken Davies.

HGCA acknowledges the assistance of the farmers whohave participated in the case studies: Chris Bailey, AndrewCragg, Richard Davey, Phillip Mortimer, Graeme Neill.

HGCA is grateful to many people who have commented ondraft versions of this guide including: Denise Ginsburg andLynn Tatnell, ADAS; John Humphreys, Atlas Fram Group;Iain Ford, BASF; Gordon Anderson-Taylor, BayerCropScience; Andrew Cragg, Brooker Farms; Dr AndyBailey, Dow AgroSciences; Professor Graham Jellis, FoliaPartners; Patrick Goldsworthy, Goldsworthy Associates;David Richardson and Ingrid den Hoed, HSE, ChemicalsRegulation Directorate; Dr Emily Boys, Dr Clare Kelly andDr James Holmes, HGCA; Clare Bend, Masstock, MandaSamson, Monsanto; Dr Mike Storey, Potato Council; PeterLutman, Rothamsted Research; Keith Norman, Velcourt; aswell as David Ellerton, Julian Hasler and David Houghton.

Edited by Dr Clare Stirling, HGCA and Geoff Dodgson,Chamberlain.

Design by Chamberlain.

Photographs courtesy of ADAS, John Deere andRothamsted Research.

HGCA Stoneleigh ParkWarwickshire, CV8 2TL

HGCAPublicationsT 0845 245 [email protected]

HGCA is the cereals and oilseeds division of the Agriculture and Horticulture Development Board (AHDB).© Agriculture and Horticulture Development Board 2010.All rights reserved.

401633

DisclaimerWhileAHDB, operating through its HGCA division, seeks toensure that the information contained within this documentis accurate at the time of printing no warranty is given inrespect thereof and, to the maximum extent permitted by lawtheAgriculture and Horticulture Development Board acceptsno liability for loss, damage or injury howsoever caused(including that caused by negligence) or suffered directly orindirectly in relation to information and opinions contained inor omitted from this document.

Reference herein to trade names and proprietary productswithout stating that they are protected does not imply thatthey may be regarded as unprotected and thus free forgeneral use. No endorsement of named products isintended, nor is any criticism implied of other alternative,but unnamed products.

HGCA Guide 50 (G50)

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