A Gowan booklet produced in association with CPM

Transcription

1 A Gowan booklet produced in association with CPM

2 2 blackgrasscontrol

3 Introduction Effective blackgrass control revolves around bringing in a number of different tactics against the grassweed 5 for 5 recommends at least five are followed for five years, only one of which is the use of herbicides. These add up to bring the 97%+ control required to prevent populations building. Within this, herbicides remain a key tool in the armoury, and it s the pre-emergence stack that now delivers the goods in the majority of cases. The level of control varies, however, and much of this variation can be reduced by better use of the tools available and a keener understanding of the job in hand. That s why CPM is pleased to support this technical guide that s been compiled by Gowan Crop Protection, the manufacturer responsible for Avadex (tri-allate). It s a product with a long history of pre-em use against grassweeds in cereals, as a different AI it is a crucial part of an anti-resistance strategy. This makes Gowan ideally placed to provide some of the key pointers that can help bring effective control. Over the following pages, this guide outlines some of the cultural control strategies to employ, and focuses on the key requirements for pre-em efficacy. There s valuable insight into Avadex itself, its role in the pre-em stack and pointers on effective application. Contents Page Importance of blackgrass control... 4 Cultural control strategies... 6 Herbicide resistance... 8 Pre-emergence control The role of Avadex Granule applicators Application checks Conclusion For most growers, blackgrass will remain a key challenge, and keeping it under control relies less on innovation staying one step ahead of the weed. Those who succeed apply knowledge on effective measures in the best way, and seek smarter ways to use trusted tools. That s what makes this guide one worth hanging on to. Tom Allen-Stevens, Editor, CPM blackgrasscontrol 3

4 Importance of blackgrass control Blackgrass (Alopecurus myosuroides) has become a major issue across northern Europe, in particular UK, Northern France and Germany with some reports in Poland and Scandinavia. Blackgrass favours moist soils (heavy clay or silt) rather than sandy soils and although soil type is a major factor for blackgrass growth throughout Europe, climate also plays an important part where cool damp conditions favour germination. Emergence Blackgrass is an annual grassweed which multiplies solely by seed propagation. For long term control seed return must be prevented so it is important to understand the biology of the plant. The number of blackgrass heads per plant can vary considerably depending on crop competition, on average 2-20 heads/plant is typical in a competitive winter cereal crop, however where there is little or no crop competition there can be up to 150 heads/plant. Each head can contain up to 100 seeds and as an example, with a high population of around 600 heads/m² the seed return can easily exceed 60,000/m². The seed viability tends to be variable, although typically about 40-60% of these seeds can germinate. Most seeds will be Each head can contain up to 100 seeds and the seed return can easily exceed 60,000/m². 4 blackgrasscontrol

5 shed between June and August meaning the majority shed before the harvest of winter wheat crops. Seeds have a relatively short period of innate dormancy (several weeks) although this is increased when seed maturation has taken place under cooler/wetter conditions. If uncontrolled, populations can increase very rapidly, in some situations by over 30-fold per annum. Survival of buried seeds in the soil is estimated to be 20-30% per year, so after three years of burial about 1-3% of seeds can still be viable this may still represent the potential for a considerable population. Blackgrass plants tend to only emerge successfully from the top 5cm of soil, which is why minimum tillage encourages blackgrass. Normally, 80% of blackgrass germination and emergence occurs in the autumn, between September and November, and consequently blackgrass is mainly associated with autumn sown crops, especially cereals. Spring-sown crops tend to be less vulnerable to competitive blackgrass, as the majority of weed plants will have emerged before sowing and can be destroyed by seedbed cultivations or a glyphosate herbicide application. However, intensive (deep) cultivations and early sowing can still result in serious infestations in spring crops. Physiology and yield reduction The major impact of blackgrass is that it can seriously reduce crop yields through competition for nutrients, especially nitrogen. The competitiveness of the weed depends greatly on the vigour of the crop which influences the tillering ability of the blackgrass. Consequently, there can be considerable variation in crop yield response to similar blackgrass populations. On average, yield losses of t/ha of wheat can be expected with blackgrass populations between plants/m² Stephen Moss calculated that 12 plants/m² can give 5% yield loss which is used to indicate the threshold where chemical application was justified. Not only is there the risk of higher yield losses, there is also the potential for rapid population increase and the difficulty of assessing weed densities on a field scale, so most farmers aim to apply herbicides to control blackgrass at much lower densities. Control of blackgrass densities of less than 1 plant/m² may be justified in high risk situations. Brome spp. require accurate identification of which species of brome are present. Italian ryegrass has been highlighted as the new potential major grassweed challenge.. Other grassweeds Italian ryegrass, brome spp. and wild oats are a huge issue in many cereal crops across the country. In the next 10 years Italian ryegrass has been highlighted as the new potential major grassweed challenge. It has the same emergence pattern as blackgrass but can be more competitive, having greater than 20 heads/plant producing 5000 seeds. There have been reports that the emergence can be delayed until the spring but this has not been confirmed in tests done by independent research agencies. Due to its aggressive nature, 5 plants/m² can cause a typical yield loss of up to 5% in cereals. In high infestations yield loss can be greater than 80%. Brome spp. are more complex and require accurate identification of which species of brome are present. Sterile brome and great brome germinate when a sterile seedbed is achieved. Rye, meadow and soft brome require sunlight to break dormancy, therefore they can have a very protracted germination period. blackgrasscontrol 5

6 Cultural control strategies Widespread herbicide resistance has ensured that chemistry alone is not sufficient to successfully manage the problem of blackgrass, instead a trip to the chemical store should be the last part of the plan when you are building a sustainable management strategy for blackgrass. Integration of a range of non-chemical control methods is absolutely vital to reduce the number of seeds in the seedbank, and so to maintain a sustainable farming system. Spring cropping The first step if you have problem blackgrass is to alter the rotation, with the introduction, or extension, of spring cropping and fallow periods. Typically, 80% of blackgrass will emerge between The blackgrass heads produced by five plants (no herbicides) Winter wheat Spring wheat Spring oats Spring barley Reduction of blackgrass heads in spring crops (Source: NIAB TAG) October and December, which means that spring crops will not be under as much weed pressure. Warm soil conditions help crops emerge quickly, and where competitive crops are used, blackgrass can be smothered. Spring barley is probably the best choice overall it is an aggressive competitor with the weed; this not only reduces the number of heads per plant, but also the size of each head. It s also a crop where there are herbicide options should they be needed. The reduction in blackgrass seed return into the following crop is considerable. Fallow periods with cover crops or grazed leys of between 2 and 3 years can be equally as effective if seed return is prohibited, but the land may not be as productive. Cultivation principles Discussions around cultivation and blackgrass very often get hijacked by a slightly counterproductive argument about the specific details and very fixed views so perhaps it s appropriate to think about the principles: Cultivations which are aimed at stimulating the germination of weed seeds should be superficial (not greater than 5cm in depth). Cultivating deeper risks bringing up seeds from the seedbank (deeper than 5cm) whilst burying freshly shed seeds so they persist in the seedbank. Encouraging germination, then spraying off new seedlings diminishes the seedbank. Ploughing takes the approach of burying fresh 6 blackgrasscontrol

7 seeds rather than trying to promote their germination and will be most effective following crops where the seed return was high. In addition, not all cultivations are solely for weed management. Moving soil to prepare for the following crop, whilst managing residues from the previous one will drive cultivation decisions. It s clear from NIAB TAG trial data (see chart below) that as an overarching strategy, carrying out the major soil movement (whether it involved inversion or non-inversion) early and leaving as long a period between that cultivation and the establishment of the crop is the best approach. Avoiding significant soil movement is imperative to prevent stimulating blackgrass germination, which is why using no-till drills for establishing spring crops produce great results in the right conditions. When it comes to cultivations and weeds, there are times when doing nothing is actually the best strategy. In hotter, sunnier and drier conditions where there are high levels of weed seeds on the soil surface it may actually be best to just leave them there to suffer those conditions; many seeds will lose viability when exposed to those conditions. Always remember that whatever the strategy for cultivations between crops to manage blackgrass, a well-established competitive crop is at the heart of in-crop weed management. Don t sacrifice the opportunity to establish a good crop on a good seedbed in order to strictly adhere to a fixed (often belief-based) cultivation strategy that might work in some circumstances but not in the ones that you are confronted with in the field. Cultivation for spring cropping Source: NIAB TAG The greatest benefit is achieved by shifting the drilling slot by three to four weeks, to the middle of October. Drilling date When returning to autumn cropping at any stage in the rotation, selecting a drilling date to allow effective blackgrass control is essential. Sowing date must be optimised to allow for early blackgrass to emerge and be destroyed, and for wetter and cooler environmental conditions to enhance residual herbicide activity. The greatest benefit is achieved by shifting the drilling slot by three to four weeks, to the middle of October. The downside to this delay in drilling is the risk of poorer crop establishment, so it is recommended to increase seed rates to at least 350 seeds/m² to ensure strong competition. Switching crop species is another effective strategy to enhance competition against blackgrass. Winter barley, especially six-row varieties, is able to smother the weed with a fast-developing early canopy reducing the number of heads per plant, and so return. Winter oats are exceptionally competitive, but with limited chemical control available, they are unviable in high blackgrass areas. When basing a blackgrass management strategy on crops that suppress the growth and seed return of weeds do take care not to do anything that compromises that underlying approach; adopting seed rates that are too low or applying too much herbicide in conditions where they can affect the growth of the crop. When it finally comes to applying a herbicide programme, think about combining modes of action across active ingredients rather than increasing the use of a single active. It s also important to stay vigilant of the yet-to-emerge blackgrass. The pre-emergence timing is often the best shot at control; make sure it is pre-emergence! Adopting effective integrated weed management strategies, which combine a range of non-chemical approaches, will facilitate the successful reduction of blackgrass on your farm. blackgrasscontrol 7

8 Herbicide resistance It is very important to understand the type of resistance present before making any decisions on chemical control strategies. With the first resistant population of weeds reported in 1981 it has steadily spread where now resistant populations of blackgrass, Italian ryegrass, wild oats and other weeds are widespread throughout UK. There is a much reduced armoury of chemical control options against these resistant weed species. Blackgrass, specifically, has resistant populations across northern Europe making it a wider problematic weed than just the UK. There are three main types of resistance found in blackgrass: Single Site Resistance (SSR) to sulfonylurea herbicides and ACCase, and Enhanced Metabolism (EM). SSR ACCase This is where the target enzyme is mutated to block the activity of fops, dims and dens herbicide Group A. This resistance is complete giving very poor control due to high selection pressure and can spread rapidly. It is the most common SSR resistance and widespread in the UK. SSR sulfonylureas This is where the target enzyme is mutated to block the activity of sulfonylureas and other related herbicides in the herbicide Group B. Similar to ACCase resistance it is becoming widespread throughout the UK. Enhanced Metabolism Also known as Non target-site resistance (NTSR), this is where the target plants are able to detoxify the herbicide before it reaches the target site. This is due to high levels of cytochrome p450 enzymes able to de-activate a range of different herbicides. The herbicide can have some effect on the blackgrass but is more sensitive to growth stages the larger the plant, the more detoxifying enzymes. EM resistance is the most common resistance found in the UK. 8 blackgrasscontrol

9 In Italian ryegrass there are the same types of resistance mechanisms as blackgrass with the predominant being EM. Even though the resistance is less of an issue than blackgrass there is an increase throughout the UK. These three types of resistance can occur individually or together in the same plant. It is now reported that multiple types of resistance occur on most farms (>80%). This is having a dramatic impact for most post-emergence herbicides giving poor control and basically making them relatively ineffective. Moving forward we cannot be wholly dependent on chemistry and we need to give chemistry a chance by using a more rounded approach, chemical and non-chemical. Taking samples of seed and having them tested is a good way to find out the type of resistance. Herbicide group classification by mode of action Group Active ingredient Chemical group MOA A clodinafop-propargyl fops ACCase inhibitors diclofop-methyl aryloxyphenoxy- Inhibition of acetyl fenoxaprop-p-ethyl propionates CoA carboxylase fluazifop-p-butyl* propaquizafop* quizalofop-p-ethyl* cycloxydim* dims tepraloxydim* cyclohexanediones tralkoxydim pinoxaden dens phenylpyrazolines B flupyrsulfuron-methyl sulfonylureas ALS inhibitors iodosulfuron-methyl-na Inhibition of acetolactate mesosulfuron-methyl synthase sulfosulfuron triazolopyrimidine pyroxsulam sulfonamide sulfonylaminopropoxycarbazone-na carbonyl-triazolinones C1 metribuzin* triazinones Photosystem II inhibitors C2 chlorotoluron ureas Photosystem II inhibitors F1 flurtamone Inhibitor of Phytone Inhibition of pigment diflufenican desaturase synthesis carotenoid biosynthesis K1 pendimethalin dinitroanilines Inhibition of microtubule organisation K3 flufenacet oxyacetamides Inhibition of cell division N tri-allate thiocarbamates Inhibition of lipid synthesis prosulfocarb not ACCase inhibition Source: Herbicide Resistance Action Committee Classification of herbicides according to site of action (extract of the full list) blackgrasscontrol 9

10 Pre-emergence control As post emergence chemical effectiveness on blackgrass is diminished or limiting, with SSR resistance to ACCase and ALS being the key mechanism for this poor control, there is a greater emphasis on pre-emergence residual herbicides in winter cereals. The table below shows the shift of emphasis based on resistance and the amount of control required for your herbicide pre-em programme. As greater reliance is on pre-em herbicides it is important not to focus on one active and stack the pre-ems to ensure there is an additive control aiming to move towards the 97% control of blackgrass required to reduce populations. As with all cropping systems it is important to obtain a stale seedbed before drilling the cereal crop in the autumn. Residual herbicides are mainly applied pre-emergence of the crop and Control required to achieve 97% control of blackgrass Pre-emergence Post-emergence 0% 99% 73% 89% 86% 79% 90% 69% Source: AHDB information sheet 30 blackgrass and will control and/or effect the subsequent emerging blackgrass. As the residuals are mainly applied to the soil it important to achieve the best possible seedbed for optimum control from these herbicides. Aim to minimise trash and any clods for a well-consolidated seedbed. For pre-emergence application, ensure there is moisture in the seedbed. Pre-em options Flufenacet (FFT) is generally considered to be the starting point for the pre-emergence application and is a key part of an anti-resistance strategy, with no known resistance currently. The huge reliance on FFT means that it needs to be protected and other active ingredients should be brought into the programme to attack the weeds with a different mode of action. Pendimethalin (PDM) is a residual herbicide which can be affected by enhanced metabolism leading to instances of reduced control. It is still effective as a pre-em treatment and is an important part of an AI stack in an anti-resistant strategy. Diflufenican (DFF) is a residual herbicide which was mainly used for broadleaf weed control but as part of a mix with other residuals (FFT) it can give extra control of blackgrass. That makes it an important part of a stack either as a tank-mix 10 blackgrasscontrol

11 partner or in a co-formulated product. In severe blackgrass situations many agronomists believe a minimum of 100g of DFF is required. Flurtamone is a residual herbicide most effective on blackgrass as a pre-em treatment. It also adds to the efficacy of FFT and is an important part of an anti-resistant strategy. It is only available in pre-formulated mixtures with FFT and DFF. Prosulfocarb Is best used pre-emergence. It can help in an anti-resistance strategy when used as part of a stack. Most blackgrass control is normally based around FFT with DFF and/or PDM as the main pre-em AIs, on average giving 70%+ control of blackgrass plants. However, this is dependent It is important not to focus on one active and stack the pre-ems. Pendimethalin is an important part of an AI stack in an anti-resistant strategy. on conditions and to achieve the best control requires moist consolidated seedbeds. From this baseline other AIs can be stacked either by tank-mixing or by sequencing to achieve optimum control. For Italian ryegrass control a similar strategy can be adopted as for blackgrass. It can always be added to with post emergence herbicide if the resistance status is known. Additional control to the 240g/ha flufenacet base Source:NIAB TAG autumn Additional %age control to a base of 240g/ha of flufenacet eg 31% additional control from Avadex Excel 15G. blackgrasscontrol 11

12 The role of Avadex Avadex should only be used as part of a programmed approach in controlling blackgrass, where it can add up to 15-30% additional control. The active ingredient in Avadex products is tri-allate which belongs to the thiocarbamate group and inhibits lipid synthesis. It is sold in a granular form as Avadex Excel 15G or a liquid formulation Avadex Factor. As a pre-emergence herbicide, the tri-allate is taken up in the coleoptile shoot as it emerges from the seed. As there is a greater emphasis on pre-em herbicides it is important to maintain an anti-resistance strategy and we know that tri-allate remains an ideal partner to stack or sequence with products as it offers a different mode of action, bringing an uplift in blackgrass control. Avadex can be used on winter cereals and spring barley with Avadex Excel 15G EAMUs on linseed, miscanthus, canary grass as well as rye and triticale. As with all pre-em herbicides, it is important to have a firm moist seedbed, devoid of any large clods, for the Avadex to work best. Avadex Excel 15G is best applied to a moist seedbed as soon as possible after drilling and rolling, pre-emergence of the crop and weeds. This allows the tri-allate to readily partition from the granule to the soil providing an herbicidal zone in the top layer of the soil. There are several ways of applying the granular formulation of Avadex using an applicator mounted behind the drill, on the rolls, mounted on a suitable vehicle or towed behind a Gator and there are many contractors around the UK with Avadex application machinery. Wherever the applicator is mounted, it is important to remember that the operator must have the PA4G certificate. However, whichever option is used the Avadex should be applied pre-emergence of the blackgrass. Both Avadex labels have a restriction on organic matter, with less than 10% being required for optimum performance and both formulations require some soil moisture. Whether Avadex Excel or Avadex Factor on winter wheat, the depth of planting is important and needs to be a minimum of 4cm to keep seed away from the herbicide zone. The depth is less important for winter or spring barley drilling. Difference between Avadex formulations Questions are often asked about the difference between the two formulations of Avadex on the market. Apart from the obvious difference between granules and liquid, Avadex Excel 15G applies 2250g/ha of tri-allate whilst Avadex Factor applies 1620g/ha of tri-allate. The difference in the amount of active ingredient applied between the two formulations can be mitigated against with an understanding of where they both fit. Avadex Excel may be more robust across a range of conditions but Avadex Factor fits better on later drilled crops in October/November shorter days with diffuse sunlight and lower temperatures and more likelihood of adequate soil moisture. Both fit well into the herbicide stack but obviously the Avadex Factor can be tank-mixed with other pre-em herbicides. 12 blackgrasscontrol

13 The relative persistency of tri-allate does not change between the two different formulations. Depending on conditions the average half-life is three months with a range of 2-6 months. This will also help in controlling other grassweeds such as brome spp, wild oats and ryegrass. The 48-hour window As mentioned before, the baseline for blackgrass control is built around 240g/ha flufenacet with the addition of tri-allate, DFF and or PDM. For Avadex Factor it is an easy option to tank-mix all your actives in a pre-em stack (the tank-mix list can be downloaded at and all applied at the same time. Avadex Excel 15G granules will obviously need to be applied separately to the flufenacet based tank-mix as a pre-em sequence and the question is always asked which way should the sequence be applied to get the best results before or after the flufenacet? The answer is very simple, it does not make a difference if the granules are applied before or after flufenacet. The important point is that it is applied pre-em of the weeds, ideally 48 hours after drilling, unless it is bone dry and nothing is growing, in which case wait for rain to allow the blackgrass to germinate. Additional control of Avadex Excel 15G Source: Gowan demonstration trials mean of seven trials Average overall control from all treatments shown; Average 544 heads/m²; Treatment bases all made up to 100g/ha DFF; Liberator contains FFT+ DFF; Crystal contains FFT+ PDM. Avadex Factor fits better on later drilled crops in October/November.. Avadex can be used on winter cereals and spring barley with Avadex Excel 15G EAMUs on linseed, miscanthus, canary grass as well as rye and triticale. The important point is that Avadex is applied pre-em of the weeds, ideally within 48 hours of drilling. blackgrasscontrol 13

14 Granule applicators Getting the timing right for optimum control is only half the battle getting the quality of application is just as important. Application equipment for the granules needs to be set up correctly and well calibrated to ensure the correct dose is applied evenly across the boom width. Gowan would always recommend a patternation test is carried out at the same time as the overall calibration procedure. There are now many manufacturers who build and sell applicators depending on your budget. The following companies are able to build an applicator either to be mounted behind rolls, a drill or on a tractor. Horstine part of Chafer Machinery Ltd. TMA4 and Cascade Opico Limited Micro-Pro 16 Stocks AG Limited various models available Keith Rennie Machinery Ltd. various models available Techneat engineering Ltd. various models available Once an applicator is chosen, where to use it is the next question mounted on the drill, on the rolls, on a small tractor or utility vehicle or towed on a buggy? Before deciding what will fit your needs you may wish to consider the following: 14 blackgrasscontrol

15 The Opico Micro-Pro features twin shock absorbers to reduce exaggerated yaw and sway on rougher terrain. Dose of Avadex Excel 15G Techneat s Avacast GR1200 is also available as a standalone 24m machine. 15kg/ha 12kg/ha The recommended rate of Avadex Excel 15G is 15kg/ha and the key to good control is the evenness with which this is spread. Any attempt to reduce the recommended rate will lead to a reduction in the distribution of the granules on the soil surface (illustrated above as granules/cm 2 ), leaving gaps in the herbicide layer and a subsequent reduction in performance. The Horstine TMA4 has 12 rotors for each of the 12 outlets to part off the right amount of product. Mounted on a set of rolls, this reduces the number of passes, if conditions are right to roll. Mounted on the rolls Conditions are not always favourable for rolling This is a consideration if Avadex is an integral part of you grass weed management strategy. Is the operator PA4G qualified? Is the height ideal to obtain the correct spread pattern? Mounted on the drill Drilling speed it is important to maintain the integrity of the spread pattern and therefore the forward speed should be no higher than that recommended by the manufacturer for even application. Ensure the outlet for the applicator is far enough away from the coulters to maintain the drilling depth of 4cm for wheat. With the movement of soil you may get some roll down which should be fine if wheat is drilled deep enough. Rolling is an option but beware pushing down the soil and chemical towards the seed if the seedbed is not firm enough. blackgrasscontrol 15

16 Application checks All granule application equipment needs to be well maintained and regularly tested. Granule applicators should undergo an NSTS re-test every six years after their first assessment. This test importantly checks the mechanisms of the granule applicator, pipework, fan, and air pressure and rate calibration. However, the test does not routinely include checking the evenness of the application across the full width of the boom, rather just the amount applied. It is important to evaluate the pattern of distribution and adjust this if it is not even otherwise striping may occur. SCS Spreader and Sprayer Testing Ltd, a national UK company, offer both the NSTS and a full width patternation test to ensure every gram of Avadex is applied evenly to the field. They can be contacted on Rob Foxall of SCS comments: It s not just how much you apply but where you apply it even coverage gives maximum benefit to your fields and ensures the most efficient use of Avadex. Granule applicators The main issue to address is striping in field. Between the NSTS tests it is important to keep the metering mechanisms checked and other regular checks which should be carried out on all applicators: Check all pipe work for blockages and splits Ensure all deflector plates are clean and at the right angle as they can be knocked during transport, which will affect the pattern of the granules. Do regular calibration throughout the season. 16 blackgrasscontrol

17 All applicators require servicing on a six-year basis to ensure even and accurate applications. Sprayer application Suitable conditions for spraying pre-emergent products are the same as for any spraying operation. As stated by the Code of Practice for Safe use of Pesticides to deliver the product to the target evenly, but there are many factors to consider. The weather, forward speed, boom height and nozzle selection. Where the focus is to mitigate drift especially on soil where there is no crop to capture drift spray. Climate/weather This the biggest influence affecting application in the UK is wind speed which will impact application. In ideal conditions the wind speed will be 2 on the Beaufort scale (light breeze) In windier conditions the drift will increase. On the other extreme avoid still humid conditions allowing the spray/vapour to linger and not reach the target. Boom height To have the lowest boom height which still allows for an even application. To obtain the lowest boom height will depend on the type of nozzle and the spacing along the boom as well as the design of the boom. Nozzles Ideally nozzle selection should be coarsest nozzle but still giving the spray quality to get the best coverage of the target. Always refer to the product label for appropriate conditions for spraying, and follow all directions including DRT and buffer zones. A full width patternation test evaluates the evenness of the application across the full width of the boom. Coarse nozzles, angled alternately forwards and backwards give the best coverage of the target. blackgrasscontrol 17

18 Conclusion There is no question now that control of blackgrass and other difficult grass weeds requires an integrated approach and a strategy relying purely on herbicides will not give the required 97+% control required to reduce seed return. The reliance just on herbicides is, in the long term, not sustainable and the need for effective chemistry is crucial in the long term as part of a holistic approach to reduce seed return. Pre-emergent chemicals are subject to seasonal variations in the weather before and after application. This will impact the effect on all active ingredients to varying degrees, so stacking will help to minimise the variation in efficacy and maximise the effectiveness of the anti-resistance strategy. The addition of Avadex Excel 15G to a flufenacetbased programme has given, across many trials over the last three years, a range of 15 to 30% additional control of blackgrass. Other active ingredients may be considered both within the first pre-emergence application and at The addition of Avadex Excel to a flufenacet-based programme has given a range of 15-30% additional control of blackgrass. a peri- or post emergence timings which will give incremental increases in control. On large farms certain non-chemical strategies can be implemented on a farm level but drilling and applications should be considered on field or block basis. Always target the main fields with 18 blackgrasscontrol

19 The need for effective chemistry is crucial in the long term as part of a holistic approach to reduce seed return. All pre-emergent residual herbicide needs to be applied on moist consolidated seedbeds and pre-emergence of the blackgrass. severe blackgrass first for drilling and applying your residual herbicides. In ideal growing conditions the first 48hrs is crucial for the application of your pre-ems. If the weather conditions are too dry then hold off spraying if possible easier said than done, where larger areas must be covered. Wind speed, travelling speed and nozzle selection are crucial to maximise efficacy of the pre-em herbicide. Post emergence contact herbicides can still have a place where the resistance status of the weed population is known. However the with the very cold conditions in spring 2018 may have delayed crop growth but not blackgrass growth and relatively good control of blackgrass plants in autumn 2017 had reduced inter-plant competition and allowed those survivors to produce large amount of tillers and heads appearing above the crop. However, other non-chemical agronomic practices needs to be implemented to reduce the burden on chemical control to make the 97+% control achievable. Rotation is the key starting point, especially putting in spring cropping, with spring barley being the most competitive in reducing the amount of blackgrass tillers/heads. This allows subsequent reduction in seed return and blackgrass germination in the following crop. The second key step in blackgrass management is delaying drilling this alone can result in a 35% reduction in blackgrass as well as presenting the pre-emergence herbicides with more ideal conditions for optimum performance shorter day length, lower temperatures, cloudier conditions etc. If all agronomic practices, best suited for your farm, have been put into place, the resistance status of your blackgrass is known and the chemical application for your base preemergence have been decided, it is important to make sure the application is done correctly. All pre-emergent residual herbicide needs to be applied on moist consolidated seedbeds and pre-emergence of the blackgrass. How effective they are will be mainly dependant on the weather, timing, soil moisture status and germination pattern of the weeds. blackgrasscontrol 19

20 In no way does CPM Ltd endorse, notarise or concur with any of the advice, recommendations or prescriptions reported in the booklet. If you are unsure about which recommendations to follow, please consult a professional agronomist. For further information contact: Gowan Crop Protection Ltd., Innovation Hub, West Common, Harpenden, Herts AL5 2JQ Website: Avadex is a registered trademark used under licence by Gowan Crop Protection Ltd. All other brand names referred to are trademarks of other manufacturers in which proprietary rights may exist.